Source: https://patents.google.com/patent/DE19507826C2/en
Timestamp: 2020-07-11 19:00:03
Document Index: 355593088

Matched Legal Cases: ['arts 108', 'art 109', 'arts 108', 'art 109', 'art 109', 'art 109', 'art 108', 'arts 74', 'arts 74', 'arts 74']

DE19507826C2 - Device for detecting malfunctions or damage to an electrical device or a rotating electrical machine - Google Patents
Device for detecting malfunctions or damage to an electrical device or a rotating electrical machine
DE19507826C2
DE19507826C2 DE1995107826 DE19507826A DE19507826C2 DE 19507826 C2 DE19507826 C2 DE 19507826C2 DE 1995107826 DE1995107826 DE 1995107826 DE 19507826 A DE19507826 A DE 19507826A DE 19507826 C2 DE19507826 C2 DE 19507826C2
DE1995107826
DE19507826A1 (en
Hideki Tokura
Ken Kimrua
1994-02-25 Priority to JP2774194A priority Critical patent/JP3187642B2/en
1995-02-21 Application filed by Kansai Electric Power Co Inc, Mitsubishi Electric Corp filed Critical Kansai Electric Power Co Inc
1995-08-31 Publication of DE19507826A1 publication Critical patent/DE19507826A1/en
2003-07-17 Publication of DE19507826C2 publication Critical patent/DE19507826C2/en
239000011162 core materials Substances 0.000 claims description 39
The invention relates to a device for Detect malfunctions or damage to an electri rule device, or a rotating elect machine, like an electric motor, one Generator or the like, and refers in particular special to a device for detecting Damage caused by aging insulation Stator winding is effected.
In recent times, the dimensions were one Plant in industry generally enlarged and one electrical equipment, such as a gas insulated system (hereinafter referred to as GIS) and a rotating one electrical machines also got bigger in theirs Dimensions and the number of installations was made likewise increased.
Because great reliability in such electri devices, they must be checked regularly serviced and inspected for a sudden Accident, how to ver a dielectric breakdown avoid. In addition, the majority of the works electrical equipment that hosts during the big one economic growth period made in Japan have been, for over twenty-five years, so that it is imperative to monitor them regularly to prevent sudden accidents during their operation to avoid.
In the prior art, an electrical process as a method of evaluating insulation aging of electrical equipment, for example with respect to the stator of a rotating electrical machine, used a high voltage on the windings the rotating electrical machine has been abandoned en after the machine has stopped operating, and the electrical properties of the Sta tors, such as insulation resistance, alternating current, dielectric loss angle, partial discharge and the same measured to the degree of aging of the iso determinations in each part.
However, in order to assess the age the use of such a known method to carry out, it is necessary to operate the electri stop device and consequently will be a lot Time, work and costs needed. It also has the procedure has the disadvantage that it is difficult frequently perform the assessment tests of aging. It also has the other disadvantage that it is not suitable for a case where the old man progresses quickly.
Thus, there is a prior art device published in Japanese Patent Gazette No. 68852/92 (Hei 4 ) (JP-B4-68852 corresponds to JP-A 59-162740) to solve the problems described above avoid. This device provides a sensor electrode made of a metal material in a slot near the stator winding and connects a measuring instrument for partial discharge to the sensor electrode in order to monitor the aging of the insulation during the operation of the electrical device. In addition, Japanese Unexamined Patent Application, published under No. 296672/92 (Hei 4 ), discloses an irregularity detecting device which reduces the partial discharge generated in its stator winding and by the stator winding progress the high-frequency signals detected using egg nes temperature detector, which is provided adjacent to the stator winding at one point to detect the irregularity of the winding of the stator.
Fig. 1 is a cross section showing the main part of a corona detecting device for a rotating high-voltage electric machine according to the prior art, which is disclosed, for example, in Japanese Patent Gazette No. 68852/92 (Hei 4 ). In the figure, the reference numeral 3 denotes a stator core or a laminated core, the reference numeral 4 a stator winding, the reference numeral 6 a slot, the reference numeral 100 a conductor of a stator winding, the reference numeral 101 a main insulation layer, the reference numeral 102 a coating of low resistance , which is provided on the surface of the main insulation layer 101 , 103 a separating element between the layers, 104 a scanning electrode, 106 a line and 107 a Corona measuring instrument. The sensing electrode 104 made of metal material is electrically connected to the low resistance coating 102 in the slot 6 of the laminated core 3 . The corona detector monitors the aging of the insulation during operation of the rotating electrical machine by providing the sensing electrode 104 between the stator windings received in the slot 6 via the separator 103 between the layers and by the line drawn out from the sensing electrode 104 106 is connected to the corona measuring instrument 107 .
Fig. 2 is a cross section showing the main part of another example of a corona detection device. In this device, the coating 102 of low resistance is divided into two parts 108 and 109 , a part 109 of which is in contact with the scanning electrode 104 .
The mode of operation is described below. When the aging of insulation occurs in rotating high voltage electrical machines shown in FIGS. 1 and 2, a partial discharge is generated on the main insulation layer 102 between the conductor 100 of the stator winding and the coating 102 of low resistance. Since the sensing electrode 104 , which is made of metal material, is electrically connected to the low-resistance coating 102 in the slot 6 , the partial electrical discharge generated during operation of the rotating electrical machine can be determined by the sensing electrode 104 .
In addition, the device shown in FIG. 2 is constructed such that it divides the low-resistance coating 102 into the parts 108 and 109 such that the sensing electrode 104 is in contact with a part 109 of them. Consequently, the partial discharge generated from the part 109 of the low-resistance coating can be determined, the part 109 being insulated from the stator core 3 , even if the part 108 of the low-resistance coating 102 is electrically contacted with the stator core 3 .
DE 35 26 149 A1 is a coupling unit for operational monitoring of high voltage windings and the connected leads electrical high-voltage machines by means of parts charge detection is known in which the generator line capacitors and phase feed specific coupling units at end potential are closed and from the coupling units partial discharge measuring lines via filter to a part charge meter. The filter can be broadband to suppress the network noise level or a high be a pass filter when a certain frequency spectrum to be examined in more detail.
US 5 256 976 describes a device for the festival represent malfunctions or damage and their position nen in a high-voltage line, in which a part discharge sensor is attached to the line, the a partial discharge is recorded and evaluated direction is connected. The partial discharge signal will analyzed by a spectrum analyzer, being before the actual measurement a defi signal generator nated high-frequency signals in the high-voltage line tion enters that of different partial discharge sensors are detected and then the respective Fre frequency spectrum is determined.
Fig. 3 is a block diagram of a device for detecting irregularities for a rotating electrical machine according to the prior art, which is published in Japanese Unexamined Patent Application under No. 296672/92 (Hei 4 ). The figure also shows a rotating electrical machine partially cut away to show the position of the partial discharge sensor located near the stator windings.
In the figure, the stator windings 4 are received in the slot 6 in the stator core 3 , which is attached to a stator frame (not shown).
The stator windings 4 consist of two windings, an upper and a lower one and are fastened by a wedge 7 . A partial discharge sensor 9 consists, for example, of a temperature detector element 8 a and lines 8 b and the sensor is inserted between the two, the upper and the lower, stator windings 4 in a predetermined slot. The Lei line wires 19 of the partial discharge sensor are connected to a circuit 110 for determining the irregularity speed via a temperature measuring instrument 22 . The lead wires are further connected to the irregularity determination circuit 110 via a filter 23 and a partial discharge measuring instrument 24 . An alarm unit 11 , a display unit 29 at irregularity and an interface 112 are also connected to the determination circuit for the irregularity 110 .
In the following the device for determining the irregularity according to FIG. 3 is described.
When abnormality occurs due to the aging of the insulation of the stator windings 4, in the stator windings 4 is a partial discharge is generated and a high-frequency current flows in the windings. The high frequency current generated by the discharge is made to the partial discharge sensor 9 also continues, the 4 e is lektromagnetisch connected to the upper and lower stator winding, and the current is supplied to the filter 23rd Since the partial discharge signal is a high-frequency signal with a frequency of more than a few kHz, the filter 23 eliminates the low-frequency signals to be used in the temperature measurement and supplies only the high-frequency component of the discharge signal to the measuring instrument 24 for the partial discharge. The partial discharge meter 24 analyzes the input signal to measure a discharge characteristic and passes the discharge characteristic to the irregularity determination circuit 110 . If the irregular-ness determining circuit 110 determines the situation as abnormal, the circuit 110 provides alarm signals to the alarm unit 11 and the display unit 29 for the irregularity.
While the electrical equipment or the electri device is in operation, are generally spoken many radio interference accompanied by the operation gene generated. For example, deliver in many genera gates that have been in operation for more than 15 to 20 years are and their insulation irregularities over the generato excitation coils must be watched Ren, the field current to the rotors of the generators deliver, direct current to the rotors via slip rings of the generators. In these slip rings is in egg some contact states of their grinding surfaces charges are generated and then radio noises generated. In addition, in a thyristor lively pulsed thyristor disturbances to his pathogen superimposed on the gerstrom. The exciters and the slip rings thus become sources of radio interference .
In addition, the charge generated by the static electricity of steam turbines and the charge caused by the induced current accompanying the generation of electricity are generated in the rotors and the like. In order for the charges on the rotors to be dissipated, a construction is generally used in which the brushes are grounded to the shafts of the rotors so that the charges are discharged to earth. However, an arc discharge is generated in some contact states of the sliding surfaces of the earth brushes and radio interference signals are also generated during this discharge. These radio interference signals show similar frequency characteristics to those of the electromagnetic wave signals which are caused by cavity discharge generated in the main insulating layers 101 of the stator windings, as shown in FIGS. 1 and 2.
Radio interference generated by transmission systems in bus lines with insulated ter phase, various types of radio communication wave signals, radio waves and so on penetrate into the power or heavy current stations. These radio interference signals are also frequently detected by the sensor that detects the partial discharge. In particular, if a sensor that is highly sensitive to high-frequency signals is used, a partial discharge sensor 9 according to FIG. 3 will also receive the radio interference signals.
These radio interference signals are of greater strength than that detects the partial discharge signals. Also lie the frequencies of the radio interference signals in the na range he that of the partial discharge signals and therefore the Detection of the partial discharge during the operation of the electrical device very difficult.
Because the procedure for detecting irregularities in state-of-the-art electrical devices and the irregularity detection device in rotating electrical machines after the State of the art as described above they do not take into account the radio interference signals, that are generated during their operation.
Even if an attempt is made to use the partial discharge signal generated during operation tect, the measurement result becomes radio interference contain, since it is impossible to to separate the radio interference. Hence is in the method and the device for detection State of the art irregularities the accuracy of the detection is very low.
The invention has for its object a direction for detecting faults or damage to create electrical devices that are generating source of the discharge signals during operation of the electrical device, where Radio interference signals from the partial discharge signals to be separated and where partial discharge signals to be determined, the small discharge dung. Furthermore, a device for Detect damage or malfunction in electrical Devices, for example with a rotating electrical machine, where exactly that Threshold for separating partial discharge signals is determined by the radio interference signals, the by only small differences in the sensitivity of the Partial discharge sensors caused errors or those in errors contained in the partial discharge measuring system are to be included and the partial discharge signals to be measured accurately. Farther the positions of the generation of the partial discharge can be specified.
This object is achieved by the features of the main claim and the subordinate claims solved.
By the measure specified in the subclaims Men are advantageous further training and improvements possible.
Embodiments of the invention are in the drawing tion and are described in the following section spelling explained in more detail. Show it:
Fig. Nik 1 shows a cross-sectional view, the direction of the main part of a corona Erfassungsvor for a rotating electrical machine according to the specific state of the technology,
Fig. 2 is a cross sectional view of a corona showing the principal part of another example of detecting device according to the prior art,
Fig. 3 is a block diagram of a detection device for irregularities of a rotating electrical machine according to the prior art, which is a partially cut-away generator to a Teilentladungssen to show sor installed in the immediate vicinity of a stator winding,
Fig. 4 is a block diagram showing a ßigkeiten Before direction for the detection of irregular shapes, which serves to illustrate the invention,
Fig. 5 is used, a characteristic curve showing an image captured by the Tei lentladungssensor Teilentla dung signal processing in the Vorrich of FIG. 4, wherein the signal strength (dBm) over the Fre frequency (MHz) is plotted,
Fig. 6 is a block diagram showing a processing Vorrich for detecting irregularities shows for electrical equipment, which is used for explaining the exporting approximately example of FIG. 16 and Pa tentanspruch 2,
Fig. 7 (a) 7 (b) and 7 (c) characteristic curves showing dung signals from the partial discharge sensor of the device according to Fig. 6 Teilentla detected, wherein the signal strength (dBm) is plotted on the Fre frequency (MHz)
Fig. 8 (a) and 8 (b) are cross sectional views showing the structure of a rotating electrical machine rule, in the embodiment of Fig. 17 of the present invention is to articulate,
Fig. 9 is a block diagram showing a Vorrich device for detecting irregularities for a rotating machine, the rotating electrical machine is partially cut away, and which is used to explain the exemplary embodiment of FIGS . 17 and 25;
Fig. 10 is a developed plan view showing a winding state of a stator winding of the rotary electric machine, the stator winding is inserted into the stator core,
Fig an Teilentla dung signal corresponding to FIG. 9 detected by the Teilentla dung sensor the rotary electric machine is provides. 11 is a characteristic curve which rakteristik the Frequenzcha, with the abscissa representing the Fre frequency (MHz) and the ordinate indicates he summed strength (dBm)
Fig. 12 is a characteristic curve showing the characteristics of the partial discharge signals when the signals progress through the stator windings of the rotating electrical machine, corresponding to Fig. 9, where the abscissa is the distance to the sensor (the number of slots) and the ordinate is the amplitude the broadband signals (mV) and the signal strength at resonance frequency (mV),
Fig. 13 is a graph showing the detected strength (dBm) versus the frequency (MHz) of partial discharge signals detected by a partial discharge sensor according to Fig. 9, using a larger bandwidth (F 1 ) of the pass frequencies of a narrow band filter circuit and is also shown
Fig. 14 is a graph showing the detected strength (dBm) versus the frequency (MHz) of partial discharge signals detected by a partial discharge sensor according to Fig. 9, using a different bandwidth (F 2 ) of the pass frequencies of a narrow band filter circuit and is also shown
Fig. 15 is a graph showing the detected strength (dBm) over the frequencies (MHz) of partial discharge signals, which were recorded by a partial discharge sensor accordingly Fig. 9, with yet another bandwidth (F 3 ) of pass frequencies of a narrow band filter circuit is used and also presented,
Fig. 16 is a block diagram showing a processing Vorrich for detecting irregularities by using the method for detecting abnormality for electrical equipment according to the present invention accordingly to claim 2,
Fig. 17 is a block diagram showing ßigkeiten Before direction for detecting irregular shapes according to the embodiment of the present invention accordingly to claim 1 a,
Are generated Fig. 18 is a characteristic diagram showing a partial discharge signal and a radio interference signal, for example in the execution according to Fig. 17, with the abscissa representing the frequency (MHz) and the ordinate the detected strength (dBm)
FIG. 19 shows a characteristic curve which shows the detected strength (dBm) over the frequency (MHz) of the partial discharge signals detected by a partial discharge sensor according to the exemplary embodiment according to FIG. 17 of the present invention, the bandwidths (F 4 , F 5 ) the pass frequencies of the narrowband filter circuits are used and also shown,
Fig. 20 is an explanatory view showing the passage after the execution frequencies for the Ver equal to the ratios of the intensity between two bandwidths corresponding to FIG. 19 show,
Fig. 21 is a graph showing the detected strength (dBm) versus frequency (MHz) of the partial discharge signals detected by the partial discharge sensor used in the embodiment of Fig. 17 of the present invention, with bandwidths (F 6 , F 7 ) of the passage frequencies the narrowband filter circuits are used and also shown,
Fig. 22 is a characteristic diagram of in the exporting approximately example the detected strength (dBm) over the Fre frequencies (MHz) to that of FIG. 17, the vorlie constricting invention notify by using shows charge sensor detected Teilentla dung signals, other bandwidths (F 8, F 9 ) of pass frequencies of the narrowband filter circuits are used and also shown,
Fig. 23 is a graph displayed on the basis of the measured data of the partial discharge signals and the radio noise of the apparatus for He version of irregularities for ei ne rotary electric machine according to an embodiment of the present invention corresponding to FIG. 17, the abscissa nalstärke the Sig ( mV) of a first narrow band filter circuit and the ordinate denotes the signal strength (mV) of a second narrow band filter circuit,
Fig. 24 is a block diagram showing a device for detecting irregularities, which can be used to explain the embodiment of Fig. 16.
Fig. 25 is a block diagram showing a processing Vorrich for detecting irregularities of a rotating electrical machine according to the embodiment of the present invention accordingly to claim 3,
Fig. 26 (a) and 26 (b) are explanatory views showing the arrangement of the gene Statorwicklun and partial discharge sensors according to the embodiment of the present invention accordingly Fig. 25 and the advancing Tenden waveforms of the charge signals notify by show
Fig. 27 (a) and 27 (b) are explanatory views showing the propagation path of the nien of the partial discharge sensors to be detected and the Funkstörsignale Kennli of the detected signals according to the embodiment accordingly Fig. 25 show
Fig. 28 is a graph showing the relationship Zvi's U-phase signals and V-Phasensig dimensional according to the embodiment accordingly Fig. 25,
Fig. 29 is a characteristic curve which strengthen the distribution of the detection frequencies (the number) on the ratios of the output signal between Teilentladungssenso the device ren for detecting irregularities of a rotating electrical machine according to the exporting approximately example of the present OF INVENTION dung corresponding to FIG. 25,
Fig. 30 is a characteristic diagram that other distributions of frequencies of the Erfas solution (the number) on the ratio s of the strength between the partial discharge sensors corresponding to FIG. 29 shows,
Fig. 31 is a characteristic diagram, the ratios for other distributions of the frequencies of the detection (the number) on the Ver strength between notify by charge sensors corresponding to FIG. 29 and 30 shows
FIG. 32 is an explanatory table for illustrating the method of determining a threshold value of the interference discrimination circles according to FIG. 25, and
Fig. 33 is a block diagram showing a processing Vorrich for detecting irregularities of a rotating electrical machine according to a further example of the present exporting approximately OF INVENTION dung according to claim 1. Fig.
FIG. 4 shows a block diagram which shows a device for detecting irregularities for electrical equipment, which is used only for further explanation. Fig. 5 is a characteristic never showing a partial discharge signal detected by the partial discharge sensor used in the irregularity detector, the abscissa representing the frequencies (MHz) and the ordinate representing the signal strength (dBm). In Fig. 4, the reference numeral 70 designates an electrical equipment such as a GIS, wherein conductors 73 a, 73 b, 73 c are arranged in the middle of a housing 72 made of metal, and are insulated by insulating spacers 71 a, 71 b to maintain a high voltage state. The GIS 70 is constructed by connecting a circuit breaker, a breaker, a current transformer and so on (they are all not shown) to the constructions of Fig. 4 used as connection units. Consequently, connecting parts 74 a and 74 b are inevitably provided in the conductors of the GIS 70 .
The housing 72 is provided with a partial discharge sensor 9 , a detection impedance element 51 , a spectrum analyzer 52 , a narrow band filter circuit 23 , a partial discharge measuring circuit 53 , a partial discharge generation processing circuit 26 and a display unit 28 for detecting partial discharges when an irregularity in the GIS 70 occurs.
The operation of the abnormality detection device will now be described with reference to FIGS . 4 and 5.
A high voltage is applied to the conductors 73 a, 73 b and 73 c while the GIS 70 is in operation. If an abnormality occurs in the GIS 70 , a partial discharge is generated that spreads over the conductor 73 a.
As for the abnormality or irregularity in the GIS 70 , for example, a case can be considered in which external substances such as metal particles remain in the case 72 or dust is moved into the GIS 70 by the potential of the electric field in the case 72 , causing uneven spots in the electric field in the housing 72 . The case can also be considered in which a gap is generated by the occurrence of cracks in the insulating spacers 71 a and 71 b or by voltage deterioration. In these cases, the turbulence of the electric field creates a partial discharge where the turbulence occurs, and then the irregularity of the GIS 70 can be determined by detecting the partial discharge.
The generation of the partial discharge allows a rapid partial discharge signal to proceed via the conductor 73 a and the housing 72 . The speed of propagation is approximately the same as the speed of light. Since the conductor 73 a has connecting parts 74 a and 74 b at its two ends and its impedance changes at both ends, part of the partial discharge signal is spread in the direction which is more distant from the generation source of the partial discharge, the reflections, the coming and going between the connecting parts 74 a and 74 b are repeated. In addition, both ends of the housing 72 are provided with the insulating spacers 71 a and 71 b, and an impedance change also occurs in these parts. As a result, the partial discharge signal propagating through the case 72 is also propagated between the two ends of the case 72 by repeating the reflections, the arrival and the return.
Thus, a partial discharge signal generated at a certain point in the GIS 70 is detected as a signal which is related to the length of the conductor 73 a and the length of the housing 72 at the point at which the discharge signal is generated, in relation to includes frequency. Since the measuring circuits also have distributed constant circuits with L, C and R components, they often have resonance frequencies, as shown in FIG. 5. FIG. 5 shows a frequency characteristic curve which is represented by recording the data of a partial discharge signal including the resonance frequencies, the data being currently measured by the spectrum analyzer 52 according to FIG. 4. In Fig. 5, the reference mark f 0 denotes the resonance frequency of the first order, the reference mark f 1 the resonance frequency of the second order, the reference mark f 2 the resonance frequency of the third order. The resonance frequencies relate to the length of the conductor 73 a in this case. The values of the resonance frequencies are consequently changed in accordance with the locations at which the partial discharge signal is generated.
This device determines the resonance frequencies from the signals detected by the partial discharge sensor 9 and specifies the generation source of a partial discharge signal from the values of the resonance frequencies.
The following is the detection of the partial discharge Signals described with these resonance frequencies.
Is entered for example if a copy signal of the partial discharge in the high voltage bus of the GIS 70 at play, with a pulse generator prior to the operation of the GIS 70 Teilentla detected dung sensor 9, the partial discharge signal with a characteristic curve of FIG. 5. This partial discharge signal from the sensing impedance element 51 is determined and is first passed to the spectrum analyzer 52 . The spectrum analyzer 52 analyzes the frequency spectrum of the partial discharge signal to determine the resonance frequency. The result of this determination is transmitted to the narrowband filter circuit 23 so that the signal pass band of the narrowband filter circuit is set in the vicinity of the resonance frequency.
The signals detected by the partial discharge sensor 9 during operation of the GIS 70 are detected by the impedance element 51 and transferred to the narrow-band filter circuit 23 in the manner mentioned above. Since the signal passband of the narrowband filter circuit 23 is in the vicinity of the resonance frequency, the signals with the frequencies in the vicinity of the resonance frequency are passed through the narrowband filter circuit 23 and transmitted to the partial discharge measuring circuit 53 . In addition, the signals are detected and amplified to be detected as partial discharge signals by the partial discharge measuring circuit 53 , and their pulse heights are analyzed at the same time and supplied to the partial discharge generation processing circuit 26 .
The partial discharge generation processing circuit 26 measures the distributions of the frequencies of the generation of the discharge and the phase characteristics of the discharge generated. The results processed by the processing circuit 26 are supplied to the display unit 28 , for example a CRT, and who is recorded at the same time. The processing circuit 26 also records the changes over time of the various characteristics and determines the degree of isolation irregularities by comparing the processed results with the recorded past statistical data and evaluation data for the abnormality, and transmits the evaluated data to the display unit 28 . The display unit 28 displays the various characteristics and indicates an irregularity when it is determined that it has occurred, and further displays an alarm in this case.
As described above, a progressive signal of the partial discharge generated in the GIS 70 has resonance frequencies corresponding to the length that changes the impedance of the conductors and the case, and has resonance frequencies corresponding to the measuring circuits, and hence the generation source of the detected discharge can be monitored of these resonance frequencies can be determined.
The description above concerns a GIS, but it applies correspondingly also other electrical equipment, then the frequency spectrum is one of a part Discharge sensor detected signal to measure the Partial discharge of the electrical equipment measured will and the resonance frequencies from the Fre frequency spectrum based on the electrical out armor and its measuring circuits. By spec the generation source of the detected signal from the values of this frequency spectrum, the Er Generation source of partial discharge in the operating state electrical equipment.
Fig. 6 is a block diagram showing an irregularity detection device for electrical equipment for explaining the embodiment of Fig. 10. FIGS. 7 (a), 7 (b) and 7 (c) are graphs of partial discharge signals detected by a partial discharge sensor of the device for detection of irregularities, where in the abscissae the frequencies (MHz) and the Ordi naten the signal strength represent (dBm).
The electrical equipment is, for example, a power generation plant. In Fig. 6, reference numeral 80 denotes a generator and 50 a transformer. The electricity generated by the generator 80 is supplied to the primary windings 82 of the transformer 50 via high voltage buses 81 a, 81 b and 81 c and is upgraded in the secondary windings 83 so that it can be directed to the transmission system. The high-voltage buses 81 a, 81 b and 81 c are operated at high voltages from 10 kV to 25 kV. Here, a partial discharge sensor 9 is arranged at a location of the high-voltage buses 81 a, 81 b and 81 c in order to detect anomalies in the high-voltage buses 81 a to 81 c, the generator 80 and the transformer 50 . Fig. 6 shows a construction in which the part discharge sensor 9 is arranged for example on the high-voltage bus 81 c alone.
The high-voltage buses 81 a, 81 b and 81 c are subjected to high voltages. Thus, when a View is caused deterioration in an insulator, a partial discharge is generated and the signal of the partial discharge propagates through the high voltage bus 81 c at high speed. The signal becomes a partial discharge signal with resonance frequencies that relate to the length of the high-voltage bus 81 c in a manner similar to that in exemplary embodiment 1. The characteristics of this signal, which is detected by the partial discharge sensor 9 , are shown in FIGS . 7 (a) to 7 (c). Fig. 7 (a) shows the frequency characteristic of a to the high voltage bus 81 partial discharge produced c signal, Fig. 7 (b) shows the frequency characteristic of a generated at the generator 80 partial discharge signal, and FIG. 7 (c) shows the frequency characteristic of a partial discharge signal, the on the transformer 50 he is witnessed. In Figs. 7 (a) to 7 (c) refers to the reference mark f a0, the resonance frequency of the high tension voltage busses 81 c, and the reference mark f b0 in Fig. 7 (b) denotes the resonant frequency of a stator winding of the generator 80, in which the partial discharge is generated. As shown in Figs. 7 (a) to 7 (c), the frequency characteristics are slightly different in accordance with the locations where the partial discharge is generated. Then, the generation source of the partial discharge can be specified in any case by processing the signal in the same manner as described in connection with FIG. 4.
That is, the frequency spectra of the signals detected by the partial discharge sensor 9 for measuring the partial discharge of the electrical equipment are measured by the spectrum analyzer 52 , and at least one resonance frequency is determined from the frequency spectra based on the electrical equipment and its measuring circuits, so that every frequency characteristic can be recorded beforehand. Thereafter, the partial discharge generation processing circuit 53 determines the partial discharge signal from the detected signals, which have frequency components near the resonance frequency and have passed through the narrow band filter circuit 23 , as for the signals detected during the operation of the electrical equipment. Thus, the partial discharge generated during the operation of the electrical equipment can be detected in the state of operation of the electrical equipment, and the location at which the partial discharge is generated can be specified from the characteristic quantity of the partial discharge.
The Fig. 8 (a) and 8 (b) are cross-sectional views showing the construction of a rotary electric machine, wherein the embodiments according to FIGS. 17 and 25 employed. Fig. 8 (a) is a vertical cross-sectional view and Fig. 8 (b) is a cross-sectional view showing the electric machine when cut along the section line Vb to Vb of Fig. 8 (a) with the exception of the stator frame the machine. Fig. 9 is a block diagram showing the device for detecting abnormalities for explaining the embodiments of FIGS . 17 and 25, wherein the rotating electric machine is partially cut away, also for displaying the position of a partial discharge sensor in the immediate vicinity the stator winding. Fig. 10 is a developed view showing the winding state of a stator winding inserted in a stator core. Fig. 11 is a Kennliniendar position showing a characteristic of a charge by the notify by sensor detected partial discharge signal, wherein the abscissa nate the frequencies (MHz) and the Ordi the signal strength (dBm) represent. Fig. 12 is a graph showing characteristics of partial discharge signals when the signals propagate through the stator windings, the abscissa being the distance to the partial discharge sensor (the number of slots) and the ordinate, the amplitudes of wideband signals (mV) and the signal strength display at resonance frequencies (mV).
9 be stands Referring to Fig. 8 (a), 8 (b) and Fig., The rotary electric machine comprised of a rotor and a stator comprising a stator frame 2, egg NEN stator core 3 or the laminated core, the stator windings 4 and so on. In Fig. 8 (a), arrow "A" denotes the direction of the axis of the rotating shaft. The stator core 3 is fixed to the stator frame 2 , and a predetermined number of slits 6 are formed in the inner circumferential surface of the stator core equally spaced in the circumferential direction, extending in the direction of the axis A. In each slot 6 , two stator windings 4 , an upper and a lower one, are received and fixed by a wedge 7 , as shown in FIG. 9. A discharge sensor 9 , which is arranged in a slot 6 for the stator windings 4 of the rotating electrical machine 1 for detecting the partial discharge in the slot 6 , is for example from a temperature detection element 8 a from a platinum resistor and lead wires 8 b of the temperature detection element 8 a and further, the discharge sensor 9 is enclosed by glass epoxy laminated sheets.
As shown in Fig. 10, the stator windings 4 are inserted into the slots 6 of the stator core 3 and connected from the line side end 60 to the neutral point end 61 of the stator windings 4 in a hexagonal shape. Twelve to twenty turns of the hexagonal connections form a phase. The numbers in the drawing indicate the numbers of the slots.
The partial discharge sensor 9 is inserted between two stator windings 4 , an upper coil and a lower coil, in a slot near the line side end 60 of the stator windings 4 . As shown in Fig. 9 shows ge, the lead wires 19 a from the partial discharge sensor 9 are wired from the end region of the stator core 3 along the inside of the stator frame 2 in order to lead a connection box 20 out of the stator frame 2 to the outside, and they are connected to a temperature measuring instrument 22 in the central control room.
A high-frequency current transformer is provided around the line wires 19 a at the output of the connection box 20 as a detector 10 a for measuring the partial discharge. The signal supplied by the detector 10 a goes through a narrowband filter circuit 23 , for example via a bandpass filter (BPF), to be transmitted to a peak hold circuit (PH) 30 . The signal is converted into a digital signal in an A / D converter (ie A / D converter) 31 and is transmitted to the comparison circuit (COM) 32 for comparing the signal strength. In addition, this device is designed to supply the signal to a partial discharge generation processing circuit 26 , a display unit 28 and an irregularity display device 29 . The narrow band filter 23 receives the output signals from the partial discharge sensor 9 and its pass frequency band is set so that it includes a resonance frequency, which is determined based on the length of the stator core 3 of the rotating electrical machine 1 . The peak hold circuit (PH) 30 , the A / D converter 31, and the signal strength comparison circuit 32 form a noise discrimination circuit 25 for determining the output signals of the narrowband filter circuit 23 as partial discharge signals, and the partial discharge generation processing circuit 26 performs its processing when the interference discrimination circuit 25 determines the generation of a partial discharge.
The following is the operation of the device described. It is used as a generator, for example described the rotating electrical machine.
While the generator is operating, a high voltage is generated in the stator windings 4 . When an irregularity occurs due to the insulation deterioration of the stator windings 4 and so on, a partial discharge in the stator windings 4 is generated, so that a high frequency current flows. The high-frequency current generated by the discharge also propagates to the partial discharge sensor 9 , which is electrostatically connected to the upper and lower gate winding 4 , and the high-frequency current flows into the lead wires 19 a of the partial discharge sensor 9 . The high frequency current is detected by the detector 10 a using a high frequency current transformer. The detected partial discharge signal is fed to the narrowband filter circuit 23 . The partial discharge is a high-speed phenomenon on the order of ns and only the high-frequency components of the partial discharge are given to the peak hold circuit 30 after the partial discharge signal has been filtered by the narrowband filter circuit 23 .
The partial discharge sensor 9 not only detects the partial discharge signals but also many radio interference noises that are generated in the generator during its operation and those that are generated outside the generator. In order to eliminate this radio interference noise for detecting the partial discharge generated in the wide range of the stator windings 4 with good accuracy, the through frequency band of the narrowband filter circuit 23 is selected so that it lies on the resonance frequency, which is based on the length of the stator core 3 was determined. This resonance frequency f 0 is determined, for example, in accordance with the following equation.
f 0 = nc / 2l√ε ( 1 ).
In this equation, "n" denotes a natural number, "c" the speed of light, "l" denotes the length of the stator windings 4 coated with a low resistance coating, and "ε" denotes the relative permeability of the main insulator of the stator windings 4 , which is usually 4 or 5. The length "l" of the stator windings 4 , which are coated with a low resistance coating, is longer than the length of the stator core, namely by more than 300 mm. Since the length of the stator core 3 is determined in accordance with the nominal sizes of a generator, the length "l" changes from device to device and thus the resonance frequency f 0 also changes from device to device.
The reason why a resonance frequency is used as a pass frequency band of the narrow band filter 23 will now be described. Referring to Fig. 10, in the case where a partial discharge is generated in the stator winding 4 in the slot 6 of the number 11 formed in close proximity to the line side end 60 of the stator windings 4 , the discharge signal in the conductors of the Stator windings 4 before. Assuming that the reference sign T, the side of the turbine, and reference numeral R indicates the side of the pathogen, and that the loading reference symbols 62 the coil end portion of the turbine side, and reference numeral 63 the coil end portion of the He motionless page designate, the propagation path of the partial discharge signal is as follows : The partial discharge signal emanating from the turbine side of slot No. 11 enters slot No. 37 via coil end area 62 of the turbine side and the signal propagates in slot 6 to pass coil end area 63 of the excitation side and then the partial discharge signal enters slot # 12 to propagate in the stator windings in slot 6 and continues in the coil end region 62 of the turbine side to slot 6 of # 38.
The partial discharge signal thus spreads in the conductors of the stator windings 4 and it is known that the partial discharge signal is damped in proportion to the propagation distance, since the signal is a high-frequency signal. This attenuation is noticeable in the case where the signal is a wideband signal. FIG. 12 shows the results of measuring the degree of attenuation of a generator with a stator core, the length of which is approximately 4 m. A broadband signal, designated B in FIG. 12, is set to 72% of the amplitude at the point which the sensor 9 is arranged at a distance of two slots from the sensor 9 and is further attenuated to 62% of the amplitude at the position at which the sensor is arranged at a distance of four slots from the sensor 9 .
But when a partial discharge signal progressing in the stator windings 4 was detected by the partial discharge sensor 9 and its frequency was analyzed, it was found that a frequency band of a partial discharge signal existed which passes through the slot 6 and is attenuated little. The results are shown in Fig. 11 and the progression characteristic of the signal with the frequency in the frequency band is denoted by the letter C in Fig. 12. FIG. 11 shows a partial discharge signal D which is generated in a slot 6 in which the partial discharge sensor 9 is arranged, and further a partial discharge signal E which is generated in the slot 6 in which the partial discharge sensor 9 is not installed. The partial discharge signal D, which is generated in the slot 6 in which the partial discharge sensor 9 is installed, has a large signal strength and drops to the signal strengths which can be observed in the frequency bands of f 0 , f 1 and f 2 . In contrast to the signal D, an increase in the strength of the partial discharge signal E generated in the slot 6 in which the partial discharge sensor 9 is not installed can be observed (the slot 6 is removed from the installed position of the partial discharge sensor 9 ) the frequency bands of f 0 , f 1 and f 2 . This mark f 0 denotes a resonance frequency which was determined in accordance with the length of the stator core, the mark f 1 denotes the first harmonic of the resonance frequency f 0 and the mark f 2 denotes the second harmonic of the resonance frequency f 0 .
Then, the signal progression characteristic C at the resonance frequency f 0 , as shown in FIG. 12, is obtained by researching the progression of the signal at the resonance frequency f 0 . This means that it is ensured that the partial discharge signal can propagate to a distance in the frequency band of the resonance frequency f 0 with almost no attenuation, although the partial discharge signal, which is a broadband signal, is attenuated in proportion to its progression. It was also ensured that the frequency characteristic with the resonance frequency is peculiar to the discharge phenomenon and that the radio interference from the outside shows different frequency characteristics. In addition, it is ensured that the signal strength of the partial discharge signal D, as shown in FIG. 11, which is generated in the slot 6 in which the discharge sensor 9 is installed, at the resonance frequency f 0 and the harmonic frequencies f 1 and f 2 is damped, however, the partial discharge signal D has a sufficient signal strength to be detected despite the damping, since the detection point is close to the point of generation of the signal.
As for the propagation properties of the partial discharge signals, partial discharge signals with broad frequency bands are attenuated in proportion to their propagation, but the partial discharge signal with a frequency of the resonance frequency f 0 propagates up to a distance with almost no attenuation. Since the pass frequency band of the narrowband filter circuit 23 is selected such that the resonance frequency f 0 is met, the partial discharge signal generated in the stator winding 4 in the slot 6 , in which the partial discharge sensor 9 is arranged, and that in the stator winding 4 in the slot 6 , which is far from the slot in which the partial discharge sensor 9 is installed, partial discharge signals generated are each detected as a strong signal and radio interference from outside can be removed by attenuation. Consequently, the partial discharge signals can be detected and further partial discharge signals generated in the wide areas of the stator windings 4 can be detected with a partial discharge sensor.
After filtering to remove radio interference from outside with a narrowband filter 23 and filtering not only the partial discharge signal that is generated in the slot 6 in which the partial discharge sensor 9 is arranged, but also the partial discharge signals that are in the wide ranges of the Schlit ze generated, the peak values of the partial discharge signals are detected by the peak hold circuit 30 and sent to the A / D converter 31 . The A / D converter 31 converts the analog output signals of the peak hold circuit 30 into digital signals in order to supply them to the signal strength comparison circuit 32 . The signal strength comparison circuit 32 compares the output signals of the A / D converter with a reference signal and only passes on the necessary signals, and furthermore the signal strength comparison circuit 20 reads the input signal levels in order to deliver them to the part discharge generation processing circuit 26 .
The partial discharge generation processing circuit 26 measures the distributions of the frequencies of the generation of the discharge and the phase characteristics of the generated discharge. The results processed by the processing circuit 26 are supplied to the display unit 28 and recorded at the same time. The processing circuit 26 also records the changes over time from these various characteristics and evaluates the degrees of isolation irregularities by comparing the processed results with the registered past statistical data and the evaluation data for the irregularities, and transmits the evaluated data to the display unit 28 The display unit 28 shows the various characteristic values. Further, the partial discharge generation processing circuit 26 transmits an irregularity signal to the irregularity display device 29 when it is determined that an irregularity has occurred, and the display device 29 indicates the occurrence of the irregularity and, in this case, gives an alarm.
The during the operation of a rotating electrical Partial discharge generated in the machine can be Condition of the operation of the rotating electrical Machine by measuring the narrowband signal with a Resonance frequency based on the length of the sta core of a generator can be detected. About that In addition, radio interference from outside can be eliminated and partial discharge signals, which are in wide ranges the stator windings are generated, detected and the Accuracy of irregularity detection consequently be improved.
It was stated above that the pass frequency band of the narrowband filter circuit 23 is selected such that it is the resonance frequency f 0 determined on the basis of the length of the stator core 3 of the generator. However, the pass frequency band of the narrow band filter circuit 23 is not necessarily limited to this.
Fig. 13 shows a characteristic curve in which the detected signal strength (dBm) of the frequencies (MHz) of the detected with the partial discharge sensor 9 partial discharge shown signals, at the same bandwidth (F 1) filter circuit of passage frequencies of the narrow band is shown 23rd As can be seen from the drawing, the pass frequency band of the narrow band filter circuit 23 is selected within an extent of ± 5% of the resonance frequency, which is determined on the basis of the length of the stator core 3 .
As has been described, a partial discharge signal has a characteristic in which the strength of the partial discharge signal changes at the resonance frequency f 0 , which was determined based on the length of the stator core 3 . Since a signal to be detected is a high-speed, low-strength pulse-like signal, the detected signal strength becomes even smaller and the sensitivity of detection becomes low when the frequency band of detection of the pulse-like signal is narrow. As a result, the sensitivity of the detection can be increased by increasing the bandwidth as shown in FIG . However, if the bandwidth is chosen too wide, radio interference signals are also detected in addition to the partial discharge signal. Fig. 13 shows the example in which the bandwidth is set to ± 5% of the resonance frequency. By setting the bandwidth F 1 to f 0 ± 5%, the detection sensitivity of the partial discharge in the slot 6 in which the partial discharge sensor 9 is arranged can be improved. The post-staging operations are identical to the processing operations described above in the embodiment.
. As shown in Figure 14, the same, we can be obtained effects by the pass frequency bandwidth F 2 of the filter circuit 23 f frequency to the resonant 0 - 10% is set, in which frequency the resonance f 0 based on the length of the stator core 3 is determined. Also, the same effects can be achieved if, as shown in Fig. 15, the pass frequency bandwidth F 3 of the filter circuit 23 is set to resonance frequency f 0 + 10%.
Here the ranges of increasing the bandwidth from the resonance frequency f 0 to f 0 ± 5%, - 10% and + 10% were determined, however the extent of the broadening is not limited to these values, but other dimensions can also be used in the range Proximity of the resonance frequency f 0 can be selected and radio interference signals are removed in order to enable measurement of the partial discharge signal by setting the extent. In addition, the bandwidth can be determined by measuring the effects of setting the extent at which the resonance frequency f 0 is selected as the middle value.
In Fig. 16 is a block diagram of an apparatus for recording irregularities using the method is shown for detecting irregularities for an electric apparatus according to one embodiment of the present invention. In this embodiment, the resonance frequency f 0 of the device and its measuring circuits is measured similarly to that described above, and the strength of a detected signal at a predetermined frequency greater than the measured resonance frequency f 0 is measured. Then each characteristic signal set of the detected signals is taken based on the strength of the two partial discharge signals, in this case the signal strength ratios.
In the exemplary embodiment, the generator shown in FIG. 6 is assumed to be an electrical device.
Reference numerals 23 a and 23 b denote narrowband filter circuits for receiving the detected by the Teilentla dung sensor 9 signal, reference numeral 33 denotes a delay circuit that receives through the narrow band filter circuit 23 a having passed signal and the received signal by a vorbe indefinitely delayed.
The frequency characteristics of a partial discharge signal generated on the high-voltage bus 81 c, a discharge signal generated on the generator 80 and a signal generated on the transformer 50 of the construction according to FIG. 6 were shown in FIGS . 7 (a) to 7 (c) and The marks f a0 in Fig. 7 (a), Fig. 7 (b) and Fig. 7 (c) denotes the resonance frequency of the high voltage bus 81 c, a mark f b0 in Fig. 7 (b) denotes the resonance frequency of the stator winding of the generator 80 in which a partial discharge was generated. No definitive resonance frequency can be found in the frequency characteristic of Fig. 7 (c). Thus, the frequencies are noticeably different from each other in accordance with where the partial discharge is generated. Since the first order resonance frequencies are different from each other, the second order resonance frequencies are of course different from each other. Thus, the generation source of the partial discharge can be specified based on the values of the resonance frequencies. In addition, the characteristics of each signal can be determined by measuring the strength ratios of the signals at resonance frequency f 0 and at a frequency f 1 different from the resonance frequency f 0 (the signal strength at frequency f 1 / signal strength at frequency f 0 ).
Referring to FIG. 16, the resonance frequency f 0 and another larger than the resonance frequency f 0, for example, the resonance frequency f 1 of the second order by measuring the detected by the partial discharge sensor 9 signal with the spectrum analyzer 52 determines. Then the resonance frequency of the first order f 0 is chosen as the pass frequency band of the narrow band filter circuit 23 a and the resonance frequency f 1 of the second order is chosen as the pass frequency band of the narrow band filter circuit 23 b. Each narrow band filter circuit 23 a, 23 b transmits signals with frequency components that each fit frequency band to Durchgangsfre. While the generator is in operation, the narrow-band filter circuit 23 a lets the signal with the resonance frequency first order f 0 and the narrow-band filter circuit 23 b passes the signal with the resonance frequency f 1 second order, and the signals are supplied to the signal strength comparison circuit 32 . The signal strength comparison circuit 32 compares the strength of the signals that have passed through the narrowband filters 23 a and 23 b in order to give the result of the comparison to the partial discharge measuring circuit 53 . The partial discharge measuring circuit 53 measures the Delay by the delay circuit 33 th output signal of the narrow band filter circuit 23a based on the result of the comparison and measures the characteristic quantities, such as the supply Erzeu make and size of the production. The operation of the partial discharge generation processing circuit 26 and the display unit 28 is the same as that described in connection with FIG. 4.
In this embodiment, the pass frequency bands of the two narrowband filter circuits 23 a and 23 b are each set to the resonance frequency of the first order f 0 and to the resonance frequency of the second order f 1 , but these pass frequency bands are not limited to these frequencies. That is, when the pass frequency bands are set to a frequency in the vicinity of the resonance frequency f 0 and a predetermined frequency larger than the frequency in the vicinity of the resonance frequency, the partial discharge signals accurately by measuring the generation sites and the characteristic amounts. how the amount of generation is detected based on the amounts of changes in the signal strength at the frequency near the resonance frequency f 0 and the signal strength at the frequency greater than the frequency near the resonance frequency f 0 .
As described above, in the case where several places exist where partial discharges are generated in electrical equipment, each Partial discharge the respective resonance frequency in over in tune with the electrical equipment and be measuring circuits and consequently it is possible to select the generate electrical discharge during operation partial discharge in the state of operation by Ver equal to the signal strengths of the resonance frequencies each Partial discharge with the signal strengths with a higher Frequency band than the resonance frequencies like the Re second order resonance frequencies. Dar moreover, this embodiment can be the part Specify discharge signal of each generation source ren.
In this embodiment, the case was at where several partial discharge signals are specified the described, but are to be recorded Signal sources do not rely on the partial discharge signals limits, but signal sources can be detected that have special frequency characteristics. For example, even if the signal sources are different types of noise, these by capturing their characteristic size in the distinguishable in the same way.
Fig. 17 shows a block diagram of a device for detecting irregularities according to another embodiment, and Fig. 18 are characteristics that show a partial discharge signal H and a radio interference signal G, which were measured during the operation of a heat turbine generator, the nominal capacity of 156000 kW and whose nominal voltage is 18 kV, with the abscissa representing the frequencies (MHz) and the ordinate representing the detected strength (dBm). In these figures, the same reference numerals as those of Figs. 8 (a) to 12 are chosen for the same parts.
According to FIG. 17, the construction of the generator 1, the structure of the partial discharge sensor 9 and its is in stallierte position and composition of the De tektors 10 a and the lead wires 19 a is the same as the 3rd of Embodiment The Ausgangssig nal of the detector 10 a divided into two parts and one part is the first narrow band filter circuit 23 a and the other part of the second narrow band filter circuit 23 b supplied. The narrowband filter circuit 23 a allows the same frequency component as the resonance frequency f 0 , which is determined on the basis of the length of the stator core 3 of the generator. One of the divided signals is given in the first narrowband filter circuit 23 a, and to the signal strength comparison circuit 32 via the A / D converter 31 supplies ge. The second narrowband filter 23 b allows a predetermined frequency component greater than the resonance frequency f 0 . The other of the divided signals is supplied to the second narrowband filter circuit 23 b and supplied to the peak hold circuit 30 and the A / D converter 31 and is further transmitted to the signal strength comparison circuit 32 . The output signal of the signal strength comparison circuit 32 is transmitted to the elimination circuit 34 .
The embodiment is constructed such that the output signal of the first narrowband filter circuit 23 a leads both the peak value holding circuit 30 and the elimination circuit 34 via a delay circuit 33 . A noise discrimination circuit 25 consists of the peak hold circuits 30 , the A / D converters 31 , the signal strength comparison circuit 32 , the delay circuit 33 and the elimination circuit 34 . The output signal of the elimination circuit 34 is supplied to the discharge generation processing circuit 26 , the display unit 28 and the display device 29 for irregularities, and the construction of these devices which process the output signal of the elimination circuit 34 is the same as that after Embodiment 3
The operation of this embodiment is described below. It has been found that there are particular differences between the frequency characteristics of the partial discharge signal H and a radio interference signal G, both of which were generated during the operation of the generator 1 , as a result of the detailed analysis of both signals measured by the partial discharge sensor 9 . Fig. 18 shows their respective frequency characteristics. In the figure, the upper characteristic at frequency f 0 denotes the frequency characteristic of the radio interference signal G from outside and the lower characteristic at frequency f 0 denotes the frequency characteristic of the partial discharge signal H. The partial discharge signal H has harmonic components up to close to 100 MHz and shows a gentle drop in signal strength proportional to higher frequencies. On the other hand, the radio interference signal G has a greater strength than the partial discharge signal H, but the radio interference signal G has fewer harmonic components and shows a steep drop in signal strength with the increase in frequency.
The partial discharge signal H according to FIG. 18 comprises the partial discharge signal D which is present at the slot on which the partial discharge sensor 9 is arranged and the partial discharge signal E which is in a slot on which the partial discharge sensor 9 is not installed (or that in a slot in a Distance from the partial discharge sensor 9 ) are generated, both signals D and E are shown in Fig. 11.
The differences between these frequency characteristics are caused by the difference in the generation phenomenon of the partial discharge signal H and the radio interference signal G and by the difference in the propagation properties of these signals H and G to the partial discharge sensor 9 . In Fig. 18, f 0 denotes the resonance frequency of the first order and f 1 the resonance frequency of the second order. From these differences between the frequency characteristics of the signals G and H, it is clear that particular differences between the signal strength at the resonance frequency f 0 , which is determined based on the length of the stator core, and the signal strength at a frequency in a prescribed frequency band are greater than the resonance frequency f 0 by comparing both signal strengths.
This embodiment detects partial discharge signals by using the characteristics described above. The resonance frequency f 0 is obtained based on the length of the stator core 3 in accordance with the equation 1, and the resonance frequency f 0 is selected as the pass frequency band of the first narrow band filter circuit 23 a. The detected by the Teilentla dung sensor 9 during operation of the generator signal is split into two parts, which is via the first narrow band filter circuit 23a directed at a part of f the resonant frequency 0 passes and the thickness of from the first narrow-band filter circuit 23 a output signal is detected by the peak hold circuit 30 . The signal strength determined by the peak value holding circuit 30 is converted from the analog signal into a digital signal by the A / D converter 31 and supplied to the signal strength comparison circuit 32 . On the other hand, the other divided signal is passed through the second narrow band filter circuit 23 b, which passes a pre-given frequency greater than the resonance frequency f 0 , for example the frequency f 1 , which is twice the frequency f 0 , and which Strength of the signal output by the second narrowband filter circuit 23 b is detected by the peak hold circuit 30 . The signal strength determined by the peak value holding circuit 30 is supplied to the signal strength comparison circuit 32 via the A / D converter. The signal strength comparison circuit 32 compares the strength of the two signals with the resonance frequency f 0 and the frequency f 1 , provided that the strength is greater than a predetermined threshold.
Based on the difference between the frequency characteristics of the partial discharge signal and the radio interference signal, it can be decided that the partial discharge signal is the signal which is the greater strength ratio of the signals in the two frequency bands {(the signal strength at frequency f 1 ) / (signal strength at the resonance frequency f 0 )}. And it can be decided that the radio interference signal is the signal with the steeper drop in signal strength proportional to the increase in frequency, that is, the signal with the smaller strength ratio of the signals in the two frequency bands.
Thus, the signal strength comparison circuit 32 distinguishes the partial discharge signal from the radio interference signal and transmits the result of the comparison to the elimination circuit 34 . In addition, the signal passed through the first narrowband filter circuit 23 a is divided in order to be delayed by a delay circuit 33 by a time which is necessary for the above-mentioned differentiation of the partial discharge signal from the radio interference signal and then the delayed signal is sent to the elimination circuit 34 The elimination circuit 34 switches its signal gate from the delay circuit 33 on and off on the basis of the discrimination results of the signal strength comparison circuit 32 in order to supply only the partial discharge signal to the partial discharge generation processing circuit 26 .
The structure and the operation of the partial discharge generation processing circuit 26 , the display unit 28 and the display device 29 for the irregularities are the same as described in connection with FIG. 9.
In this embodiment, the second narrow band filter 23 b is set such that a signal with a frequency f 1 , which is twice as large as the resonance frequency f 0 , is passed, but the pass frequency band of the second narrow band filter circuit 23 b is not on this frequency is limited, but may have a frequency band that passes a certain frequency greater than the resonance frequency f 0, and by adjusting the frequency band, the partial discharge signal from the radio interference signal can be distinguished based on the difference in the drop in signal strength proportional to the frequency.
Thus, by comparing the signal strength at the resonance frequency f 0 , which is determined on the basis of the length of the stator core of a rotating electrical machine, and the signal strength at a predetermined frequency, greater than the resonance frequency f 0 , a partial discharge signal is separated from radio noise, wherein the separated radio interference signal is eliminated using the frequency characteristics of the signals detected by a partial discharge sensor, and consequently the partial discharge generated during the operation of the rotating electrical machine can be detected in the operating state of the rotating electrical machine. Furthermore, by eliminating the radio interference signals, a partial discharge signal caused by a discharge in which only a small electric charge is discharged can also be measured.
Fig. 19 is a characteristic diagram showing the detection bands of the first narrow-band filter circuit 23 a and the second narrow-band filter circuit 23 b of the device for detecting irregularities of the insulation in rotating electrical machines, for example, a generator according to another exemplary embodiment of the present invention , where the abscissa denotes the frequencies (MHz) and the ordinate the detected strength (dBm). Fig. 19 shows the pass frequency bandwidths F 4 and F 5 of the narrow band filter circuits 23 a and 23 b. The structure of the other circuits of this embodiment are the same as that according to the previous embodiment.
The following is the operation of this embodiment Example described.
As described in connection with FIG. 9, the signals detected by the partial discharge sensor 9 have characteristic curves in which the signal strength at the resonance frequency f 0 , which is determined on the basis of the length of the stator core 3 of a generator, varies. This resonance frequency f 0 is characterized in that it is different for each generator, since the structure differs depending on the nominal capacities and the generation specifications of the generators and so on. In the previous exemplary embodiment, partial discharge signals are distinguished from radio interference signals on the basis of the ratios of the signal strength at resonance frequency f 1 of the second order to the signal strength at resonance frequency f 0 of the first order.
In the case where the bandwidths for detecting the Resonance frequencies are narrow, as in the previous off example, it becomes easy to fill the gap between the detected signals and the resonance fre generate sequences. When the gap is captured Band in a band where the signal strength is strong varies, the gap (distance) of the sig strength, then it becomes difficult to identify the characteristics of the Differentiation between the frequency characteristics of the Partial discharge signal and a radio interference signal deliver.
Then, the detection of the mean values of the through frequency bands of the narrow band filter circuits 23 makes the detection errors small and it becomes possible to reliably grasp the characteristics of the frequency characteristics of the signals. That is, it is necessary to choose the optimum detection frequencies f 0 and f 1 and the optimal detection bandwidths at the frequencies f 0 and f 1 .
As shown in Fig. 19, the Durchgangsfre frequency bandwidth F 4 of the first narrow band filter circuit 23 a is set to f 0 ± 10%, where f 0 denotes the resonance frequency of the first order, which is determined based on the length of the stator core 3 , and the pass frequency band F 5 of the second narrow band filter circuit 23 b is set to f 0 × 1.5 ± 10%, where f 0 denotes the first-order resonance frequency. Since the first order resonance frequency f 0 of this generator is 24 MHz, the through frequency band of the first narrowband filter 23 a is fixed at 24 MHz and its bandwidth F 4 is fixed at 24 MHz ± 10%. The pass frequency band of the second narrowband filter circuit 23 b is set to 35 MHz, which is approximately 1.5 times the resonance frequency f 0 of the first order and the bandwidth F 5 is set to 35 MHz ± 10%.
Fig. 20 illustrates the results of the discrimination of the partial discharge signals from Radiostörsignalen on the basis of the measured data of the partial discharge in the generator during its operation under USAGE dung this apparatus for detecting irregular shapes ßigkeiten. The abscissa of FIG. 20 indicates the ratios of the signal strength at Setting the pass frequency bands of the first and second narrowband filter circuit 23 a and 23 b of 24 MHz and 35 MHz, which is approximately 1.5 times the resonance frequency f 0 first order. The ordinate of FIG. 20 denotes the ratios of the signal strength by setting the pass frequency bands of the first and second narrowband filter circuits 23 a, 23 b to 24 MHz and 47 MHz, which is approximately twice as large as the first order resonance frequency f 0 . In FIG. 20, the markings 0 denote partial discharge signals and markings x radio interference signals.
Referring to Fig. 20, from the point of view of the ratios of the strength at 24 MHz and the strength at 35 MHz, the data can be clearly separated as follows: the data with strength ratios greater than 0.5 denote discharge signals and the data with smaller signal ratios denote radio interference signals . On the other hand, from the standpoint of the ratios of the strength at 24 MHz and the strength at 47 MHz, the data can be separated but not clearly separated as follows: the data with a strength ratio greater than 0.25 denotes partial discharge signals and the data with a smaller strength ratio denotes radio interference signals. The comparison between the data distributions from the point of view of the abscissa and the ordinate, in particular around the limit values for separating the data of the partial discharge signals and the data of the radio interference signals, makes it clear that the setting of the frequencies for obtaining the signal strength distributions of the abscissa at 24 MHz and 35 MHz provides better sensitivity.
After separating the partial discharge signals from the radio interference signals by the signal strength comparison circuit 32 , the separated results are supplied to the elimination circuit 34 . The structure and operation of the elimination circuit 34 , the delay circuit 33 , the partial discharge generation processing circuit 26 , the display unit 28 and the display device 29 for irregularities are the same as in the previous embodiment.
Thus, in this embodiment, the through frequency band of the first narrowband filter circuit 23 a is set to the resonance frequency f 0 ± 10% and the pass frequency of the second narrow band filter circuit 23 b is set to 1.5 times the resonance frequency f 0 ± 10%. From the values of the strength distributions of the two narrowband filter signals, partial discharge signals can be clearly separated from radio interference signals when a rotating electrical machine is operating.
Fig. 21 is a graph showing frequency characteristics of a partial discharge signal H and a Funkstörsignals G when partial discharge during loading drive the same turbine generator as measured in the previous embodiment. The frequency band F 6 of the first narrow-band filter circuit 23 a is set to a range from the first-order resonance frequency 24 MHz to 24-15% MHz, and the frequency band F 7 of the second narrow-band filter circuit 23 b is set to a range of 35 MHz, which is 1 , 5 times the resonance frequency f 0 corresponds to the first order, up to 35 - 15% MHz. That is, the bandwidths occupy frequency bands of 15% in the direction of the low frequencies from the resonance frequency f 0 and from the resonance frequency 1 , 5 × f 0 . In this case, as in the previous embodiment, the following effect is obtained: partial discharge signals can be clearly separated from radio interference signals based on the values of the ratios of the strength of the two narrowband signals. Otherwise, the structure is as described in connection with FIG. 17.
As shown in FIG. 22, in the case where the pass frequency bandwidth F 8 of the first narrow band filter circuit 23a takes 15% in the direction of higher frequencies from the first order resonance frequency f 0 , and the pass frequency bandwidth of the second narrow band filter circuit 23b becomes 15 % in the direction of the higher frequencies from the frequency 1 , 5 × f 0 is seen, which has the following effect: partial discharge signals can be clearly separated from radio interference signals on the basis of the values of the strength ratios of the two narrowband signals.
The description relates to bandwidths of the narrowband filter circuits 23 a and 23 b of ± 10% of f 0 and f 1 - 15% of f 0 and f 1 and 15% of f 0 and f 1 with respect to the exemplary embodiments 7 and 8, but the Bandwidths of the present invention are not limited to these values. The values can be selected in a frequency band that includes the resonance frequency f 0 and a predetermined frequency greater than the resonance frequency, provided that the values clearly reflect the characteristics of the characteristics.
Fig. 23 is a graph showing the results of measuring the partial discharge signals and radio noise during the operation of a heat turbine generator whose rated capacity is 600 MW and its rated voltage is 19 kV, using the irregularity detection apparatus according to another embodiment. In this device for detecting irregularities, the center frequency of the pass frequency band of the first th narrowband filter circuit 23 a is fixed to 13 MHz, which is the resonance frequency of the first order, and the bandwidth of the pass frequency band is 3 MHz. The center frequency of the Durchgangsfre frequency band of the second narrowband filter circuit 23 b is fixed at 24.5 MHz, which is the second-order resonance frequency, and the bandwidth 48776 00070 552 001000280000000200012000285914866500040 0002019507826 00004 48657 of the through frequency band is 3 MHz. The structure of the other components is the same as described in connection with FIG. 17.
The abscissa of Fig. 23 denotes the output signal strength (mV) of the first frequency band filter circuit 23 a and the ordinate of Fig. 23 denotes the output signal strength (mV) of the second narrow band filter circuit 23 b. The • markings denote radio interference signals and the 0 markings denote partial discharge signals. As is evident from the figure, the partial discharge signals 0 can never be separated from the radio interference signals of, for example, a straight line whose rise is 0.16. This means that the data is distinguished as follows; the data above the straight line are data of the partial discharge signals and the data below the straight line are data of the radio noise.
In cases of rotating electrical machines, for example generators, the dimensions of their stator cores 3 and their stator windings 4 differ depending on their nominal capacitances and thus by selecting the pass frequency bands of the first and second narrowband filter circuits 23 a, 23 b, the device for each generator for detecting irregularities can be obtained, which can clearly separate the partial discharge signals from radio interference signals, in order to detect irregularities in rotating electrical machines, which has any nominal capacity, without being limited to the frequency bands which are in connection with the exemplary embodiments according to FIGS. 19 and Fig. 21 are shown.
The frequency characteristics of the signals also differ somewhat in accordance with the generators to be measured. Thus, the threshold for discriminating signals is not limited to the decision using the ratios of the two signal strengths, the decision being shown in connection with the embodiment of Fig. 19, it is also possible to make decisions based on the values of the Signal strength to meet itself, as is shown in connection with the embodiment of FIG. 19 ge. In addition, the decision can also be made based on values obtained by calculating the differences between two signal strengths. In addition, the threshold values used in the decision can be decided from the signal characteristics measured with respect to each rotating electrical machine.
Fig. 24 is a block diagram showing an apparatus for detecting irregularities on a ULTRASONIC electrical device. In the figure, the same reference numerals as in FIG. 6 denote the same parts and the following description can be used to explain the exemplary embodiment according to FIG. 16.
In Fig. 24, the reference numeral denotes a generator and 50 a transformer. The electricity or electricity generated by the generator 80 is supplied to the primary windings 82 of the transformer 50 via the high voltage buses 81 a, 81 b and 81 c and is highly transformed to the secondary windings 83 to be supplied to the transmission system. The high-voltage buses 81 a, 81 b and 81 c who operated at high voltages from 10 kV to 25 kV. Here, the partial discharge sensors 9 are provided on each part of the high-voltage buses 81 a, 81 b and 81 c in order to detect irregularities in the high-voltage buses 81 a to 81 c of the generator 80 and the transformer 50 .
The partial discharge sensors 9 a, 9 b and 9 c are provided for each high-voltage bus 81 a, 81 b and 81 c and the sensors 9 a, 9 b, 9 c are grounded via the detection impedance elements 51 . The signals detected by the detection impedance elements 51 are supplied to the spectrum analyzer 52 and the narrowband filter circuits 23 . The signals passed through the narrow band filter circuits 23 are supplied to the partial discharge generating processing circuit 26 via the partial discharge measuring circuit 53 . The partial discharge generation processing circuit 26 in turn outputs the processed results to the display unit 28 . The partial discharge measuring circuit 53 consists of a signal strength comparison circuit 32 and an analysis circuit 54 for the pulse height.
The operation will be described with reference to Figs. 24, 7 (a), 7 (b) and 7 (c).
The high-voltage buses 81 a, 81 b and 81 c are subjected to high voltages. Thus, if deterioration is caused in an insulation, a partial discharge is generated and the signal of the partial discharge continues through the high-voltage buses 81 a, 81 b and 81 c at high speed. The signal becomes a partial discharge signal with resonance frequencies, which are determined on the basis of the lengths of the high-voltage buses 81 a, 81 b and 81 c and the measuring circuits. The frequency characteristic of the partial discharge signal generated on the high-voltage bus 81 a is shown in Fig. 7 (a).
If a partial discharge is generated on the high-voltage bus 81 c, a partial discharge signal associated with the partial discharge is detected by the partial discharge sensor 9 c and continues through the generator 80 or the windings and the housing in the interior of transformer 59 in order to reach the high-voltage buses 81 a and 81 b to be transmitted at the same time. Then the signal is also detected by the partial discharge sensors 9 a and 9 b. The extension sensors of the Teilentla 9 a and 9 But values b detected are less than the tektierte of the partial discharge sensor 9 c de value since the sen to the high voltage bus 81 a and 81 b continuing partial discharge signal is highly attenuated.
In the case where the on the high voltage bus 81 a generated partial discharge signal from the partial discharge sensors 9 a, 9 b and 9 c is detected, the value of the REN from the partial discharge sensor 9 a detected signal is greater and the values of the Teilentladungssenso 9 b and 9 c detected signals are smaller in the same way.
In the same way, in the case where the on the high voltage bus 81 b partial discharge signal generated by the partial discharge sensors 9 a, 9 b and 9 c is detected, the value of the of the Teilentladungssen sor 9 b detected signal is greater and the values of signals detected by the partial discharge sensors 9 a and 9 c are smaller.
In addition, in the case where the partial discharge signal generated on the generator 80 is detected by the partial discharge sensors 9 a, 9 b and 9 c, the partial discharge signal relating to the length of the windings and the generator 80 related resonance frequencies, the values The signals detected by the partial discharge sensors 9 a, 9 b and 9 c differ from one another and the differences depend on the location of the U phase, the V phase and the W phase of the windings of the generator 80 on which the part discharge was generated.
This means that in the case in which the partial discharge was generated on the U-phase winding, the partial discharge signals generated by the partial discharge are detected by the partial discharge sensor 9 a in a higher signal level and by the partial discharge sensors 9 b and 9 c with smaller ones Signal levels is detected. In the case where the partial discharge was generated at the V-phase winding, the partial discharge signal is detected by the partial discharge sensor 9 b with a larger signal level and by the partial discharge sensors 9 a and 9 c, each with smaller signal levels. In the case in which the partial discharge was generated at the W-phase winding, the partial discharge signal from the partial discharge sensor 9 c is detected with a larger signal level and from the partial discharge sensors 9 a and 9 b each with smaller signal levels. In the case where the partial discharge generated, for example, on the W-phase winding of the generator 80 is detected by the partial discharge sensor 9 c, the frequency characteristic of the detected signal is shown as in FIG. 7 (b).
Is generated in the case where the partial discharge in the genera tor 80, which signal is coupled to the windings of the generator 80 relating Resonanzfre sequences of the three partial discharge sensors 9 a, 9 b and 9 c measured by the difference of its characte ristic amount in accordance with its production site.
Is generated in the case where the partial discharge in the Trans formator 50, a signal is having a frequency characteristic corresponding to the propagation characteristic of the partial discharge signal in the transformer 50 by the partial discharge sensors 9 a, 9 b and 9 c detected as a signal differing has properties in accordance with the location at which the partial discharge was generated.
By detecting the resonance frequencies and the strength of the signals detected by the various partial discharge sensors 9 a, 9 b and 9 c, the partial discharge signals with different characteristic quantities can be separated from the high-voltage buses 81 a, 81 b and 81 c, the generator 80 and the transformer 50 to specify the generation source.
The signals detected by the partial discharge sensors 9 a, 9 b and 9 c are transmitted to the narrowband filter circuits 23 and the spectrum analyzer 52 via the detection impedance elements 51 . The spectrum analyzer 52 analyzes the frequencies of the signals detected by the partial discharge sensors 9 a, 9 b, 9 c and selects a resonance frequency of a signal from the partial discharge sensor which delivers the largest signal level in the vicinity of its resonant frequency in order to transmit the signal to the narrowband filter circuits 23 to deliver. The narrowband filter circuits 23 select their Durchgangsfre frequencies based on the signals from the spectrum analyzer, for example, all the pass frequency bands of the three narrowband filter circuits 23 are set to the same value.
Of the partial discharge signals, only the predetermined frequency band components that have passed through the narrowband filter circuits 23 are transmitted to the partial discharge measuring circuit 53 . In the partial discharge measuring circuit 53 , the signal strength comparison circuit 32 compares the strength of the transmitted signals and the pulse height analysis circuit 54 analyzes the pulse heights of the partial discharge pulses. The pulse signals whose heights have been analyzed are supplied to the partial discharge generation processing circuit 26 . The operation of the following partial discharge generation processing circuit 26 and the display unit 28 is the same as described in connection with FIG. 6.
As described above, in this embodiment example the frequency spectra of the von Number of signals detected by partial discharge sensors measure and the crossover frequencies of the narrowband filter circles are selected by selecting the Basis of electrical equipment and measurement circles determined resonance frequency from the frequency spectra determined the signal strength at the reso frequency of the signals of the various partial discharges comparison sensors. The can during of the operation of the electrical equipment Partial discharge can be recorded in the operating state. In addition, signals with different charak teristic quantities in the of the partial discharge signals detected by the sensors are included, ge be separated to partial discharge signals from each Er to specify generation source.
The Fig. 25, 26 (a), 26 (b), 27 (a), 27 (b) and 28 relate to an apparatus for detecting regularities irregu according to another embodiment. Fig. 25 is a block diagram showing the irregularity detection device according to this embodiment. Figs. 26 (a), 26 (b), 27 (a) and 27 (b) are explanatory diagrams to show the progressive characteristics of the To describe partial discharge signals and the radio interference signals, Fig. 28 is a graph showing the results of measuring the partial discharge signals and the radio interference signals with the irregularity detection device. The same reference numerals as those denoting in Fig. 8 (a) to FIG. 12, the same parts.
As shown in FIGS. 25, 26 (a) and 26 (b), the measuring circuit for the signals measured by the partial discharge sensors 9 (a), which is installed in the U-phase of the stator winding 4 , has a malfunction terscheidungskreis 25 a provided, in the same way, the measuring circuit for the sensor from the partial discharge sensor 9 b, which is arranged on the V-phase of the stator winding 4 , signals are provided with an interference discrimination circuit 25 b and the measuring circuit for that of the partial discharge sensor 9 c, which is arranged on the W phase of the stator winding, hen detected signals with an interference discrimination circuit 25 c.
The interference discrimination circuit 25 a consists of a peak hold circuit 30 , an A / D converter 31 , a signal strength comparison circuit 32 d, a delay circuit 33 and an elimination circuit 34 a. The interference distinction circuit 25 b consists of a peak value circuit 30 , an A / D converter 31 , a signal strength comparison circuit 32 e, a delay circuit 33 and an elimination circuit 34 b. In addition, the interference discrimination circuit 25 c consists of a peak holding circuit 30 , an A / D converter 31 , a signal strength comparison circuit 32 f, a delay circuit 33 and an elimination circuit 34 c.
This embodiment is constructed so that it transmits the phases of the voltages of the stator windings 4 to the partial discharge generation processing circuit 26 via a phase detector 36 for detecting the phases of the voltages applied to the stator windings 4 of a rotating electrical machine, namely the phases of the voltages Stator windings 4 of the generator generated voltages in the case of this embodiment.
The structure of the narrow band filter circuits 23 , the display unit 28 and the display device 29 for irregularities is the same as in FIG. 9.
According to FIGS. 4 to 23 were the Vorrich obligations for detecting partial discharge signals on the basis of the signals described, which have been detected by a partial discharge sensor. In contrast, in this embodiment, a plurality of partial discharge sensors are provided in the slots of each phase of the gate windings of a generator to separate partial discharge signals from radio noise by using the signals from two or three of the sensors. In addition, the structure of this embodiment makes it possible to specify the phases of the partial discharge generated.
Referring to FIGS. 25, 26 (a) and 26 (b) of the partial discharge sensor 9 is a U-phase installed in close proximity to the stator coil 4 and the detector 10 a detects the partial discharge signals the U- phase. The output signals of the detector 10 a are supplied to a narrow band filter 23 . The narrowband filter 23 only allows the frequency components in the vicinity of the resonance frequency f 0 , which is determined on the basis of the length of the stator core, and transmits them to the interference discrimination circuit 25 a, as described in connection with FIG. 9.
The interference discrimination circuit 25 a branches the input signals and the peak values of the signals who are detected by the peak hold circuit 30 to be given to the A / D converter 31 . The A / D converter 31 converts the input analog signals into digital signals and delivers them to the signal strength comparison circuits 32 d, 32 e and 32 f.
In the same way, the digital signals of the partial discharge signals of the V phase are supplied to the signal strength comparison circuits 32 d, 32 e and 32 f, and the digital signals of the partial discharge signals of the W phase are also given to the signal strength comparison circuits.
The signal strength comparison circuit 32 d compares the partial discharge signals of the U phase with the partial discharge signals of the other phases, that is to say it compares the partial discharge signals of the U phase with the partial discharge signals of the V phase and compares the partial discharge signals of the U phase with the partial discharge signals of the W phase. The signal amplifier comparison circuit 32 d separates partial discharge signals from radio interference signals and also specifies the phases of the generation of the partial discharge, and transmits the results to the eliminating circuit.
The method of separating the partial discharge signals from the radio interference signals and specifying the phases of generating the partial discharge will be described with reference to Figs. 26 (a), 26 (b), 27 (a) and 27 (b).
The Fig. 26 (a) and 26 (b) illustrate the propagation of the partial discharge signals paths in the Statorwicklun gen 4, when the partial discharge is generated in the stator winding 4 and signals the characteristics of the partial discharge, which of the partial discharge sensors 9a, 9b and 9 c are recorded. Is generated, for example, in the case where the partial discharge A at the U-phase stator coil 4 as shown in Fig. 6 (a) is shown, it holds that in the slot of the U phase installed partial discharge sensor 9 a the partial discharge signal with almost no Attenuation, which signal has a large peak "a" as shown in Fig. 26 (b). On the other hand, by the partial discharge sensors 9 b and 9 c to be detected signals of the V-phase and W-phase attenuated as it it be construed, having windings extending through the stator have spread 4, and they are then passed through the Partial discharge sensors 9 b and 9 c are detected as small signals, the peak values of which are identified by "b".
In the case where the partial discharge on the V phase or W phase is generated, recorded in the same way the partial discharge sensor of the phase in which the part is generated, a larger signal and the discharge Detect partial discharge sensors of the other phases smaller signals.
When the peak values of the signals are measured, the lengths of the signal lines affect the measurement values. However, in this embodiment the lines are set up to be the same length ge so that only the influences of the slurry routes influence the peak values.
The interference discrimination circuits 25 a, 25 b and 25 c are constructed in such a way that they evaluate the signals which two partial discharge sensors detect in a time difference of 200 ns as partial discharge signals from the same generation source, taking into account the progressive properties in the rotating electrical machine.
On the other hand, the radio interference signals are also detected by the partial discharge sensors 9 . Fig. 27 (a) is a partial cross-sectional view typically showing, for example, the generator 1 as a rotating electrical machine. The rotor 5 is provided with a brush 11 , which is geer det from an earth conductor 12 to derive the voltage on the shaft, wherein the voltage is generated on the rotor 5 . It is assumed that radio noise is generated on this part.
When the discharge A is generated on the brush 11 of the rotor 5 , the brushes 11 being the generation source of radio interference signals, the discharge signal flows through the earth conductor 12 and at the same time spreads through the rotor 5 and is electrostatically coupled to the stator windings 4 out. Then a high frequency current flows through the stator windings 4 . At the same time, the discharge signal is electrostatically coupled to the partial discharge sensors 9 a, 9 b and 9 c if the same and the partial discharge sensors 9 a, 9 b and 9 c detect radio interference signals. The partial discharge sensors 9 a, 9 b and 9 c detect the signals of the same size, the peak values of which are labeled "a", as shown in Fig. 27 (b).
The size of the detected signals does not relate to the positions of the windings of the U phase, the V phase and the W phase and the relationship between the stator windings 4 and the partial discharge sensors 9 a, 9 b and 9 c, but rather relates to the size on the propagation properties, which are formed by the electrostatic coupling between the rotor 5 and the stator windings 4 . The propagation properties relate to the frequency of the discharge signal and the floating electrostatic capacitance values, which are determined in accordance with the construction of the rotor 5 and the stator windings. The signals to be detected are high-frequency signals from 10 to 50 MHz and all constructions of the stator windings 4 , in which the rotor and the partial discharge sensors 9 a, 9 b and 9 c are installed, are the same and consequently detect the partial discharge sensors 9 a, 9 b and 9 c each the signals with the same size.
In Fig. 28, the so measured results are Darge provides. The abscissa denotes the strength of the partial discharge signals in the U phase and the ordinate denotes the strength of the partial discharge signals in the V phase. It is evident from the figure that the partial discharge generated in the U phase (& ⊲↙≽≻∵) concentrates on the ordinate and the partial discharge generated in the V phase (0) concentrates on the abscissa and further radio interference signals ( Δ) concentrate in positions between them. As a result, the partial discharge signals can be clearly separated from the radio interference signals. The partial discharge, through which a small amount of an electrical charge is discharged, can also be detected precisely by eliminating the radio interference signals. In addition, the locations at which the partial discharge signals were generated can be specified.
The partial discharge signals in the W phase cannot be differentiated from the radio interference signals from FIG. 28, but the partial discharge signals in the W phase can be strengthened in the same way by comparing the signal between the output signals of the partial discharge sensor 9 a in the U phase and Teilentla the dung sensor 9 c in the W-phase, or by comparison of the signal strength between the outputs of the partial discharge sensor 9 b in the V-phase and the partial discharge sensor 9 c in the W-phase are separated.
As described above, the narrow band filter 23 in the irregularity detection device according to this embodiment passes the frequency components near the resonance frequency f 0 , which is determined based on the length of the stator core 3, to be supplied to the noise discrimination circuit 25 to deliver. Then, the interference discrimination circuit 25 simultaneously detects the signals from the plurality of partial discharge sensors 9 a, 9 b and 9 c to the signals which have the difference in signal strength as partial discharge signals and the signals having the same signal strength as Radio interference to evaluate.
In addition, it becomes possible to specify that the phase at which the partial discharge sensor 9 , which has detected a larger signal among the detected multiple signals, is installed, is the phase of generating the partial discharge.
When performing the above-mentioned evaluation and specification, the characteristic amounts of the signals are easy to grasp, since only the signals having the frequencies in the vicinity of the resonance frequency f 0 , which is determined based on the length of the stator core, are passed.
The partial discharge generation processing circuit 26 records discharge waveforms and processes the input data in the distributions of the frequencies of the generation of the discharge and the phase characteristics of the generated discharge for each generation phase. The processed data are stored ge and transmitted to the display unit 28 . The processing circuit 26 also stores the changes over time of these various characteristics and evaluates the degree of the irregularities of the insulation by comparing the processed results with the stored past statistical data and evaluation data for the irregularities to transmit the evaluated data to the display unit 28 .
It is very effective information for detecting the irregularities in the insulation of a rotating electrical machine, which is made possible by measuring the generation situation of partial discharge signals for each phase of the stator windings 4 . In the case where there is an irregularity in the insulation in the rotating electrical machine, it is necessary to determine the operating condition after the occurrence in accordance with the places where the irregularities have occurred and the degree of deterioration , and the ability to measure the generation situation of the partial discharge for each phase brings with it the effect that it is possible to collect the information for the evaluation of the operating states and this during the operation of the rotating electrical machine.
Another embodiment relates to the reference value for separating the partial discharge signals from radio interference signals from the detected signals using the structure shown in FIG. 25. FIG. 29 is a characteristic curve showing the distribution of the frequencies of the detection (the number) depending on the ratios of the Output signal strengths between partial discharge sensors (the output signal strength of the U-phase sensor / the output signal strength of the V-phase sensor in this case) of the device for detecting irregularities for a rotating electrical machine, for example one shows. The structure of the device according to the invention is the same as that according to the exemplary embodiment according to FIG. 25.
The histogram of the relationship between the output signal strength of the U-phase sensor, the output signal strength of the V-phase sensor of the partial discharge signals, which are detected during the operation of the generator, and the frequencies of the detection is never drawn as a characteristic with three peaks corresponding to FIG. 29. The plotted signals are the signals that have each passed the narrowband filter circuits 23 and the characteristic curve is plotted by recording the ratios of the output signals from two narrowband filter circuits on the abscissa of the figure. The two peaks of the characteristic curve show partial discharge signals and one peak of the characteristic curve shows radio interference signals, that is, the peaks show V-phase discharge signals (I), radio interference signals (J) and U-phase discharge signals (K), each of smaller ratio values. In this case, W-phase discharge signals are included in the middle peak, but no problem arises even if they are treated as radio interference signals in this case. The value at the bottom of the sipe between the I-tip and the J-tip in Fig. 29 shows the threshold of the separation of the V-phase discharge signal and the radio interference signals and the value at the bottom of the sipe between the J-tip and the K-peak shows the threshold value of the separation of the U-phase discharge and the radio interference signals.
Thresholds can be the same in the cases the strength relationships between the output signals of the V-phase sensor and the W-phase sensor and the Strength relationships between the output signals of the W-phase sensor and the U-phase sensor determines who the.
Now the method of determining the threshold values for the separation of the signals will be described in detail. There is a case where the distributions of the histograms shown in FIG. 30 overlap and a case where the distributions of the histograms shown in FIG. 31 do not overlap. Fig. 30 shows the case where the values at the bases of the peak of the partial discharge signals (I) and the peak of the radio noise (J) overlap. In this case, the partial discharge signals are separated from the radio interference signals by using the value at the intersection of the envelopes of the histograms as the threshold.
In the case where the peaks of the partial discharge signals (K) and the radio interference signals (J) do not overlap as shown in Fig. 31, the partial discharge signals from the radio interference signals are obtained by using the value of the base and the base point, respectively the envelope of the partial discharge signals (K) separated as a threshold.
By obtaining these threshold values of the measurement object in advance and using these threshold values as threshold values of the signal strength comparison circuits 32 d, 32 e and 32 f, the partial discharge signals can be separated exactly from the radio interference signals and the radio interference signals can be eliminated by the eliminating circuits 34 a, 34 b and 34 c .
Thus, the output signal strengths of each partial discharge sensor 9 a, 9 b and 9 c of the stator windings 4 are compared, and the partial discharge generation processing circuit 26 specifies the frequency of the partial discharge generation, the strength of the partial discharge generated, the phase characteristic of the partial discharge generated and the point of generation Partial discharge by using the comparison values. The operation of the display unit 28 and the display device 29 for the irregularities is the same as in FIG. 25.
According to this embodiment, by Obtain the thresholds for separating parts charge signals of radio interference signals previously from His programs of a generator the threshold values for the Separation can be determined precisely, even if small Errors due to differences between sensations of every partial discharge sensor in every phase and by the differences between the measuring systems occur at any stage. Consequently, the partial discharge tion signals can be measured accurately.
Fig. 32 is an explanatory table showing the criteria for distinguishing the partial discharge signals from the radio interference signals in a device for detecting irregularities for a rotating electrical machine, such as a generator, according to another embodiment of the present invention. The structure of the device for detecting irregularities according to the thirteenth embodiment is the same as that shown in FIG. 25. FIG. 32 shows the criteria for distinguishing partial discharge signals from radio interference signals at the interference discrimination circuits 25 a, 25 b and 25 c.
In this embodiment, sensors with the same sensitivities were used as partial discharge sensors 9 a, 9 b and 9 c, and the length of the lead wires 19 a, 19 b and 19 c of the partial discharge sensors 9 a, 9 b and 9 c are the same. By measuring the output signals of each partial discharge sensor 9 a, 9 b and 9 c, which are provided in a generator with a nominal capacity of 156000 kW and a nominal voltage of 18 kV, and by performing statistical analyzes for the measured output signal strength of each partial discharge sensor 9 a , 9 b and 9 c by using histograms as shown in FIG. 29, threshold values were set in accordance with FIG. 32. In this embodiment, L 1 in the figure is set to 3 and L 2 in the figure to 1/3.
The criteria for evaluation in the case of a comparison between the output signal strength of the U-phase partial discharge sensor and the V-phase partial discharge sensor are as follows:
1. The signals detected only by the U-phase partial discharge sensor or the signals that match the next comparison expression are evaluated as partial discharge signals generated in the U-phase stator winding.
L 1 (= 3) <output signal strength of the U phase / output signal strength of the V phase
2. The signals detected only by the V-phase partial discharge sensor or the signals that match the next comparison expression are evaluated as partial discharge signals generated in the V-phase stator winding.
Output signal strength of the U phase / Output signal strength of the V phase <L 2 (= 1/3)
3. The signals that match the next comparison printout are evaluated as radio interference signals.
L 1 (= 3) <output signal strength of the U-phase / output signal strength of the V-phase <L 2 (= 1/3).
In the same way, in the case where the output signal strength of the V-phase partial discharge sensor and the W-phase partial discharge sensor and the output signal strength of the W-partial phase discharge sensor and the U-phase partial discharge sensor are respectively compared, and furthermore the threshold values of the signal strength comparison circuits 32 d, 32 e and 32 f determined by using the values of the results of the comparisons, partial discharge signals can be easily separated from radio interference signals and it becomes possible to eliminate the radio interference signals with the eliminator circuits 34 a, 34 b and 34 c.
After the elimination of the radio interference signals, the partial discharge generation processing circuit 26 specifies the frequency of the generation of the partial discharge, the strength of the generated partial discharge, the phase characteristic of the generated partial discharge and the generated position of the partial discharge. The operation of the display unit 28 and the display device 29 is the same as described in connection with the embodiment of FIG. 25.
In this embodiment, the threshold values L 1 and L 2 are set to 3 to 1/3, but the threshold values L 1 and L 2 are not limited to these values. Other values can be selected, such as the threshold values that were obtained from the histograms in connection with previous exemplary embodiments.
These threshold values L 1 and L 2 are fixed to the ratios of the signal strengths of the narrowband output signals, but the threshold values L 1 and L 2 need not be limited to them. For example, they can be determined as the difference between the signal strengths of the narrowband output signals.
Fig. 33 is a block diagram showing an irregularity detecting device for a rotating electrical machine according to another embodiment. Referring to the figure, the signal 10 d detected by the detector 10 a is divided and entered into the first narrow band filter circuit 23 a and the second narrow band filter circuit 23 , each signal to the signal strength comparison circuit 32 a via the peak value holding circuit 30 and the A / D Converter 31 is transmitted and the results of the comparison of the signal strength comparison circuit 32 a is supplied to the eliminating circuit 34 a. The output signal of the first narrowband filter circuit 23 a is divided in order to be entered into the above-mentioned peak holding circuit 30 and the delay circuit 33 and to be transmitted to the elimination circuit 34 a. What does this by the detector 10 Detek formatted signal b 10 e and also the detected signal c from the Detek tor 10 10 f are concerned, the exporting is approximately example constructed so that these signals are processed in the same way.
The device for detecting irregularities is thus provided with circles in each winding of the U phase, the V phase and the W phase, which have the strength of the same frequency components as the resonance frequency f 0 , which is determined by the length of the stator core is compared with the strength of a predetermined frequency component greater than the resonance frequency f 0 by using the frequency characteristics of the signals output by a partial discharge sensor.
In addition, the strength of the signal 10, as in the embodiment of FIG. 25 d, which has the first narrow band filter circuit 23 a, the peak hold circuit 30 and the A / D converter 31 passes, and the Staer ke of the signals 10 e, and f 10, which correspond to the circles, through which the signal 10 d has passed, pass through the signal strength comparison circuit 32 b, to be delivered to the eliminators 34 a, 34 b and 34 c.
This embodiment is constructed so that it the narrowband output signals from the plurality of Partial discharge sensors in the U-phase stator winding, the V-phase stator winding and the W-phase stator winding are arranged at the same time detected and the narrowband output signals as by Partial discharge caused signals evaluated in the case in which they are different in signal strength, and continue to output the narrowband signals as through Signals caused by radio interference are evaluated in the case in which they have the same signal strength.
The signals output by the eliminating circuits 34 a, 34 b and 34 c are transmitted to the partial discharge generation processing circuit 26 , the display unit 28 and the device 29 for displaying irregularities.
In the following the operation of the execution example is described. As described for the embodiment of Fig. 17, the frequency is characteristic of the partial discharge signals and the radio interference signals generated during operation of a rotate de electric machine and charge sensor of the notify by 9 are detected each other at differently, due to the differences of the generation phenomenon between the partial discharge and the radio noise and due to the differences in the propagation properties of these signals to the partial discharge sensor 9 . Then, in this exporting approximately example he given by the partial discharge sensor 9 a framed signals through the narrow band filter circuit 23 a, the f the same frequency component as the resonance frequency of 0 to pass through, which is determined by the length of the stator core, and through the narrow band filter circuit 23 b, the a predetermined frequency component greater than the resonance frequency f 0 , for example a frequency component that is twice the resonance frequency f 0 , and then who the signals based on the strength ratios of the first narrow band filter 23 a and the second narrow band filter 23rd b output signals evaluated as follows: the signals that have greater signal strength ratios are caused by a partial discharge and the signals that have small signal ratios are affected by radio interference. This process is carried out in parallel with each of the U-phase, V-phase, and W-phase measuring systems.
At the same time, the signals 10 d detected by the U-phase partial discharge sensor 9 a, the signals detected by the V-phase partial discharge sensor 9 b and the signals 10 f detected by the W-phase partial discharge sensor 9 c through the first narrowband filter circuits 23 a, the peak hold circuits 30 and the A / D converters 31 are given to be compared with each other by the signal strength comparison circuit 32 b. The signal strength comparison circuit 32 b evaluates the signals which have the signal strengths different from others as signals caused by partial discharge and evaluates the signals which have the same strength as those of the other signals as radio interference signals. The results of the evaluation by the signal strength comparison circles 32 b are delivered to the eliminator circles 34 a, 34 b and 34 c.
On the other hand, the delayed by the first narrowband filter circuits 23 a through given signals from the delay circuits 33 to a period of time 23 is ses for evaluating the Signalstärkevergleichskrei b necessary, and then to the Elimi nierkreise 34 a, 34 b and transferred c 34th The delayed signals are separated by the elimination circuits 34 a, 34 b and 34 c in accordance with the results of the evaluation, and only the partial discharge signals are supplied to the partial discharge signal generation processing circuit 26 . The structure and the operation of the partial discharge generation processing circuit 26 , the display unit 28 and the display device 29 for irregularities are the same as described in connection with FIG. 9.
Thus, the device for detecting dirt is separated gelemalien of the exemplary embodiment tion signals from radio interference signals from the detected Signals based on the difference in the characteristics nien and disconnects the partial discharge at the same time Radio interference signals based on the Differences between the signal strengths of the output signals from the plurality of partial discharge sensors. The This means that this device separates the partial discharge signals from the radio interference signals from the same Signals through the simultaneous use of the two Method.
An effect can be obtained that it is possible Lich, the signals that are near the threshold worth the separation, to separate and the impossible definitely in accordance with a procedure are to be separated.
This means that, as described in connection with FIG. 30, the threshold value of the separation is determined as an intersection in a separation method in which the envelopes of the distributions of the histograms overlap. In this case, it is possible that the data lying in the range from the intersection to the base value, namely the data smaller than the value at the intersection in the frequencies of the detection, are separated incorrectly. But it is ensured that even if the envelopes of the distributions of the histograms overlap in the case where the histograms are determined in accordance with the strength distributions of the signals detected by a partial discharge sensor and in two different frequency bands, as in the cases of the embodiments of Fig. 16 to Fig. 23 are the histograms do not overlap the envelope curves of the distributions in the case where the same signals are detected by a plurality of partial discharge sensors, as in the cases of FIGS. 24 and Fig. 25 .
It was also ensured that it was correct to detect the signals with the device of the exemplary embodiment according to FIGS. 16 to 23 and to record their frequency characteristics in order to ensure whether the signals detected by only one partial discharge sensor among a large number of partial discharge sensors reliably detected the partial discharge signals in the measurement of the device for detecting the irregularities in FIGS. 24 and 25.
As described above, the last accomplishment example with the effect that it is possible is, the signals near the threshold of the Separation to separate clearly, which is definitely impossible in Must be separated according to a procedure.
1. A device for detecting malfunctions or damage to a rotating electrical machine, which comprises a stator provided with grooves having a predetermined length, the grooves receiving the stator winding, with at least one discharge sensor arranged in a groove for the stator winding of the machine and detects a partial discharge and which is connected to an evaluation device for detecting the partial discharge, which has a display device for displaying malfunctions or damage, characterized in that the evaluation device has a first band pass filter circuit ( 23 a) with a pass-through area which corresponds to a resonance frequency determined by the length of the stator core is adapted and comprises a second bandpass filter circuit ( 23 b) with a pass band for a frequency higher than the resonance frequency and a partial discharge processing circuit ( 26 ) which takes into account the signal strength of the output signals of the bandpass filter circuit se ( 23 a, b) determines whether faults or damage have occurred.
2.Device for detecting malfunctions or damage to an electrical device with at least one high-voltage line with at least one discharge sensor which is arranged on the high-voltage line and detects a partial discharge and which is connected to an evaluation device for detecting the partial discharge, which is a Display device for displaying malfunctions or damage, characterized in that the evaluation device has a first bandpass filter circuit ( 23 a) with a pass band which is adapted to a resonance frequency dependent on the length of the high-voltage line and a second bandpass filter circuit ( 23 b) with a pass band higher than the resonance frequency and a partial discharge processing circuit ( 26 ) which, taking into account the signal strength of the output signals from the bandpass filter circuits ( 23 a, b), determines whether interference or damage has occurred.
3. A device for detecting malfunctions or damage to a rotating electrical machine, which comprises a stator provided with grooves having a predetermined length, the grooves receiving the stator winding, with at least one discharge sensor arranged in a groove for the stator winding of the machine and a partial discharge is detected and which is connected to an evaluation device for detecting the partial discharge, which has a display device for displaying faults or damage, since characterized in that a plurality of discharge sensors ( 9 a, 9 b, 9 c) are provided , which are arranged in slots for each phase of the stator windings of the rotating electrical machine, that the evaluation device has a plurality of bandpass filter circuits with a pass band that is adapted to a resonance frequency determined by the length of the stator core, that each discharge sensor has a bandpass filter circuit ( 23 ) and the Au s gears of the bandpass filter circuits are each connected to a noise discrimination circuit ( 25 a, 25 b, 25 c), the noise discrimination circuits being connected to one another and depending on the differences in the signal strength of the output signals of the band filter circuits ( 23 ), a part of the discharge signal distinguishes from noise and that the evaluation device further comprises a partial discharge processing circuit which, taking into account the signal strength of the output signals of the bandpass filter circuits ( 23 ), determines whether interference has occurred, the noise discrimination circuit ( 25 a, 25 b, 25 c) each having an elimination circuit ( 34 a, 34 b, 34 c) which, depending on the decision of the respective signal strength comparison circuit ( 32 d, 32 e, 32 f), passes the output signal of the respective bandpass filter circuit ( 23 ) to the partial discharge processing circuit ( 26 ) or not.
4. The device according to claim 1, characterized in that the evaluation device comprises a noise discrimination circuit ( 25 ) which is connected to the first and the second bandpass filter circuit ( 23 a, 23 b) and, depending on their output signals, differentiates the partial discharge signal from the noise and forwards the partial discharge signal to the partial discharge processing circuit ( 26 ).
5. The device according to claim 4, characterized in that the noise discrimination circuit ( 25 ) has a signal strength comparison circuit ( 32 ), depending on the strength of the output signals of the bandpass filter circuits ( 23 a, 23 b) ent decides whether noise or the partial discharge signal is present.
6. The device according to claim 5, characterized in that the first bandpass filter circuit ( 23 a) via a delay circuit ( 33 ) is connected to an eliminating circuit ( 34 ), the output signal of the first depending on the decision of the signal strength comparison circuit ( 32 ) th pass bandpass filter circuit ( 23 a) to the partial discharge processing circuit ( 26 ) or not.
7. Device according to one of claims 4 to 6, characterized in that the noise discrimination circuit ( 25 ) has a first and a second peak hold circuit ( 30 ), each of which is connected to the first and second bandpass filter circuits.
8. Device according to one of claims 4 to 7, characterized in that a plurality of discharge sensors ( 9 a, 9 b, 9 c) are provided, which are arranged in slots for each phase of the stator windings, that each discharge sensor has a first and a second band-pass filter circuit (23 a, 23 b) and a noise discrimination circuit (25 d) is associated with each noise ticket-making circuit (25 d) depends on the Ausgangssigna len of the associated band-pass filter circuits (23 a, 23 b) and of the output signals of the first band-pass filter circuits ( 23 a) each phase distinguishes the partial discharge signal from the noise.
9. The device according to claim 8, characterized in that each noise discrimination circuit ( 25 d) has a further signal strength comparison circuit ( 32 b) which receives signals from the first band pass filter circuits ( 23 a) of each phase and with which in each noise discrimination circuit ( 25 d) provided assigned elimination circuit ( 34 a, 34 b, 34 c) is connected.
10. The device according to claim 3, characterized in that each noise discrimination circuit ( 25 a, 25 b, 25 c) has a signal strength comparison circuit ( 32 d, 32 e, 32 f) which decides depending on the output signals of all bandpass filter circuits ( 23 ) whether there is noise or a partial discharge signal.
11. The device according to one of claims 3, 8 to 10, characterized in that a phase detector ( 36 ) is provided which detects the phase of the voltages of the stator windings and supplies the detection result to the partial discharge processing circuit ( 26 ).
12. The apparatus according to claim 2, characterized in that the evaluation device a signal strength comparison circuit ( 32 ) which is connected to the first and second bandpass filter circuit ( 23 a, 23 b) and the strengths of the signals given by the first and second bandpass filter circuit compares, and has a partial discharge measuring circuit ( 53 ) which is connected to the signal strength comparison circuit ( 32 ) and which measures the output signal of the first bandpass filter circuit ( 23 a) relative to the output signal of the second bandpass filter circuit ( 23 b).
DE1995107826 1994-02-25 1995-02-21 Device for detecting malfunctions or damage to an electrical device or a rotating electrical machine Expired - Fee Related DE19507826C2 (en)
JP2774194A JP3187642B2 (en) 1994-02-25 1994-02-25 Electrical device abnormality detection method and rotating electrical machine abnormality detection device
DE19507826A1 DE19507826A1 (en) 1995-08-31
DE19507826C2 true DE19507826C2 (en) 2003-07-17
ID=12229462
DE1995107826 Expired - Fee Related DE19507826C2 (en) 1994-02-25 1995-02-21 Device for detecting malfunctions or damage to an electrical device or a rotating electrical machine
US (3) US5680059A (en)
JP (1) JP3187642B2 (en)
CA (1) CA2139068C (en)
DE (1) DE19507826C2 (en)
GB (1) GB2286934B (en)
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