What is the logical relationship among the "five protections" of the high-voltage switch cabinet?

The "five protections" of the high-voltage switch cabinet are not independent entities; instead, they form a closed-loop interlocking logic centered around the "legality of equipment operation status". The core objective is to eliminate two fatal operations: "operating dangerous parts while energized" and "supplying power with hidden dangers". The relationship between the two is as follows: Based on the "breaker disconnection state" as the core premise, and with the "grounding switch and cabinet door status" as the boundary conditions, they are sequentially locked and mutually restricted.

I. Core Logical Mainline: Trip operation is the "unlock prerequisite" for all risky operations. The circuit breaker is the main control switch of the high-voltage circuit. Only when it is in the tripped state can the interlock of the disconnect switch and the grounding switch be released. 1. Main Logical Chain: Circuit breaker tripped → Disconnect switch operable → No electricity in the line and bus → Grounding switch operable → Cabinet door operable  Reverse illegal operations will be directly locked: Circuit breaker closed → Disconnect switch locked → Grounding switch unable to close → Cabinet door unable to open
2. Direct Constraints Corresponding to "Five Preventions"
"Preventing the opening and closing of disconnectors with load" is the first line of defense: it mandates that "the circuit breaker should be tripped first, and then the disconnectors should be operated", to avoid arc explosions when disconnectors are operated with current.
"Preventing incorrect tripping or closing of circuit breakers" is the logical master switch: through secondary circuit interlocks (such as only when the disconnectors are in place and the grounding switches are tripped, can the circuit breakers be closed), it avoids incorrect human contact or program errors leading to incorrect actions of the circuit breakers.
II. Boundary Logic: "Dual Protection" of Grounding Switches and Cabinet Doors
The states of the grounding switches and the cabinet doors are the last line of defense for personnel safety, forming "reverse constraints" with the main line.
1. Bidirectional Locking Function of Grounding Switches
Forward: Only when the disconnectors are tripped and the circuit is de-energized → the grounding switches can be closed (to prevent closing the grounding switches with current).
Reverse: After the grounding switches are closed → the circuit breakers are forcibly locked (to prevent closing the circuit breakers with the grounding switches) → the disconnectors cannot be closed, completely eliminating the risk of power supply.
2. Final Locking Logic of the Cabinet Door
"Preventing entering the energized bay" is the ultimate protection. Its unlocking conditions rely on two states simultaneously:
The circuit breaker is in the tripped state;
The grounding switch is in the closed state (has been reliably grounded).
As long as any one of the conditions is not met, the cabinet door cannot be opened, physically preventing personnel from contacting the energized components.