Why Is It Forbidden To Work On Equipment That Is Only Disconnected From The Power Supply By A Circuit Breaker?

Although the circuit-breaking capacity of Lv Pole Mounted Circuit Breakers is very strong, its breaking stroke is very limited.
The moving and static contacts of the circuit breaker are in the organic arc extinguishing chamber. Whether they are broken or not is only indicated by the opening and closing indicator plate, which is not obvious in appearance.
More importantly, the operating energy of the vacuum circuit breaker is not disconnected in the deactivated state. If there is a problem with its control circuit or secondary mixed lines, accidental contact, misoperation, etc., the circuit breaker operating mechanism will be activated and automatically closed to energize the equipment.
In addition, when the circuit breaker's opening device is opened, if its operating mechanism fails and the circuit breaker is not actually opened, the position indicator may still be brought to the opening position by the (mechanism), resulting in a virtual opening of the circuit breaker, causing an illusion.
Therefore, the "Safety Regulations" have clearly stated: It is forbidden to work on equipment that is only disconnected by the circuit breaker. When the power is cut off for maintenance, the circuit breaker must be withdrawn from operation, the load-side disconnector and the busbar-side disconnector must be disconnected, and an intuitive and obvious air insulation gap must be created to meet the requirements of work safety.