Single action automatic reclosing scheme for 6 — 10 kV overhead and cable transmission lines

The essence of automatic reconnection is the rapid restoration of power to users or system connections by automatically turning on switches that are turned off by protective devices in the event of damage to system elements or accidental shutdown.

Most often, automatic reclosing with one action is used on critical overhead and cable power lines of 6 and 10 sq. In fig. 1 shows a diagram of the automatic reclosing of a 6-10 kV line carried out using spring drive PP-67… Protection circuits not shown. In this circuit, a single instant auto-close device is provided using an auto-reclose sliding contact that pulses the EV's closing solenoid, causing the switch to turn on. This occurs when the circuit breaker is tripped by the protection when the pulse passes through the closed contact of the BCA.

The lever system that drives the contact block on the shaft is designed so that the latter decelerates to some extent in the intermediate position. This increases the pulse time given by the sliding contact. In this regard, the angle of rotation of the drive shaft must be at least 95 °. Compliance with this condition guarantees the correct operation of all auxiliary contacts.

Rice. 1. Scheme of instantaneous automatic closing of a line 6 — 10 kV

When the breaker is de-energized by the solenoid, the EO or auto-reclose button does not trip because the BKA auxiliary contact closes with each breaker closure and opens when the breaker is manually or remotely tripped.

One time automatic reclosing is provided by the fact that the action of the slip contact is short-lived and when the circuit breaker is re-triggered by the protection (failure to reclose), the slip contact gives an impulse to the drive which is not yet prepared to close because the preparation time for the drive to operate when closed (spring coil) is longer than the breaker open time.

Rice. 2. Automatic reclosing scheme with time delay

In the scheme shown in fig. 2, after an emergency shutdown, the circuit breaker does not turn on immediately, but with a certain time delay (0.5 — 1.5 s), determined by the duration of the contact closure of the time relay PB1. After the switch is turned off, the PBO relay receives power and, closing its contact with a time delay, gives a command to start the automatic closing device.

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