Breaker failure protection means that when the relay protection action of the faulty electrical equipment issues a trip command and the circuit breaker refuses to move, the protection action information of the faulty device and the current information of the rejected circuit breaker constitute a discriminating failure of the circuit breaker, which can be compared Short time limit cut off other related circuit breakers in the same plant station to minimize the power outage range, thus ensuring stable operation of the entire power grid, avoiding serious burning of faulty components such as generators and transformers and collapse of the power grid.
Circuit breaker failure protection
(1) Start-up circuit : It consists of the exit relay of all the outgoing protection devices on the set of busbars and the identification component that determines whether the fault is eliminated or not. It can only allow the failure protection action when it satisfies both the condition that the protection device exit relay of the fault line (device) does not return and the fault still exists within the protection range.
(2) Time component : The timing is started after the protection action of the group of busbars. The action time limit does not need to cooperate with other protections. It only needs to avoid the sum of the circuit breaker trip time and the protection return time (0.3S).
(3) Outlet loop : The trip circuits of all circuit breakers on the set of busbars are connected together by an exit relay.
Breaker failure protection start-up process
figure 1 
figure 2
The basic principle block diagram for realizing the failure protection of the busbar circuit breaker of Fig. 1 can be explained by using Fig. 2. Therefore, the protection device connected to the components of a group (or a section of the bus), when its outlet relay acts to trip the circuit breaker itself, also starts the common time relay in the failure protection, the delay of the relay should be greater than the fault The sum of the circuit breaker trip time of the component and the return time of the protection device, therefore, does not hinder the normal resection fault, causing other circuit breakers (such as QF2, QF3) connected to the group (segment) busbar to trip, Thus, the fault of the K point is removed, and the backup function of the QF1 is rejected.
In order to improve the reliability of failure protection, the first step is to form an AND gate for the start of failure protection. This other condition is usually to detect the current of each phase, the current continues to exist, indicating that the circuit breaker is out of order, and the fault has not been cleared. Customization of current components, if it meets the sensitivity requirements, should be set as much as possible than the load current. In order to improve the reliability of the outlet circuit, low-voltage components and/or zero-sequence overvoltage components or negative-sequence overvoltage components should be installed. The intermediate relay contacts controlled by the latter are connected in series with the relay contacts of the fish outlets to form a trip of the fail-safe protection. Loop. The delay can be divided into two levels, a shorter one (delay I) jumper busbar breaker or a segmented circuit breaker; a longer one (delay II) jumps all outlet breakers with power. Figure 2 shows the logic block diagram of the breaker failure protection. The reliability measures used to prevent malfunctions from malfunctioning are to be meticulous and thoughtful.
Since the circuit breakers fail to protect and the busbar protection action must trip all the circuit breakers of the power supply on the busbar, the exit trip circuits of the two can be shared, and in many cases they are assembled on the consent screen.
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