Patent Description:
A conventional fault-point-locating device monitors the pressure in each tank equivalent to a gas section, and detects an increase in the pressure caused by a ground fault or a short circuit, so as to locate a fault point where the ground fault or the short circuit has occurred. In a breaker tank in which a breaker is accommodated, the pressure in the tank can also be increased due to an arc generated during current interruption other than the ground fault or the short circuit. The fault-point-locating device is thus required to be capable of distinguishing a short circuit in the breaker tank from current interruption by a breaker.

Patent Literature <NUM> discloses a fault-point-locating device provided with current transformers between a breaker tank and each of the tanks adjacent to the breaker tank, so as to monitor a ground fault in the breaker tank on the basis of the polarity of a current flowing through each of the current transformers. According to Patent Literature <NUM>, in order to monitor a ground fault in the breaker tank forming a three-phase simultaneous gas-insulated switchgear, the current transformers are provided respectively between the breaker tank and a busbar tank, between the breaker tank and a cable head tank, and between the breaker tank and an earth.

Patent Literature <NUM> relates to a failure point locating device.

Patent Literature <NUM>, according to its abstract, states that, to enable location of a fault point by a method wherein a plurality of terminals are provided in an electromagnetic direction of a ground fault current path and current between terminals is checked to detect a ground fault current easily with handy construction, a transmission wire is arranged near center axes of gas insulated switch (GIS) tanks made up of a conductor of a low impedance and filled with SF6 gas. Then, terminals are connected to a nut connected to flanges and ground fault current sensors are provided between the respective terminals. In such a condition, when a ground fault occurs at a point P, a ground fault current flows through the tanks in a direction of earth centered on the point P, thereby enabling detection thereof with the sensors. When phases of the sensors are compared, any ground fault point P can be located when existing within a detection section of a ground fault current sensor with normal and opposite phases adjacent to each other.

Patent Literature <NUM>, according to its abstract, states that, to get the information of an accident early by accurately judging an accident block, using the magnitude of a zero-phase current for detection of an accident, a gas-insulated switchgear, where a container for accommodating each element is divided into a plurality of gas blocks, are provided with a current detector, which detects the currents of three-phase buses built in insulating spacers for dividing each gas block, a current change detector, which seeks the temporal change from the output of the zero phase current detector, and an accident block judging part, which judges the gas block of accident occurrence by comparing the magnitude of the zero-phase current with the specified judgment level.

In a case where a three-phase separating gas-insulated switchgear monitors a ground fault in a breaker tank for each phase, when the technique disclosed in Patent Literature <NUM> described above is applied to the three-phase separating gas-insulated switchgear, the number of current transformers required for this gas-insulated switchgear is three times larger than that required for a three-phase simultaneous gas-insulated switchgear. Thus, many current transformers are needed for locating a fault point in the breaker tanks. According to the technique disclosed in Patent Literature <NUM> described above, there is a problem that the gas-insulated switchgear needs to be provided with many constituent elements to locate a fault point.

The present invention has been achieved to solve the above problems, and an object of the present invention is to provide a fault-point-locating device that makes it possible to reduce the number of constituent elements to be provided in a gas-insulated switchgear to locate a fault point in a tank in which a breaker is accommodated.

According to the present disclosure, fault-point-locating devices as defined in the independent claims are provided. Further embodiments of the invention are defined in the dependent claims. Although the invention is only defined by the claims, the below embodiments, examples, and aspects are present for aiding in understanding the background and advantages of the invention.

The fault-point-locating device according to the present invention has an effect where it is possible to reduce the number of constituent elements to be provided in a gas-insulated switchgear to locate a fault point in a tank in which a breaker is accommodated.

A fault-point-locating device according to embodiments of the present invention will be described in detail below with reference to the drawings.

<FIG> is a block diagram illustrating a configuration of a fault-point-locating device according to a first embodiment of the present invention. <FIG> is a diagram illustrating a schematic configuration of a gas-insulated switchgear that is a target for locating a fault point by the fault-point-locating device illustrated in <FIG>. A gas-insulated switchgear <NUM> illustrated in <FIG> is installed in power facilities such as a power plant or a substation.

In the gas-insulated switchgear <NUM>, a voltage is applied to a busbar for three phases including a U-phase, a V-phase, and a W-phase. Wires for the three phases branch off from the busbar toward a target to/from which power is transmitted/received. Breakers are connected to branch wires that are the wires that branch off from the busbar. The busbar, the branch wires, and the breakers are accommodated respectively in tanks filled with insulating gas. The gas-insulated switchgear <NUM> is a so-called "three-phase separating gas-insulated switchgear" in which the branch wires for three phases are individually accommodated in separate tanks. In the three-phase separating gas-insulated switchgear, a ground fault may occur, while a phase-to-phase short circuit does not occur.

The gas-insulated switchgear <NUM> includes a breaker tank 12a that is a first tank, a breaker tank 12b that is a second tank, and a breaker tank 12c that is a third tank. A breaker for a U-phase that is a first phase is accommodated in the breaker tank 12a. A breaker for a V-phase that is a second phase is accommodated in the breaker tank 12b. A breaker for a W-phase that is a third phase is accommodated in the breaker tank 12c. The busbar is accommodated in a busbar tank <NUM>. Tanks other than the busbar tank <NUM> and the breaker tanks 12a, 12b, and 12c are connection tanks <NUM>. A branch wire or a device connected to the branch wire is accommodated in each of the connection tanks <NUM>.

The busbar tank <NUM>, the breaker tanks 12a, 12b, and 12c, and the connection tanks <NUM> illustrated in <FIG> form a single unit. A plurality of units are provided in the gas-insulated switchgear <NUM>.

The breaker tank 12a is installed on a stand 14a. The breaker tank 12b is installed on a stand 14b. The breaker tank 12c is installed on a stand 14c. The busbar tank <NUM> and the connection tanks <NUM> are installed on their respective stands similarly to the breaker tanks 12a, 12b, and 12c. <FIG> omits illustrations of the stand on which the busbar tank <NUM> is installed, and the stands on which the connection tanks <NUM> are installed.

The stands 14a, 14b, and 14c are installed on a metal base <NUM>. The stand 14a supports the breaker tank 12a on the metal base <NUM>. The stand 14b supports the breaker tank 12b on the metal base <NUM>. The stand 14c supports the breaker tank 12c on the metal base <NUM>. The metal base <NUM> is provided in each unit.

A grounding electrode <NUM> is connected to the metal base <NUM>. The breaker tanks 12a, 12b, and 12c are connected to the grounding electrode <NUM> through the stands 14a, 14b, and 14c, respectively, and through the metal base <NUM>. The grounding electrode <NUM> connects the metal base <NUM> to a grounding mesh <NUM>. The grounding mesh <NUM> is provided underground in the power facilities. The grounding mesh <NUM> is made of copper wires laid into a net. The spacing between the copper wires is approximately <NUM> meter to <NUM> meters. Each of the copper wires has a cross-sectional area of approximately <NUM><NUM>.

The busbar tank <NUM>, the breaker tanks 12a, 12b, and 12c, and the connection tanks <NUM> are provided respectively with pressure sensors <NUM>. Each of the pressure sensors <NUM> detects the pressure in the tank. The pressure sensor <NUM> provided on the breaker tank 12a is referred to as "pressure sensor 15a". The pressure sensor <NUM> provided on the breaker tank 12b is referred to as "pressure sensor 15b". The pressure sensor <NUM> provided on the breaker tank 12c is referred to as "pressure sensor 15c".

Current transformers (CTs) 16a, 16b, and 16c detect a current. The CT 16a is attached to one of the columns that form the stand 14a. The CT 16b is attached to one of the columns that form the stand 14b. The CT 16c is attached to one of the columns that form the stand 14c. The CT 16a, 16b, or 16c is a so-called "through-type current transformer".

A fault-point-locating device <NUM> illustrated in <FIG> locates a fault point in the gas-insulated switchgear <NUM>. The fault-point-locating device <NUM> is installed along with the gas-insulated switchgear <NUM> in the power facilities. Each of the pressure sensors <NUM> provided in the gas-insulated switchgear <NUM> is connected to the fault-point-locating device <NUM> through a signal line. Each of the pressure sensors <NUM> outputs a pressure signal indicating the result of pressure detection to the fault-point-locating device <NUM>. Each of the CTs 16a, 16b, and 16c provided in the gas-insulated switchgear <NUM> is connected to the fault-point-locating device <NUM> through a signal line. Each of the CTs 16a, 16b, and 16c outputs a current signal indicating the result of current detection to the fault-point-locating device <NUM>.

The fault-point-locating device <NUM> includes a computation unit <NUM> to perform various types of computational processing, a pressure-signal input unit <NUM> to which a pressure signal is input from each of the pressure sensors <NUM>, a current-signal input unit <NUM> to which a current signal is input from each of the CTs 16a, 16b, and 16c, and a display unit <NUM> to display information. The computation unit <NUM> includes a determination unit <NUM> to determine whether a pressure increase has occurred in each of the tanks, a measurement unit <NUM> to measure a current waveform, and a location processing unit <NUM> to perform a process of locating a fault point. The determination unit <NUM> processes a pressure signal to determine whether a pressure increase has occurred. The measurement unit <NUM> processes a current signal to measure a current waveform. The display unit <NUM> displays the result of location of the fault point by the location processing unit <NUM>.

Location of a fault point by the fault-point-locating device <NUM> is described here. The determination unit <NUM> monitors whether a pressure increase has occurred in the busbar tank <NUM> and the connection tanks <NUM> on the basis of pressure signals from the pressure sensors <NUM> provided on the busbar tank <NUM> and the connection tanks <NUM>. When the determination unit <NUM> determines that a pressure increase has occurred in any one of the busbar tank <NUM> and the connection tanks <NUM>, the location processing unit <NUM> locates the tank in which a pressure increase is determined to have occurred as a fault point. As described above, when a ground fault has occurred in any of the busbar tank <NUM> and the connection tanks <NUM>, the location processing unit <NUM> determines a fault point in the busbar tank <NUM> and the connection tanks <NUM> on the basis of the result of determination performed by the determination unit <NUM> regarding whether a pressure increase has occurred.

On the basis of pressure signals from the pressure sensors 15a, 15b, and 15c, the determination unit <NUM> monitors whether a pressure increase has occurred in the breaker tanks 12a, 12b, and 12c. On the basis of current signals from the CTs 16a, 16b, and 16c, the measurement unit <NUM> monitors whether the CTs 16a, 16b, and 16c have detected a current. That is, the measurement unit <NUM> monitors whether a current flows from the breaker tank 12a via the stand 14a to the grounding electrode <NUM>, monitors whether a current flows from the breaker tank 12b via the stand 14b to the grounding electrode <NUM>, and monitors whether a current flows from the breaker tank 12c via the stand 14c to the grounding electrode <NUM>. When the CTs 16a, 16b, and 16c have detected a current, the measurement unit <NUM> measures a waveform of the current detected by each CT.

When a pressure increase is determined to have occurred in one of the breaker tanks 12a, 12b, and 12c, and when a current flowing between the one breaker tank and the grounding electrode <NUM> is out of phase with a current flowing between either of the other two breaker tanks and the grounding electrode <NUM>, and a current flowing between the other of the other two breaker tanks and the grounding electrode <NUM>, then the location processing unit <NUM> locates the one breaker tank as a fault point. In the manner as described above, on the basis of the determination result of whether a pressure increase has occurred, and the measurement result of the waveform of the currents, the location processing unit <NUM> performs a process of locating a fault point in the breaker tank 12a, the breaker tank 12b, and the breaker tank 12c.

As illustrated in <FIG>, it is assumed that a ground fault has occurred at a position <NUM> in the breaker tank 12a. Due to the occurrence of a ground fault in the breaker tank 12a, the pressure in the breaker tank 12a increases.

Due to the ground fault, a ground-fault current <NUM>, that is a portion of the current having flowed between the branch wire and the breaker tank 12a, flows from the breaker tank 12a through the connection tank <NUM> and the busbar tank <NUM> to a transformer that is a power supply in the power facilities. In addition, a ground-fault current <NUM>, that is a portion of the current having flowed between the branch wire and the breaker tank 12a, flows through the stand 14a to the metal base <NUM>. The CT 16a detects the ground-fault current <NUM>. A ground-fault current <NUM>, that is a portion of the ground-fault current <NUM> having flowed to the metal base <NUM>, flows from the metal base <NUM> through the grounding electrode <NUM> and the grounding mesh <NUM> to the transformer.

A ground-fault current <NUM>, that is a portion of the ground-fault current <NUM> having flowed to the metal base <NUM>, flows from the metal base <NUM> through the stand 14b to the breaker tank 12b. The CT 16b detects the ground-fault current <NUM>. A ground-fault current <NUM>, that is a portion of the ground-fault current <NUM> having flowed to the breaker tank 12b, flows from the breaker tank 12b through the connection tank <NUM> and the busbar tank <NUM> to the transformer.

A ground-fault current <NUM>, that is a portion of the ground-fault current <NUM> having flowed to the metal base <NUM>, flows from the metal base <NUM> through the stand 14c to the breaker tank 12c. The CT 16c detects the ground-fault current <NUM>. A ground-fault current <NUM>, that is a portion of the ground-fault current <NUM> having flowed to the breaker tank 12c, flows from the breaker tank 12c through the connection tank <NUM> and the busbar tank <NUM> to the transformer.

<FIG> is a diagram for explaining a process to be performed by the location processing unit included in the fault-point-locating device illustrated in <FIG>. A graph illustrated on the upper side of <FIG> shows a relation between time and a pressure detected by the pressure sensor 15a. A graph illustrated on the lower side of <FIG> shows a relation between time and a current detected by the CTs 16a and 16b.

A time T1 represents the time at which a ground fault has occurred at the position <NUM>. When a ground fault has occurred at the position <NUM>, the gas-insulated switchgear <NUM> causes respective breakers in the breaker tanks 12a, 12b, and 12c to perform an opening operation. A time T2 represents the time at which current interruption is completed by the opening operation of the breakers. The ground fault continues during the period from the time T1 to the time T2.

Since a ground fault has occurred at the position <NUM>, the pressure detected by the pressure sensor 15a increases during the period from the time T1 to the time T2. At or after the time T2, the pressure gradually decreases due to heat dissipation from the breaker tank 12a. When the pressure detected by the pressure sensor 15a starts increasing, and then the amount of pressure increase becomes greater than a threshold ΔP set in advance, then the determination unit <NUM> determines that a pressure increase has occurred. The threshold ΔP is set for each individual tank on the basis of the result of calculation of a minimum pressure increase at the occurrence of a ground fault. It is allowable that the threshold ΔP is set to a different value for each individual tank, or is set to a common value among all the tanks provided in the gas-insulated switchgear <NUM>.

As a ground fault has occurred at the position <NUM>, the ground-fault currents <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are generated. When the CT 16a detects the ground-fault current <NUM>, the measurement unit <NUM> measures the current waveform of the ground-fault current <NUM> on the basis of a current signal from the CT 16a. When the CT 16b detects the ground-fault current <NUM>, the measurement unit <NUM> measures the current waveform of the ground-fault current <NUM> on the basis of a current signal from the CT 16b. When the CT 16c detects the ground-fault current <NUM>, the measurement unit <NUM> measures the current waveform of the ground-fault current <NUM> on the basis of a current signal from the CT 16c. The graph on the lower side of <FIG> illustrates a current waveform I1 of the ground-fault current <NUM> and a current waveform I2 of the ground-fault current <NUM>.

Since the ground-fault current <NUM> and the ground-fault current <NUM> flow in directions opposite to each other, the current waveform I1 and the current waveform I2 have opposite phases to each other. That is, the ground-fault current <NUM> is <NUM> degrees out of phase with the ground-fault current <NUM>. Since the ground-fault current <NUM> and the ground-fault current <NUM> flow in the same direction, the current waveform of the ground-fault current <NUM> is in phase with the current waveform <NUM>. That is, there is not phase shifting between the ground-fault current <NUM> and the ground-fault current <NUM>. Therefore, only the current waveform I1, that is one of the three current waveforms obtained by measurement by the measurement unit <NUM>, is out of phase with the other two current waveforms. Illustrations of the current waveform of the ground-fault current <NUM> are omitted since the current waveform of the ground-fault current <NUM> is identical to the current waveform I2 except that the current waveform of the ground-fault current <NUM> has an amplitude different from that of the current waveform <NUM>.

The location processing unit <NUM> locates the breaker tank 12a as a fault point on the basis of the determination in the determination unit <NUM> that a pressure increase has occurred in the breaker tank 12a, and on the basis of the fact that only the current waveform I1 of the current waveforms measured by the measurement unit <NUM> is out of phase with the other current waveforms. When a ground fault has occurred in the breaker tank 12b or the breaker tank 12c, the location processing unit <NUM> also locates the fault point in the same manner as performed on the breaker tank 12a.

In the breaker tanks 12a, 12b, and 12c, when the breaker interrupts the current due to reasons other than the ground fault, the ground-fault currents <NUM>, <NUM>, and <NUM> are not detected, while the determination unit <NUM> determines that a pressure increase has occurred. Accordingly, on the basis of whether the ground-fault currents <NUM>, <NUM>, and <NUM> are detected, the location processing unit <NUM> can distinguish a short circuit having occurred in the breaker tanks 12a, 12b, and 12c from current interruption performed by the breaker due to reasons other than the ground fault.

The path through which the ground-fault currents <NUM>, <NUM>, and <NUM> flow from the breaker tanks 12a, 12b, and 12c through the connection tanks <NUM> and the busbar tank <NUM> to the power supply has an impedance lower than the impedance on the path through which the ground-fault current <NUM> flows through the grounding electrode <NUM> and the grounding mesh <NUM> to the power supply. A specific example is given in which the grounding mesh <NUM> has an impedance per unit distance, where the value of impedance is of the order of magnitude of <NUM> ohm, and in contrast to that, the surface of the tank has an impedance per unit distance, where the value of impedance is of the order of magnitude of <NUM> milliohms. The value of impedance on the path passing through the surface of the tank is smaller by an order of magnitude than the value of impedance on the path passing through the grounding mesh <NUM>. Accordingly, the paths of the ground-fault currents <NUM>, <NUM>, and <NUM> have a lower impedance than that on the path of the ground-fault current <NUM>.

When the ground-fault current <NUM> flows to the metal base <NUM>, then due to the difference between the impedance values as described above, the ground-fault current <NUM> flows to the grounding electrode <NUM>, and additionally the ground-fault currents <NUM> and <NUM> flow through the stands 14b and 14c to the breaker tanks 12b and 12c, respectively, and further the ground-fault currents <NUM> and <NUM> flow from the breaker tanks 12b and 12c, respectively, to the busbar tank <NUM>. In this manner, the ground-fault current <NUM> flowing through the stand 14b to the breaker tank 12b is generated, and the ground-fault current <NUM> flowing through the stand 14c to the breaker tank 12c is generated, making it possible for the CTs 16b and 16c to detect the ground-fault currents <NUM> and <NUM> whose current amount is sufficient for the measurement unit <NUM> to measure a current waveform.

In the fault-point-locating device <NUM>, three CTs 16a, 16b, and 16c are installed per unit, so that the fault-point-locating device <NUM> can monitor a ground fault in the breaker tanks 12a, 12b, and 12c. The fault-point-locating device <NUM> can locate a fault point by using a smaller number of CTs, that is, the CTs 16a, 16b, and 16c, as compared to a case where CTs are needed between the breaker tank 12a and each of its adjacent tanks, between the breaker tank 12b and each of its adjacent tanks, and between the breaker tank 12c and each of its adjacent tanks.

The breaker tanks 12a, 12b, and 12c are not limited to being connected to the grounding electrode <NUM> through the metal base <NUM>. The stands 14a, 14b, and 14c may not be necessarily installed on the metal base <NUM>. The breaker tanks 12a, 12b, and 12c are grounded by connecting a grounding wire provided on each of the breaker tanks 12a, 12b, and 12c to the grounding mesh <NUM>. In this case, the ground-fault current <NUM> having flowed from the stand 14a to the grounding mesh <NUM> partially flows through the grounding mesh <NUM> to the stand 14b and to the stand 14c. This can result in generating the ground-fault currents <NUM> and <NUM> similarly to the case when the metal base <NUM> is used.

Next, a hardware configuration of the fault-point-locating device <NUM> is described. The function of the computation unit <NUM> included in the fault-point-locating device <NUM> is implemented by using a processing circuitry. The processing circuitry is dedicated hardware installed in the fault-point-locating device <NUM>. The processing circuitry may be a processor that executes programs stored in a memory.

<FIG> is a first diagram illustrating an example of the hardware configuration of the fault-point-locating device according to the first embodiment. <FIG> illustrates the hardware configuration of the fault-point-locating device <NUM> when the functions of the fault-point-locating device <NUM> are implemented by using the dedicated hardware. The fault-point-locating device <NUM> includes a processing circuitry <NUM> to perform various types of processing, an interface <NUM> through which the fault-point-locating device <NUM> is connected to external devices, an external storage device <NUM> to store therein various types of information, and a display device <NUM> that is an output device. The processing circuitry <NUM>, the interface <NUM>, the external storage device <NUM>, and the display device <NUM> are connected to be capable of communicating with each other.

The processing circuitry <NUM> as dedicated hardware is a single circuit, a combined circuit, a programmed processor, a parallel-programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. The functions of the determination unit <NUM>, measurement unit <NUM>, and the location processing unit <NUM> are implemented by using the processing circuitry <NUM>.

The functions of the pressure-signal input unit <NUM> and the current-signal input unit <NUM> are implemented by using the interface <NUM>. The external storage device <NUM> stores therein the result of location by the location processing unit <NUM> and the threshold ΔP to be used for determination by the determination unit <NUM>. The display device <NUM> displays the result of location and other information on a screen. The function of the display unit <NUM> is implemented by using the display device <NUM>. It is allowable that the fault-point-locating device <NUM> includes an input device through which the threshold ΔP and other information is input.

<FIG> is a second diagram illustrating an example of the hardware configuration of the fault-point-locating device according to the first embodiment. <FIG> illustrates the hardware configuration of the fault-point-locating device when the function of the computation unit <NUM> is implemented by using hardware that executes the programs. The fault-point-locating device <NUM> includes a processor <NUM>, a memory <NUM>, the interface <NUM>, the external storage device <NUM>, and the display device <NUM>. The processor <NUM>, the memory <NUM>, the interface <NUM>, the external storage device <NUM>, and the display device <NUM> are connected to be capable of communicating with each other.

The processor <NUM> is a CPU (Central Processing Unit), a processing device, a computation device, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor). Each of the functions of the determination unit <NUM>, the measurement unit <NUM>, and the location processing unit <NUM> is implemented by the processor <NUM>, software, firmware, or a combination of software and firmware. The software or firmware is described as a program to be stored in the memory <NUM> that is a built-in memory. The memory <NUM> is a nonvolatile or volatile semiconductor memory, and is a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory).

According to the first embodiment, the fault-point-locating device <NUM> measures a waveform of a current flowing between the breaker tank 12a and the grounding electrode <NUM>, a current flowing between the breaker tank 12b and the grounding electrode <NUM>, and a current flowing between the breaker tank 12c and the grounding electrode <NUM>. On the basis of a determination result of whether a pressure increase has occurred in the breaker tanks 12a, 12b, and 12c, and on the basis of a measurement result of the waveform of the currents, the fault-point-locating device <NUM> performs a process of locating a fault point in the breaker tanks 12a, 12b, and 12c. The fault-point-locating device <NUM> can reduce the number of CTs to be installed for measurement of the current waveform to the CTs 16a, 16b, and 16c. With this configuration, the fault-point-locating device <NUM> achieves an effect of reducing the number of constituent elements to be provided in the gas-insulated switchgear <NUM> to locate a fault point in a tank in which a breaker is accommodated.

In the fault-point-locating device <NUM> according to a second embodiment, when it is determined that a pressure increase has not occurred in any of the tanks included in the fault-point-locating device <NUM>, that are other than the breaker tanks 12a, 12b, and 12c, the fault-point-locating device <NUM> locates one of the breaker tanks 12a, 12b, and 12c as a fault point on the basis of a measurement result of the waveform of a current flowing between the breaker tank 12a and the grounding electrode <NUM>, a current flowing between the breaker tank 12b and the grounding electrode <NUM>, and a current flowing between the breaker tank 12c and the grounding electrode <NUM>. In the second embodiment, constituent elements identical to those of the first embodiment are denoted by like reference signs, and configurations different from those of the first embodiment are mainly described.

<FIG> is a diagram illustrating a schematic configuration of a gas-insulated switchgear that is a target for locating a fault point by the fault-point-locating device according to the second embodiment of the present invention. In the gas-insulated switchgear <NUM> illustrated in <FIG>, the pressure sensors <NUM> are provided respectively on the busbar tank <NUM> and the connection tanks <NUM>. That is, some of the tanks included in the gas-insulated switchgear <NUM>, other than the breaker tank 12a, the breaker tank 12b, and the breaker tank 12c, are respectively provided with the pressure sensors <NUM>. In the second embodiment, the pressure sensor <NUM> is not provided on any of the breaker tanks 12a, 12b, and 12c.

The fault-point-locating device <NUM> according to the second embodiment has a configuration identical to that of the fault-point-locating device <NUM> illustrated in <FIG>. In the second embodiment, a pressure signal is input to the pressure-signal input unit <NUM> from the pressure sensors <NUM> provided respectively on the busbar tank <NUM> and the connection tanks <NUM>. The determination unit <NUM> monitors whether a pressure increase has occurred in the busbar tank <NUM> and the connection tanks <NUM> on the basis of pressure signals from the pressure sensors <NUM> provided on the busbar tank <NUM> and the connection tanks <NUM>. When the determination unit <NUM> determines that a pressure increase has occurred in any one of the busbar tank <NUM> and the connection tanks <NUM>, the location processing unit <NUM> locates the tank in which a pressure increase is determined to have occurred as a fault point.

On the basis of current signals from the CTs 16a, 16b, and 16c, the measurement unit <NUM> monitors whether the CTs 16a, 16b, and 16c have detected a current. When a pressure increase is determined not to have occurred in any of the tanks other than the breaker tanks 12a, 12b, and 12c, that is, in any of the busbar tank <NUM> and the connection tanks <NUM>, and when a current flowing between one of the breaker tanks 12a, 12b, and 12c and the grounding electrode <NUM> is out of phase with a current flowing between either of the other two breaker tanks and the grounding electrode <NUM>, and a current flowing between the other of the other two breaker tanks and the grounding electrode <NUM>, then the location processing unit <NUM> locates the one breaker tank as a fault point. When a pressure increase is determined not to have occurred in any of the busbar tank <NUM> and the connection tanks <NUM>, the location processing unit <NUM> locates the fault point in the breaker tank 12a, the breaker tank 12b, and the breaker tank 12c on the basis of a measurement result of the waveform of the currents in the same manner as in the first embodiment. Also in the second embodiment, the function of the computation unit <NUM> included in the fault-point-locating device <NUM> is implemented by using a processing circuitry similarly to the first embodiment.

In the same manner as in the first embodiment, the fault-point-locating device <NUM> according to the second embodiment can also reduce the number of CTs to be installed for measurement of a current waveform to the CTs 16a, 16b, and 16c. In the fault-point-locating device <NUM>, the breaker tanks 12a, 12b, and 12c do not need to be provided with the pressure sensors <NUM>, so that the fault-point-locating device <NUM> can reduce the number of the pressure sensors <NUM> to be installed for locating a fault point. With this configuration, the fault-point-locating device <NUM> achieves an effect of reducing the number of constituent elements to be provided in the gas-insulated switchgear <NUM> to locate a fault point in a tank in which a breaker is accommodated.

The configurations described in the above embodiments are only examples of the content of the present invention.

Claim 1:
A fault-point-locating device (<NUM>) that is configured to locate a fault point in a gas-insulated switchgear (<NUM>) including a first tank (12a) having a breaker for a first phase accommodated therein, a second tank (12b) having a breaker for a second phase accommodated therein, and a third tank (12c) having a breaker for a third phase accommodated therein, the fault-point-locating device (<NUM>) comprising:
a measurement unit (<NUM>) configured to measure a waveform of a current flowing between the first tank (12a) and a grounding electrode (<NUM>), a waveform of a current flowing between the second tank (12b) and the grounding electrode (<NUM>), and a waveform of a current flowing between the third tank (12c) and the grounding electrode (<NUM>), the first tank (12a), the second tank (12b), and the third tank (12c) being connected to the grounding electrode (<NUM>);
a location processing unit (<NUM>) configured to perform a process of locating the fault point in the first tank (12a), the second tank (12b), and the third tank (12c) on a basis of a measurement result of a waveform of each of the currents, wherein the location processing unit (<NUM>) is configured to locate the fault point on a basis of one of the currents being out of phase with each of the other two of the currents; and
a determination unit (<NUM>) configured to determine whether a pressure increase has occurred in each of the first tank (12a), the second tank (12b), and the third tank (12c),
characterized in that the location processing unit (<NUM>) is configured to perform the process of locating the fault point on a basis of a determination result of whether the pressure increase has occurred, and a measurement result of a waveform of each of the currents.