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Measures to Prevent Incorrect Operation of Vacuum Circuit Breakers

The vacuum circuit breaker has fast breaking speed, strong de-ionization, and is not easy to form arc reignition. It not only effectively limits the overvoltage in system operation, but also the moving and static contacts are not easily burned by the arc, and there will be no leakage of other media. Therefore, the maintenance is easy and its service life is long. These are the advantages that the low-oil circuit breaker doesn’t have. However, at present, accidents of the vacuum circuit breaker opening and closing knife-switch with load happen frequently, which causes the whole circuit breaker to burn out, resulting in shutdown, power outage and even serious consequences of personnel burns.


Ⅰ. Reasons for accidents of vacuum circuit breaker opening and closing knife-switch with load


1. When operating the vacuum circuit breaker, the operator still uses the method of operating the low oil circuit breaker. The handle of the low oil circuit breaker cart is lifted up at the lowest position of the panel to immediately open the knife-switch, and the cart handle is not raised to a higher than horizontal position or equal to the horizontal position. At this time the circuit breaker is still in the closed state and then pushed into the operating position.


2. The time for the auxiliary machines in the power plant to switch to hot standby is generally 1:00 to 5:00 in the morning. At this time, the operators are not in good spirits, and the opening and closing indicators are not carefully checked. Or the indicators are unclear. It was mistakenly determined that the circuit breaker in the inspection position must be in the open state, and it was pushed into the operating position naturally.


3. The horizontal position of the handle of the vacuum circuit breaker cart is relatively high. The horizontal position of the handle corresponds to the switch opening position, so that the operator who is slightly shorter does not lift the handle to the horizontal position and mistakes it for the horizontal position, and the switch has been tripped open.


4. The circuit breaker itself lacks technical measures to prevent from opening and closing the knife-switch with load, and the manufacturer did not manufacture this type of circuit breaker in accordance with the requirements of the five preventions.


Ⅱ. Measures to prevent misoperation of vacuum circuit breakers


1. Install a brake device on the hand-carried vacuum circuit breaker. When the circuit breaker is closed, the moving mechanism of the circuit breaker is blocked so that the circuit breaker cannot move when the circuit breaker is closed. When the circuit breaker is in the inspection position, if it is in the closed state, it cannot be pushed into the running position.


2. Improve the push-pull handle of the circuit breaker to ensure that the circuit breaker will trip reliably as long as the circuit breaker handle is lifted.


3. Add a miniature alarm device the size of a mobile phone to the handcart type vacuum circuit breaker that has been put into operation.


Specific method: Introduce a normally open auxiliary contact of the vacuum circuit breaker into a microphone jack on the circuit breaker panel. When the operator operates the switch, first insert the alarm plug into the jack, and the alarm immediately emits a sharp voice or the voice prompt of switch closed, operation prohibited so as to remind the operator to disconnect the circuit breaker first, and then operate.


If the normally closed contact circuit breaker is in the open state, after the alarm plug is inserted into the jack, an audible prompt will sound that switch opened, operation allowed. If the vacuum circuit breaker is in the closed position, when the alarm plug is inserted into the jack, there is no sound, and no operation is allowed at this time. In this way, a safety line of defense is added to prevent misoperation, and it is a simple technical measure to prevent accidental opening and closing of the breaker.


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