Accumulator operated relay test device 1

Abstract

A method and test device for testing protection relays, the test device having a signal generator. The signal generator supplies a signal as pulses having pause times, which alternate over time. Signal level is reduced during the pause times and at least one pulse has an amplitude at least higher than one of the preceding pulses. A supply voltage is supplied by an accumulator providing electric energy for generating the pulses. Via the accumulator, a greater mobility and flexibility is ensured, and fuel-fed power units or emergency power units may be omitted. In order to reduce the load (average energy) on the accumulator, the signal generator emits the signal as pulses having pause times. The pulse amplitudes may have an increasing trend to reach a switching threshold. This allows the use of smaller and more compact, which is important for a portable test device.

Claims

1. A method for testing a protection relay comprising: generating a signal in a test device, and supplying the signal to the protection relay, wherein the test device includes a signal generator configured to output the signal as pulses having pause times, wherein the pulses of the signal and the pause times alternate over time, the level of the signal is reduced during the pause times and at least one pulse has an amplitude which is higher than at least one of a preceding pulse, and supplying a supply voltage from an accumulator to the test device as electric energy for generating the pulses.

2. The method of claim 1, wherein the signal represents a voltage or a current.

3. The method of claim 1, wherein the protection relay switches within a reaction time after the signal has reached a signal threshold, and the method further comprising determining in the test device a level of the signal upon reaching the signal threshold.

4. The method of claim 3, further comprising determining the reaction time.

5. The method of claim 1, wherein amplitudes of the pulses of the signal increase over time.

6. The method of claim 1, wherein the pause times depend on an amplitude of at least one pulse of the signal.

7. The method of claim 1, wherein the signal during the pause times is smaller than 1% of a preceding pulse.

8. The method of claim 1, wherein an adaptation device is supplied with the supply voltage, and the method further comprises supplying the signal generator with an intermediate voltage by the adaptation device.

9. The method of claim 8, further comprising deactivating at least a part of the adaptation device by an emergency-off circuit.

10. The method of claim 1, wherein a form of the signal is determined by a control unit and a result of the control unit is processed by a digital/analog converter in order to generate the signal (S) and the digital/analog converter drives the signal generator.

11. The method of claim 5, wherein the amplitudes of the pulses increase over time by a fixed signal difference.

12. The method of claim 7, wherein the signal during the pause times is zero.

13. The method of claim 1, further comprising deactivating at least a part of the signal generator by an emergency-off circuit.

14. A test device for testing a protection relay comprising: a signal output configured to output a signal; a signal generator configured for outputting the signal in a form of pulses having pause times, wherein the pulses of the signal and the pause times alternate over time, a level of the signal is reduced during the pause times and at least one pulse has an amplitude which is at least higher than one of a preceding pulse; and an accumulator, which provides a power voltage for the test device.

15. The test device of claim 14, wherein the test device comprises an adaptation device configured to convert the power voltage into an intermediate voltage to be supplied to the signal generator.

16. The test device of claim 15, wherein the adaptation device comprises at least one of a step-up converter or a step-down converter.

17. The test device of claim 14, wherein the signal generator comprises at least one of a voltage source or a current source.

18. The test device of claim 14, wherein the signal output comprises a plurality of signal outputs that are configured to output a plurality of signals.

19. The test device of claim 14, further comprising an emergency-off circuit configured to deactivate at least a part of the signal generator.

20. The test device of claim 14, wherein the accumulator has an energy density of at least 500 J/g.

21. The test device of claim 14, wherein the test device is configured as a portable test device.

22. The test device of claim 14, further comprising a control unit configured to determine a form of the signal and a digital/analog converter configured to process a result of the control unit in order to generate the signal.

23. A test arrangement comprising the test device of claim 14, wherein the test device is connectable to a protection relay, having a signal input and a switching output, so that the signal output from the signal output of the test device is supplyable to the signal input of the protection relay, and a reaction input of the test device is connectable to the switching output of the protection relay.

24. The test device of claim 15, further comprising an emergency-off circuit configured to deactivate at least a part of the adaptation device.

Description

(1) The present invention is explained in the following with reference to FIGS. 1 to 6, which show, as an example, schematically and in a non-limiting way, advantageous embodiments of the invention. In particular:

(2) FIG. 1 shows a protection relay 2 in a power supply network 6

(3) FIG. 2 shows a protection relay 2 which is connected to a test device 4,

(4) FIG. 3 shows a possible structure of a test device 4,

(5) FIG. 4 shows the plot of a signal S having fixed pause times .sub.1=.sub.2=.sub.3=.sub.4=.sub.5

(6) FIG. 5 shows the plot of a signal S having a pulse threshold S.sub.1

(7) FIG. 6 shows the plot of a signal S having strictly monotonic increasing pause times .sub.1<.sub.2<.sub.3<.sub.4<.sub.5

(8) In FIG. 1 a protection relay 2 is connected via the signal input SE and the switching output A with the electrical power supply network 6. The electrical power supply network 6 can also be a line section or a line branch of a large power network. An optionally present signal converter 1 measures a presignal S.sub.n (primary variable)when the signal is represented by a current, the signal converter 1 is usually designed as a current converter or current sensorof the power supply network 6 and converts this into a signal S (secondary variable), which is supplied to the protection relay 2 via the signal input SE. For example, in low-voltage networks, it is also possible to supply the secondary signal S.sub.n directly to the protection relay. For example, in the case of a function as overcurrent time protection, the protection relay 2 is designed such that it switches the switching output A, and thus opens the associated circuit breaker 3 of the electrical power supply network 6 as soon as a specific preset signal threshold S.sub.s is exceeded for a fixed period of time. Thus, the electrical circuit of the power supply network 6 (or of the respective network segment) is interrupted, whereby, for example, protection against overcurrents is ensured in the electrical power supply network 6.

(9) In order to determine the signal threshold S.sub.s at which the protection relay 2 actually switches, the protection relay 2 is disconnected from the power supply network 6 and connected to a test device 4, as shown in FIG. 2. The test device 4 has a signal output SA and a reaction input R. For the functional test, the connection from the protection relay 2 to the signal converter 1 (or, if no current converter is present, the connection to the power supply network 6) and to the power switch 3 is interrupted and the signal output SA of the test device 4 is connected with the signal input SE of the protection relay 2, as well as the switching output A of the protection relay 2 is connected with the reaction input R of the test device 4. The test device 4 in turn is supplied by a accumulator 5, which is preferably integrated in the test device 4, via a supply input V with a supply voltage U.sub.v. To test the protection relay 2, a signal S is sent from the test device 4 to the protection relay 2.

(10) If, for example, the protection comprises an over-current time protection, the protection relay 2 switches within a reaction time t.sub.A after the signal S has reached the signal threshold S.sub.S to be determined. The test device 4 determines the level, i.e. the amplitude, of the signal S, at which the protection relay 2 reacts.

(11) For this purpose, an evaluation unit 7 is provided in the test device 4, which is connected to the reaction input R and detects a switching pulse of the protection relay 2 which is output at the switching output A.

(12) A signal generator G outputs the signal S as pulses P with pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5, at the signal output SA, whereby the pulses P of the signal S and pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 alternate over time t (FIG. 3). During the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5, the amplitude of the signal S is lowered to a low value, for example 1% of the previous amplitude or even zero. At least one pulse P has a higher amplitude than at least one of the preceding pulses P in order to reproduce an ascending signal S, as shown in FIG. 4 in an exemplary manner. By implementing the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5, the accumulator 5 is less stressed.

(13) An embodiment in which also the response time t.sub.A of the protection relay 2 is determined by the test device 4, preferably in the evaluation unit 7, is also particularly advantageous. The response time t.sub.A of the protection relay 2 thus describes the time from the signal S reaching the signal threshold S.sub.s until the switching of the reaction output R.

(14) An adaptation device X located in the test device 4 can convert the supply voltage U.sub.V of the accumulator 5 into an intermediate voltage U.sub.x, which in turn supplies the signal generator G, as also shown in FIG. 3.

(15) The adaptation device X can convert high voltages into low voltages and low currents into high currents, or vice versa, too.

(16) This adaptation device X may include a step-up converter and/or a step-down converter.

(17) Moreover, at least part of the adaptation device X and/or of the signal generator G can be deactivated by means of an emergency-off circuit N, as required.

(18) This part of the adaptation device X may, for example, comprise power electronics, which is part of a converter circuit. Since high currents are difficult to separate cleanly, it is possible to realize an emergency-off circuit N, with the targeted deactivation of (redundant) circuit parts, such as, for example, the power electronics.

(19) The test device 4, or the signal generator G, may include a voltage source and/or a current source and generate a voltage or current signal S.

(20) In addition, the form of the signal S can be calculated by a control unit E, wherein the result of the control unit E is processed by a digital/analog converter DAC for generating the signal S and the digital/analog converter DAC drives the signal generator G.

(21) For this purpose, an input unit 8 may be provided in the test device 4, which is connected to the control unit E, through which for example a determined test to be executed may be set up. The control unit E and the digital/analog converter DAC can be located in the signal generator G.

(22) Furthermore, the signal generator G can have n>1 signal outputs which generate n signals S.sub.n so that a protection relay 2 of a multi-phase network can be tested simultaneously for all n phases.

(23) Advantageously, n=3, whereby a three-phase network can be simulated. Thus, a three-phase protection relay 2 can be tested. However, the n signals S.sub.n do not necessarily have to be the same.

(24) Furthermore, the test device 4 can have a second number of reaction inputs R in order to detect different reactions of the protection relay 2, such as, for example, a triggering or an excitation.

(25) A signal S is generated at a certain level (amplitude) over a pulse duration t.sub.s and lowered after the pulse duration t.sub.s for a pause time .sub.1, .sub.2, .sub.3, .sub.4, .sub.5. Pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 in the range of 500 ms to 1 s are the rule. The length of the pulse duration t.sub.s must be at least as great as the response time t.sub.A of the protection relay 2, since otherwise the correct function of the protection relay 2 can not be tested. At least a pulse duration t.sub.s of 10 ms is required in most cases, usual pulse durations t.sub.s are approximately 30 ms, but pulse durations in the second range are also possible. The decisive factor here is the reaction time t.sub.A of the protective relay 2, which in turn depends on the level of the signal to be switched. A higher current has normally to be switched faster, i.e. with a shorter reaction time t.sub.A than for a lower current.

(26) The pulse duration t.sub.s is shown as a constant in FIGS. 4 to 6, but may also vary, for example, depending on the magnitude of the signal S. This can be used, for example, to keep the energy of a pulse P low by reducing the pulse durations t.sub.s with increasing amplitude. After the pause time .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 has elapsed, the signal is supplied, increased by the signal difference S for a further pulse duration t.sub.s, whereupon again a pause time .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 follows. This advantageously takes place until the protection relay 2 responds or triggers. Advantageously, the signal difference S is always constant and positive. However, it is also conceivable that the signal difference S is variable, or negative or zero in sections, which may depend, for example, on the current level of the signal S. In order to reach the signal threshold S.sub.s, however, at least one pulse P must have a higher amplitude than at least one of the preceding pulses P, unless the amplitude of the first pulse P of the signal S reaches the signal threshold S.sub.s. In this case, the protection relay 2 switches immediately.

(27) The pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 of the signal S which continue between the individual pulses P of the signal S can always have the same length, but also depend on the current amplitude of the signal S or another factor.

(28) Since the choice of the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 preferably depends on the selected pulse duration t.sub.s, it is therefore possible to react both to variable pulse durations t.sub.s, and the average energy of the pulses P may be lowered in sections, for example. A lower energy consumption of the test device 4 and thus a lower energy absorption from the accumulator 5 will result in a lower load on the accumulator 5.

(29) FIG. 4 shows an exemplary plot of a signal S over time t. The dashed envelope of the pulses of signal S interrupted by pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 indicates the rising signal S, wherein in this example the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 are constant and the level of successive pulses P of the signal S at a constant signal difference S increases linearly.

(30) A plot according to FIG. 5 is also possible, in which the pause times .sub.1, .sub.2, are increased as soon as the amplitude of the current pulse P of the signal S reaches a pulse threshold S.sub.1. With a constant signal difference S, this results in the envelope shown with a dashed line in the form of a rising signal S, wherein the slope of the signal S is being reduced after reaching a pulse threshold S.sub.1. The advantage of increasing the pause times with increasing amplitude lies in the fact that the average accumulator load must not increase with amplitude, since the longer pauses can compensate for the increasing power requirements for the pulses.

(31) In the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 the level of the signal S is reduced. Advantageously, the signal S in the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5, may be set to a value of less than 1% of the previous pulse P, or even to zero, as shown in FIGS. 4-6, which can extend the life of the accumulator 5.

(32) Advantageously, the accumulator 5 can have an energy density of at least 500 J/g.

(33) Advantageously, the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 increase continuously as the signal S increases. The pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 can thus be strictly monotonically increasing from pulse P to pulse P, resulting in a dashed envelope for the signal S with a slope reduced over time t. This embodiment is also shown in FIG. 6 with a constant signal difference S.

(34) Of course, it is also conceivable that the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 are reduced (for example, in sections), or remain constant in sections.

(35) Of course, mixed variants of the just mentioned profiles, as well as further variations of the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 as well as of the signal difference S are possible depending on the current amplitude of the pulse P. Thus, for example, a plurality of pulse thresholds S.sub.1 may be present and the signal difference S and/or the pause times .sub.1, .sub.2, .sub.3, .sub.4, .sub.5 may be changed several times.

(36) The test device 4 can be have a portable configuration, due to the low weight, by using an accumulator 5, which is particularly advantageous for a use in the field.