Device and method for testing protection circuit of high-voltage switchgear

Abstract

To provide a test device (20) for testing a Rogowski coil (4).SOLUTION: A test device (20) includes: an associated protection device (8) connected to a coil via a conductor (13); means (21) for generating at least one test voltage; conversion means (22) that converts the test voltage to a voltage that represents a secondary signal generated by a Rogowski coil (4) and includes output terminals (231, 232) for connection to a conductor (13); and means (226) for processing an output voltage of the coil.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] Rogowski sensors are known for measuring current in Gas Insulated Switchgears (GIS).

[0002] It may also be implemented on a printed circuit board as disclosed in US5414400. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent No. 5,414,400 Summary of the Invention

[0004] Figure 1A shows a Rogowski coil 4 according to US5414400, comprising a plate 11 of printed circuit, for example made of epoxy resin, the coil comprising a deposit of copper 3 on each face of the plate, the deposit on one face being connected to a through hole 6 on the other face via a plated through hole 5 passing through the plate. The coil has terminals 7, 9.

[0005] As shown in Fig. 1B, the Rogowski coils 4 are usually connected to protection circuits 8, which can open switches or circuit breakers 15 in case of some default, for example a current surge or short circuit 17 in the GIS. Such a contingency could be very dangerous for the workers and the whole system, if high voltages occur, such as tens of amperes or even more than 100,000 amperes, and could cause a power outage lasting several months. It is necessary to test whether the protection circuits, switches and circuit breakers work properly. However, it is of course impossible to simulate a real default 17, since very high currents (up to 100,000 amperes) are required.

[0006] For this reason, test circuits have been developed to test protection circuits 8, 15. A conventional test of a protection circuit is shown diagrammatically in Fig. 2A, where reference number 2 indicates a conductor in which a Rogowski coil 4 is arranged to measure the current circulating therein, the coil 4 generating a secondary voltage signal which is fed to a system 8 including an integrator 6, a compensation stage 61 and a digitalization stage 63 to test a protection device 15, for example against overcurrents.

[0007] More precisely, the magnetic field generated by the primary current circulating in the conductor 2 usually generates a voltage at the terminals 7, 9 of the coil. This voltage is, for example, of the order of 50 mV / kA at 50 Hz. As shown in FIG. 2B, this voltage V rogo is integrated in integrator 6.

[0008] The primary current flowing in the conductor 2 can be digitized and processed. In Figure 2B, the coil is represented by an equivalent circuit including an inductance 41 and a resistance 42 in series.

[0009] Typically, as shown in FIG. 2A, a test current is injected directly into the protection system 8, and in particular into the digitization stage 63, to test the protection functions and devices 15.

[0010] However, the components located upstream of the digitization stage, in particular the wire 13 and the integrator 6, as well as the coil 4 itself, are not tested. Moreover, the current injected as test current is not representative of the secondary voltage signal output by the coil 4. In other words, the test is performed under conditions that are not representative of the actual signal generated by the coil 4 when it is measuring the current in the conductor 2.

[0011] Therefore, there is a challenge to find new methods and new test apparatus for testing Rogowski coils and their associated circuitry to overcome one or more of the problems noted above.

[0012] In particular, there is a need for new test methods and new apparatus suitable for testing the protection circuitry of a Rogowski coil and the conductors between that circuitry and the coil.

[0013] Also needed are new test methods and new apparatus suitable for generating test signals representative of the actual signal generated by coil 4 when measuring the current in conductor 2 and when a default (such as default 17 in FIG. 1B) occurs.

[0014] The invention first relates to a test device for testing, for example, a Rogowski coil and an associated protection device connected to said coil via a conductor. The test equipment is - means to generate at least one test voltage, comprising for example an overvoltage, and to apply said test voltage to the terminals of a Rogowski coil; - means to process an output voltage of said coil.

[0015] For example, according to one embodiment of the present invention, a test apparatus for testing a Rogowski coil and an associated protection device connected to said coil via a conductor comprises: - means to generate at least one test voltage; - transformation means to transform said test voltage into a voltage comprised between 0.5 V and 10V, representative of a secondary signal generated by said Rogowski coil, said transformation means comprising output terminals for connection to conductors; - means to process an output voltage of said coil.

[0016] The voltage output by the device according to the invention represents the output signal of the Rogowski coil.

[0017] Said transformation means can comprise a capacitive circuit, comprising for example at least 1 capacitor, for example 2 capacitors. A resistor can be arranged in parallel to said at least one capacitor.

[0018] Preferably, said at least one resistor has an impedance much smaller than the impedance of said coil and said at least one capacitor.

[0019] In a test device according to the invention, said means to generate a test voltage can comprise an alternative current generator. For example, said alternative current generator comprises a controller and preferably at least one memory storing or to store data of at least one, preferably several, waveform(s) which can be used for testing.

[0020] In a test device according to the invention, the transforming means may comprise one or more electrical components, such as, for example, at least one resistor and / or at least one capacitor, and may further comprise means for varying at least one electrical characteristic of at least one of the electronic components.

[0021] Said at least one electrical characteristic of at least one of said electronic components can be varied on the basis of one or more tests performed on a Rogowski coil tested with a device according to the invention.

[0022] In an embodiment, said transformation means can comprise terminals to provide said means to process with a signal from a Rogowski coil under test.

[0023] The invention also concerns a Rogowski coil and an associated protection system connected to said coil via conductors, said conductors comprising connectors to connect a test device according to the invention.

[0024] Said Rogowski coil can further comprise a memory storing one more characteristic, for example the sensitivity and / or the resistance and / or the inductance, of said coil. One or more conductors can connect said memory to at least one part, for example a compensation stage, of said protection system.

[0025] Said protection system can comprise one or more switch(es) and / or one or more circuit breaker(s), the test device comprising means to detect whether at least one switch or at least one circuit breaker opens when a default is detected.

[0026] The invention applies to a single-phase conductor or to one or more phase(s) of a system having several, for example 3, phases. Thus, the invention also concerns a single phase or a 3 phase GIS, comprising at least one conductor, at least one Rogowski coil around said at least one conductor and at least one test device according to the invention.

[0027] The invention also relates to a method for testing a Rogowski coil according to the invention, said coil being arranged around a main conductor, said method comprising the steps of: - interrupting any primary current circulating in said main conductor; - connecting a test device according to the invention to said conductors; - injecting in said conductors one or more test signal(s) generated by said test device; - processing a signal from said coil to decide whether the coil and its protection system is defective or not, for example by detecting whether said protection system is triggered.

[0028] In the device or method according to the invention, a protection system connected to the Rogowski coil comprises: an integration means, or an integration stage or device; - a compensation means, or a compensation stage or device; - a digitization means or a digitization stage or device, - signal filtering means, or a filtering stage or device; - protection means, for example one or more switch(es) and / or one or more circuit breaker(s); [Brief description of the drawings]

[0029] [Figure 1A] 1 shows an embodiment of a Rogowski coil according to the prior art. [Figure 1B] FIG. 1 illustrates a circuit breaker default and open. [Diagram 2] 2A and 2B show a prior art test system. [Diagram 3] 1 shows a test system according to the present invention. [Figure 4] 1 illustrates an embodiment of a test circuit according to the present invention. [Diagram 5] FIG. 5 is an equivalent circuit diagram of the circuit in FIG. [Figure 6] A three-phase system is shown including three conductors, each associated with a Rogowski coil, one or more of which may be provided with the device according to the invention. [Figure 7] 1 shows a measurement system associated with a Rogowski coil. [Figure 8] 1 shows a test signal and a detected secondary signal. [Figure 9A] Voltages including simulated defaults are shown. [Figure 9B] The current including the simulated default is shown. [Figure 9C] An enlarged portion of FIG. 9B is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] One embodiment of the present invention is shown in FIG.

[0031] This is applied to a Rogowski coil 4, for example as disclosed above in connection with Figure 1A, which is arranged around the conductor 2 in order to measure the current circulating in said conductor. The coil 4 generates a secondary voltage signal which is fed to an integrator 6 forming part of a protection system 8, which controls one or more protection devices, for example one or more switches and / or circuit breakers 15, for example in the event of an overcurrent.

[0032] The test device 20 according to an embodiment of the invention is connected as follows: a current is injected into the conductor 13 between the coil 4 and the integrator 6, which is representative of the signal that will flow at the terminals of the coil 4 when the current through the conductor 2 is being measured. In other words, a test current of a few A or tens of A, for example 1 A to 50 A or 100 A, results in a current at the output of the test device 20 that is very comparable to the current generated by the coil when a primary current of a few tens of kA flows through the conductor 2.

[0033] The test apparatus 20 comprises a current generator or source 21 capable of generating a current of, for example, 0 to 100 A, and an interface tool or device 22. Alternatively, a voltage source could be used instead of the current source and impedance 220 (see below), but it is preferred to use a current source to simulate the primary current.

[0034] FIG. 4 shows an embodiment of the test device 20 in more detail.

[0035] The generator 21 comprises an electronic circuit 210 for controlling an AC power source 213 to generate a first AC voltage across its output terminals 211, 212, which are connectable to input terminals 221, 222 of an interface device 22. The generator 21 is thus able to supply a voltage (the first AC voltage) to the interface device 22. This first AC voltage, applied across a resistor 220 and capacitors 223, 224 of the interface device, is a test voltage V, which represents the voltage at the terminals of the coil 4. test can be generated.

[0036] The generator 21 may further include one or more memories 214 for storing one or more predefined values, e.g. waveform data for simulating overcurrents, overstrengths or overvoltages of one or more phases, for testing elements or components downstream of the coil 4 (including the protection devices 8). An overcurrent (overvoltage) is a current (voltage) that the machine can only accept for a very short time. A machine can permanently accept a rated current of, e.g., 3000 Aeff, but can only accept an overcurrent higher than the rated current, e.g., at least twice the rated current, for a short time, e.g., from 10 ms to a few seconds, or from 50 ms to 5 seconds.

[0037] An operator and / or computer or controller can select one or more of these data files and the electronic circuitry 210 can provide corresponding signals to the system (interface device 22) that configure or simulate said one or more simulated defaults.

[0038] The interface device 22 comprises a resistor 220 and inlet terminals 221, 222 for supplying the output voltage supplied from the generator 21 to the resistor 220. The resistor 220 has a value such that an alternating current i1 circulating therein is representative of the primary current normally circulating in the conductor 2, for example 50-100 kA.

[0039] As will be explained below, the value of resistor 220 can be adapted depending on the test being performed.

[0040] The terminals of the resistor may be connected to the outlet terminals 231, 232 of the interface device 22, for example via one or more capacitors 223, 224.

[0041] The one or more capacitors 223, 224 are test capacitors, which in particular block any direct current or voltage components from being fed into the system consisting of the conductor 13 and the protective device 8. As will be explained below, the value of these capacitors can be adapted depending on the test to be carried out.

[0042] The voltage across the output terminals 231, 232 is representative or closely equivalent to the secondary voltage at the output of coil 4, including between 0.5V and 10V, for example.

[0043] The interface device 22 may further include a microcontroller 226 and a display device 228, as described below.

[0044] The output terminals 231, 232 of the interface device 22 can be connected to the conductor 13 (upstream of the protection system 8) via a conductor test plug or connector 131, 132. The system 20 can thus provide a test signal (voltage) on the conductor 13 that closely resembles the secondary voltage generated by the coil 4 detecting the primary current in the conductor 2. This test signal allows testing the conductor 13 and all other components between the coil 4 and the system 8 (and including the coil 4). The system 8 includes not only an integrator 6, but also a compensation stage 61 (in which information about the sensitivity, resistance, inductance of the coil 4 is input from a memory (e.g. EEPROM 80)) and / or one or more filters and / or one or more protection devices 15 (e.g. one or more switches and / or circuit breakers) to protect against defaults such as overcurrents, overstrengths, and / or earth faults, etc.

[0045] In particular, in this way it is possible to test one or more protective devices of the system 8, 15. If the test device 20 injects a signal containing one or more defaults into the conductor 13, but the protective device does not trigger the switch or circuit breaker 15 and / or does not interrupt the current flowing in the conductor 2, it is determined that the protective system is not working properly and a check and possibly repair is required. In other words, it can be checked whether the simulated default is verified by the system and whether a signal is generated to open the switch and / or circuit breaker 15. If the protective device triggers the switch or circuit breaker 15 or interrupts the current flowing in the conductor 2, the protective system is determined to be working properly.

[0046] A signal representative of the current in the system 8 can be obtained, for example, via a conductor 83 which can be connected to test plugs 831, 832 of the conductor 83 connecting the memory 80 to the compensation stage 61. This signal can be provided to the inlet terminals 241, 243 of the interface device 22 and then provided, for example, to the microcontroller 226 and the display device 228.

[0047] 8 is an example of a test voltage (curve I) generated by a test device of the present invention. Curve II (90° out of phase with respect to curve I) is the voltage measured or detected between plugs 831, 832.

[0048] The microcontroller 226 can be programmed or adapted to adjust parameters of the electrical components of the interface device 22, for example the resistors 220 and / or the capacitors 223, 225, depending on the signals received from the system 8. One or more data from the one or more memories 80, in particular one or more of the above-mentioned data relating to the coil 4, can also be supplied to the microcontroller 226. Rogowski coils can have different characteristics from one another, in particular different sensitivities, and therefore information about these characteristics, for example sensitivity, can be read from said memory 80 and used when adjusting the electrical components of the interface device 22.

[0049] Figure 5 shows an equivalent diagram of the circuit disclosed above in relation to Figure 4, together with an integrator stage 6 (forming part of the protection system 8). The references indicate the same elements or components as above. Reference number 213' is a current source connected to the terminals of resistor 220. The Rogowski coil 4 is represented by resistor 42 and capacitor 41. The secondary signal generated by coil 4 is integrated by an integrator.

[0050] When it is necessary to carry out a test according to the invention, any current circulating in the primary circuit (in conductor 2) is interrupted, so the Rogowski coil does not generate a secondary voltage and is ready for testing.

[0051] For testing, the system 8 and conductors 13 remain connected to the coil 4. The interface device 22 is connected to the generator 21 and conductors 13 as shown in the figure. The test circuit is therefore connected in parallel with the Rogowski coil 4.

[0052] The current source 213' generates a test current IT that represents a default current, for example a short circuit current.

[0053] The test current is applied to resistor 220 (which has a small impedance R220 relative to the impedance of the other branches of circuit 15 (capacitors 222, 223 and coil 4); for example: 10xR 220 < Z CT1 +Z4+Z CT2 ) is mainly circulated.

[0054] The voltage across 220 (for example 1 V at 5 A, R220 = 0.2 Ω) closely matches the voltage across coil 4 when the conductor is carrying the primary current. The voltage across resistor 220 URS (in phase with current I) is equal to the sum of the voltages across capacitors 223, 224 and coil 4 (U RS =V C1 +V C2 +V test ). V test simulates the behavior of the Rogowski coil 4 in response to the primary current and depends on the respective values ​​of the capacitors 223, 224, the resistor 42 and the inductance 41. Preferably, the values ​​of the capacitors 223, 224 and the resistor 42 are V testPreferably, the values ​​of capacitors 223, 224 and of resistor 42 are selected so that Vtest is comparable to the voltage at the terminals of coil 4 when it is subject to primary current IT. The values ​​of capacitors 223, 224 are also selected so that Vtest is comparable to the voltage at the terminals of coil 4 when it is subject to primary current IT, as shown in FIG. test is preferably selected to be 90° out of phase with the current generated by generator 13′ (curve I is the test voltage and curve II is the current: R 220 = 200mΩ, C 224 =C 223 =6 μF). For this reason, these impedances are preferably much higher than the impedance Lcoil of the coil 41 (10xZ 41 < Z CT1 +Z CT2 ).

[0055] One or more capacitors CT1, CT2, in the idle state (no primary current flowing in conductor 2), act like coupling capacitors and allow an induced current or a test AC current to flow through the Rogowski coil.

[0056] The voltage developed at the terminals of the Rogowski coil reflects the behavior of the coil as if it were detecting a current in the conductor 2.

[0057] When a current (primary signal) flows through conductor 2, the Rogowski coil generates a secondary signal, in which the resistance of the coil does not play a significant role.

[0058] Tests performed in accordance with the present invention utilize the resistance of the Rogowski coil (by passing a current through it) to generate a secondary voltage independent of the Rogowski effect.

[0059] Examples of values ​​that can be used in a test device according to the invention are: - effective current (rms) I, in A T , - Resistance 220 between 0.1Ω and 1Ω, - Voltage U RS The amplitude of is about 1V, - Capacitors 223 and 224 are between 1uF and 10uF each, - R coil (resistance value of resistor 42) is between 10Ω and 100Ω, - L coil (Inductance 41) is between 10μH and 200μH, -V test The effective voltage (rms) of is between 10 mV and 100 mV (for example, V test (peak value up to 10V) - Current I test is between 1μA and 10μA. A more accurate value will be selected based on the actual characteristics of each system.

[0060] The test device according to the invention has the following advantages: The main circuit (including coil 4, conductor 13 and system 8) is protected from common mode signals via capacitors 223, 224.

[0061] A fault in the Rogowski coil (e.g., a break or short circuit in wire 3) will result in V test can be detected because it affects the protection system 8. In fact, the whole chain from the Rogowski coil 4 to the protection system 8 (including filtering and / or integration stages) can be tested. This is different to the case of a normal digital signal that is sent directly to the protection system 8 (see Figure 2A).

[0062] As with conventional circuits, complex waveforms can be injected through the test circuit according to the present invention.

[0063] A test circuit according to the invention allows injecting currents of the order of some Amp into the protection circuit 8 and the coil 4, which are representative of a primary current (in conductor 2) of several tens or hundreds of kA.

[0064] When the test device according to the invention is implemented, the primary circuit circulating in the conductor 2 is interrupted and the Rogowski coil 4 does not generate any voltage. Tests implementing the invention can now be carried out.

[0065] The invention has been disclosed in relation to one conductor 2 or one phase.

[0066] 6 shows an enclosure 60 including three conductors 2, 102, 202, for example those of a three-phase system, around which a Rogowski coil 4, 104, 204 is arranged. Each of these coils can be tested with a test device or method according to the invention. For example, the same test device 20 can be used in succession on the conductors 13 associated with each of the three Rogowski coils.

[0067] In any embodiment according to the invention, the signal from each test can be provided to a control unit, such as a computer or controller or microprocessor (not shown), for sampling and / or processing the signal, which can generate a test signal as shown in FIG. 9A, including some defaults. FIG. 9A shows test voltages for each of the three phases, including defaults (sudden voltage drops in two phases) simulated at about t=0.1, which causes a surge in current i in those phases (see FIG. 9B). The device 21 or 210 (FIGS. 3, 4) can be programmed such that an alarm is triggered when the simulated current increases above a threshold 300 (here about 5 A).

[0068] FIG. 7 represents a Rogowski coil 4 mounted around a conductor 2. The signal from the coil is sent to a converter 32 and converted into an optical signal. Other signals from one or more other sensors, for example a capacitive sensor 34, can also be converted into an optical signal by a converter 36. The optical signals can be combined in a combination unit 28. The combination unit can consist of a microprocessor for processing the data and can have a computing function. The Rogowski coil 4 can be tested according to the teachings of the present invention. The same system can also be implemented for multiple coils, for example as in FIG. 6.

[0069] The test device 20 according to the invention can be easily disconnected and connected to the test plugs 131, 132 of the conductor 13 connected to the terminals of the Rogowski coil 4. The test according to the invention therefore does not require the implementation and operation of switching elements which may generate disturbances. In fact, the current through the secondary of the Rogowski coil is rather weak, so that if the conductor needs to be interrupted to carry out a test, another test must be carried out to reconnect the conductor, namely a continuity test (the signal may be weakened due to the contact impedance of the connection).

[0070] The test device 20 according to the present invention provides flexibility since the interface device 22 is capable of the following operations: - Disconnect it from conductor 13 and connect it to conductor 13 of another Rogowski coil. and / or disconnected from the generator 21 and connected to a separate test signal generator. [Explanation of symbols]

[0071] 2, 102, 202: conductor 3: copper 4: Rogowski coil 5, 6: through hole 6: integrator 7, 9: end 8: protection circuit / protection system 11: plate 13: wire / conductor 15: switch / circuit breaker / protection circuit 17: default 20: test equipment 21: current generator / current source 22: interface tool / interface device 28: coupling unit 32, 36: converter 34: capacitive sensor 41: inductance 42: resistor 60: housing 61: compensation stage 63: digitization stage 80: memory 83, 93: conductor 104, 204: coil 131, 132: connector 210: electronic circuit 211, 212: output terminal 213: current source 214: memory 220: impedance / resistance / resistor 221, 222: input terminal 223, 224: Capacitor 226: Microcontroller 228: Display device 231, 232: Outlet terminal / output terminal 241, 243: Input terminal 300: Threshold 831, 832: Test plug

Claims

1. A test device (20) for testing a Rogowski coil (4) and an associated protection device (8) connected to said coil via a conductor (13), comprising: - means (21) for generating at least one test voltage including an overvoltage; - transforming means (22) for transforming said test voltage to a voltage between 0.5V and 10V, said transforming means (22) comprising output terminals (231, 232) for connection to said conductor (13) and a capacitive circuit; means (226) for processing the output voltage of said coil and detecting whether the protection device (15) of said coil has been triggered; A test device (20).

2. 2. The device according to claim 1, wherein the transforming means (22), the capacitive circuit, comprises at least one or at least two capacitors (223, 224, CT1, CT2).

3. 3. The test device (20) of claim 2, wherein the conversion means (22) comprises at least one resistor (Rs, 220) connected in parallel with the at least one capacitor (223, 224, CT1, CT2).

4. 4. The test device (20) of claim 3, wherein the at least one resistor (Rs, 220) has an impedance much smaller than an impedance of the at least one capacitor (223, 224, CT1, CT2) and the Rogowski coil.

5. 2. The test device (20) of claim 1, wherein the means (21) for generating the test voltage comprises an alternating current generator (21).

6. 6. The test device (20) of claim 5, wherein the alternating current generator (21) comprises a controller (210) and at least one memory (214) for storing data of at least one waveform, preferably a plurality of waveforms, that can be used for testing.

7. The test device (20) of claim 1, wherein the conversion means (22) comprises one or more electrical components, such as at least one resistor (220) and / or at least one capacitor (231, 232), and further comprises means (226) for changing at least one electrical characteristic of the electronic component.

8. 8. The test device (20) of claim 7, wherein the means (226) is capable of varying at least one electrical characteristic of the electronic component based on one or more tests performed on the coil (4).

9. 2. A test device (20) according to claim 1, wherein the conversion means (22) comprises terminals (241, 243) for supplying the signal from the coil (4) to the means (226).

10. A Rogowski coil (4) and an associated protection system (8) connected to said coil via a conductor (13), said conductor (13) including a connector (131, 132) for connecting a test device as claimed in any one of claims 1 to 10.

11. The Rogowski coil (4) according to claim 10, further comprising a memory (80) for storing one or more characteristics of the coil (4), such as sensitivity and / or resistance and / or inductance.

12. The Rogowski coil (4) of claim 11, further comprising one or more conductors (83) connecting the memory (80) to at least one part of the protection system (8), such as a compensation stage (61).

13. 11. The Rogowski coil (4) of claim 10, wherein the protection system (8) includes one or more switches (15) and / or one or more circuit breakers, and the testing device includes means for detecting whether the one or more switches (15) or the one or more circuit breakers are open when a default is detected.

14. A single or three phase GIS comprising at least one conductor (2, 102, 202), at least one Rogowski coil (4, 104, 204) and at least one device according to any of the claims 1 to 9.

15. 14. A method for testing a Rogowski coil according to any one of claims 10 to 13, wherein the coil (4, 104, 204) is arranged around a main conductor (2, 102, 202), the method comprising the steps of: - interrupting the primary current flowing through said main conductor (2, 102, 202); - connecting a test device (20) according to any one of claims 1 to 9 to said conductor (13); - injecting one or more test signals generated by said test device (20) into said conductors (13); - processing the signal from the coil to determine whether there is a fault in the coil and the protection system (8), for example by detecting whether the protection system (8) has been triggered.

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