In power systems, circuit breakers are not only key components for controlling and protecting power equipment, but also play an important role in preventing the spread of faults. Circuit breaker failure protection is one of the important measures to ensure the stable operation of power systems. This article will elaborate on the provisions of circuit breaker failure protection to help understand and implement these key safety measures to ensure the safety and reliability of power systems.
UEW5-3200 Universal Circuit Breaker
1. For circuit breaker tripping failure, circuit breaker failure protection should be configured according to the following requirements:
a) Power grids with voltage levels of 220 kV and above should be equipped with circuit breaker failure protection;
b) For some important parts of 110 kV (66 kV) power grids, when the fault removal time does not meet the stability requirements when the remote backup protection removes the fault, circuit breaker failure protection should be configured;
c) For generators or generator-transformer groups with a capacity of 100 MW and above, the generator circuit breaker or the high-voltage side circuit breaker of the generator-transformer group should be equipped with failure protection.
2. For circuit breakers with phase-splitting operation, only the situation of single-phase refusal (failure) of the circuit breaker can be considered. For three-phase operated circuit breakers, in addition to considering the single-phase refusal (failure) of the circuit breaker, the three-phase refusal (failure) of the circuit breaker should also be considered.
3. In order to improve the reliability of the circuit breaker failure protection, the following conditions should be met at the same time before the protection can be started:
a) The relay protection device on the faulty power equipment does not return after the outlet that can be instantly reset (after the fault is removed, the return time of the protection outlet that starts the circuit breaker failure protection should not be greater than 30 ms);
b) The electrical quantity discrimination element that determines that the circuit breaker is not disconnected does not return after the action (the action time and return time of the discrimination element should not be greater than 20 ms, and its return coefficient should not be less than 0.9).
4.. In order to improve the reliability of the circuit breaker failure protection, the locking element should be configured according to the following requirements. Among them:
a) Under the single busbar and double busbar connection mode, voltage blocking elements should be configured;
b) Under the double circuit breaker connection modes such as one and a half circuit breaker connection (3/2 connection), 4/3 connection, bridge connection, angle connection, etc., voltage blocking elements may not be configured;
c) When the generator, transformer and high-voltage shunt reactor fail, measures should be taken to release the voltage blocking to prevent the voltage blocking element from being insufficiently sensitive;
d) For faults on long lines with insufficient sensitivity of the voltage blocking element, measures should be taken to release the voltage blocking.
5. The circuit breaker failure protection should be operated according to the requirements to follow the tripping of the circuit breaker, trip the adjacent circuit breaker, lock the reclosing switch, and start the remote tripping according to the connection mode.
a) Under the connection modes such as one and a half circuit breaker connection (3/2 connection) and 4/3 connection, the circuit breaker failure protection should be operated after a short delay to trip the three phases of the circuit breaker again, and then after a longer delay to trip other adjacent circuit breakers.
b) Under the single busbar and double busbar connection mode, the circuit breaker failure protection can be delayed to trip the bus tie circuit breaker and the sectionalized circuit breaker related to the refusal circuit breaker with a short delay, and then trip all branches or all active branches connected to the same busbar with the refusal circuit breaker after a time limit; it can also be simultaneously operated to trip all branches or all active branches connected to the same busbar with the refusal circuit breaker after only a time limit, including the bus tie circuit breaker and the sectionalized circuit breaker. Under the double busbar connection mode, the circuit breaker failure protection should be able to automatically identify the operating position of the connection element and selectively trip all branches or all active branches connected to the same busbar.
c) For lines equipped with reclosing switches, the reclosing switch should be locked after the circuit breaker failure protection is activated.
d) When the transformer circuit breaker fails, the circuit breakers on other sides of the transformer or the circuit breakers on the power supply sides should also be tripped. When the circuit breaker on either side of the transformer has failure protection, the circuit breaker failure protection on that side should be configured to trip the circuit breakers on all sides through the transformer protection device.
e) When the line circuit breaker or line transformer group circuit breaker fails, the remote tripping should also be initiated to trip the circuit breaker on the other end of the relevant line to remove the fault.
f) When the generator end circuit breaker or the high-voltage side circuit breaker of the generator transformer group fails, it should also act to shut down the unit.
6. When the circuit breaker failure protection is activated and the output is in the form of contacts through the busbar protection device, transformer protection device, remote tripping signal transmission device, etc., anti-false operation measures should be configured.
UEM5Z1 Electronic MCCB Circuit Breaker
Note: Measures to prevent false operation may include the use of high-power (not less than 5W) intermediate relays, double-contact verification (such as “two-out-of-two” logic AND gate output), and the addition of on-site auxiliary judgment criteria for circuit breaker failure protection to the busbar protection device (such as voltage locking logic).
Post time: 7 月-19-2024