The “five-prevention” is a mandatory safety standard for medium-voltage switchgear in the power industry, designed to prevent personal injury and major equipment accidents caused by human misoperation. All qualified MV switchgear must have complete five-prevention functions.
- Prevent misoperation of circuit breakersIt prevents accidental opening/closing of breakers through electrical interlocks and padlock mechanisms. Only authorized personnel can operate important circuits, avoiding production interruption and safety accidents caused by misoperation.
- Prevent pulling/pushing the breaker handcart under loadThe handcart can only be racked in/out when the circuit breaker is in the open position. Operating under load will generate a strong arc, burn out contacts and cause a three-phase short circuit, leading to equipment explosion and personal injury.
- Prevent closing the earthing switch while the line is liveThrough live voltage indicators and mechanical interlocks, the earthing switch can only be operated when the busbar/line is confirmed de-energized. Closing the earthing switch on a live line will cause a malignant three-phase earth fault and severely damage equipment.
- Prevent energizing the circuit when the earthing switch is closedWhen the earthing switch is closed, the circuit breaker cannot be closed and the handcart cannot be racked to the working position. Energizing with an earth connection will cause a short-circuit accident.
- Prevent accidental entry into live compartmentsThe cable compartment door can only be opened when the corresponding circuit breaker is open and the earthing switch is closed. Doors of other live compartments cannot be opened, preventing personnel from accidentally entering live areas.
Our KYN28A switchgear and RMUs adopt both mechanical and electrical interlocks, fully meeting five-prevention requirements, with optional forced program locks for higher safety.