SU1737610A1 - Device for directed current protection of line - Google Patents

Abstract

Use: designed to protect dead-end power lines with branches to transformer substations. SUMMARY OF THE INVENTION: By introducing into the winding circuit of the current relay an additional resistor, shunted by the open contact of the latching relay with a return delay, as well as a pulse relay with a similar delay, it is possible to control the rate of current increment in the line, which is an additional criterion, along with the direction of the power overload and short-circuit modes, and increased protection sensitivity when it is installed on a dead-end line. 2 Il.

Description

(L

WITH

The invention relates to electrical engineering, in particular, to devices for back-up protection of power lines with branches to transformer substations in deadlock mode of operation.

A device for back-up protection of a transmission line with branches, containing a maximum current or distance protection, reacting to short-circuit currents behind the tapping transformers of the line, is known.

However, the possibilities of providing long-distance backup using current or distance protection on dead-end lines are limited by the need to detun them from the increase in load on the lines in transients, therefore such protection loses its purpose, completely, as a result of which

redundancy protection branch transformers.

The closest to the present invention is a device for current directional protection of a line, containing measuring current and voltage transformers, the primary windings of which have leads for connection respectively to the circuit of the protected line and to the power direction relay buses with a closing contact supplying it, the current winding and winding the voltage of which is connected to the secondary windings of current transformers and voltage, respectively, a current relay with a closing contact, a time relay and a pointing relay with a closing contact E, wherein the first terminal locking time relay contact connected to the positive terminal of an operational power source, a second terminal of said contact

vj with vj about

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is intended to be included in the circuit breaker trip circuit, and the closing contact of the pointer relay is intended to be included in the alarm circuit.

The protection reacts to an increase in the current in the line, taking into account its direction, which increases the selectivity of the action for short-circuit load currents during deadlock operation of the line.

The disadvantage of this device is its reduced sensitivity on the condition that seasonal changes in the load on the line are taken into account with an increase in the number and power of the connected transformers.

The purpose of the invention is to increase the sensitivity of protection when it is installed on a dead-end line, taking into account the change in the total load according to the consumption schedules of the connected emergency substations.

This goal is achieved by the fact that a device for current directional protection of a line containing measuring current and voltage transformers, the primary windings of which have leads for connecting respectively to the circuit of the protected line and to its supply buses, a power direction relay with a closing contact, a current winding and the voltage winding of which is connected to the secondary windings of current transformers and voltage respectively, a current relay with a closing contact, over time, a pointer relay with closing contacts the first output of the closing contact of the time relay is connected to the positive terminal of the operating power source, the second output of the indicating contact is intended to be included in the circuit breaker trip circuit, and the closing contact of the indicating relay is connected to the alarm circuit, the intermediate current transformer is additionally inserted, the primary winding which is included in the secondary circuit of the measuring current transformer, the first resistor connected in series with the winding of the current relay in the secondary th intermediate winding of the current transformer, the relay closing and fixing with the two break contacts, impulse relay with normally open contact, a second resistor and first and second capacitors. The plates of the latter are connected in parallel to the winding, respectively, of the latching relay and the pulse relay, the first terminals of which are combined with the first terminals of the windings of the indicating relay and the time relay and connected to the negative terminal of the operational power source. In the winding circuit of the pointer relay are connected in series

closing contact of the impulse relay; first closing contact of the latching relay; and closing contact of the current relay. The second output of the latter is combined with

the leads of the disconnecting contact of the latching relay and the closing contact of the indicating relay connected to the winding circuit of the impulse relay and connected to the positive terminal of the operating power source

between the connection point of the closing current contact with the first disconnecting contact of the latching relay and the second input of the latching relay coil, the second disconnecting contact of which is connected parallel to the first resistor. The breaker contact of the pointer relay and the second resistor are connected in series, the connection point of which is connected to the second terminal of the time relay winding through the closing contact of the power direction relay.

FIG. 1 is a circuit diagram of current directional line protection; in fig. 2 is a vector diagram of voltages and line currents under load and short circuit conditions.

The device for the current directional protection of the line contains the measuring element 1 of the current relay connected through a resistor 2 from the intermediate transformer 3 in the circuit of the transformer 4 of the current of the line 5, which through the switch 6 is connected to the busbars 7 of the substation with the transformer 8

voltage from which, together with the current transformer 4, the power direction relay 9 is turned on.

In the opening circuit of the circuit breaker 6 line 5 is established the closing contact 10

a time relay, the coil 11 of which is connected through the closing contacts 12 of the power direction relay 9, the opening contacts 13 of the pointing relay and the closing contacts 14 of the relay 1 of the current line control 5.

The coil 15 of the indicator relay is connected to the same contacts 14 through the closing contacts 16 of the pulse relay and the opening contacts 17 of the latching relay, the coil 18 of which, together with the capacitor 19

connected to the common point of pins 12 and 13 through a resistor 20. Open contact 21 of the latching relay is connected in parallel to resistor 2, and the closing contact 22 of the latching relay is connected to the coil circuit 23 of the pulse relay in parallel with the connected capacitor 24. Closing contact 25 of the pointer relay is included in the signal circuit overload line 5, which is connected to the transformers 26 branches.

The device works as follows.

With an increase in the current in line 5, the current relay 1 trips, closes its contact 14. This triggers the latching relay 18, which de-energizes the resistor 2 with its contact 21, which increases the current relay 1 setting. If this does not return the current relay 1, then when the contacts 12 of the power direction relay 9 are closed with a time delay exceeding the operating time of the transformer protection 26, the time relay 11 is activated, and the circuit 10 closes the trip circuit of the switch 6.

The setting of the current relay 1 when the resistor 2 is turned on is sufficiently sensitive to short-circuits behind the transformers 26, and when the resistor 2 is bridged, it is one and a half times smaller, but greater than the total load current of all the branches of the line 5. The power direction relay 9 has a 45 ° operation limit, which in relation to the direction of the short circuit current (70 °) it has a margin of 25 °, as well as a margin for non-operation at a load current angle of 20 ° (figure 2).

If, with a gradual increase in the current in the line, after the operation of the current relay 1 and the relay 18, the current relay 1 returns, then the current relay 1 is returned, then the line does not switch off. The latching relay 18 due to the discharge of the capacitor 19 disappears with a delay exceeding the time duration of possible overloads. After that, resistor 2 is shunted by pin 21.

If Kg of this time point is the operating current in the line does not exceed the setting of the (minimum) current relay 1, then the circuit returns to its original state. If the overload on the lines continues, then the contacts 14 of the current relay 1 are closed again and trigger the pointer relay 15 through the closed contacts 16 of the pulse relay 23 and closed when the relay 18 is locked and the contacts 17 are closed. At the same time, the relay 18 does not lock again because contact The index relay 13 opens earlier than the capacitor 19, which shunt the latching relay coil, is charged through the resistor 20. The closure of contact 25 of the pointer relay gives a signal that the line is overloaded. Before cavitation of the pointer relay 15 by personnel on duty, the protection remains derived to prevent its false action from overload,

Claims (1)

Claims An apparatus for current directional protection of a line, comprising measuring current and voltage transformers, the primary windings of which have leads for connecting, respectively, to the circuit of the protected line and to its supply buses, a power direction relay with a closing contact, the current winding and winding of which connected to the secondary windings of current and voltage transformers, respectively, a current relay with a closing contact, a time relay and a pointing relay with closing contacts, the first the time relay contact is connected to the positive terminal of the operating power source, the second output of the contact is intended to be included in the circuit breaker disconnecting circuit, and the closing contact of the indicator relay is intended to be included in the alarm circuit, characterized in that installing her 5 on a dead-end line, an intermediate current transformer, the primary winding of which is connected to the secondary winding of the current transformer, the first resistor, is additionally introduced into it; 0 connected in series with the winding of the current relay to the secondary winding of the intermediate current transformer, latching relay with closing and two opening contacts, a pulse relay with a closing contact, a second resistor and first and second capacitors, the plates of the latter are connected in parallel to the windings of the latching relay and the pulse relay, respectively the first conclusions of which are combined with 0 by the first leads of the windings of the pointer relay and the time relay and are connected to the negative terminal of the operating power source, the closing circuit is connected in series to the winding circuit of the pointer relay. 5 contact of the pulse relay, the first opening contact of the latching relay and the closing contact of the current relay, the second output of the latter is combined with the terminals of the switching relay of the latching relay and the closing contact of the pointing relay connected in the winding circuit of the pulse relay and connected to the positive terminal of the operational power supply between the connection point of the shorting relay contact current relay with 5, the first disconnecting contact of the latching relay and the second terminal of the winding of the latching relay, the second disconnecting contact of which is connected in parallel to the first resistor, the disconnecting contact of the indicating relay and the second resistor, the connection point of which is not connected to the power to the second output through the closing contact of the relay to the time relay winding.  CU2H. 10 P  about t to / 1. 6 Ub 2