Hazards caused by transmission mechanism failure o

Harm caused by the failure of the transmission mechanism of the circuit breaker

in small hydropower stations, the oil circuit breaker is often used as the main circuit breaker, and the oil circuit breaker often adopts the electromagnetic operating mechanism, the model is cdi0i or cdi0ii. Due to the control circuit failure and operation of the circuit breaker, and the mechanical failure of the transmission mechanism, the circuit breaker may not complete the normal operation. This paper discusses several mechanical failures of circuit breaker transmission mechanism encountered in a small hydropower station, and analyzes the possible losses and hazards

1. The main drive rod from the operating mechanism to the circuit breaker fell off

the circuit breaker was closed at one time, and the circuit breaker could not be closed. After checking, its control circuit, control power supply, closing power supply, etc. were normal, and all electrical reasons were eliminated. It is judged that it is the mechanism reason. Carefully check the inside of the operating mechanism, and no fault is found. After disconnection, manually close it with the force adding rod. No. 3: the thickness is uniform. Observe that the transmission mechanism does not transmit force at all. Check several inflection points of the transmission mechanism, and find that the cotter pin used for connection is broken and falls off. After treatment, resume operation

the reason for this kind of fault is that the circuit breaker operates too frequently, causing the cotter pin to fall off due to fatigue damage; The model of the cotter pin is wrong, and the small pin replaces the large one, which is too stressed; Iron nails are temporarily used on site to replace cotters, etc. Small power stations in remote mountainous areas often make the latter two mistakes because it is difficult to shop, so it may delay the time to find the fault due to a small open-end sale, resulting in large power generation losses

2. Transmission device failure from the main transmission rod to each phase circuit breaker

there are many forms of such failures: when the circuit breaker is in the closing or opening state, adjust the screw rod, operate the circuit breaker in the opposite direction, or the one-phase, two-phase, or three-phase transmission device does not transmit force, and the consequences may be different due to the different positions of the circuit breaker in the main wiring

(1) when the circuit breaker is in the off state, one phase of the transmission mechanism falls off:

when a power station is in the non power generation operation mode, operate the circuit breaker to close, and reverse the power to the power station through the system. After the closing command is issued, there is a closing impact sound in the high-voltage switch room; The breaker closing indicator light is on; But at the same time, the fault sound bell rings, "the secondary circuit is disconnected", "the single-phase grounding of 35kV system reaches the automatic average cooling and constant temperature of the sample" light signs are on; 35kV bus voltmeter indication is disordered; The contactor at the low-voltage side of the station transformer was not automatically put into operation, and there was a fault in the 35kV system that could not ensure normal operation, so the circuit breaker was immediately tripped to find out

after taking safety measures, carefully check the primary and secondary side windings and fuses, In addition to team member Po Chun Hsu said: "After chemical treatment to modify the industrial polyethylene, it was found that there was no abnormality except that the B-phase fuse on the secondary side was blown. Therefore, it was suspected that the fault might exist in the circuit breaker or the primary system of 35kV bus. When pulling out the circuit breaker truck and slowly trying in with the force adding rod, it was found that the A-phase transmission rod did not act, and it was checked that the cotter pin of the connecting part of the inflection point of the transmission rod fell off. After treatment, it returned to normal.

the essence of the above fault is the A-phase transmission rod of the circuit breaker No force, resulting in B and C phases have been closed and a phase has not been closed, that is, only B and C phases have voltage on the 35kV bus. The three-phase voltage applied to the primary winding is asymmetric, resulting in B-phase fuse fusing, zero sequence voltage and single-phase grounding protection action. Thanks to the protective action, otherwise it will cause serious consequences