What are the five-prevention of the switchgear?
Sep 10, 2020
The switchgear is equipped with a series of five-proof interlocking devices to prevent danger and corresponding misoperation from causing serious consequences. They are：
| Five-prevention requirement | Detailed measures |
| Prevent pushing and pulling trolleys with loads. | If the circuit breaker is already in closing status, the interlocking rod moves backward. At this moment, movement of closing spring release plate can not raise the lever to release the lock latch. When the circuit breaker is in closing status, the trolley will be hampered and will not move if the circuit breaker trolley is pulled by mistake. |
| Prevent circuit breakers from mal-operation. | Operations on completely closed door conditions fully ensure the safety of operators. There is a mechanical interlock between circuit breaker trolley and the switchgear. Only when the circuit breaker trolley in TEST and SERVICE positions, the closing can be conducted. |
| Prevent switching-on earthing switch in live condition. | Circuit breaker trolley is in SERVICE position. And earthing switch can not operate with mechanical interlock. |
| Prevent earthing switch from energizing in earth position. | When earth switch is closed, then with mechanical interlock, the circuit breaker, the entrance operating can not be conducted in the circuit breaker trolley. And the trolley can not enter into SERVICE position. Then the primary circuit can not be connected. Only when earthing switch is in opening position, the trolley can rock from TEST position to SERVICE position. |
| Prevent from entering into energized separation. | The busbar compartment, circuit breaker compartment and cable compartment are separated to each other. When the trolley is moved to TEST position or REMOVED position, the shutter will automatically close and the primary stationary contact is isolated completely. When the cable compartment is fitted with voltage indicator or mechanical interlock, the back door can open only after earthing switch is closed. If the back door is not closed, earthing switch can not open. |
| Secondary plug. | When the trolley is in SERVICE position, the secondary plug is locked and can not be removed. |
