Device for actuating opening/closing commands for a high-voltage circuit breaker

Abstract

 Device for actuating opening/closing commands for a high-voltage circuit breaker, the special feature of which consists in the fact that it comprises, for each pole of the circuit breaker, pulse generating means designed to generate a pulse after receiving a command for opening/closing of a circuit breaker and oscillator means designed to convert the pulse into a train of pulses for driving transformer means which are arranged in series with the oscillator means and the output signals of which cause opening or closing of one or more circuit switching means so as to allow the supplying of voltage to a coil actuating the commands for opening/closing the respective pole associated therewith.

Description

[0001] The present invention relates to a device for actuating opening/closing commands for a high-voltage circuit breaker, in order to disconnect/connect components of a power plant (generators, lines, transformers, user loads, etc.).

[0002] As is known, high voltage circuit breakers are normally used in all those situations where it is required to interrupt in very short periods of time high short-circuit currents, such as those which may occur, for example, downstream of an electric power station, prior to a transmission line.

[0003] High-voltage circuit breakers generally consist of three separate poles (in the case of three-phase lines) each mounted on its own support and connected by means of connecting rods.

[0004] The control cabinet is mounted on the central support.

[0005] The operating elements of the circuit breaker are of the hydraulic type provided with an energy storage system in the form of a precompressed nitrogen tank.

[0006] Any opening and closing action of the circuit breaker is performed by an electrical actuator which may be in particular a solenoid valve, an electromagnet or any other electrically actuated system which activates the mechanisms intended for opening and closing the circuit breaker.

[0007] For the sake of simplicity of the description below, this electrical actuator will be identified as a solenoid valve.

[0008] Actuation of the opening or closing command is performed by energization of a corresponding electromagnet with which the operating element is equipped. In practice, energization of a coil (one for each pole) actuates a corresponding solenoid valve intended for actuation of a corresponding opening or closing command.

[0009] Release of the energy stored in the storage system causes displacement of the movable parts of the circuit breaker.

[0010] The storage system generally consists of a sealed cylinder and a piston separating two fluids: nitrogen and oil. The storage device is kept under pressure by means of a high-pressure motor pump actuated by the contacts of a pressure circuit breaker.

[0011] The energy produced by the rapid, but partial expansion of the compressed nitrogen is transmitted hydraulically to the jacks of the circuit breaker by means of a valve.

[0012] As already mentioned, all the hydraulic and electric components are inside a single cabinet mounted on the support of the central pole.

[0013] At present, therefore, the system for controlling a high-voltage circuit breaker, which must be able to operate using voltages variable between 145 and 170 kV and with currents of the order of 1250-3150 A, is of the electro-mechanical type, i.e. based on relays which open or close the contacts of the circuit breaker.

[0014] The relay logic which is commonly used has, however, various drawbacks.

[0015] Firstly, the relay logic requires a large number of wiring cables and this results in large dimensions of the control cabinet.

[0016] Moreover, this type of logic is lacking in terms of flexibility since the functions which can be performed by the logic are rigid, predefined and therefore cannot be modified by the user so as to be able to add others of interest to them.

[0017] In addition, the relay logic performs solely control functions (actuation) of the circuit breaker, without moreover being able to perform monitoring of the circuit breaker in order to detect beforehand possible malfunction situations.

[0018] Finally, the large number of wiring cables results in susceptibility to malfunctions which adversely affects the reliability of the circuit breaker, in particular during the opening function which is the command which it is required should always be able to be carried out for the purposes of safety.

[0019] The main task of the present invention is therefore that of providing a device for actuating opening/closing commands for a high-voltage circuit breaker which is of the electronic type.

[0020] Within the scope of this task, one object of the present invention is that of providing a device for actuating opening/closing commands for a high-voltage circuit breaker which ensures a high degree of reliability as regards execution of the opening command.

[0021] Another object of the present invention is that of providing a device for actuating opening/closing commands for a high-voltage circuit breaker, which allows monitoring of the state of the actuation coils of the solenoid valves intended to perform the opening/closing commands.

[0022] A further object of the present invention is that of providing a device for actuating opening/closing commands for a high-voltage circuit breaker which can be inserted into an electronic system for on-line control of such a circuit breaker.

[0023] Yet another object of the present invention is that of providing a device for actuating opening/closing commands for a high-voltage circuit breaker which can be connected in series with one or more similar devices.

[0024] Last but not least, an object of the present invention is that of providing a highly reliable device which can be easily manufactured at a competitive cost.

[0025] This task, as well as these and other objects which will emerge more clearly below are achieved by a device for actuating opening/closing commands for a high-voltage circuit breaker, characterized in that it comprises, for each pole of the circuit breaker, pulse generating means designed to generate a pulse after receiving a command for opening/closing a circuit breaker and oscillator means designed to convert said pulse into a train of pulses for driving transformer means which are arranged in series with said oscillator means and the output signals of which cause opening or closing of one or more circuit switching means so as to allow the supplying of voltage to a coil actuating the commands for opening/ closing the respective pole associated therewith.

[0026] The task and the objects described above are also achieved by a method for actuating commands for opening/closing a high-voltage circuit breaker, characterized in that it comprises for each pole of the circuit breaker the steps consisting in:

• after receiving an opening/closing command, generating a pulse coinciding with the leading edge of said pulse;
• generating a train of pulses with a duration equivalent to the duration of said pulse for driving transformer means;
• using output signals of said transformer means to drive circuit switching means designed to open/close a circuit supplying voltage to a coil actuating the pole of said circuit breaker so as to cause opening or closing of said pole.

[0027] Further characteristic features and advantages of the invention will emerge more clearly from the description of a preferred, but not exclusive embodiment of the device according to the invention, illustrated by way of a non-limiting example in the accompanying drawings, in Figure 1 illustrates a block diagram of the circuit configuration of the device according to the invention, relating to the operation of one of the actuating coils.

[0028] With reference to Figure 1, the device according to the invention, which can be integrated onto a single board, is shown solely in the circuit portion relating to energization of a single coil.

[0029] It is to be understood that the portion which is illustrated and which will be described below is in fact physically repeated a number of times equal to the number of coils to be operated.

[0030] Therefore, in the case of a three-pole high-voltage circuit breaker, there are three coils for the opening command and three coils for the closing command: in total, therefore, there will be six circuit arrangements identical to that illustrated in the accompanying drawing.

[0031] Moreover, given that the device according to the invention can be integrated into an electronic control system for management of a high-voltage circuit breaker, forming the subject of a co-pending patent application in the name of the same applicant of the present application (this co-pending patent application is understood as being included herein for all reference purposes) which envisages duplication of the opening and closing commands, this device shall be integrated in a redundant manner within the control system mentioned above.

[0032] With reference now to Figure 1, the circuit configuration for operation of a coil, indicated in its entirety by the reference number 1, comprises a pair of terminals 2a, 2b designed to receive differentially the commands supplied from an external microprocessor, not shown, forming part of the control system described in the co-pending patent application to which reference was made above.

[0033] These commands are sent by the microprocessor via an input/output interface board, also not shown, to which the device according to the invention is connected.

[0034] The commands arriving at the terminals 2a and 2b relate to opening/closing of the circuit breaker and hence to energization of the coil for actuating the pole of the circuit breaker which in the figure is indicated by the reference number 100.

[0035] The reference number 3 indicates a differential amplifier for amplification of the incoming signals at the terminals 2a and 2b.

[0036] Downstream of the differential amplifier 3 there are pulse generating means 4 which, following a command coming from the microprocessor, generate a pulse with a maximum duration equal to 30 ms.

[0037] The pulse generating means suitably comprise for example a monostable which produces at its output a pulse with a maximum duration of 30 ms.

[0038] The correct duration of the command from the microprocessor is 25 ms and therefore if the command has the correct predefined duration, the pulse generated by the monostable terminates exactly at the trailing edge of the command signal.

[0039] In the opposite case, i.e. if for any reason the duration of the command signal should exceed 25 ms, for example owing to a malfunction of the microprocessor, then the monostable nevertheless resets the pulse to zero within a maximum time period of 30 ms.

[0040] This is performed in view of the fact that the actuation coil 100 used is a low-voltage coil (about 24V) which is energized for a brief period (30 ms at the most) at a much higher voltage, for example about 110 V, so that the stroke times of the piston actuated indirectly by it are very limited, therefore allowing very fast opening (or closing) of the pole of the circuit breaker.

[0041] In Figure 1, the monostable 4 is shown divided into the blocks 4a and 4b in order to highlight the different behaviour in the case where the command signal should have the predetermined duration (25 ms), block 4a, and therefore the pulse generated by the monostable drops at the trailing edge of the command signal.

[0042] The block 4b, on the other hand, relates to the case where the command signal has a duration greater than the predetermined duration and the monostable 4 generates a pulse which, however, has a maximum duration of 30 ms.

[0043] This ensures that the coil 100 of the circuit breaker pole is energized for a maximum period of time equal to 30 ms. Longer times would in fact result in damaging of the coil itself on account of the high supply voltage which is applied to the terminals of the coil in order to speed up operation thereof.

[0044] Oscillator means 5 arranged downstream of the monostable 4 convert the pulse generated by the monostable 4 into a series of spaced pulses (train of pulses) having a total maximum duration of 30 ms.

[0045] The duration of the train of pulses is equivalent to the duration of the pulse signal generated by the monostable 4 and may therefore be equal to a minimum of 25 ms or a maximum of 30 ms.

[0046] The time values indicated above must be understood as being purely indicative since nothing prevents one using different supply voltages and different pulse values. The condition which must nevertheless be satisfied is that the duration of the energization pulse of the coil 100 must not be greater than the capacity of the coil for withstanding a supply voltage which is considerably greater than its normal operating voltage.

[0047] The stage after the oscillator means 5 comprises a decoupling transformer 6 for performing galvanic decoupling, which comprises a primary winding 6a and two secondary windings 6b and 6c which allow division of the output of this transformer 6.

[0048] The output of the first secondary winding 6b passes into rectifier means 7b consisting of a diode bridge and drives first circuit switching means advantageously formed by a first FET switch 8b.

[0049] Similarly the output of the second primary winding 6c passes into rectifier means 7c also consisting of a diode bridge, is shunted by means of a high-pass filter advantageously consisting of capacitive means 9 and drives second circuit switching means advantageously formed by a second FET switch 8c.

[0050] The FET 8b has its own source terminal connected to the drain terminal of the FET 8c and the drain terminal connected to one of the terminals of the coil 100.

[0051] The source terminal of the FET 8c on the other hand is connected to the negative supply voltage of 110 V.

[0052] The positive supply voltage (+110V) is supplied to the other terminal of the coil.

[0053] The first FET 8b is driven by a continuous signal while the second FET is driven by a pulsed signal having a minimum duration equal to the pulse of 30 ms.

[0054] The two FETs 8b and 8c therefore act as two circuit breakers for closing or opening the coil 100.

[0055] The circuit portion described above relates to the command actuating part of the device according to the invention.

[0056] The remaining part of the circuit illustrated in Figure 1, on the other hand, relates to the function of monitoring the continuity of the coil 100 in order to check that it is intact - a fundamental requirement for correct operation thereof.

[0057] Second oscillating means 10 produce a signal which passes into a second transformer and from here into a rectifier, advantageously of the half-wave type, so as to be injected into the coil 100.

[0058] This signal is reread and decoupled by means of an opto-isolator 13, is filtered and then amplified by amplification means 14 so as to finally be sent to the input/output interface board and from here to the microprocessor.

[0059] With reference to the sole figure cited, operation of the device according to the invention is as follows:

[0060] The coil 100 is, as explained above, a low-voltage coil which is supplied for a short period at a voltage much higher than the normal voltage in order to speed up as far as possible the stroke of the piston actuated by it.

[0061] Obviously this high supply voltage cannot be withstood by the coil 100 for too long a period of time otherwise the coil itself will be damaged.

[0062] To this end, after receiving an opening/ closing command signal from an external control unit such as a microprocessor, a pulse is generated by the monostable 4 and the generation of this pulse coincides with the leading edge of the command signal.

[0063] The pulsed signal produced by the monostable 4 has a predetermined maximum duration equivalent to the capacity of the coil 100 for withstanding over time a supply voltage much higher than its rated voltage.

[0064] Therefore, in the case where the command signal from a microprocessor is a correct signal with a normal time duration, the generated pulse terminates at the trailing edge of the command signal.

[0065] On the other hand, should the command signal, owing to malfunctions of any kind, have a duration greater than the normal predefined duration, the pulse generated by the monostable 4 would terminate in any case within the maximum predetermined time period.

[0066] In this way the coil 100 is protected from possible damage.

[0067] The pulse generated by the monostable 4 is then converted into a train of pulses by the oscillator 5. The train of pulses has a duration equivalent to the overall duration of the pulse produced by the monostable.

[0068] The train of pulses has the function of driving the transformer 6 which has two secondary windings 6b and 6c.

[0069] The output signals from the two secondary windings 6b and 6c are respectively rectified by the bridge rectifiers 7b and 7c.

[0070] One of the bridge rectifiers (the rectifier 7c in the figure) has connected in series a high-pass filter 9 which shunts the signal output from the rectifier.

[0071] Therefore the two FETs 8b and 8c are respectively supplied by a continuous signal and by a shunted signal.

[0072] In order for the coil 100 to be energized, both the FETs 8b and 8c must be conducting.

[0073] The fact of having two different command signals for the FETs 8b and 8c results in an additional degree of safety for the device.

[0074] In fact a first safety factor (command with a continuous signal) is provided by the fact that the duration of the pulse is in any case predefined, independently of the duration of the opening/closing command.

[0075] The second safety factor (command with a shunted signal) is necessary since the case could arise where the pulse or the train of pulses does not have a correct duration both following a correct opening/ closing command and following an incorrect opening/ closing command and owing to a fault of the oscillator 5.

[0076] In this case, if two identical signals driving the two FETs 8b and 8c were available, the latter would remain in the conductive state for too long a period of time and the coil 100 would burn out.

[0077] On the contrary, by shunting one of the two signals it is ensured that at least one of the two FETs 8b and 8c after a certain period of time (defined by the characteristics of the high-pass filter 9) is no longer in the conductive state, therefore opening the circuit and preventing the coil from burning out.

[0078] The device according to the invention therefore has a dual internal safety feature.

[0079] The first one consists in the temporal definition of the duration of the pulse and the train of pulses and the second one consists in shunting of one of the two driving signals of the FETs 8b and 8c.

[0080] The circuit part for detecting the continuity of the coil provides a further guarantee as to actuation of the opening/closing commands.

[0081] During the detection phase, the oscillator 10 generates a signal, by means of the transformer 11, which is injected into the coil 100 after being rectified by the half-wave rectifier 12.

[0082] The signal injected into the coil 100 is re-read at the coil output and decoupled by the opto-isolator 13, and then amplified by the amplifier 14 so as to be then sent to the input/output board (not shown).

[0083] In this way monitoring of the continuity of the coil 100 is performed.

[0084] It has been noted in practice how the device according to the invention fully fulfils the predetermined task since it allows electronic control of actuation of the commands for opening/closing a high-voltage circuit breaker with a high degree of safety.

[0085] As previously explained, the device according to the invention comprises, for each coil of the circuit breaker, a circuit similar to that shown in the accompanying drawing.

[0086] In practice, if the device according to the invention is inserted into a circuit breaker control and monitoring system as described in the abovementioned co-pending patent application, each three-phase (with three-pole) circuit breaker has three coils for the opening command and three for closing.

[0087] The device according to the invention may for example be integrated onto a board which advantageously groups together the circuits for the command opening or closing all three poles.

[0088] Two or more similar boards may be connected together.

[0089] Detection of the continuity of the coil is of fundamental importance for correct and safe operation of the high-voltage circuit breaker.

[0090] Finally, as seen, the device according to the invention allows opening and closing of a high-voltage circuit breaker to be performed electronically, overcoming the drawbacks associated with relay logic used hitherto, and with the additional advantage of ensuring a much greater degree of operating safety.

[0091] The device thus conceived may be subject to numerous modifications and variations, all of which falling within the scope of the inventive idea.

[0092] Thus, for example, the time values for duration of the pulses may be different from those illustrated, and likewise the circuit switching means 8b and 8c may be of a different type from the FETs shown.

[0093] Finally all the details may be replaced by other technically equivalent elements.

[0094] In practice, the materials used, provided that they are compatible with the use specified, as well as the dimensions, may be of any kind in accordance with requirements and the state of the art.

[0095] In the case where the technical features in the claims are followed by reference numbers and/or letters, said reference numbers and/or letters have been added with the sole purpose of facilitating understanding of the claims and therefore said reference numbers and/or letters do not have any effect on the scope of each element identified purely by way of example by said reference numbers and/or letters.

Claims

1. Device for actuating opening/closing commands for a high-voltage circuit breaker, characterized in that it comprises, for each pole of the circuit breaker, pulse generating means designed to generate a pulse after receiving a command for opening/closing a circuit breaker and oscillator means designed to convert said pulse into a train of pulses for driving transformer means which are arranged in series with said oscillator means and the output signals of which cause opening or closing of one or more circuit switching means so as to allow the supplying of voltage to a coil for actuating the commands for opening/closing the respective pole associated therewith.

2. Device according to Claim 1, characterized in that said pulse generating means comprise a monostable designed to generate a pulse, the maximum duration of which is determined by the capacity of said coil to withstand the supply voltage without suffering damage.

3. Device according to Claim 1, characterized in that said oscillator means generate a train of pulses, the time duration of which is equal to the overall duration of said pulse, said train of pulses supplying said transformer means arranged downstream of said oscillator means.

4. Device according to Claim 1, characterized in that said transformer means comprise a transformer with a primary winding and two secondary windings, the output signal of each of said two secondary windings driving a respective one of said one or more circuit switching means.

5. Device according to Claim 4, characterized in that respective rectifying means are provided between said two secondary and said respective circuit switching means.

6. Device according to Claim 1, characterized in that said one or more circuit switching means each consist of an FET.

7. Device according to Claim 6, characterized in that it comprises a pair of FETs connected in series.

8. Device according to Claim 5, characterized in that, downstream of one of said rectifying means, there are provided shunting means designed to shunt the signal output from said rectifying means, the output signal from said rectifying means arranged downstream of one of said secondary windings being sent to the input of said circuit switching means, said shunting means comprising a high-pass filter.

9. Device according to Claim 1, characterized in that it comprises amplification means arranged upstream of said pulse generating means, said amplification means being designed to amplify the opening/closing commands received.

10. Device according to Claim 1, characterized in that it also comprises means for checking the continuity of said coil, said means for checking the continuity of said coil comprising oscillator means designed to drive a transformer for injecting a signal into said coil, said rectifier means arranged downstream of said transformer, and signal detection means designed to detect the output signals from said coil in order to check the continuity of said coil.

11. Device according to Claim 10, characterized in that said signal detection means comprise an opto-isolator and amplifier means designed to amplify the output of said opto-isolator.

12. Method for actuating commands for opening/closing a high-voltage circuit breaker, characterized in that it comprises for each pole of the circuit breaker the phases consisting in:

- after receiving an opening/closing command, generating a pulse coinciding with the leading edge of said pulse;

- generating a train of pulses with a duration equivalent to the duration of said pulse for driving transformer means;

- using output signals of said transformer means to drive circuit switching means designed to open/close a circuit supplying voltage to a coil actuating the pole of said circuit breaker in order to cause opening or closing of said pole.

13. Method according to Claim 12, characterized in that said pulse has a predefined time duration independent of the time duration of said opening/closing command and determined by the maximum capacity of said coil to withstand the given supply voltage.

14. Method according to Claim 12, characterized by the fact that it comprises a phase involving rectification of the output signals from said transformer means.

15. Method according to Claim 12, characterized in that said phase of driving said circuit switching means by means of signals emitted from said transformer means comprises shunting at least one of said signals for driving at least one of said circuit switching means.

16. Method according to Claim 12, characterized in that it also comprises a phase which consists in detecting the continuity of said coil, said phase comprising the following steps:

- injecting a signal into said coil; and

- detecting the signal output from said coil.

17. Method according to Claim 16, characterized in that said step which consists in injecting a signal into said coil comprises:

- generating a signal by means of oscillator means; and

- rectifying said signal and supplying it to said coil.

18. An electronic system for controlling and monitoring a circuit breaker characterized in that it comprises at least one device for actuating commands for opening/closing a high-voltage circuit breaker as claimed in Claim 1.

Drawing