Circuit breaker failure protection is an important secondary protection. When a fault occurs in the system, if the relay protection operates correctly and issues a trip command but the circuit breaker fails to trip for some reason, the failure protection system takes over.
Its core function is to trip all other circuit breakers adjacent to the failed circuit breaker within the same substation within a short time delay, thereby minimizing the scope of the power outage, preventing severe damage to primary equipment such as generators and transformers, and preventing the collapse of the power grid.
1
Operating Principle
Faulted Circuit Interlock employs a "dual-criterion" logic, requiring both of the following conditions to be met before it operates: First, the protection of the faulty equipment has issued a trip signal; second, current is still detected flowing through the faulty circuit breaker, indicating that the fault has not yet been cleared. Once these two conditions are met, the protection first attempts to trip the faulty circuit breaker after a short delay. If this fails, it trips the adjacent circuit breakers after a long delay. Additionally, voltage interlock elements (such as busbar undervoltage or negative-sequence voltage) are used to further confirm the presence of a fault and prevent false tripping.
2
Typical Application Scenarios (Using a 3/2 Configuration as an Example)
Failure of an Edge Circuit Breaker: If an edge circuit breaker fails to trip, the failure protection will trip all circuit breakers on its busbar and initiate a remote trip to isolate the power supply on the opposite side of the line.
Failure of the Central Circuit Breaker: If the central circuit breaker fails to trip, the failure protection will trip the side circuit breakers on both sides of it and initiate a remote trip to isolate the power source on the opposite side of the line.
If the failure protection does not initiate a remote trip, although backup protection may eventually clear the fault on the opposite side, the fault clearance time will be significantly prolonged, which is extremely detrimental to system stability and equipment safety. Therefore, modern failure protection systems generally include a remote trip function.
In summary, circuit breaker failure protection serves as the last line of defense for the safe operation of power grids and plays an indispensable role in grids at 220 kV and above.
Our address
No. 1 East Gaoxin Avenue in the High-Tech Development Zone of Baoji City, Shaanxi Province, China
Phone Number
+86 15332289620 (whatsapp/ Telegram/ Wechat)
