Apparatus and method for testing protection circuit in high voltage / switchgear

Abstract

The invention relates to an apparatus and a method for testing a protection circuit in a high voltage / switchgear. The invention relates to 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; -transformation means (22) for transforming said test voltage into a voltage representative of a secondary signal generated by said Rogowski coil (4), said transformation means (22) comprising output terminals (231, 232) for connection to a conductor (13); -means (226) for processing the output voltage of the coil.

Description

Background Art

[0001] Rogowski sensors are known for measuring current in gas insulated switchgear (GIS).

[0002] They may be implemented on a printed circuit board as disclosed in US5414400.

[0003] Figure 1A A Rogowski coil 4 according to US5414400 is shown, comprising a board 11 of printed circuitry, for example made of epoxy resin; the coil comprises copper deposits 3 on each face of the board, the deposits on one face being connected to the deposits on the other face via plated through holes 5 through the board. The coil has terminals 7,9.

[0004] like Figure 1B As illustrated in FIG, the Rogowski coil 4 is usually connected to a protection circuit 8 which can disconnect the switch or circuit breaker 15 in case of any default, such as a surge of current or a short circuit 17 in a GIS. Such a default can generate currents up to tens of A or events above 100,000 A, which are very dangerous for the operating personnel and for the entire system and can cause interruptions of several months. It is necessary to test whether the protection circuit and the switch or circuit breaker 15 operate correctly. But of course it is impossible to simulate a real default 17, because very large currents (up to 100,000 A) are required: portable generators can generate at most tens or hundreds of A.

[0005] For these reasons, test circuits have been developed to test protection circuits 8, 15. Figure 2A The conventional test of a protection circuit is schematically illustrated in Figure 2A , reference numeral 2 designates a conductor around which a Rogowski coil 4 is arranged in order to measure a current flowing therein, the coil 4 generating a secondary voltage signal which is supplied to a system 8 comprising an integrator 6, a compensation stage 61 and a digitizing stage 63 in order to test a protection device 15 for example an overcurrent.

[0006] More precisely, the magnetic field generated by the primary current that usually circulates in the conductor 2 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. Figure 2B As shown in rogo The voltage V 输出 represents the primary current flowing in conductor 2 and can be digitized and processed. Figure 2B In FIG. 4 , the coil is represented by an equivalent circuit including an inductor 41 and a resistor 42 connected in series.

[0007] Usually, if Figure 2A , a test current is injected directly into the protection system 8, in particular directly into the digitization stage 63, in order to test the protection function and the device 15. However, the components located upstream of the digitization stage, in particular the conductor 13 and the integrator 6, as well as the coil 4 itself, are not tested. Moreover, the current injected as test current does not represent the secondary voltage signal output by the coil 4; in other words, the test is performed under conditions that do not represent the actual signal generated by the coil 4 when it measures the current in the conductor 2.

[0008] Therefore, in order to overcome one or more of the above problems, there exists a problem of finding new testing methods and new testing apparatus for Rogowski coils and their associated circuits.

[0009] In particular, there is a need for a new test method and a new device suitable for testing the protection circuit of a Rogowski coil and the conductors between said circuit and said coil.

[0010] There is also a method for generating a signal indicating when it is measuring the current in the conductor 2 and when a defect (such as Figure 1B The defect 17) is the need for a new test method and a new device for the test signal of the actual signal generated by the coil 4. Summary of the invention

[0011] The invention firstly relates to a testing device for testing, for example, a Rogowski coil and an associated protection device connected to said coil via a conductor, comprising: - means for generating at least one test voltage (including for example an overvoltage) and applying said test voltage to the terminals of the Rogowski coil; - means for processing the output voltage of said coil.

[0012] For example, according to one embodiment of the present invention, a testing device for testing a Rogowski coil and an associated protection device connected to the coil via a conductor comprises: - means for generating at least one test voltage; - transformation means for transforming said test voltage into a voltage representative of the secondary signal generated by said Rogowski coil comprised between 0.5 V and 10 V, said transformation means comprising an output terminal for connection to a conductor; - means for processing the output voltage of said coil.

[0013] The output signal of the Rogowski coil is represented by the voltage output by the device according to the invention.

[0014] The transforming means may comprise a capacitive circuit, the capacitive circuit comprising, for example, at least one capacitor, for example, two capacitors. A resistor may be arranged in parallel with the at least one capacitor.

[0015] Preferably, the at least one resistor has an impedance which is much smaller than the impedance of the coil and the at least one capacitor.

[0016] In the test device according to the invention, the means for generating the test voltage may comprise an AC generator, for example, comprising a controller and preferably at least one memory storing or to store data of at least one, preferably several waveforms that can be used for the test.

[0017] In the testing device according to the present invention, the transformation component may include one or more electrical components, such as at least one resistor and / or at least one capacitor, and may further include a component for changing at least one electrical characteristic of at least one of the electronic components.

[0018] The at least one electrical characteristic of at least one of the electronic components may be changed based on one or more tests performed on a Rogowski coil which is tested with the device according to the invention.

[0019] In one embodiment, the transforming component may include terminals to provide the component to process signals from the Rogowski coil under test.

[0020] The invention also relates to a Rogowski coil and an associated protection system connected to said coil via a conductor comprising a connector to which a test device according to the invention is connected.

[0021] The Rogowski coil may further comprise a memory storing one or more characteristics of the coil, such as sensitivity and / or resistance and / or inductance. One or more conductors may connect the memory to at least one part of the protection system, such as a compensation stage.

[0022] The protection system may comprise one or more switches and / or one or more circuit breakers, the testing device comprising means for detecting whether at least one switch or at least one circuit breaker is opened when a defect is detected.

[0023] The invention is applicable to a single-phase conductor or one or more phases of a system having several (e.g. 3) phases. Therefore, the invention also relates to a single-phase or three-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.

[0024] The invention also relates to a method according to the invention for testing a Rogowski coil, said coil being arranged around a main conductor, said method comprising: - interrupting any primary current flowing in said main conductor; - connecting a test device according to the invention to said conductor; - injecting one or more test signals generated by said testing device into said conductor; - Processing the signal from the coil to determine whether the coil and its protection system are defective, for example by detecting whether the protection system is triggered.

[0025] In an apparatus or method according to the invention, a protection system connected to a Rogowski coil may include one or more of the following: - an integrating component, or an integrating stage or device, - Compensating components, or compensating stages or devices; - a digitizing component, or a digitizing stage or device; - signal filtering components, or filtering stages or devices; - Protection components, such as one or more switches and / or one or more circuit breakers. The present invention thus provides the following technical solutions: 1. A testing 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, said test voltage comprising an overvoltage; - a transformation component (22) for transforming the test voltage into a voltage comprised between 0.5 V and 10 V, the transformation component (22) comprising an output terminal (231, 232) for connection to a conductor (13), the transformation component (22) comprising a capacitive circuit; - means (226) for processing the output voltage of the coil and detecting whether the protection device (15) of the coil is triggered. 2. As in the device of technical solution 1, the conversion component (22) and the capacitive circuit include at least one or at least two capacitors (223, 224, CT1, CT2). 3. In the device of technical solution 2, the transformation component (22) includes at least one resistor (Rs, 220) connected in parallel to the at least one capacitor (223, 224, CT1, CT2). 4. In the device of technical solution 3, the at least one resistor (Rs, 220) has an impedance much smaller than the impedance of the at least one capacitor (223, 224, CT1, CT2) and the impedance of the Rogowski coil. 5. In the device of technical solutions 1 to 4, the component (21) for generating the test voltage includes an AC generator (21). 6. As in the device of technical solution 5, the AC generator (21) includes a controller (210) and at least one memory (214) to store data of at least one, preferably several waveforms that can be used for testing. 7. In the device of any one of technical solutions 1 to 6, the transformation component (22) includes one or more electrical components, such as at least one resistor (220) and / or at least one capacitor (231, 232), and further includes a component (226) for changing at least one electrical characteristic of at least one of the electronic components. 8. In the device of technical solution 7, the component (226) is capable of changing at least one electrical characteristic of at least one of the electronic components based on one or more tests performed on the coil (4). 9. In the device of any one of technical solutions 1 to 8, the transformation component (22) includes terminals (241, 243) to provide the component (226) with a signal from the coil (4). 10. A Rogowski coil (4) and an associated protection system (8) connected to the coil via a conductor (13), comprising connectors (131, 132) on the conductor (13) for connecting a test device according to any one of technical solutions 1 to 10. 11. The Rogowski coil (4) according to technical solution 10 further includes a memory (80), which stores one or more characteristics of the coil (4), such as sensitivity and / or resistance and / or inductance. 12. The Rogowski coil (4) according to technical solution 11 further includes one or more conductors (83) connecting the storage (80) to at least a part of the protection system (8), such as the compensation stage (61). 13. According to the Rogowski coil (4) of any one of technical solutions 10 to 12, the protection system (8) includes one or more switches (15) and / or one or more circuit breakers, and the testing device includes a component for detecting whether at least one switch or at least one circuit breaker is disconnected when a defect is detected. 14. A single-phase 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 as in any one of technical solutions 1 to 9. 15. A method for testing a Rogowski coil according to any one of technical solutions 10 to 13, wherein the coil (4, 104, 204) is arranged around a main conductor (2, 102, 202), the method comprising: - interrupting any primary current circulating in said main conductor (2, 102, 202); - Connecting a test device (20) as in any one of technical solutions 1 to 9 to the conductor (13); - injecting one or more test signals generated by the test device (20) into the conductor (13); - Processing the signal from the coil to determine whether the coil and its protection system (8) are defective, for example by detecting whether the protection system (8) is triggered. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] - Figure 1A An embodiment of a Rogowski coil according to the prior art is shown; - Figure 1B The diagram illustrates the disconnection and defect of a circuit breaker according to the prior art; - Figure 2A and 2B A test system according to the prior art is shown; - Figure 3 A test system according to the present invention is shown; - Figure 4 An embodiment of a test circuit according to the present invention is shown; - Figure 5 Shows Figure 4 Equivalent diagram of the circuit; - Figure 6 shows a 3-phase system comprising 3 conductors, each conductor being associated with a Rogowski coil, one or more of which can be provided with a device according to the invention; - Figure 7 A measuring system associated with a Rogowski coil is shown, which measuring system can be provided with a device according to the invention; - Figure 8 The test signal and the detected secondary signal are shown; - Figures 9A-9C The voltage ( Fig. 9A ) and current ( Fig. 9B ) waveform examples, including simulated defects, Fig. 9CShows Fig. 9B The enlarged part. DETAILED DESCRIPTION

[0027] Figure 3 An embodiment of the present invention is shown in FIG.

[0028] It is applied to the Rogowski coil 4, for example as above in combination Figure 1A As disclosed, the coil 4 is arranged around a conductor 2 in order to measure the current flowing in the conductor. The coil 4 generates a secondary voltage signal which is supplied to an integrator 6 which forms part of a protection system 8 which controls one or more protection devices, such as one or more switches and / or circuit breakers 15, for example in the event of an overcurrent.

[0029] A test device 20 according to one embodiment of the invention is connected to the conductor 13 between the coil 4 and the integrator 6 so as to inject in said conductor a current representative of the signal at the terminals of the coil 4 while it is measuring the current circulating in the conductor 2. In other words, a test current of a few A or tens of A (for example between 1 A and 50 A or 100 A) results at the outlet of the test device 20 in a current quite comparable to the current generated by the coil when a primary current of tens of kA circulates in the conductor 2.

[0030] The test device 20 comprises a current generator or source 21 capable of generating a current of, for example, between 0 and 100 A and an interface tool or device 22. Alternatively, a voltage source may be used instead of the current source and impedance 220 (see below), but a current source is preferably used in order to simulate the primary current.

[0031] Figure 4 A more detailed representation of one embodiment of the testing apparatus 20 is shown.

[0032] The generator 21 comprises an electronic circuit 210 which controls an AC source 213 to generate a first alternating voltage between its outlet terminals 211, 212. The terminals can be connected to the inlet terminals 221, 222 of the interface device 22. Thus, the generator 21 is able to supply a voltage (a first alternating voltage) to the interface device 22. This first alternating voltage applied to the resistor 220 and the capacitors 223, 224 of the interface device is able to generate a test voltage V representing the voltage at the terminals of the coil 4. 测试 .

[0033] The generator 21 may further comprise one or more memories 214 to store waveform data in order to simulate one or more defects, such as overcurrent or overintensity or overvoltage on one or more phases, to test components or assemblies downstream of the coil 4, including the protection device 8. An overcurrent (respectively, an overvoltage) is a current (respectively, a voltage) that the machine cannot accept except for a very short period of time: the machine has a rated current that it can accept permanently, for example 3000A eff, but it can accept an overcurrent higher than the rated current (for example at least 2 times the rated current) only for a short period of time (for example a few tens of ms and a few seconds, or between 50 ms and 5 s); after the end of this period of time, the machine must be stopped or the current interrupted.

[0034] An operator and / or computer or controller may select one or more of these data files, and the electronic circuit 210 may provide a corresponding signal to the system (interface device 22) that includes or simulates the one or more simulated defects.

[0035] The interface device 22 comprises a resistor 220 and input terminals 221, 222 to supply said resistor 220 with the output voltage provided by the generator 21. The resistor 220 has a value such that the alternating current i1 circulating therein represents the primary current normally circulating in the conductor 2, for example between 50 and 100 kA.

[0036] As explained below, the value of resistor 220 may be adapted depending on the test being performed.

[0037] The terminals of the resistor may be connected to the outlet terminals 231 , 232 of the interface device 22 (eg via one or more capacitors 223 , 224 ).

[0038] The one or more capacitors 223, 224 are test capacitors. In particular, this / these (one or more) capacitors will block any DC or DC voltage component so that it is not supplied to the system including the conductor 13 and the protection device 8. As explained below, the value of these (one or more) capacitors can be adapted depending on the test performed.

[0039] The voltage between the outlet terminals 231 , 232 represents or is fairly comparable to the secondary voltage at the outlet of the coil 4 ; for example, it is comprised between 0.5V and 10V.

[0040] The interface device 22 may further include a microcontroller 226 and a display device 228, as explained below.

[0041] The outlet terminals 231, 232 of the interface device 22 can be connected to the conductor 13 (upstream of the protection system 8) via a test plug or connector 131, 132 of said conductor. Thus, the system 20 can provide a test signal (voltage) to the conductor 13, which is very similar to the secondary voltage generated by the coil 4 detecting the primary current in the conductor 2. The test signal allows testing the conductor 13 and all other components between (and including) the coil 4 and the system 8, which includes the integrator 6 and the compensation stage 61 (this stage is fed with information about the sensitivity and / or resistance and / or inductance of the coil 4 from a memory (e.g. an 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 defects such as over current or over strength and / or ground faults.

[0042] In particular, it is thus possible to test the one or more protection devices of the system 8, 15: if the testing device 20 injects a signal comprising one or more defects into the conductor 13, but the protection device does not trigger the switch or circuit breaker 15 and / or does not interrupt the current circulating in the conductor 2, it is determined that the protection system is not working correctly and that a check and possible repair should be carried out. In other words, the simulated defect is seen by the system and it is possible to check whether a signal for opening the switch(es) and / or the circuit breaker(s) 15 is generated. If the protection device triggers the switch or circuit breaker 15 or interrupts the current circulating in the conductor 2, it is determined that the protection system is working correctly.

[0043] A signal representing the current inside the system 8 can be derived via a conductor 93, which can be connected, for example, to test plugs 831, 832 of a conductor 83, which connects the memory 80 to the compensation stage 61. This signal can be supplied to the input terminals 241, 243 of the interface device 22 and then, for example, to the microcontroller 226 and to the display device 228.

[0044] Figure 8 is an example of a test voltage (curve I) generated by a test device according to the present invention, and curve II (90° out of phase with respect to curve I) is the voltage measured or detected between plugs 831, 832.

[0045] Depending on the signals received from the system 8, the microcontroller 226 can be programmed or adapted to adjust the parameters of the electrical components of the interface device 22, such as the resistor 220 and / or the capacitor(s) 223, 225. One or more data of the memory 80 (in particular the one or more data mentioned above about the coil 4) can also be provided to the microcontroller 226. The Rogowski coils can have different properties from each other, in particular different sensitivities; therefore, information about these properties (e.g. sensitivity) can be read from the memory 80 and can be used when adjusting the electrical components of the interface device 22.

[0046] Figure 5 The above combination Figure 4 Equivalent diagram of the disclosed circuit together with the integrating stage 6, which forms part of the protection system 8. Reference numerals refer to the same elements or components as above. Reference numeral 213' is a current source connected to the terminals of the resistor 220. The Rogowski coil 4 is represented by a resistor 42 and a capacitor 41. The secondary signal generated by the coil 4 is integrated by the integrator 6.

[0047] When the test according to the invention has to be carried out, any current flow in the primary circuit (in conductor 2) is interrupted. The Rogowski coil thus does not generate any secondary voltage and is ready for the test.

[0048] For the test, the system 8 and the conductor 13 remain connected to the coil 4. Figure 4 As shown in FIG. 1 , the interface device 22 is connected to the generator 21 and to the conductor 13. Thus, the test circuit is connected to the Rogowski coil 4 in parallel.

[0049] The current source 213 ′ generates a test current I T , the test current I T Indicates defect current, such as short-circuit current.

[0050] The test current flows mostly through the resistor 220 (which has a relatively small impedance R relative to the impedance of the other branches of the circuit (capacitors 222, 223 and coil 4). 220 ); for example: 10xR 220 <Z CT1 +Z4+Z CT2 .

[0051] When the primary current is flowing in the conductor, the voltage at the terminals of 220 (for example, for 5A and R 220 =0.2Ω is 1V) is quite comparable to the voltage at the terminals of the coil 4. The voltage U between the terminals of the resistor 220 RS (with current I TThe voltage between the terminals of capacitors 223 and 224 and the terminals of coil 4 is equal to U RS =V C1 +V C2 +V test . V test The behavior of the Rogowski coil 4 in response to the primary current is simulated and depends on the respective values ​​of the capacitors 223, 224 of the resistor 42 and the inductor 41. Preferably, the values ​​of the capacitors 223, 224 and the resistor 42 are selected so that when the coil 4 is subjected to the primary current I T When V test is comparable to the voltage at the terminals of coil 4. The values ​​of capacitors 223, 224 are also preferably selected so that V test With respect to the current generated by generator 213', the phase is shifted by 90°, as Figure 8 As shown in (curve I is the test voltage, and curve II is the current, for the circuit shown in this figure and having the following characteristics: R 220 =200mΩ, C 224 =C 223 = 6 μF): For this reason, their impedance is preferably greater than the impedance L of the coil 41. 线圈 Much higher (10xZ 41 <Z CT1 +Z CT2 )

[0052] The one or more capacitors CT1, CT2 behave like coupling capacitors, allowing the derived or tested alternating current to flow in the Rogowski coil, which is in an idle state (no primary current is flowing in conductor 2). The voltage generated at the terminals of the Rogowski coil reflects the behavior of the coil as if it were detecting current in the conductor.

[0053] When a current (primary signal) flows in the conductor 2, the Rogowski coil generates a secondary signal, wherein the resistance of the coil does not play any significant role.

[0054] The test performed according to the invention exploits the resistance of the Rogowski coil (by passing a current therethrough) to generate a secondary voltage independently of the Rogowski effect.

[0055] Example values ​​that may be used for a test device according to the present invention are as follows: - Effective current (rms) I T , - a resistor 220 between 0.1Ω and 1Ω; - Voltage amplitude U of about 1V RS ; - capacitors 223 and 224 each between 1 μF and 10 μF; - R between 10Ω and 100Ω 线圈 (resistance of resistor 42); - L between 10μH and 200μH 线圈 (inductor 41); - V between 10mV and 100mV 测试 The effective voltage (rms) (e.g., with a V of up to 10 V) 测试 peak value); - Current I between 1 μA and 10 μA 测试 .

[0056] A more precise value will be chosen based on the actual characteristics of each system.

[0057] The testing device according to the present invention provides the following advantages.

[0058] The main circuit (including the coil 4 , the conductor 13 and the system 8 ) is protected from common mode signals through the capacitors 223 , 224 .

[0059] A defect in the Rogowski coil (e.g. a cut or short in wire 3) can be detected as it will affect V 测试 In practice, the entire chain from and including the Rogowski coil 4 to the complete protection system 8, including any filtering and / or integration stages, can be tested, which is not the case with digital signals that are usually sent directly to the protection system 8 (e.g. Figure 2A middle).

[0060] Just as with conventional circuits, complex waveforms may be injected through the test circuit in accordance with the present invention.

[0061] The test circuit according to the invention allows injecting into the protection circuit 8 and the coil 4 a current of the order of a few amperes, which represents a primary current (in the conductor 2 ) of tens or hundreds of kA.

[0062] When implementing the test device according to the invention, the primary circuit circulating in the conductor 2 is interrupted and therefore no voltage is generated by the Rogowski coil 4. A test implementing the invention can be performed.

[0063] The invention is disclosed in connection with one conductor 2 or one phase.

[0064] Figure 62 shows a housing 60 containing three conductors 2, 102, 202 (e.g. conductors of a 3-phase system), around each of which a Rogowski coil 4, 104, 204 is arranged. Each of these coils can be tested with a test device or a test method according to the invention. For example, the same test device 20 can be connected in series to the conductor 13 associated with each of the three Rogowski coils.

[0065] In any embodiment according to the present invention, the signal from each test can be provided to a control unit, such as a computer or controller or microprocessor (not shown in the drawings), to sample and / or process the signal; it can generate such as Fig. 9A The test signal shown in includes certain defects. Fig. 9A The test voltages for each of the three phases are shown, including a simulated defect at about t=0.1 (a sudden drop in voltage on two phases) which generates a surge in the current i of these phases (see Fig. 9B ). Device 21 or 210 ( Figure 3 , 4 ) can be programmed so that an alarm is triggered when the analog current increases above a threshold of 300 (here approximately 5A).

[0066] Figure 7 2 shows a Rogowski coil 4 implemented around a conductor 2. The signal from the coil can be sent to a converter 32 to convert the signal into an optical signal. Other signals from one or more other sensors (such as a capacitive sensor 34) can also be converted into optical signals by a converter 36. The optical signals can be merged in a merging unit 28. The merging unit may include a microprocessor to process the data and may have computing capabilities. The Rogowski coil 4 can be tested according to the teachings of the present invention. The same system can be implemented for several coils, such as for example Figure 6 Same as in.

[0067] The test device 20 according to the invention can be easily disconnected from and connected to the test plugs 131, 132 of the conductors 13 connected to the terminals of the Rogowski coil 4. Therefore, the test according to the invention does not require the implementation or activation of any switching elements that could cause interference. In fact, the current circulating on the secondary side of the Rogowski coil is quite weak: if the conductors have to be interrupted to carry out the test, other tests (i.e. continuity tests) should be performed to reconnect the conductors (the contact impedance of the connection may cause a signal attenuation).

[0068] The test device 20 according to the present invention provides flexibility because the interface device 22 can be: - disconnected from conductor 13 and connected to conductor 13 of another Rogowski coil; - and / or disconnected from the generator 21 and connected to another test signal generator.

Claims

1. A testing 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, said test voltage comprising an overvoltage; - a transformation component (22) for transforming the test voltage into a voltage comprised between 0.5 V and 10 V, the transformation component (22) comprising an output terminal (231, 232) for connection to a conductor (13), the transformation component (22) comprising a capacitive circuit; - means (226) for processing the output voltage of the coil and detecting whether the protection device (15) of the coil is triggered.

2. The device as claimed in claim 1, wherein the transformation component (22) and the capacitive circuit include at least one or at least two capacitors (223, 224, CT1, CT2).

3. The device as claimed in claim 2, said transforming means (22) comprising at least one resistor (Rs, 220) connected in parallel to said at least one capacitor (223, 224, CT1, CT2).

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

5. The device as claimed in claims 1 to 4, said means (21) for generating a test voltage comprising an alternating current generator (21).

6. The device as claimed in claim 5, wherein the AC generator (21) comprises a controller (210) and at least one memory (214) for storing data of at least one, preferably several waveforms that can be used for testing.

7. An apparatus as claimed in any one of claims 1 to 6, wherein the transformation component (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 a component (226) for changing at least one electrical characteristic of at least one of the electronic components.

8. The apparatus of claim 7, said means (226) being capable of changing at least one electrical characteristic of at least one of said electronic components based on one or more tests performed on the coil (4).

9. The device as claimed in any one of claims 1 to 8, wherein the transforming 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), comprising connectors (131, 132) on said conductor (13) for connecting a test device according to any one of claims 1 to 10.

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