WO2017220465A1

WO2017220465A1 - Testing device and method for testing a monitoring device with travelling wave capture

Info

Publication number: WO2017220465A1
Application number: PCT/EP2017/064887
Authority: WO
Inventors: Heinz Lampl; Thomas Hensler
Original assignee: Omicron Electronics Gmbh
Priority date: 2016-06-20
Filing date: 2017-06-19
Publication date: 2017-12-28
Also published as: EP3472635A1

Abstract

In order to make it possible to test a monitoring device with travelling wave capture in the field, as are also installed in real operation, provision is made for the temporal profile of a low-frequency fault voltage (U_F(t)) and/or the temporal profile of a low-frequency fault current (I_F(t)) of a fault (F) on a current conductor (3) and the time (t_A, t_B) at which a travelling wave (W) starting from the fault location (F) arrives at a predetermined location (x, L-x) of the current conductor (3) to be calculated in the testing device (10), and for a voltage amplifier (14) for generating the temporal profile of the low-frequency fault voltage (U_F(t)) and/or a current amplifier (15) for generating the temporal profile of the low-frequency fault current (I_F(t)) to be controlled by a control unit (11) in the testing device (10) in order to output the low-frequency fault voltage (U_F(t)) at a voltage output of the testing device (10) and/or the low-frequency fault current (I_F(t)) at a current output of the testing device (10), and for a voltage pulse generator (16) for generating a voltage pulse and/or a current pulse generator (17) for generating a current pulse to be controlled by the control unit (11) at the calculated time (t_A, t_B) of the arrival of the travelling wave (W) in order to superimpose a voltage pulse on the fault voltage (U_F(t)) and/or to superimpose a current pulse on the fault current (I_F(t)).

Description

Test apparatus and method for testing a traveling wave detection monitor

The present invention relates to a test apparatus for testing a traveling wave detection monitor, and a method of testing a traveling wave detection monitor.

An energy transmission network essentially consists of energy generators, switchgears, substations and power lines (overhead lines or underground cables). To the power transmission network electrical consumers are connected. Furthermore, as a rule, there are still various monitoring and safety devices which switch off certain network sections, for example in the case of faults in the energy transmission network. The power lines extend over many kilometers. An important functionality of the monitoring of a power transmission network is therefore not only the detection of errors, but also the most accurate location of errors. The faster an error is detected, the faster the network section can be switched off. The more accurately the fault location can be determined, the quicker a fault can be found and corrected by the maintenance personnel and the faster a disconnected network section can be switched on again. There is a wealth of methods for error detection and fault location in the prior art.

One of these methods is the method of detecting traveling waves. This method is based on the fact that in the event of a fault starting from the fault location, a traveling wave propagates in both directions via the power line. The time that elapses until the traveling wave is detected in a stationarily arranged protective device can be measured and concluded therefrom with the known propagation speed of the traveling wave to the fault location. After a traveling wave can also be triggered on other events on the power line, for example in the case of a switching operation, these methods can also distinguish between errors and other events. When traveling wave process often the arrival of a traveling wave at both ends of a conductor is detected with two temporally exactly synchronized protection devices, which allows easy determination of the fault location. This method is described, for example, in Schweitzer EO, et al., "Locating Faults by the Traveling Waves They Launch", 40th Annual Western Protective Relay Conference, Oct. 2013. The traveling wave is highly transient with flank rise times in the range of a few 100ns and can In high-voltage networks, the traveling wave on the conductor can reach peak currents of a few 100 to 1000 A and voltage peaks of a few 100 to 1000 kV., These are usually very high primary currents and voltages on the power line via current / voltage converter on transformed lower secondary values and these supplied to the protection devices. On the secondary side, too, high current and voltage peaks occur. In addition, from the shape of the traveling wave can also be closed to certain types of errors, for example, a single-pole ground fault (short circuit of a conductor to ground) generates a different traveling wave than a conductor-conductor fault between two conductors. The method of detecting traveling waves enables a very rapid and accurate detection and location of errors. In a new generation of protection devices, the method of detecting traveling waves is therefore used not only to detect and locate a fault, but also to generate a tripping pulse for switchgear for disconnecting network sections.

However, the method of traveling wave detection is not only used in protective devices, but also in fault locations, ie in devices that are used only to locate a fault, or fault recorder, so devices only record the error. Protective devices, fault locators and fault recorders, as well as other devices for monitoring and / or diagnosing an energy transmission network are generally referred to below as monitoring devices.

Monitoring devices are placed in power transmission network fixed at specific locations. For safety reasons, the monitoring devices must be checked for proper operation during commissioning and, as a rule, also at regular intervals. In this case, a monitor is tested directly in the field on site by the monitor is separated from the power transmission network and / or connected to a switchgear and is connected to a special tester. The tester can be used to simulate various network conditions and to check the correct response of the monitor to it.

The testing of this traveling wave functionality in monitoring devices, however, is very difficult, since an error not only generates a traveling wave with very high-frequency current / voltage curves, but also has low-frequency current / voltage components. Conventional testers have only a limited bandwidth in the kHz range, i. currents and / or voltages can only be output in this frequency range. This is sufficient for conventional tests because only the fundamental (mains frequency typically 50 or 60 Hz) and some harmonics must be covered for the test. A high-frequency traveling wave (with frequencies in the MHz range) can not be simulated with such conventional test equipment due to the limited bandwidth. Conventional testing devices can therefore not simulate realistic current / voltage characteristics of a traveling wave. On the other hand, high bandwidth amplifiers (in the MHz range) that use high frequency current

/ Voltage waveforms are not available for field testing because they can not simultaneously provide the necessary low frequency current and voltage values. NEN. For example, the low-frequency fault currents can be up to 100A (secondary values). So it would be an amplifier required, on the one hand can generate very high currents and voltages and on the other hand, at the same time can generate very high-frequency currents and voltages. In addition, such amplifiers usually can not provide the required for the replica of a traveling wave steep flanks of the current and / or voltage signals. In addition, for a field test in a system with monitoring devices at both, or even more ends, the power line must also use multiple distributed test equipment, which further complicates the test.

A practicable testing such monitoring devices with traveling wave detection in the field is therefore not known until today. Today's standard is the testing of the monitoring equipment in the laboratory before commissioning in the field. In many cases, in the laboratory, after the input transducers in the monitoring device, which convert the high voltages and currents (secondary values) into small, processable electrical signals, a high-frequency small signal is simulated to simulate a traveling wave. A complete check of all functions of the monitoring device is thus no longer possible. In addition, this procedure in the field is hardly practicable, as to the monitor would have to be opened.

The object of the invention is therefore to specify a test device and a test method for a monitoring device with traveling wave detection, which enable an integrated test of the monitoring device in the field, as they are also installed in real operation.

This object is achieved with the features of the independent claims. It is not necessary to simulate the high-transient wave propagation for testing the monitoring device; it is sufficient to apply the low-frequency fault currents and / or error voltages to the monitoring device if a high-frequency current and voltage pulse superimposes these low-frequency error variables at the correct time to simulate the arrival of the traveling wave becomes. This separation of the low frequency and the high frequency error components makes it possible to use simple voltage amplifiers and current amplifiers. Likewise, it is also possible to use simple pulse generators for generating the voltage and current pulses. In this way, realistic tests on monitoring devices with traveling wave detection can be realized directly in the field with simple means.

In order to be able to generate the voltage pulses and / or current pulses at the correct time, it is advantageous if a synchronization interface is provided on the test device in order to connect the test device to a, preferably high-precision, time synchronization source. This is particularly advantageous when several test equipment must work together for a test. If a test control unit is provided as part of the test apparatus, wherein the simulation unit is implemented in the test control unit, several distributed monitoring devices can be tested particularly advantageously. All that is required is to connect the test control unit to the several testers for testing the monitoring equipment. The fault simulation can then be carried out centrally on the test control unit. For this purpose, the testers are preferably synchronized with one another in terms of time.

The subject invention will be explained in more detail below with reference to Figures 1 to 5, which show by way of example, schematically and not by way of limitation advantageous embodiments of the invention. It shows

1 shows a topology of a power transmission network with monitoring devices,

2 shows the principle of traveling wave detection,

3 shows a test configuration for testing the monitoring devices by means of testing devices according to the invention,

4 shows an embodiment of a test device according to the invention and

5 shows a preferred embodiment of the tester for testing several involved

Monitoring equipment.

1 shows schematically a part of a power transmission network 1 with a line section 2 with a power line 3. The power line 3 can be designed as an overhead line or as underground cable, which is irrelevant to the invention. With A, B, the ends of the line section 2 and the power line 3 are designated. The ends A, B are often provided by substations 4 or switchgear 5. At the ends A, B, monitoring devices 6 are also often provided in power transmission networks 1, e.g. the error detection and fault location are used. The monitoring devices 6 can also trigger switching operations of a switchgear 5, as indicated by dashed lines in Figure 1. As a rule, a monitoring device 6 detects the voltage and / or the current on the power line 3 in order to fulfill its function. Of course, an energy transmission network can also be multiphase. In this case, monitoring devices 6 may be provided at each phase, or multi-phase monitoring devices 6 may be used. Similarly, other network topologies are conceivable. For example, could also branch off between the ends A, B in Figure 1, a further power line, as indicated by dashed lines in Figure 1, at the end C, a further monitoring device 6 could be arranged.

2, the known principle of traveling wave detection is briefly explained. An error F on the power line 3 generates a current and a voltage pulse which propagates in both directions as a traveling wave W. In addition to this high-frequency traveling wave (in the MHz range), in the event of a fault, low-frequency current and voltage components (in the kHz range). The propagation velocity v _{w of} the traveling wave W is approximately the speed of light and is known. At the ends A, B of the power line 3 monitoring devices 6 are arranged with traveling wave detection, which detect the voltage U _L and / or the current I _L on the power line 3 and evaluate. Before a monitoring device 6, a current and / or voltage converter can also be connected in order to transform the high primary currents and / or voltages on the power line 3 into lower secondary currents and / or voltages which are supplied to the monitoring device 6 , Thus, the time t _A i or t _B i of the arrival of the traveling wave W in the respective monitoring device 6 can be detected. Likewise, the distance L between the two monitoring devices 6 is known. Assuming that the two monitoring devices 6 are exactly synchronized in time, which is indicated by the dashed connection, the fault location x can easily be derived from the relationship

^{X = "} ^ ( ^{L +} ( ^t A ^{" t} B) ^'V w). For this purpose, the monitoring devices 6 exchange the arrival times t _A , t _B. It is also indicated in FIG. 2 that the traveling waves W are also reflected at locations of a change in the propagation medium (power line 3). It thus comes at the monitoring devices 6 to multiple detections of traveling waves W. For the calculation of the fault location x therefore the different arrival times are to be distinguished, which is ensured by the monitoring devices 6. If only one monitoring device 6 is used at only one end A or B, the error location x can be determined from the multiple arrival of the traveling wave W, eg according to x = ^ ^A1 ^ ^A2 ^ · v _w .

To check the monitoring devices 6 with traveling wave detection in the field, the monitoring device 6 or the cooperating monitoring devices 6 are suspended from the power line 3 and connected to a test device 10, as shown in Figure 3. A test device 10 generates a test voltage U _T and / or a test current I _T , which are supplied to the connected monitoring device 6 via its respective voltage and current input. Normally, the tester 10 generates the secondary quantities according to the current / voltage transformers of the power line 3. Alternatively, however, it is also possible to feed the primary variables into the converters, with which the test apparatus 10 would then have to generate the primary variables. For this purpose, of course, appropriate cables for connecting the monitoring device 6 may be provided with a tester 10. Of course, a tester 10 may be executed again multi-phase, for example, to be connected to a multi-phase monitoring device 6. In order to enable a realistic on-site test, a test apparatus 10 generates the temporal current course I _T (t) and voltage curve U _T (t), which at a certain point of the power line 3 in the case of a specific error F at a Failure point x can be expected. The test apparatus 10 is constructed as explained below with reference to FIG.

In the test apparatus 10, a simulation unit 12 (hardware and / or software) is provided, in which the time course of the low-frequency component of the error quantities, ie the low-frequency fault currents l _F (t) and / or low-frequency error voltages U _F (t) are simulated , For this purpose, a line model that simulates these error variables can be implemented in the simulation unit 12. In the simple case, the line model can be a model of the line with fixed quantities. However, a more realistic line model with a dynamic simulation of the transient curves of current and voltage can also be implemented. However, the time profile of the low-frequency component of current and voltage on the power line 3 need not be calculated with particularly high sampling rates. In principle, it is sufficient if the low-frequency fault current I _F (t) and / or the low-frequency fault voltage U _F (t) are calculated, for example, at a sampling rate in the kHz range (that is to say a few current or voltage values per ms) Reduced paperwork. Of course, there is nothing wrong with using a higher sampling rate for the simulation. The simulation thus calculates the low-frequency fault current I _F (t) and the low-frequency fault voltage U _F (t) at a location of the power line 3 which lies at a distance x or Lx from an assumed or predetermined fault location F, thus in particular the time course the low-frequency error quantities at the ends A, B at which the monitoring device 6 is arranged. Low frequency means frequency components between fundamental (50Hz / 60Hz) and harmonics up to the single-digit kHz range, eg 1 -3kHz. The simulation can also simulate various types of faults (eg earth faults, line faults, etc.) with different characteristics. For this purpose, the test can also be configured via a user interface 13, for example by specifying a fault location F and / or a fault type.

The simulated time profile of the low-frequency error variables is fed to a control unit 1 1, which thus controls a voltage amplifier 14 and / or a current amplifier 15, for example via digital-to-analog converter DAC. At the respective sampling instants, the voltage amplifier 14 generates the low-frequency voltage component U _{Tn of} the test voltage U _T requested from the simulation. The current amplifier 15 generates at the respective sampling times the demanded from the simulation low-frequency current component l _{Tn of} the test current l _T. The voltage amplifier 14 and the current amplifier 15 need for this no high bandwidth (no fast voltage or current changes) and can thus be easily realized.

The high-transient (ie high-frequency) traveling wave W, which is detected by a monitoring device 6 with traveling wave detection per se, can thus due to the low Bandwidth, however, can not be generated. For this purpose, a voltage pulse generator 16 and / or a current pulse generator 17 are provided in the test apparatus 10.

In addition to the low-frequency error variables, therefore, the simulation unit 12 also calculates the time t _A , t _{B of} the arrival of the traveling wave W at the location of the monitoring device 6, for example using the above equations. The time t _A , t _{B of} the arrival of the traveling wave W could, however, also be calculated from a highly dynamic simulation model with high sampling rates of the calculation (> 1 MHz). The necessary requirements, such as the distance L between two monitoring devices 6 or a propagation velocity v _{w of} the traveling wave W, are known or can be configured again via the user interface 13 for this purpose. At the determined time t _A , t _{B of} the arrival of the traveling wave W, the control unit 11 activates the voltage pulse generator 16 and / or the current pulse generator 17, which then generate a high-voltage voltage pulse U _T and / or current pulse I _T simulating the traveling wave W low-frequency voltage component U _Tn or the low-frequency current component l _Tn superimposed and output as an error voltage U _T at a voltage output or as a fault current l _T at a current output.

For the voltage pulse U _T and / or current pulse l _Tp , the rising edge of the respective pulse is important, since these are also detected in the monitoring device 6. From the known characteristic of a traveling wave W, flank rise times in the range of several 100ns and pulse durations in Ι Ομβ-ΒβΓβίοϊι at currents in the range of 1 to 100A (secondary value) or voltages in the range of 50 to 250V (secondary value) are typical. These requirements can be achieved with conventional or simply constructed pulse generators.

For the examination of a monitoring device 6, the timing accuracy of the switching on of the voltage pulse U _T and / or the current pulse I _{T is} important because the fault location is determined therefrom. If only one monitor 6 is being tested, it does not necessarily have to be synchronized to one global time. Here, for example, an internal clock is sufficient. If at the same time two remote monitoring devices 6 are tested, but also the most accurate timing synchronization of the two testers 10 is advantageous. The aim is to achieve temporal accuracies in the 100ns range. For this purpose, a test device 10 may also have a synchronization interface 18 to a time synchronization source 19, such as a GPS clock with a typical accuracy of less than 100 ns. On this time synchronization source 19 then multiple testers 10 can synchronize.

When two or more monitors 6 are simultaneously tested in the field, each monitor 6 is connected to a tester 10. Here are different Audit scenarios conceivable. Each involved testing device 10 can control itself, for example, whereby the individual testing devices 10 are synchronized with each other in time in order to simulate the traveling waves W at the right time. One of the testing devices 10 involved could also take over the control of other testing devices 10 involved in the test. In this case, it would also be sufficient to carry out the simulation of the traveling wave W, and possibly also of the low-frequency error variables, only in a test device 10, which can then send the simulation result and / or corresponding control signals to the other test devices 10. For this purpose, the test devices 10 can be connected to one another via a data communication network via which the simulation result and / or the control signals can be transmitted. For this purpose, corresponding data communication interfaces in the test devices 10 are then provided. The temporal synchronization of the test devices 10 could also take place via the data communication network.

In a further possibility, as shown in FIG. 5, a test control unit 20, for example a computing unit with corresponding test software, can be provided, which is connected to the test devices 10 involved in the test. If the two testers 10 are too far apart, the connection may also be realized via suitable data communication interfaces. The test control unit 20 can be used to control the synchronized execution of the test, for example the start of the test. After the tester 10 are synchronized in time, they can each output the test voltage U _T and / or the test Ström l _T synchronized in time. In a preferred embodiment, however, the test control unit 20 may also include the simulation unit 12 and the low-frequency error variables U _F (t), l _F (t) and the times t _A , t _{B of} the occurrence of the traveling wave W at the location of the Monitor monitors 6, as shown in Figure 5. In this case, the test control unit 20 thus forms part of the testing device 10 involved. In the individual test devices 10, only the control unit 1 1 is then available,

Voltage amplifier 14 and / or the current amplifier 15, and the voltage pulse generator 16 and / or the current pulse generator 17 installed.

For a multiphase test apparatus 10, preferably only one simulation unit 12 and control unit 11 are provided, which can simulate the traveling wave propagation of all phases.

The simulation unit 12 can also be integrated in the control unit 11. The simulation unit 12 can also be implemented as software, e.g. as simulation software with a simulation model.

Claims

claims

1 . Test device for testing a monitoring device (6) with traveling wave detection, in which test device (10) a voltage amplifier (14) for generating a low-frequency error voltage (U _F (t)) and / or a current amplifier (15) for generating a low-frequency fault current (l _F (T)), a voltage pulse generator (16) for generating a voltage pulse (U _T ) and / or a current pulse generator (17) for generating a current pulse (l _T ) are provided, wherein the output of the voltage amplifier (14) and the output of the voltage pulse generator (16) are connected to a voltage output of the tester (10) and the output of the current amplifier (15) and the output of the current pulse generator (18) are connected to a current output of the tester (10) and in the tester (10) further comprises a simulation unit (12) is provided, in which a simulation model is implemented, the timing of the low-frequency error voltage (U _F (t)) and / or the low-frequency Error current (l _F (t)) as well as from a given fault location (F) outgoing propagation of a traveling wave (W) on a conductor (3) simulated by the low-frequency error voltage (U _F (t)) and / or the low-frequency fault current (l _F (t)) of the error (F) and the time (t _A , t _B ) of the arrival of the traveling wave (W) are calculated at a predetermined location of the conductor (3), and wherein in the tester (10) further Control unit (1 1) is provided, which controls the voltage amplifier (14) for generating the time course of the low-frequency error voltage (U _F (t)) and / or the time course of the low-frequency fault current (l _F (t)) and the calculated time (t _a, _B t) of the arrival of the traveling wave (W) the voltage pulse generator (16) for generating a voltage pulse and / or current pulse generator (17) controls to generate a current pulse.

2. Testing device according to claim 1, characterized in that on the test device (10) has a synchronization interface (18) is provided to connect the tester (10) with a time synchronization source (19).

3. Testing device according to claim 1 or 2, characterized in that a test control unit (20) is provided as part of the test apparatus (10), wherein the simulation unit (12) in the test control unit (20) is implemented.

4. test arrangement with at least two test devices (10) according to one of claims 1 to 3, characterized in that the at least two test devices (10) are synchronized with each other in time.

5. Test arrangement according to claim 4, characterized in that the at least two test devices (10) are connected to a test control unit (20) with a simulation unit (12) wherein the simulation unit (12) for the at least two test devices (10) in each case the time profile of the low-frequency error voltage (U _F (t)) and / or the low-frequency fault current (l _F (t)) and the time (t _A , t _B ) of the arrival of the traveling wave (W) at a predetermined location (x, Lx) of the conductor (3) calculated.

6. A method for testing a monitoring device (6) with traveling wave detection, wherein the monitoring device (6) is connected to the test device (10) and in the tester (10) the time course of a low-frequency error voltage (U _F (t)) and / or temporal progression of a low fault current (l _F (t)) of a fault (F) on a current conductor (3) and the time (t _a, t _B) of the arrival of a the fault location (F) outgoing traveling wave (W) at a predetermined location (x, Lx) of the current conductor (3) are calculated and in the tester (10) a voltage amplifier (14) for generating the time course of the low-frequency error voltage (U _F (t)) and / or a current amplifier (15) for generating the temporal Low-frequency fault current (l _F (t)) are controlled by a control unit (1 1) to at a voltage output of the tester (10) the low-frequency error voltage (U _F (t)) and / or at a current output of the tester (10) the low-frequency fault current (l _F (t)) and the calculated time (t _A , t _B ) of arrival of the traveling wave (W) a voltage pulse generator (16) for generating a voltage pulse and / or a current pulse generator (17) for generating a current pulse be controlled by the control unit (1 1) to superimpose the fault voltage (U _F (t)) with a voltage pulse and / or the fault current (l _F (t)) with a current pulse.