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What is the significance of five prevention of high voltage switchgear
October 23 , 2020

In order to ensure the safe operation of power network, the safety of equipment, person, and prevent misoperation, GB3906--1991 (3 ~ 35 kV AC metal Enclosed Switching Equipment) is clearly stipulated metal enclosed switching equipment shall have the following functions:

1、To prevent opening and closedisconnector(Isolate handcart)on-load.

2、To prevent mis-opening and mis-closing of circuit breakers, load switches, contactors (suggestive).

3、To prevent closing circuit breaker, load switch and other switch when the earthing switch is in closed position.

4、To prevent mis-closing earthing switch when alive.

5、To prevent stay into Charged compartment.


The above five functions of electrical misoperation prevention are referred to as the "five prevention". The "five prevention" of high voltage switchgear in order to standardize the safe operation process, it is an important measure to realize the safe operation. High voltage switchgear without five prevention function has serious hidden danger of misoperation.

3 ~ 35 kV AC metal Enclosed Switching Equipment


The correct closing process of high voltage switchgear is as follow: Close the back door first, then the front door, then open the earthing knife; Open the earthing knife first, then close the disconnector; Close the disconnector first, then close the circuit breaker.


The correct opening process of high voltage switchgear is as follows: open circuit breaker first, then open disconnector; open disconnector first, then close the earthing knife; close earthing knife first, then open the front door first, then the back door.


The five prevention function is to prevent the wrong operation, when the forced opening of the door and disconnector, the circuit breaker to achieve automatic trip and so on.


The realization offive prevention

KYN series mid-mounted type high-voltage switchgear are generally not equipped with disconnector (non-standard KYN switchgear shall be interlocked with program locks on the operating mechanism). Theinterlock between the circuit breaker and the earthing knife and door panelis controlled by the interlock mechanism of the cabinet itself. Generally, the cabinet has been installed and debugged before leaving the factory. The incoming line cabinet and the metering cabinet are equipped with electromagnetic locks.


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