SU1721687A1 - Device for redundancy of failures of protections and switches - Google Patents

Abstract

The invention relates to relay protection of elements of electrical systems and power supply systems and can be used to back up failures of protections and switches connected to common buses with a voltage of 6-10 kV. The purpose of the invention is to increase speed. The goal is achieved by introducing diodes 12, 13 connected by cathodes to the second input of the first measuring unit 14, connecting the output of the second measuring unit 17 to the prohibiting input of the logical block BENE 18 and the input of the second delaying unit 20 and having terminals for connecting contacts 15,16 of the output relay of the back-up protection attachments. When a short circuit occurs at one of the energized connections and the protection does not respond to this connection, the first measuring unit 14 is triggered and the second measuring unit 17 does not work, and a signal to the actuating unit 22 passes through the blocks 18-21. 1 Il. (Ls

Description

The invention relates to relay protection of elements of electrical systems and power supply systems and can be used to back up failures of protection and breakers of connections connected to common buses with a voltage of 6-10 kV.

The purpose of the invention is to increase speed.

The drawing shows a diagram of an electrical network with one power supply and two feed connections and a block diagram of the proposed device.

The electrical network consists of a busbar section 1, to which a power supply connection 2 is connected with a switch 3 and a power supply connection 4.5, on which 6.7 current measuring transformers are installed. The device for redundancy of protection and breaker failures contains converters 8.9 of secondary connections currents to voltages, rectifier bridges 10.11 and one rectifier diode 12-13 at each connection. The outputs of converters 8.9 are connected to the inputs of the respective bridge rectifiers 10, 11, the negative outputs of which are combined and connected to the first input terminal of the measuring unit 14. The diodes of the diodes 12, 13 are connected to the positive outputs of the corresponding rectifying bridges 10, 11, and the cathodes diovi

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IDs 12.13 are combined and connected to the second input of the first measuring unit 14. The first output of contacts 15.16 of the output relays of the corresponding redundant protection of connections 4.5 is connected to the positive output of the corresponding rectifying bridge 10.11, and the second terminals of these contacts 15.16 combined and connected to one of the inputs of the second measuring unit 17, the other input of which is connected to the negative outputs of the rectifying bridges 10,11. The output of the first measuring unit 14 is connected to the input of the logical BANCH unit 18, the output of which is connected to the input of the first delay block 19. The output of the second measuring unit 17 is connected to the inhibit input of the logical block BANCH 18 and the input of the second delay block 20. The output of the first delay block 19 is connected to the first input of the logical block OR 21, the second input of which is connected to the output of the second delay block 20, and the output of the logical block OR 21 is connected to the input of the execution unit 22. The number of redundant connections is excellent two, respectively varies the number of current-to-voltage converters, rectifying bridge, rectifying diodes and redundant protection relay contacts.

The device works as follows.

When the negative outputs of the rectifying cops 10 11 and the cathodes of diodes 12.13 are combined, a maximum voltage isolation circuit is formed, and the maximum of the voltages at the outputs of the converters 8 and 9 is applied to the input of the first measuring unit 14. A current proportional to the short circuit current is fed to the input of the first measuring unit 14. If this voltage is greater than the setpoint of the first measuring unit 14, then it is triggered, i.e. The first measuring unit 14 detects the occurrence of a short circuit on the energized connections. To the input of the second measuring unit 17, the voltage from the outputs of the converters 8 or 9 is supplied only when the contacts of the 15 or 16 outputs of the relay of redundant protections are closed, i.e. the actuation of the second measuring unit l 17 indicates the actuation of the reservable protection of any of the supplied connections in the event of a short circuit on this connection. In the event of a short circuit at one of the energized connections and the failure of the protection to operate, this is about the connection

the first measuring unit 14 is triggered and the second measuring unit 17 is not triggered. At the same time, there is no signal at the prohibiting input of the BAN 18 unit. Therefore, from the output of the first measuring unit 14, through the BANNER unit 18, the signal is fed to the input of the first delay unit 19. With a given time delay, the first delay unit 19 is also triggered through the logic unit

OR 21 sends a signal to the executive unit 22, which acts on the opening of the switch 3 of the supply connection 2. In the event of a short circuit on any of the supplied connections and operation

protection of the damaged connection, the first 14 and second 17 measuring units are triggered. In this case, a signal is given to the prohibiting input of the logical block BAN 18 and the first block of delay 19 is not

it works. In this case, the signal from the output of the second measuring unit 17 is fed to the input of the second delay unit 20, which with a given time in case of failure of the breaker of the damaged element acts through the logic block OR 21 and the actuating element 22 to disconnect the bus section. The current-to-voltage converter can be made as a transreactor or intermediate

the current transformer loaded on active resistance. Instead of current-to-voltage converters connected to the secondary windings of measuring current transformers, other current sensors that are not connected to current transformers, for example, made on the induction principle, can be used. The measuring unit can be made in the form of a semiconductor voltage measuring device. Logic blocks OR, BAN and the delay unit can be performed either by using semiconductor elements or on an electromechanical relay. The executive unit may

be implemented using an electromechanical relay. The proposed device has a greater response time than the prototype, which is determined as follows. In a known device, protection and switch failures are reserved with the same dwell time. The response time of devices in the implementation of the backup functions Ts.z. defined by the expression

tc.a. tc.3. pred max + At, (1)

where tsz.predmaks - the maximum time of protection of the reserved elements; At - time delay stage.

The time delay stage At is usually chosen by the expression

At T.OTKL.V + tnorp (+) + tnorp (-) -Yiner + taan.,

(2)

“off” —the switch of the redundant element is turned off; tnorp (+) - positive for the response time of the redundant protection; tnorp (-) - the error in the response time of the backup protection (backup device) is negative; Tyner inertial error of backup protection; taan - stock time.

The proposed device distinguishes the failure mode of protection of the reserved element from the failure mode of its switch and may have different time delay in these cases. In the event of a protection failure, the response time of the proposed device is Gs. (specified by the first delay block) can be determined by the expression

t s.oz t sz.pred.maks + Ato.a. (3)

where is at о.з. - time delay in case of failure of protection of the reserved item.

Since the proposed device has information about the fact of the operation or non-operation of the relay protection of redundant powered elements directly from the relay contacts of these protections, when choosing the time delay level Ato.3. there is no need to take into account the shutdown time of the switch of the redundant powered element T.OTKL.B. In this case, the time delay level Ato.s. can be calculated by the expression

(four)

Ato.3 tnorp (+) + tnorp (-) + 1iner + tsanSince the time Ato.s. less time At, the proposed device in case of failure of the protection of the reserved element operates with a shorter time delay than the prototype. Moreover, the off time of the switch Ltkl.v is about 0.1 s, and the elimination of this component can significantly reduce the time delay stage and the time to turn off the damage. In the event of a failure of the switch of a damaged element, the time delay of the proposed device (specified by the second delay unit) can be calculated from the known expressions for the device.

typoe toiioi.B + tnorpH + 1iner + taan (5)

The time after which the command is issued to turn off the switch of the backup power supply in case of a failure of the switch of the reserved power supply unit ts is equal to

tc.oB 1sz.pred + typos, (6)

where Tcz.pred is the time of protection operation of the damaged redundant element with the failed switch.

Since time is typoB. by (5) is less than step At by (2) due to the absence of tnorp. (+) component in (5), the proposed device operates with a shorter time delay than the prototype, and if the switch fails even in the event of a short circuit on the connection, the operation of the main protection of which is maximum (i.e.

if TSs. TS.p.pred.max.).

Thus, the proposed device will operate with a shorter time delay than the prototype, both in case of a failure of protection and a failure of the switch of the damaged element.

Claims (1)

Claims device for backing up protection and switch failures, containing current-to-voltage converters by the number of powered connections with leads for connecting to the secondary windings of corresponding current transformers of protections, two outputs of each current-to-voltage converter are connected to the inputs of the corresponding rectifying bridges, negative outputs which are interconnected and connected to the first inputs of the first and second measuring units, the output of the second measuring unit connected to the prohibiting input of the logical block PROHIBITION, the logical block OR, the first delay block, characterized in that, in order to increase speed, diodes are additionally introduced into it according to the number of feed connections and the second delay unit, while the diodes anodes are connected to the positive outputs of the corresponding rectifying bridges, which also have leads for connecting to the first pins of the corresponding contacts of the output relays of the corresponding redundant protection of connections, the cathodes of the diodes are interconnected and connected to the second input of the first measuring unit, the output of which is connected to the input of the logical block BANCH, the output of which through the first delay unit is connected to the first input of the logical block OR, the second input which is connected to the output of the second delay unit, and the output is intended to be connected to the input of the execution unit to turn off the switch of the busbar supply section connection, the second input of the second dimension with the input of the second delay unit. the control unit has a terminal for connecting to the second terminals of the respective contacts of the output relays of the redundant protection of connections, and its output