RU81604U1 - DEVICE FOR MAXIMUM CURRENT PROTECTION OF INPUT TO BUSBAR SECTION - Google Patents

Abstract

The utility model relates to devices for the relay protection of elements of the electrical system and is designed to disable short circuits on the low voltage buses of the step-down substations and to reserve the shutdown of short circuits on the elements connected to these buses. The essence of the utility model lies in the fact that the device for maximum current protection of the input to the busbar section has an accelerated protection circuit for disconnecting the input circuit breaker to the busbar section, connected in parallel with the circuit breaker circuit of this switch with a time delay selected according to the selectivity conditions with the operating time overcurrent protection of elements connected to these buses. The technical result consists in reducing the time for switching off short circuits on sections of busbars of low voltage of lowering substations by introducing into the device an accelerated disconnection circuit of an input switch to the section of busbars. A device for maximum current protection of the input to the busbar section contains current transformers and current relays of phases A and C, a voltage transformer, a voltage trigger, including a reverse sequence voltage filter relay and a minimum voltage relay, a time relay, the first and second intermediate relays, the first and a second indicator relay and a chain of time-disconnecting contacts of the time relay of the maximum current protection of the elements connected to the busbar section. 2 ill.

Description

The utility model relates to devices for the relay protection of elements of the electrical system and is designed to disconnect short circuits (short circuits) on the low voltage buses of the step-down substations and to reserve shutdowns of short circuits on the elements connected to these buses.

Known devices for maximum current protection input to the section of busbars, designed to disable short-circuit on the low voltage buses of step-down substations and backup shutdown short-circuit on the elements connected to these buses [1, Fig.1.1, p.8-10; fig. 1.4, p.20-22; fig. 1.5, s 24-27; fig.2.1, p.32-59]. Such devices provide tripping of input switches on busbar sections of step-down substations during short-circuit on these buses, as well as on short-circuit on elements connected to buses, in case of failure of protection or circuit breakers of these elements.

Closest to the claimed device is a device for overcurrent protection (MTZ) with a combined voltage start, installed on the inputs to the busbar sections (SS) of the low voltage substation [2, Fig. 46.38, p. 485-487], containing current relays connected to current transformers of phases A and C, a voltage trigger, including a reverse sequence voltage filter relay and a minimum voltage relay connected to a voltage transformer

sections of the secondary school, an intermediate relay that repeats the action of the trigger on voltage, a time relay and an indicator relay.

However, the effect of these devices on opening input circuit breakers on the secondary section of the substation low voltage during short-circuit on buses and on short-circuit on elements connected to these buses occurs with the same time delay selected from the selectivity conditions in accordance with the duration of the maximum current protection joining the school. Disabling short-circuit in sections of the secondary school with a time delay leads to an increase in the size of equipment damage, the duration of the voltage reduction for consumers, reduces the efficiency, the actions of automatic reclosure devices of input switches and devices of automatic switch-disconnectors of section switches.

The objective of the utility model is to accelerate the operation of the device for maximum current protection installed on the input to the secondary section of the secondary voltage of the substation, in the case of short circuit on the buses while ensuring the selectivity of its action in the short circuit on the elements connected to these buses.

This task is achieved by the fact that the device for maximum current protection, containing current relays of phases A and C, the windings of which are connected to the secondary windings of current transformers installed in phases A and C of the input to the busbar section, a starting voltage element, including a voltage filter relay reverse sequence, the winding of which is connected to the terminals of phases A, B and C of the secondary winding of the transformer

the voltage of the busbar section, and the undervoltage relay, the winding of which is connected to the terminals of the phases A and B of the secondary winding of the voltage transformer through the NC contact of the filter-voltage relay of the reverse sequence, and the NC contact is connected to the positive pole of the operating current source by its first output and the second through the winding of the first intermediate relay is connected to its negative pole, a time relay, the first output of which is through parallel closing contacts of the currents x phase A and C relays and a series-making contact of the first intermediate relay connected to the positive pole of the operating current source, the second terminal of the time relay winding is connected to its negative pole and the contact closing with time delay through the winding of the first indicator relay connects the positive pole of the operating source current with a trip circuit of the input switch to the busbar section, and the make contact of the first indicator relay is included in the alarm circuit of the protection operation, exc It means that a second intermediate relay and a chain of maximum time overcurrent protection contacts of the elements connected to the busbar section are connected in series between the disconnecting contacts of the time relay, the winding of the second intermediate relay connected with the first output of the time relay winding and the second the output is connected to the negative pole of the operating current source, a chain of maximum disconnecting contacts of the time relay

the current protection of the connections through the winding of the second indicator relay and the make contact of the second intermediate relay connected in series connects the positive pole of the auxiliary current source to disconnect the input switch to the busbar section, and the make contact of the second indicator relay is connected to the alarm circuit.

The essence of the utility model is as follows. Figure 1 shows the section of the secondary school low voltage of the substation, on the supply input of which the claimed device is installed for maximum current protection. The circuit contains switches 1 ₁ , ..., 1 _n elements connected to the SS section, an input switch 1 _{(n + 1)} to the SS section, current transformers 2 ₁ , _... , 2 _n maximum current protection (MTZ) connections, current transformers 2 _{(n + 1) of the} claimed device for maximum current protection, voltage transformer 3 sections of the secondary school, windings 4 of ₁ and 5 ₁ current relays of phases A and C connected to the secondary windings of current transformers 2 _{(n + 1)} phases A and C the input to the section of the secondary school, respectively, the winding 6 ₁ and the opening contact 6 _{2 of the} negative voltage filter-relay relay and winding 7 ₁ undervoltage relay.

Winding 6 _{1 of the} negative sequence voltage filter relay is connected to the terminals of phases A, B and C of the secondary winding of the voltage transformer 3, and winding 7 _{1 of the} undervoltage relay through the opening contact 6 _{2 of the} reverse sequence voltage relay is connected to the terminals of phases A and B of the secondary transformer voltage 3.

Figure 2 shows the circuit diagram of the direct operating current circuit of the device for maximum current protection. The circuit contains the closing contacts 4 ₂ and 5 _{2 of the} current relays of phases A and C, respectively, opening contact 7 _{2 of the} undervoltage relay, winding 8 ₁ and making contact 8 _{2 of the} first intermediate relay, winding 9 ₁ and contact 9 ₂ closing with time delay , winding 10 ₁ and making contact 10 _{2 of the} first indicator relay, winding 11 ₁ and making contact 11 _{2 of the} second intermediate relay, a chain of series-connected opening contacts 12 ₁ , _... , 12 _n time relay MTZ of connections of the section SS, winding 13 ₁ and normally open contact 13 ₂ W cerned index relay, the positive pole 14 and negative pole 15 of DC voltage source.

Opening contact 7 _{2 of the} undervoltage relay with its first output is connected to the positive pole 14 of the operating current source, and the second output through the winding 8 _{1 of the} first intermediate relay is connected to its negative pole 15. The first conclusions of the winding 9 _{1 of the} time relay and winding 11 _{1 of the} second intermediate relay through parallel interconnected shorting pin 4 ₂ and 5 ₂ current relay phases a and C, respectively, and connected to them closing pin 8 ₂ of the first auxiliary relay connected to the positive pole Control current source 14, and the second terminals of the windings _{1 September} and November ₁ these relays connected to its negative pole 15 that closes with a time delay pin 9 ₂ times through relay winding 10 ₁ of the first index relay connects the positive pole of DC voltage source 14 to the chain

tripping of the input switch 1 _{(n + 1)} to the secondary section, and the make contact 10 _{2 of the} first indicator relay is included in the alarm circuit of the protection operation. A chain of disconnecting contacts 12 ₁ , ..., 12 _n connected in series to each other of the MTZ time connections of the secondary section through a winding 13 _{1 of the} second indicating relay and a closing contact 11 _{2 of the} second intermediate relay connected in series connects the positive pole 14 of the operating current source to the disconnection circuit the input switch 1 _{(n + 1)} to the secondary section, and the make contact 13 _{2 of the} second indicator relay is included in the alarm circuit of the protection operation.

The device operates as follows.

In the normal operation mode of the substation equipment, through the switches 1 ₁ , ..., 1 _n , 1 _{(n + 1)} and current transformers 2 ₁ , ..., 2 _n , 2 _{(n + 1), the} connections and input to the secondary section flow load currents. Current relays of all MTZ are in an unworked state. There is a normal operating voltage on the secondary section, as a result of which current flows through the winding 7 _{1 of the} undervoltage relay, because due to the lack of voltage in the reverse sequence of contacts 6 _{2 the} voltage filter relay is closed. The undervoltage relay is tripped, so its contact 7 _{2 is} open. Contacts 4 ₂ and 5 _{2 of the} current relay are open, contact 8 _{2 of the} first intermediate relay is open, because no current flows through its winding 8 ₁ . As a result of the lack of current in the winding circuits 9 _{1 of the} time relay and 11 _{1 of the} second intermediate relay, they are in an inoperative state and the trip circuit of the input switch 1 _{(n + i)} to the SS section is open

contacts 9 ₂ and 11 _{2 of the} indicated relays. Both indicator relays are also in an inoperative state and the alarm circuits for the operation of the protection are open by their contacts 10 ₂ and 13 ₂ .

In the event of a short circuit on the SS section (point K1 in Fig. 1), current K3 flows through the switch 1 _{(n + 1)} and input current transformers 2 _{(n + 1)} to the SS section, and the voltage on the SS section decreases. As a result of this, the input MTZ current relays are activated and close their contacts 4 ₂ and 5 ₂ in the winding circuit 9 _{1 of the} time relay and 11 _{1 of the} second intermediate relay.

Reducing the voltage on the sections of the NW causes the minimum voltage relay to return, which closes its contact 7 ₂ in the winding circuit of the first intermediate relay. A current flows through winding 8 ₂ . The first intermediate relay trips and closes its contact 8 ₂ . Winding 9 ₁ time relay and winding 11 _{1 of the} second intermediate relay receive power. The second intermediate relay without time delay closes its contact 11 ₂ in the trip circuit of the input switch 1 _{(n + 1)} to the SS section. Since none of the overcurrent protection elements connected to the secondary section works in this mode, the chain of the NC contacts 12 ₁ , ..., 12 _n connected in series to these timers remains closed and the circuit breaker 1 _{(n + 1)} trips input to the SS section occurs without delay.

At the same time, the second indicator relay is activated, the contact of which 13 ₂ closes the signaling circuit of the accelerated operation of the input overcurrent protection section of the secondary school.

In case of a short circuit on any of the elements connected to the section of the secondary school (for example, at point K2 in Fig. 1), the current K3 flows not only through the switch 1 _{(n + 1)} and current transformers 2 _{(n + 1) of the} input to the section of the secondary school , but also through the switch 1 _i and current transformers 2 _i , damaged connection. The maximum current protections installed on the input to the SS section and on the damaged element begin to work. Current relays and start relays are triggered by the voltage of the indicated protections, as a result of which the windings of their time relay are supplied with power. The time relay MTZ of the damaged element instantly opens its contact 12 _i in the accelerated circuit of the input MTZ to the section. The accelerated circuit of this protection is taken out of service. The MTZ of the damaged element is activated and with a time delay shorter than the time of the MTZ input to the SS section, it trips the switch 1 _i . Short circuit in the wiring diagram is eliminated by the protection and circuit breaker of the damaged element.

If for some reason the switch 1 _{i of the} damaged element does not open, then with a longer time set on pin 9 _{2 of the} input time relay MTZ to the SS section, the disconnection circuit of the input switch 1 _{(n + 1)} will be closed. Thus, redundancy of the protection failure or circuit breaker of the damaged element connected to the SS section is carried out with the maximum current protection installed at the input to the SS section. The disconnection of the input switch 1 _{(n + i)} to the SS section will occur in this case with a time delay selected by the condition

selectivity with MTZ response times of busbar connections.

In a similar way, circuit breaker 1 _{(n + 1)} will trip in case of a short circuit in the secondary section and a failure in the operation of the accelerated MTZ input circuit.

A device of this type can be used to accelerate short-circuit shutdown on the substation’s medium voltage buses while ensuring its selectivity in case of short circuits on the elements connected to these buses in the absence of power sources on the medium voltage side.

Instead of the opening contacts of the MTZ time relay of the elements connected to the busbar section, the accelerating circuit of the claimed protection device can be used in series with each other and opening contacts of the starting current relays of the MTZ connections, if they are of a separate design with make contacts, for example, when used in MTZ circuits PCT static current relays.

The inventive device for maximum current protection of the input to the section of the secondary school can be performed without starting the voltage, if you exclude from its circuit the starting voltage element and the first intermediate relay.

Thus, the inventive device for maximum current protection of the input to the busbar section provides accelerated short-circuit disconnection at the secondary section and redundant short-circuit protection at the elements connected

to these tires, with a time delay selected from the conditions of selectivity of the protection. Disabling short-circuit on sections of the secondary school without time delay leads to a decrease in the size of equipment damage and the length of time for voltage reduction among consumers, increases the efficiency, the actions of automatic reclosure devices of input switches and devices of automatic switch-disconnectors of section switches.

Literature

1. Guidelines for relay protection. Vol. 13A. Relay protection of step-down transformers of autotransformers 110-500 kV: Schemes. - M .: Energoatomizdat, 1985.

2. Electrical reference book: 4TT 3. Production, transmission and distribution of electrical energy / Under total. ed. professors MPEI V.G. Gerasimova and others (Ch. ed. A.I. Popov). - 9th ed. - M.: Publishing House MPEI, 2004.

Claims (1)

A device for overcurrent protection, containing phase A and C current relays, the windings of which are connected to the secondary windings of current transformers installed in phases A and C of the input to the busbar section, a voltage starting element, including a reverse sequence voltage filter relay, the winding of which is connected to the terminals of phases A, B and C of the secondary winding of the voltage transformer of the busbar section, and the undervoltage relay, the winding of which through the opening contact of the filter-relay of the reverse sequence voltage connected to the terminals of phases A and B of the secondary winding of the voltage transformer, and the NC contact with its first output is connected to the positive pole of the operating current source, and the second output through the winding of the first intermediate relay is connected to its negative pole, a time relay, the first output of which is through parallel connected between themselves the making contacts of the current relays of phases A and C and the making contact of the first intermediate relay connected in series with them are connected to the positive pole of the source quickly about current, the second terminal of the time relay winding is connected to its negative pole and a contact that closes with a time delay through the winding of the first indicator relay connects the positive pole of the operating current source to the disconnect circuit of the input switch to the busbar section, and the make contact of the first indicator relay is connected to the alarm circuit on the operation of the protection, characterized in that a second intermediate relay, a second indicating relay and a chain of disconnecting the clocks of the time relay of the maximum current protection of the elements connected to the busbar section, and the winding of the second intermediate relay with its first output is connected to the first output of the time relay winding, and the second output is connected to the negative pole of the operating current source, a chain of relay relay contacts connected in series time of the maximum current protection of the connections through the winding of the second indicator relay and the make contact of the second intermediate relay connected in series yvaet positive pole of DC voltage source with a circuit disconnection on the input switch section busbar, and a make contact of the second relay index included in the alarm circuit of the protection is activated.