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High-voltage switchgear is not equipped with gas protection; gas protection is a type of non-electrical protection used in oil-immersed transformers, rather than in high-voltage switchgear. Do not confuse a \"high-voltage cabinet\" with a \"transformer\". The working principle of gas protection is as follows: Principle of light gas operation: When a minor fault occurs inside the transformer (such as local overheating or partial discharge), the insulating oil decomposes due to heat, producing gases. These gases gradually accumulate above the gas relay, causing the oil level to drop. This in turn causes the float in the relay to sink, activating the light gas contacts and generating an alarm signal. Principle of operation for heavy gas protection: When a serious fault occurs inside the transformer (such as inter-phase short circuit or turn-to-turn short circuit), a large amount of gas is generated, and the oil flow creates pressure that impacts the baffle of the gas relay. When the speed of the oil flow reaches the set value (usually 1.2 m/s), the baffle moves, closing the contacts for heavy gas protection and thereby triggering an immediate shutdown of the power supply to prevent the expansion of the fault. This protection is primarily designed to address faults inside the tank, such as inter-turn or inter-phase short circuits in the windings, core failures, low oil level or oil leakage, and poor contact in the tap changer. Since high-voltage switchgear is usually dry-type or gas-insulated (such as with SF6), it lacks an oil-based medium, and therefore is not suitable for installing gas protection.