What are the "five protections" of a high-voltage switch cabinet?

The "five protections" in the electrical industry usually refer to the "five preventions" (five safety interlock functions for preventing electrical maloperation), which are the core mandatory requirements for ensuring the safety of personnel and equipment.
I. Core Contents of Five-Prevention (Standard Definition)
1. Prevent opening or closing of disconnectors under load
When the circuit breaker is closed (under load), the operation of disconnectors is locked to avoid arc generation, short circuits, or equipment damage.
2. Prevent incorrect opening or closing of circuit breakers
Only with correct instructions and meeting operation conditions can circuit breakers be opened or closed, eliminating unplanned malfunctions that cause system failures.
3. Prevent closing of grounding switches (or hanging grounding wires) while energized
When the busbar / line is energized, the closing of grounding switches is locked to prevent short circuits, electric shock, and equipment explosions.
4. Prevent closing of circuit breakers with grounding switches (or grounding wires) engaged
When the grounding switch is in the closed position, the closing of the circuit breaker is locked to avoid metallic short circuits caused by energized grounding wires.
5. Prevent entering energized compartments by mistake
The cabinet door / compartment can only be opened when there is no electricity and the grounding switch is closed. When energized, it is forcibly locked to protect personnel safety.
II. Implementation Methods (Mechanical + Electrical + Microcomputer Interlocking)
Mechanical Interlocking: Mechanical linkage between the handcart position, grounding switch, and cabinet door. Incorrect operations directly jam the mechanism.
Electrical Interlocking: Secondary circuit with auxiliary contacts, when the logic is not met, the control power is cut off, and operation is impossible.
Microcomputer Five-Prevention: Computer key authorization, energized display, electromagnetic lock, to achieve programmed prevention of errors.
III. Confusion Points: Electrical Five-Prevention vs Relay Protection
Electrical Five-Prevention (Five protections): Preventive measures against human operational errors, it is a safety interlock.
Relay Protection: Fault protection (overcurrent, instantaneous trip, zero sequence, overvoltage, undervoltage, etc.), automatic tripping in response to electrical faults.