Introduction to the Five Protection Functions of 10kV High Voltage Switchgear

The "five protections" include:

Prevent opening and closing isolation switches (isolation plugs) with load;

Prevent accidental opening and closing of circuit breakers;

Prevent closing the circuit breaker when the grounding switch is in the closed position;

Prevent accidental closing of the grounding switch when energized;

Prevent accidental entry into charged intervals;

The above five measures to prevent electrical misoperation, abbreviated as "five precautions", are important measures to ensure equipment and personal safety and prevent misoperation.

1. The "five prevention" interlocking of handcart circuit breakers:

Some high-voltage switchgear cabinets are equipped with status displays to observe the status of circuit breakers, and mechanical indicators for the opening and closing status of circuit breakers are installed on the circuit breaker panel. The position of the handcart circuit breaker is interlocked with the secondary plug. After the handcart enters the cabinet, there is the following interlocking between the secondary plug and the handcart position

1) Only when the handcart is in the test position can the secondary plug be inserted and removed.

2) During the process of pushing the handcart from the test position to the working position and reaching the working position, the secondary plug cannot be unplugged (the secondary plug is locked).

3) Power lock: The closing mechanism can only be automatically unlocked when the control power supply is normally locked and the circuit is intact. When incoming maintenance is required; To ensure the safety of maintenance personnel, after removing the control circuit fuse, the on duty personnel are unable to close the circuit breaker either remotely or locally, as well as manually operated.

4) Hand operated circuit breaker; After the circuit breaker is closed in the working position, the forward and backward mechanisms are locked and cannot be exited. The handcart can only be shaken when the circuit breaker is in the open state. This is to prevent the handcart contact of the circuit breaker from being separated with load (pulling the isolation switch with load).

5) When the handcart is locked in the testing position, the electrical control circuit on the handcart can be connected, and the circuit breaker can be closed and opened for testing operations. At the same time, the handcart chassis and the interlocking mechanism of the grounding switch can be released, and the operation of the grounding switch can be carried out. When the grounding switch is closed, the interlocking mechanism locking device on the operating shaft of the grounding switch prevents the circuit breaker chassis from entering the vehicle. Only after the grounding switch is opened and the circuit breaker is locked, can the circuit breaker car enter the working position. This is to prevent the grounding switch from accidentally closing when it is in the closed position (to prevent live closing of the grounding switch) and (to install grounding wire).

6) If the circuit breaker has been closed in the test position and the entry mechanism is locked by the closing mechanism, the handcart cannot be moved forward. Only when the circuit breaker is opened can the locking of the entry mechanism be released and the vehicle can enter the working position; This is to prevent the circuit breaker handcart from connecting the contact under load (closing the isolation switch under load). Simultaneously locking with the grounding switch locking device, the operating hole automatically closes and locks, making it impossible to operate the grounding switch; (To prevent live closing of the grounding switch).

7) Interlocking between grounding switch and cable compartment cover plate: The lower door of the switchgear and the door panel of the cable compartment can only be opened when the grounding switch is closed. When the grounding switch is in the open state, the rear door or cover plate of the lower door and cable room cannot be opened; (To prevent accidental entry into live spaces), (To prevent live installation of grounding wires).

8) The handcart circuit breaker adopts an automatic partition to isolate the static contacts of the live part. When the circuit breaker exits the cabinet, the partition automatically closes the static contacts of the live part. At the same time, it also prevents (from accidentally entering the charged space) as shown in the figure

9) It is also possible to install live alarm devices in barriers, doors, and windows to remind inspectors and operators that the equipment inside the doors and barriers is powered.

2. Interlocking of isolation switches and circuit breakers (to prevent load opening and closing of isolation switches):

1) Anti error (operation) mechanical program lock, which is a lock used for high-voltage switchgear. This lock forces operators to operate electrical equipment correctly according to the prescribed safety operating procedures, thereby avoiding the occurrence of accidental operations.

2) After the circuit breaker is closed, the program key cannot be forcibly removed to operate the isolation switch or open the cabinet door. Only when the circuit breaker is fully open can the key be removed to operate the isolation switch.

3) Only when the isolation switch is fully opened and in the open state can the partition be installed, and after the partition is in place, the key can effectively open the circuit breaker and cable room door lock.

4) Only by locking the cabinet door, removing the key and partition, can the key be used to operate the partition; The key can only be removed after the isolation switch is fully closed in place; Only then can the circuit breaker be effectively operated to close and open

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