Fault Analysis and Treatment of Outdoor High Voltage Vacuum Circuit Breaker

The advantages of the vacuum circuit breaker are not only oil-free equipment, but also its long electrical life, mechanical life, large breaking capacity, continuous breaking capacity, small size, light weight, and frequent operation. It is free from fire, operation and maintenance, and is quickly recognized by the power department for operation, maintenance and technical personnel.

The quality of the high-voltage vacuum circuit breakers produced in the early stage was not stable enough. During the operation, the current-carrying voltage was too high, and some vacuum interrupters still had air leakage. With the wide application of vacuum circuit breakers, the occurrence of faults has also occurred from time to time. This paper analyzes the common faults of outdoor high-voltage vacuum circuit breakers and gives the treatment methods.

1. Common vacuum circuit breakers are not operating normally.

1.1 Circuit breaker rejection, rejection

It is shown that after the circuit breaker is closed (open) command, the closing (opening) electromagnet acts, the iron core ejector will close (open) the scorpion top open, and the closing (opening) spring releases energy. Drive the circuit breaker to close (open), but the circuit breaker arc extinguishing chamber can not be closed (open).

Analysis of the cause of the failure: When the operation mechanism is refused, the failure reason is generally analyzed first, whether it is a secondary circuit failure or a mechanical partial failure, and then processed. After checking that the secondary circuit is normal, it is found that the gap of the universal joint head connected to the main arm of the operating mechanism is too large. Although the operating mechanism operates normally, it cannot drive the opening and closing of the circuit breaker, resulting in the circuit breaker not being able to divide normally. Closed.

Treatment method: Check the clearance of all connected parts of the operating mechanism, and replace the new high-hardness qualified parts with the unqualified parts.

1.2 Circuit breaker misclassification

It is manifested that the circuit breaker is in normal operation and trips under unexplained conditions.

Fault reason analysis: When the circuit breaker is in normal operation state, the circuit breaker cannot be opened when there is no external operation power supply and mechanical opening action. When it is confirmed that no erroneous operation has been performed, the secondary circuit and the operating mechanism are inspected. It is found that the auxiliary switch contact in the operating mechanism box has a short circuit phenomenon, and the opening power supply is connected to the opening coil through the short circuit point, thereby causing a false opening. The reason is that the top of the circuit breaker mechanism box leaks rain, and the rainwater flows down the output arm, which falls on the mechanism auxiliary switch, causing the contact to be short-circuited.

Treatment method: check all possible leak points and effectively block; install a sealing rubber sleeve on the output arm link; open the heating device in the mechanism box.

1.3 After the circuit breaker mechanism stores energy, the energy storage motor does not stop.

It is shown that after the circuit breaker is closed, the operating mechanism of the operating mechanism starts to work, but after the spring energy is full, the motor is still running.

Analysis of the cause of the fault: After the circuit breaker is closed, the energy storage motor of the operating mechanism starts to work, and after the spring energy is full, the spring has stored energy signal. There is a pair of normally open auxiliary contacts and a pair of normally closed contacts of the circuit breaker in the energy storage circuit. After the circuit breaker is closed, the normally open contact of the auxiliary switch is turned on, the energy storage motor starts to work, and the spring is full of energy. The mechanism rocker arm opens the normally closed contact of the travel switch, the energy storage circuit is de-energized, and the energy storage motor stops working.

The reason why the outdoor high-voltage vacuum circuit breaker energy storage motor has been working all the time is that after the spring is full of energy, the mechanism rocker arm fails to open the normally closed contact point of the travel switch, the energy storage circuit is always charged, and the energy storage motor cannot stop working.

Treatment method: adjust the installation position of the travel switch so that the normally closed contact of the travel switch can be opened when the rocker arm is at the highest position.

1.4 Circuit breaker DC resistance increases

It is shown that after the circuit breaker is running for a certain period of time, the contact resistance of the arc chamber contact is continuously increased.

Analysis of the cause of the fault: Since the contacts of the vacuum interrupter are butt joints, the contact resistance of the contacts is too large. The contacts are prone to heat during the current carrying, which is not conducive to the conduction and breaking circuit, so the contact resistance value must be less than the requirements of the factory specification.

The pressure of the contact spring has a great influence on the contact resistance and must be measured with an overtravel pass. The gradual increase in contact resistance also reflects the electrical wear of the contacts and is complementary. The electrical wear of the contact and the change of the contact opening distance of the circuit breaker are the fundamental reasons for the increase of the DC resistance of the circuit breaker.

Treatment method: adjust the contact opening distance and overtravel of the arc extinguishing chamber. The method of measuring the contact resistance can be measured by the DC voltage drop method required by the “Procedure” (current should be above 100A), otherwise the arc extinguishing chamber should be replaced.