SU1686579A1 - Device for differential protection of double system of combined buses - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to relay protection of electrical networks with a voltage of 110-220 kV for bus systems with a fixed connection of connections. The purpose of the invention is to increase the sensitivity and speed. For this, three AND elements, four OR elements, setpoint changing block, and NO element are introduced into the device. time memory element. 1 il. Yo

Description

The invention relates to the field of electrical engineering, in particular, to relay protection of electrical networks with a voltage of 110 kV and above for bus systems with a fixed connection of interconnects, having automatically disconnected the damaged bus system.

The aim of the invention is to increase the sensitivity and speed.

The drawing shows a block diagram of a device for differential protection of a double busbar system

The device contains transformers 1-4 of current connection and transformer 5 of current in the busbar circuit.

The secondary windings of transformers 1-4 of the current connections are assembled in a differential circuit and connected to the first inputs of the starting block 6 and the selective

unit 7 for current, the secondary winding of the transformer 5 current is connected to the second input of the latter, and the first and second outputs of the selective unit 7 for current are connected to the first inputs of the first element OR 8 of the first bus system and the second element OR 9 of the second bus system, respectively. The presence of a signal on the first or second outputs of the selective block 7 is determined by the current direction of the current through the bus connecting switch (USV). The outputs of the elements OR 8 and 9 are connected to the first inputs of the first element AND 10 and the second element AND 11, respectively, as well as the inputs of the third element OR 12. The second inputs of the elements AND 10 and 11 are combined and connected to the output of the starting unit 6.

The outputs of the elements And 10 and 11 are connected through the fourth and fifth elements OR 13

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and 14 with the inputs of the tripping blocks of the switches of the first bus system 15 and the second bus system 16, respectively, as well as with the third inputs of the elements OR 8 and 9.

The outputs of the fourth and fifth elements OR 13 and 14 are connected to the first and second inputs of the sixth element OR 17, the output of which is connected to the third input of the same element OR 17 through the temporary memory element 18 and the input of the setpoint changing unit 19, the output of which is connected with the second input of the start-up unit 6. The output of the latter is simultaneously connected to the second inputs of the first and second elements AND 10 and 11 and the first input of the third element AND 20, the second input of which through the element NOT 21 is connected to the output of the third element OR 12, the inputs of which are connected to Exit of the first and second OR elements 8 and 9 and the output of the third AND gate 20 is connected simultaneously to the first inputs of the fourth and fifth elements 13 and OR 14.

The electoral unit 22 is connected via its inputs to the voltage transformers of the first bus system 22 and the second bus system 24. The outputs of the electoral unit 22 are connected to the second inputs of the first and second elements OR 8 and 9. The presence of a signal at the first or second outputs The selective block 22 is determined by the voltage vector of the voltage difference between the damaged and intact bus systems. The outputs of the breaker breaker units of the first 15 and second 16 bus systems are via make contacts. 25-28 Relays 29-32 of the connection selection to the first bus system and through contacts 33-36 of the connection selection relay 37-40 to the second bus system are the disconnect switch disconnection circuits. At the connections, switches 41-44 are provided for controlling the connection selection relay connections to the first and second bus systems. The output of the starting block 6 is also connected to the input of the block 45 of the busbar disconnecting switch.

The drawing shows two systems (bus) (15) rail and (16) HCS of connection L1, L2, T1, T2, the number of which is determined by the electrical connections of the substations and is not limited by this device. Each connection can be connected to the first or second bus system using disconnectors 46-53. The drawing also shows a busbar switch 54 and connection switches 55-58.

The device works as follows.

In case of a fault on the first bus system in the mode with the bus-connecting switch 54 turned on and connections with switches 55 and 56. connected with disconnectors 46 and 48 to the first bus system, connections with switches 57 and 58 connected with

0 disconnectors 51 and 53 to the second bus system. From the short-circuit currents in the current transformer 1-5 circuits, the starting unit 6 and the selective unit 7 for current simultaneously operate. The signal from the output of the starting block 6

5 enters through the shutdown unit 45 to disconnecting the busbar switch 54, and the signal from the output of the electoral block 7 is current through the first element OR 8 to the first input of the first element AND 10, to the second input of which a signal comes from the output of the starting block 6. signal appears at the output of the element And 10, which simultaneously enters through the element OR 13 to the input of the shutdown unit

5 switches of the first bus system 15 and the element OR 8, providing a signal at the output of the first element AND 10 until the signal from the output of the starting block 6 disappears at the second input of the element 10. The device ensures reliable shutdown of all switches of connections connected to the damaged bus system, irrespective of the sequence of disconnection of the connection switches and the switch nasoadinitive switch.

At the outputs of the electoral block 22, there are no signals at the voltage, since at its inputs signals of the same st and n.sh.

0When the connection is fixed

The connections 41 and 42 are set to the position N, and the switches 41 and 42 are set to N.N. This ensures that relays 29, 30 and

5 39, 40. The contacts of the indicated relays 25, 26 and 35, 36 prepare the corresponding circuit breaker trip circuits. When a signal appears at the output of block 15, the first bus system is disconnected

0 switches 55 and 56. After turning off the indicated switches, the circuit returns to its original state.

The scheme works similarly with short circuits on the second bus system and with any change in the connection fixation.

When the short circuit on the first bus system in the open busbar switch 54 mode, the selective unit 7 does not work due to the lack of current on its

the second input, because the current in the circuit of the transformer 5 current is missing. At the same time, the starting block 6 and the selective block 22 on voltage are operating. The signal from the output of the selective unit 22 is supplied to the second input of the first element OR 8. Next, the circuit operates similarly to the indicated one and acts to open the switches 55 and 56. These ensure reliable disconnection of the damaged bus system in the presence of both long and short bypass links between bus systems, while starting the power supply unit 22, the voltage responds to the difference in voltage levels of the first and second bus systems.

To increase the sensitivity of the start-up unit 6, a setpoint change unit 19 is provided. At the same time, a safe action of the breaker failure protection at any of the bus systems accompanied by the failure of the switch of any connection, including the connection with a weaker power supply, is ensured.

With simultaneous short circuits on the first and second bus systems, the current selective unit 7 and the selective unit 22 do not operate on voltage, since there is no current in the busbar circuit 54, and the voltage on both bus systems is the same.

In this mode, the disconnection of the connections of the first and second bus systems is ensured by the presence of signals at the first and second inputs of the third element I 20, coming from the outputs of the starting block 6 and the element NO 21, since there is no start signal at the input of the last one. The latter is determined by the absence of signals at the input of the fourth element OR 13. The signal from the output of the element AND 20 through the elements OR 13 and 14 is fed to blocks 15 and 16 of the opening of the switches of the first and second bus systems, ensuring the disconnection of all connections.

In fixation violation mode, when all connections are connected to one bus and short circuit system on this bus system. The disconnection of all connections is ensured by the presence of signals at the inputs of blocks 15 and 16 of the opening of the switches of the first and second bus systems. These signals come from the output of the third element And 20 similarly to the mode of simultaneous short circuits on the first and second bus systems, when the selective blocks for current 7 and for voltage 22 do not work and, therefore, there are no signals at their outputs.

Thanks to this solution, the sensitivity of the protection is increased, the speed in switching off the damaged bus system in all modes, both with the busbar switch turned on and off, in the presence of both long and short circuit breaks between bus systems.

Claims (1)

The invention The device for differential protection of a double busbar system with a bus-connecting switch and a fixed connection of connections, containing current transformers installed on all connections data bus and busbar breaker, the secondary windings of current transformers installed on the connections are assembled in a differential circuit and connected to the first the inputs of the starting block and the current selective block, the secondary winding of the current transformer installed on the busbar switch, the selective voltage block whose inputs are connected to the secondary windings of the voltage transformers installed on the first and second bus systems, the starting output to the second input of the last unit connected to to the input of the busbar disconnecting switch block, the first and second outputs of the current selective block are connected to the first inputs of the first and second elements, respectively, OR, blocks switching off the switches of the first and second bus systems, the outputs of which are connected to the first terminals of the closing contacts of the connection relay of the connection of the first and second bus systems respectively, the second terminals of the respective closing contacts of the connection selection relay connection of the first and second bus systems are combined and intended to be included in the trip circuit switches of connections, windings of the indicated relays through control switches, are intended for inclusion in the operational power supply circuit, characterized in that, in order to increase sensitivity and speed, four OR elements, three AND elements, and the HE element are additionally introduced. temporary memory element, setpoint change block, while the outputs of the selective block are connected to the second inputs of the first and second OR elements, the outputs of which are connected to the inputs of the third OR element and the first inputs of the first and second AND elements, respectively, the second inputs of which are combined and connected to the output of the starting block, the outputs of the first and second elements AND are connected to the third inputs of the first and second elements OR, respectively, and to the first inputs of the fourth and fifth elements OR. the second inputs of which are combined and connected to the output of the third element I, and their outputs are connected to the inputs of the tripping blocks of the switches of the first and second bus systems respectively and the first and second inputs of the sixth OR element, between the output and the third input of which a temporary memory element is included, the output of the sixth element OR is connected to the second input of the starting block, the output of which is connected to the first input of the third element AND, the second input of which through the element NOT connected to the output of the third element OR. jtouL. J7 №J az u fcgsfc -feULo |  Olshiml Str yb-m Oml-bm lg; ODMA.IMM P