APPARATUS AND METHOD FOR DETECTING GAS

An apparatus detects gas in a high-voltage device, which is filled with an insulating medium. The apparatus has: an inlet configured for introducing a carrier gas; an outlet configured for discharging the carrier gas; at least one gas sensor configured to detect a gas; a first pump configured to convey the carrier gas in the apparatus; a membrane which comprises at least one semipermeable basic material, which is at least partially surrounded by the insulating medium, and which is arranged to be at least partially subjected to an incident flow of the carrier gas; a second pump configured to convey the carrier gas into the apparatus and out of the apparatus; and a separating column, which is arranged before the gas sensor. The gas sensor is a sensor array.

FIELD

The present disclosure relates to an apparatus and a method for detecting multiple gases in high-voltage devices which are filled with insulating medium, in particular high-voltage transformers.

BACKGROUND

WO 2012/120113 A1 has disclosed a system and a method for monitoring gases in power transformers which are cooled with oil. The system consists in this case of a bar and a main housing. The bar has two lines running in the interior and is positioned in the oil of the power transformer. The lines are connected to one another via two oil chambers and a pump such that the oil can be sucked in from the power transformer via a line to the first oil chamber and subsequently conducted back into the power transformer through the other line via the second oil chamber. The pump is in this case arranged in a line section between the oil chambers. An additional region with a temperature sensor and with a moisture sensor is situated before the pump. Both oil chambers have a wall which consists of a semipermeable basic material. Gases contained in the oil of the power transformer can migrate into the interior of the main housing through the wall. An additional gas sensor detects the gases which accumulate in the main housing of the system. Additionally, two valves having in each case one filter are arranged at the housing. One of the valves is used for sucking-in of air from the surroundings by means of a pump. The air is released from the interior of the main housing by way of the second valve. The system is controlled via a controller.

The above-described system is of highly complex construction. The multiplicity of individual parts used makes the system not only expensive, but also maintenance-intensive. The valves for the exchange of air wear particularly quickly and thus constitute a weakness in the system. The flat configured membrane can rupture particularly quickly in the event of a sudden pressure increase and in particular during the evaluation of the carrier gas.

SUMMARY

In an embodiment, the present disclosure provides an apparatus that detects gas in a high-voltage device, which is filled with an insulating medium. The apparatus has: an inlet configured for introducing a carrier gas; an outlet configured for discharging the carrier gas; at least one gas sensor configured to detect a gas; a first pump configured to convey the carrier gas in the apparatus; a membrane which comprises at least one semipermeable basic material, which is at least partially surrounded by the insulating medium, and which is arranged to be at least partially subjected to an incident flow of the carrier gas; a second pump configured to convey the carrier gas into the apparatus and out of the apparatus; and a separating column, which is arranged before the gas sensor. The gas sensor is a sensor array.

DETAILED DESCRIPTION

Aspects of the present disclosure provide an apparatus for detecting gas molecules in a high-voltage device filled with insulating medium that is of inexpensive, maintenance-friendly and substantially wear-free construction, and provide a method for detecting gases in high-voltage devices filled with liquids that ensures reliable and accurate operation of the apparatus.

According to a first aspect, the present disclosure provides an apparatus for detecting multiple gases in a high-voltage device which is filled with an insulating medium, having:

an inlet for introducing and an outlet for discharging a carrier gas;

at least one gas sensor for detecting a gas;

a first pump for conveying the carrier gas in the apparatus;

a membrane which consists at least of at least one semipermeable basic material, is at least partially surrounded by the insulating medium, and is at least partially subjected to an incident flow of the carrier gas;

a second pump for conveying the carrier gas into the apparatus and for conveying it out of the apparatus;

characterized in that:

a separating column is provided and is arranged before the gas sensor, and the gas sensor is designed as a sensor array.

One advantage provided by aspects of the present disclousre is that the extension of the apparatus to include the combination of a separating column and a sensor array is both particularly expedient and particularly accurate. Sensor arrays are multiple particularly compact semiconductor sensors which are arranged on a unit. In this way, a measurement chamber can be of particularly compact design. Furthermore, sensor arrays are significantly more expedient in comparison with conventional sensors from the area of gas-in-oil analysis. The arrangement of a separating column before the sensor array makes possible pre-separation of the gases and thus improves the selectivity of the overall apparatus. Separating columns are commonly used in laboratory setups, although not in apparatuses directly at high-voltage devices. Furthermore, the separating column allows the number of individual sensors in the sensor array to be reduced. The measurements are simplified, which minimizes the computational outlay in the case of the data processing. Consequently, the central control device can be constructed with the simplest means, which has a positive effect on the costs of the apparatus. This combination leads overall to an inexpensive, robust, low-maintenance apparatus that is less susceptible to faults. A further advantage is that what is circulated is the carrier gas and not the insulating medium. In this way, it is possible for fresh carrier gas, such as for example ambient air, to be introduced into the apparatus before the enrichment and detection and to be discharged from the apparatus after the detection.

The sensor array may be designed in any desired manner according to requirement, for example as a semiconductor sensor consisting of oxides of metals or transition metals, such as for example stannic oxide (SnO2) or tungsten oxide (WO3), and/or doped with noble metals, such as for example platinum (Pt) or palladium (Pd). The sensor array may, for example, be constructed on the basis of the pellistor principle a/or be a Taguchi gas sensor.

The separating column may be designed in any desired manner according to requirement, for example either from metal or from fused silica. Internally, it may be lined with a defined stationary phase, for example with viscous polyorganosiloxanes. The length of the separating column is preferably approximately 0.5 to 1.0 m. The separating column may be of the column type PoraBond Q, WP Plot Q, Hayesep N or Hayesep Q.

The high-voltage device may be designed in any desired manner according to requirement, for example as a high-voltage transformer, power transformer, on-load tap-changer, circuit breaker, condenser bushing or some other oil-filled piece of electrical equipment.

The insulating medium may be of any desired type according to requirement, for example an insulating oil or ester liquid.

The gas to be detected may be of any desired type according to requirement and, for example, contain at least one hydrocarbon compound and/or other gas molecules and/or other gas atoms.

The semipermeable membrane may be of any desired form according to requirement and, for example, at least partially consist of Teflon.

The pumps may be designed in any desired manner according to requirement, for example as membrane pumps.

It may be provided that:

a valve having at least two operating states is provided.

The valve may be designed in any desired manner according to requirement, for example as a Valco 6-port valve or else as a Valco 8-port valve. It is preferably possible for the valve to be switched into at least two operating states.

It may be provided that:

an inlet, a first line and a filter are provided, and the first line is connected to a sixth connection of the valve;

the membrane is connected at one side to a first connection of the valve via a first connecting line and at the other side to the second connection of the valve via a second connecting line;

the first pump is arranged in the first connecting line;

a measurement chamber in which there are arranged sensors for temperature, moisture and pressure and/or gas sensors is provided;

a fourth connecting line connects the separating column to the measurement chamber via a fourth connection of the valve;

the measurement chamber is connected to an outlet via a second line.

It may be provided that

a sample loop is connected to a third connection of the valve via a third connecting line and to a fifth connection of the valve via a fourth connecting line.

The sample loop may be of any desired form according to requirement and, for example, at least partially consist of Teflon.

It may be provided that:

the sensors in the measurement chamber, the first pump, the second pump and the valve are connected to a control device; and

the sensors in the measurement chamber, the first pump, the second pump and the valve are controlled on the basis of the measurements of the sensors in the measurement chamber.

It may be provided that:

the inlet has a first line, a pump and a filter.

It may be provided that:

the membrane is of at least partially spiral-shaped form and/or of at least partially meandering form and/or of at least partially helical form.

It may be provided that:

at least one temperature sensor is provided.

It may be provided that:

the outlet has a second line.

It may be provided that:

a line or connecting line for transport of the gases to be analyzed, which line or collecting line has a pump, is present.

It may be provided that:

a measurement chamber in which there are arranged sensors for determining temperature, ambient moisture, pressure and different gases is provided.

It may be provided that:

at least one thermal element is arranged in the measurement chamber.

It may be provided that:

the temperature sensor and the thermal element are connected to a control device, and

the thermal element is controlled on the basis of the measurements of the temperature sensor.

It may be provided that:

during the operation of the first pump, the second pump functions as a closed valve, and during the operation of the second pump, the first pump functions as a closed valve.

It may be provided that:

the thermal element is in the form of a Peltier element.

It may be provided that:

the measurement chamber is lined internally with an inert material, platinum or gold or some other noble metal.

According to a second aspect, the present disclosure provides a method for detecting multiple gases in a high-voltage device, which is filled with an insulating medium, by means of an apparatus as described above, wherein:

in a first step, a measurement chamber is flushed with a carrier gas in that the carrier gas is conveyed into the measurement chamber through the separating column and conveyed out of the measurement chamber;

in a second step, the carrier gas is conveyed through a membrane and is enriched by gas which flows through the membrane;

in a third step, a sensor in the measurement chamber measures the gas after it has passed through the separating column.

It may be provided that:

in the first and third steps, the valve is in a first operating state for flushing of the measurement chamber and for measurement of the gases;

in the third step, the valve is in a second operating state for enrichment of the carrier gas.

It may be provided that:

the carrier gas is transported into the measurement chamber through a valve, a sample loop, the fourth connecting line and the separating column, and, at the measurement chamber, the gases collected in the membrane are detected by the sensors.

It may be provided that:

during the flushing, the carrier gas is sucked in through a first line, is conveyed into the measurement chamber through the valve and via the separating column, and is discharged through the outlet.

It may be provided that:

the flushing of the measurement chamber is realized by means of the second pump.

It may be provided that:

the conveyance of the carrier gas is realized by means of a first pump.

It may be provided that:

the amount and/or the type of the gas in the measurement chamber are/is determined before and/or after the carrier gas has been conveyed out.

It may be provided that:

the amount and/or the type of the gas in the measurement chamber are/is determined before and/or after the carrier gas has been conveyed.

Identical reference signs are used for identical or identically acting elements of the present disclosure. Furthermore, for the sake of clarity, in the individual figures, only reference signs necessary for the description of the respective figure are illustrated. The illustrated embodiments constitute merely examples of the configuration of the apparatus according to the present disclosure, and thus do not constitute a conclusive delimitation of the present disclosure.

FIG.1shows, in a schematic illustration, a first embodiment of an apparatus1for detecting gas molecules, ions or gases4in a high-voltage device3which is filled with a liquid or an insulating medium2. The high-voltage device3may be designed as a high-voltage transformer, power transformer, on-load tap-changer, circuit breaker or condenser bushing.

The apparatus1has a membrane or capillary13that consists of at least one semipermeable basic material and that is of tube-like or hose-like construction. The tube-like membrane13may be shaped in any desired manner, for example so as to be spiral-shaped and/or helical and/or meandering. Due to this advantageous configuration of the membrane13, it is suitable for particularly high pressures. The membrane13is situated in the high-voltage device3or at least in a part of the high-voltage device with accessibility in relation to the insulating medium2. Consequently, the membrane13may be arranged in a Buchholz relay, in a line of the cooling means, etc. Due to the tube-like configuration and the basic material which is gas-permeable (semipermeable) in one direction, molecules of the gas4can pass into a circuit of the apparatus1.

The membrane13is connected at one end, which forms the entry of the membrane, to a first connection20.1of a valve20via a first connecting line31and, at the other side, at another end, which forms the exit of the membrane, to the second connection20.2of the valve20via a second connecting line32. A first pump9is arranged in the second line32.

The apparatus furthermore has a sample loop21. A sample loop is a gas-tight capillary with a defined volume. This is normally produced from fused silica. However, it may also consist of a suitable plastic. The sample loop21is connected to the third and fourth connections20.3,20.4of the valve20via a third and a fourth connecting line33,34. The apparatus1furthermore has a first line7, which, at one side, has an inlet5and, at the other side, is connected to a fifth connection20.5of the valve20. A filter15and a second pump10are arranged in the first line7.

A separating column19is arranged between the sixth connection20.6and the measurement chamber11via a fifth connecting line35. The measurement chamber11is moreover connected to an outlet6via a second line8.

The measurement chamber11has a thermal element14, for example a Peltier element, with the aid of which temperature control of the measurement chamber11is carried out. In addition, at least one gas sensor12and one temperature sensor18are arranged in the measurement chamber11.

The gas sensor12is designed as a sensor array. The sensor array consists of multiple semiconductor sensors. The semiconductor sensors consist of oxides of metals or transition metals, such as for example stannic oxide (SnO2) or tungsten oxide (WO3), and, for improvement of selectivity, are doped with noble metals, such as for example platinum (Pt) or palladium (Pd). The sensor array is constructed on the basis of the pellistor principle, although this does not constitute the only design. Taguchi gas sensors are classical semiconductor sensors.

The measurement chamber11is lined or coated internally with an inert material, such as for example gold. This coating offers the advantage that the gases4cannot, in the interior, be deposited or condense and non-reproducibly taken up, in the process enter into at least polar physical bonding and thus be absent in the overall gas balance, whereby incorrect values would be measured in comparison with a laboratory analysis.

The separating column19may consist either of metal or of fused silica. Internally, it is lined with a defined stationary phase, for example with viscous polyorganosiloxanes. The length of the separating column is approximately 0.5-1.0 m. Common column types are PoraBond Q, WP Plot Q, Hayesep N and Hayesep Q.

The valve20has different operating states/positions. In the case of these, the individual connections are internally connected in such a way that different circuits or connections of individual components among one another are formed in the apparatus1.

In a first operating state, as is illustrated inFIG.2, for example a circuit for enrichment of the carrier gas16is produced. Here, the first and fourth connections20.1,20.4and the second and third connections20.2,20.3are internally connected. The first pump9conveys the carrier gas16through the second connecting line32, the capillary13and the sample loop21. Since the pressure in the interior of the high-pressure device3is at all times higher than the pressure of the surroundings and thus also the pressure in the apparatus1, the gases4released in the insulating medium2pass into the circuit of the apparatus1through the semipermeable membrane13. The carrier gas16is enriched through repeated conveyance or circulation. The valve20is likewise connected to the central control device17. Air from the surroundings may be used as carrier gas16.

FIG.3illustrates a second operating state of the valve20. Here, the fifth and third connections20.5,20.3and also the fourth and sixth connections20.4,20,6of the valve20are internally connected to one another. Fresh carrier gas16(for example ambient air) is conveyed into the apparatus1by means of second pump10via the inlet5of the first line7. The carrier gas16situated in the sample loop21is introduced firstly into the separating column19and then into the measurement chamber12. Subsequently, the carrier gas16and the sucked-in air are conveyed to the outlet6through the second line8. The gas sensor12, the temperature sensor18and the thermal element14in the measurement chamber11and also the first and second pumps9,10are connected to a central control device17. The control of the thermal element14is realized on the basis of the measurements of the temperature sensor18.

The valve20may preferably be designed as a Valco 6-port valve or else as a Valco 8-port valve. The valve may assume two operating states internally. With the use of a Valco 6-port valve, the individual parts of the apparatus1are connected to the valve20in a specific way. This is illustrated inFIG.4. Here, it is only ever possible for in each case two adjacent connections of the valve to be internally connected to one another. In this way, the valve can be actuated in a particularly expedient and simple manner. The membrane13is connected at one end, which forms the entry of the membrane, to a first connection20.1of a valve20via a first connecting line31and, at the other side, at another end, which forms the exit of the membrane, to the second connection20.2of the valve20via a second connecting line32. A first pump9is arranged in the second line32.

The apparatus furthermore has a sample loop21. The sample loop21is connected to the third and fifth connections20.3,20.5of the valve20via a third and a fourth connecting line33,34. The apparatus1furthermore has a first line7, which, at one side, has an inlet5and, at the other side, is connected by way of a sixth connection20.6to the valve20. A filter15and a second pump10are arranged in the first line7.

A separating column19is arranged between the fourth connection20.4and the measurement chamber11via a fifth connecting line35. The measurement chamber11is moreover connected to an outlet6via a second line8.

In a first operating state, as is illustrated inFIG.5, for example a circuit for enrichment of the carrier gas16is produced. Here, the first and fifth connections20.1,20.5and the second and third connections20.2,20.3are internally connected. The fifth and fourth connections20.4,20.5are likewise connected to one another. This is unimportant for the enrichment. The first pump9conveys the carrier gas16through the second connecting line32, the capillary13and the sample loop21. Since the pressure in the interior of the high-pressure device3is at all times higher than the pressure of the surroundings and thus also the pressure in the apparatus1, the gases4released in the insulating medium2pass into the circuit of the apparatus1through the semipermeable membrane13. The carrier gas16is enriched through repeated conveyance or circulation. The valve20is likewise connected to the central control device17. Air from the surroundings may be used as carrier gas16.

FIG.6illustrates a second operating state of the valve20. Here, the fifth and fourth connections20.3,20.4and also the fifth and sixth connections20.5,20.6of the valve20are internally connected to one another. Fresh carrier gas16(for example ambient air) is conveyed into the apparatus1by means of second pump10via the inlet5of the first line7. The carrier gas16situated in the sample loop is introduced firstly into the separating column19and then into the measurement chamber12. Subsequently, the carrier gas16and the sucked-in air are conveyed to the outlet6through the second line8.

FIG.7shows a flow diagram for a method for detecting gases in a high-voltage device3, which is filled with a liquid2, by means of the apparatus1that comprises the following steps:

Step100: Firstly, the apparatus1is flushed. In this case, the valve20is in the second operating state. The first pump9is in the switched-off state, while the second pump10is in the switched-on state. The carrier gas16, for example ambient air, is sucked in via the inlet5, that is to say the filter15and the first line7. In this case, the carrier gas16passes through the filter15, the valve20, the sample loop21, the separating column19and the measurement chamber11before it passes to the outlet6. The apparatus1is flushed in this manner.

Step101: The flushing is ended after a predetermined time or on the basis of the measurements of the gas sensors12in the measurement chamber11. The parameters ascertained in the measurement chamber11at the conclusion serve as starting point or zero point for the further measurements.

Step102: In the enrichment phase of the embodiments inFIGS.3and6, the valve20is switched into the first operating state and the first pump9is switched on, whereby the carrier gas16in the apparatus1is conveyed or circulated. The second pump10is in the switched-off state. The carrier gas16is moved in a circuit between the sample loop21and the membrane13. Since the pressure in the interior of the high-pressure device3is higher than the pressure in the apparatus1, gases4pass into the apparatus1from the insulating medium2through the membrane13, which is permeable to gas molecules in one direction. This results in enrichment of the carrier gas16. The duration of the enrichment may be configured to be variable.

Step103: After the enrichment phase, the switching of the valve20into the second operating state is realized. The enriched gas in the sample loop21is transported with the carrier gas16into the measurement chamber11through the separating column19, and the amount and the type of the gases4in the measurement chamber11are determined via the gas sensor12. After the determination of the gases4, the apparatus1is flushed by way of the continued sucking-in of fresh ambient air.

The method described may be carried out either permanently or else a few times a day. Discontinuous operation of the apparatus1can lead to an increase in the service life of the gas sensors12used in the measurement chamber11.

LIST OF REFERENCE SIGNS

31First connecting line

32Second connecting line

33Third connecting line

34Fourth connecting line

35Fifth connecting line