Turn the SA handle counterclockwise 45 º to the "trip" position, SA6-7 on, HR and R are short, excite YT through the +WC → SA6-7 KL → QF normally open contact → -WC, and the circuit breaker trip. After the circuit breaker is tripped, the normally open contact is disconnected, the normally closed contact is closed and the green light indicates that the circuit breaker has been tripped. After releasing the handle, the SA is reset to the "after tripping" position.
When the circuit breaker manually or automatically overlaps on the fault line, the protection device will trip the action, and if the operator still puts the control switch in the "close" position (SA5-8 contact on), or the automatic device contact KM1 is not reset, the circuit breaker SA5-8 will close again. Because of the line fault, protection and action trip, resulting in many "jump-close" phenomenon.
This phenomenon is called a "jump". If the circuit breaker jumps will not only cause the destruction of the circuit breaker, but also expand the accident, the so-called "anti-hop" measure, is to use the mechanical "anti-jump" locking device or the electrical "anti-jump" wiring in the control circuit, to prevent the "anti-jump" measure of the circuit breaker.
The control circuit shown in Figure 4 adopts the electrical "jump-proof" wiring. Its KL is a jump locking relay with two coils, one current starting coil attached in the trip circuit and another voltage protection coil connected in parallel with the closing contact coil through its own normally open contact KL1. The operating principle of the normally closed contact KL2, in the closing loop is as follows:
When closed with a control switch (SA) or automatic device (KM1), if closed on the fault line, the protection will act and the KOM contacts close to trip the circuit breaker. When the tripping circuit is connected, the KL current coil is charged and KL operates. The closed contact KL2 turns off the closing circuit and the voltage of contact KL1 turns KL self-retaining coil.
At this time, if the closing pulse is not lifted (e. g. SA is not returned or KM1 is stuck), the KL voltage self-holding coil is self-maintained through the contact of contact SA5-8 or KM1, opening the KL2 for a long time and reliably breaking the closing circuit so that the circuit breaker cannot be closed again. Only the circuit can return to normal state when the closing pulse is off (i. e. KM1 off or SA5-8 off) and the KL voltage since the holding coil is powered off.
The function of KL3 in FIG. 4 is used to protect the outlet relay contact KOM and prevent KOM from being burned before QF. The resistance R1 is to ensure that the signal relay can operate reliably when there is a serial signal relay in the outlet circuit.