How does a gas relay work?

Date: July 29, 2025 10:31:33

Gas RelayIt is a "monitoring sentinel" for internal transformer faults, and its core working principle is to utilize the internal transformer faults generated when thegas (i.e. gaseous substance)maybeoil slick, triggering relay action to realize fault warning or trip protection. It is like the "breathing sensor" of the transformer, which can keenly capture internal abnormalities and send out signals.

Why do gas relays sense faults?

When the transformer is in normal operation, there is only a small amount of gas or almost no gas generated inside, and the gas and oil inside the gas relay are in a stable state and will not trigger the action. However, when there is a fault inside the transformer (e.g. insulation breakdown, winding short circuit, core overheating, etc.), the fault point will generate gas (e.g. hydrogen, methane, etc.) due to high temperature, or form an oil shock due to intense gas production, and these changes will be accurately captured by the gas relay.

Two core mechanisms of action for gas relays

There are two key components inside the gas relay:Upper open cup (light gas element) respond in singingLower baffle (heavy gas element)The specific action logic is as follows:

 

Type of protection trigger condition course of action corresponds English -ity, -ism, -ization
Light gas protection Minor internal malfunctions (e.g., local overheating, insulation deterioration) that produce small amounts of gas that collect in the upper part of the relay Gradually increase the gas, so that the oil level in the relay drops, the upper opening cup due to the gravitational moment is greater than the buoyancy moment and tilt, driving the contact closure Alarm signals to alert staff to check for potential faults within the transformer
heavy gas protection Serious internal failure (such as winding short circuit, iron core burning), instantaneous generation of a large amount of gas, the formation of a strong oil flow shock High-speed oil flow impacts the lower baffle, which deflects the lower baffle and drives the contacts to close. Direct activation of circuit breaker tripping, cut off the transformer power supply to prevent the expansion of the fault

Motion performance under different faults

  • minor breakdown: If local overheating of the iron core leads to decomposition of the insulating oil, the gas generated slowly rises to the upper part of the gas relay, and after the oil level drops to a certain level, the light gas operates and sends out a "light gas signal".
  • serious malfunctionIf the winding short-circuit generates an arc, a large amount of gas is decomposed instantly, and the speed of oil flow can reach 1.0-1.2m/s (the setting value of some relays), which impacts the lower baffle plate, and the heavy gas operates and triggers the tripping.
  • Lower oil level: If the transformer is leaking oil causing the oil level to drop slowly, the light gas will also act to signal when the oil level is below the upper open cup.

Key Considerations

  • mounting position: It must be mounted horizontally on the connecting pipe between the tank and the oil pillow to ensure that the gas can be gathered smoothly and that the oil flow is directed correctly to impact the baffle.
  • Sensitivity adjustmentThe operating gas volume of light gas is generally set to 250-300mL, and the operating oil speed of heavy gas is usually 0.6-1.5m/s (adjusted according to the transformer capacity), which needs to be calibrated regularly to ensure the accuracy of the parameters.
  • routine maintenance: It is necessary to regularly discharge the air accumulated in the relay (non-faulty air accumulation, such as air bubbles generated by oil temperature changes) to avoid false operation; at the same time, check whether the contact contact is good, to prevent poor contact leading to protection failure.

Summary: "Fault warning and emergency braking system" for transformers

The gas relay monitorsgas quantityrespond in singingOil flow rate, perfectly realizes the hierarchical protection against internal transformer faults: light gas is responsible for "early warning" and heavy gas is responsible for "emergency braking". This dual protection mechanism, which can detect potential problems in time and also quickly cut off the power supply in case of serious faults, is one of the core components to ensure the safe operation of transformers. Understanding its working principle helps to more accurately determine the type of transformer failure and improve the efficiency of equipment maintenance.
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