GB2054872A - Electronic trigger - Google Patents

Abstract

The invention relates to an electronic trigger for a switching device which has separate channels (b,s,k) for responding to an overload and a short-circuit and which has components for processing measured values and supplying voltage, the electronic trigger being provided with special inputs (21) for the connection of a calibrating device capable of simulating the voltage supply and at a low level, the operational signals for the measured values. <IMAGE>

Description

SPECIFICATION Electronic trigger The invention relates to an electronic trigger for a switching device having separate channels for overload and short circuit. These triggers usually have a b-channel for detecting overload currents and an s- and a k-channel for detecting shortcircuit currents. The b-channel operates with a characteristic matched, for example, to the destruction characteristic of the device to be protected or to the characteristic of a bimetal trigger having a thermal delay and is simulated by electronic means. When the set response value is reached or when it is exceeded, the switch is triggered after a delay corresponding to the current/time characteristic.The s- and k-channels serve to detect short-circuit currents; the s-channel is provided with a time delay to make it possible to delay the operation of protective devices in energy distribution devices, while the k-channel operates without any time delay. The current response values of the s- and k-channels may be adjusted continuously. The time delay of the s-channel may be adjusted either continuously or in stages. Furthermore, additional components are provided for detecting the measured values or processing them and for voltage supply. The measurement signals pass from the device processing the measured values to the individual channels in which trigger signals are produced when a fault current occurs and these trigger signals in turn act on an electromagnetic trigger for triggering the circuit breaker.The voltage may be supplied either by an external supply or may be produced by converters located at points along the main current paths.

These triggers are calibrated in known manner, for example, requiring a particularly expensive test device with a test transformer which produces the test current required for calibration and the auxiliary voltages. In order to achieve this, the actual operating conditions have to be simulated and this is very expensive. The normal inputs of the means for processing measured values or for voltage supply are used for calibration. Thus normal operating conditions are produced.

The invention seeks to enable calibration of the above-mentioned triggers with simple means or to check the calibrated values produced by a calibration which has already been carried out.

According to the invention, there is provided an electronic trigger for a switching device having separate channels for responding to an overload and a short-circuit and having components for processing measured values and supplying voltage wherein the electronic trigger is provided with special inputs for connection of a calibrating device capable of simulating operational signals for the measured values and voltage supply.

It is possible, for example, to simulate the measured signals simply and easily and without expense by means of a special calibration device of said type, for example in the form or a small case. Furthermore, the supply voltage for such a trigger may be produced using simple means. In this way it is possible to become independent of a special and expensive test transformer which, in the first instance, would have to be used to produce the currents which are to be monitored and then the measured signals would have to be derived therefrom via measurement converters. In the present case, the measured values, which are small in relation to the large operating currents may be produced directly in the calibration device and may be applied to the special inputs.These special inputs may be provided at the input of the channels and of the supply component and may be connected to the calibration device by means of a calibration connector arranged on the trigger.

This calibration connector is preferably combined with a test connector which is already present, to form one connector only. The invention makes it possible to carry out calibration quickly on site, and moreover makes it easy to adapt to any changed operating conditions. Combining the test connector with the calibration connector makes it possible to check the device as to its functioning and to calibrate the response values, trigger characteristics and delay times.

As soon as the set response values in the b- or s- and k-channel are reached or have been exceeded, the switch may be triggered to means of an electromagnetic operating current trigger connected after the switch. Thus the b-channel may operate with a long delay and the s-channel with a short delay, while the k-channel may not have any delay, i.e. operates only in its natural time. According to the size of the incoming excessive current, the switch is triggered only after a fairly long delay as in the case of the b-channel or after a short delay as in the s-channel. From the point in time when the current response values which have been set are reached until actual triggering of the switch a reiatively large period of time may pass.

The point in time when the set response values in the channels are reached when an excessive current occurs may be detected directly and without delay via the calibration inputs and/or by means of special circuit elements and may be evaluated using corresponding signals of these circuit elements. Therefore it is possible to prepare and/or carry out other subsequent measures at the point in time when the current response values which have been set are reached. Therefore it is no longer necessary to wait until there is a failure in operation. i.e. until finai triggering of the switch in order to be able to take counter-measures.

Rather, it is possible to see without delay whether the set response values have been reached. Even at this time measures may be taken, for example when there is a b-channel having a long delay, without waiting for the actual triggering of the switch. The signals produced when detecting the point in time when an excess current occurs, may by way of example, be immediately indicated by display elements e.g. light-emitting diodes in the trigger circuit elements. Therefore a fault may be indicated long before the switch is actually triggered after a delay.

The signals produced at the point in time when detection of an excess current occurs may be used to implement a particular operation before disconnection of the switching device caused by the relevant channel becomes effective. This may be used with a b-channel with a long delay, for example, to take a direct action in disconnecting another branch at the point in time when the current response value is reached, i.e. before the actual disconnection of the switching device is complete. The same is true in general in the case of an s-channel, which may be delayed briefly.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which Figure 1 shows a block circuit diagram of one embodiment of the invention and Figure 2 shows an example of the embodiment of fig. 1. in a schematic diagram.

In Fig. 1. a three-phase mains current path, shown as 10 which can be interrupted by a contact system 11 of a switching device (not shown in greater detail) with the aid of an operating current trigger 12. The operating current trigger 12 obtains its trigger signals 13 from the electronic trigger shown schematically in the block circuit diagram. Current supply 14 to the electronic trigger is effected via a current converter 1 5 which is located in the switching device on parts of the mains current paths.The measured signals reach a b-channel 18, s-channel 1 9 and k-channel 20 from special measurement converters 1 6 via a measurement value preparation device 17, the said measurement converters 1 6 being capable of association as unit with the current converters 1 5 and being located at special parts of the main current paths too. The b-channel serves to respond to an overload, the schannel and the k-channel serve to respond to a short circuit. Therefore the s-channei may be provided with a short delay. The trigger signals 1 3a, 1 3b, produced in the individual channels in the case where there is a fault current, act on the electromagnetic operating current trigger 12 which triggers the switching device.A test and calibration connector is designated 21 and is connected via lines 22 to 26 to the inputs of the current supply 14, the inputs of channels 18, 19, 20 and to the output carrying the trigger signal 13. The electronic trigger may be checked as to its functioning via this connector 21. In addition this calibration connector serves for calibration of this electronic trigger or for checking the calibration values from a calibration which has already been carried out. Therefore the operational signals for the supply voltage and for the three channels are simulated with the aid of a special calibration device not shown. It is possible, with such an arrangement, to avoid the large expense on calibration which would otherwise be necessary, where the entire apparatus has to be set in operation by means of a test transformer.

The point in time at which the current response value set in the channels is reached may be detected for example by means of the calibration inputs 23-25 which are not used for calibration in normal operating conditions. Furthermore, two additional circuit elements 27, 28 are provided for detecting these points in time.

These points in time may be indicated for example by light-emitting diodes 27a in the circuit elements 27, 28 and/or may be applied to the calibration connector 21 with the aid of special outputs 29, 30 and thus used for additional switching commands.

The contacts of the calibration connector 21 are designated 31 to 35. The electronics are supplied with the supply voltage Uv via 31. in each case one measurement signal corresponding to the set current is passed to each channel via the contacts 32, 33 and 34; for the b-channel this is Ub, for the s-channel this is Us and for the k-channel this is Uk. When the respective channel is triggered, the trigger signal U5 appears at the contact 35. At the same time the internal LED indication appears in the circuit element 36, 37.

The measurement of the time difference between applying the measurement signal and the appearance of the trigger signal makes it possible to check the trigger characteristics in the b-channel, check the basic delay in the s/k-channel and additionally to check the settable delay times in the s-channel. When the individual channels respond, the "response threshold exceeded" display appears in each case.

Fig. 2 shows an example of embodiment of distribution using a high-voltage switch 38, a lowvoltage switch 39 and three other low-voltage switches 40 to 42. The switch 39 may be set for example to a delay time of 300 ms and the switches 40 to 42 in each case may be set to a delay time of 200 ms. The switch 39 has an electronic trigger in accordance with Fig. 1. In the normal case the switch 40 would disconnect after 200 ms in the case of short-circuit at the load M1, since the switch 40 is set to this delay time.

However, in accordance with the present embodiment the point in time at which the shortcircuit occurs is detected in the switch 39 so that the signal thus achieved may already be used to disconnect the switch 41 as indicated by the broken line 43. It is possible to maintain a deliberate sequence of stepping the parts of the system, which is required for operation, when an excess current (overload, short-circuit) of a particular level occurs.

Claims (9)

1. An electronic trigger for a switching device having separate channels for responding to an overload and a short-circuit and having components for processing measured values and supplying voltage wherein the electronic trigger is provided with special inputs for connection of a calibrating device capable of simulating operational signals for the measured values and voltage supply.

2. A trigger according to Claim 1, wherein the special inputs are provided at the input to the separate channels and to the supply component.

3. A trigger according to Claim 2, wherein a calibration connector is arranged on the trigger for connection of the special inputs.

4. A trigger according to Claim 3, wherein the calibration connector is combined with a test connector.

5. A trigger according to any one of Claims 1 to 3, wherein when an excessive current occurs, it is possible to detect the point in time when the response values set in the channels have been achieved directly and without delay by means of the calibration inputs and/or special circuit elements and it is also possible to evaluate this point in time by means of corresponding signals from these circuit elements.

6. A trigger according to Claim 5, wherein the signals produced when directly detecting the points in time when an excessive current occurs may be displayed immediately by display elements in the circuit elements of the trigger.

7. A trigger according to Claim 5, wherein the signals produced when directly detecting the point in time when an excessive current occurs may be used deliberately to carry out a particular operation before the switching device is switched off by the relevant channel.

8. A trigger according to any one of claims 5 or 7, wherein the signals produced when directly detecting the point in time when an excessive current occurs may be utilized by terminals of the special circuit elements or may be detected by means of additional terminals of the test connector.

9. An electronic trigger for a switching device substantially as described herein with reference to the drawings.