Top Ten Benefits of Transformer Pressure Relief Valves Principle of Operation

Date: August 4, 2025 08:25:52

transformerspressure relief valveIt is the key protection device to ensure the safe operation of the transformer, and its design and function are centered around the rapid release of internal over-voltage, preventing equipment damage and accident expansion, mainly with the following ten advantages:

1. Fast response to overvoltage conditions

When the transformer internal short circuit, insulation breakdown and other faults produce a large amount of gas or oil flow impact, the pressure relief valve can be in a very short period of time (usually milliseconds) action, quickly open the valve to release the pressure, to avoid the tank rupture due to overpressurization, the response speed is far better than the traditional safety devices.

2. Precise control of action pressure

Through the precise spring mechanism and sealing design, the pressure relief valve can be set to the precise operating pressure value (usually 0.035MPa~0.15MPa) according to the rated parameters of the transformer (e.g. capacity, oil pillow pressure, etc.), which ensures the reliable sealing under the normal operating pressure, and only activates in the case of real overpressure, avoiding the false operation.

3. Automatic reset function

After the fault is removed and the internal pressure drops to the normal range, the valve can be automatically closed and the sealing state restored without manual intervention, which reduces the maintenance workload and at the same time ensures that the transformer will return to the normal operating conditions (e.g., oil level, insulation, etc.) within a short period of time.

4. Effective protection of equipment integrity

By releasing the overpressure in time, the pressure relief valve can prevent the transformer tank, bushing, radiator and other components from deformation and rupture due to overpressure, avoiding oil leakage, insulating oil contamination or secondary damage to the internal components, and reducing the maintenance cost of the equipment.

5. Reducing the risk of fire and explosion

In case of internal transformer failure, high temperature and pressure may trigger insulating oil combustion or gas explosion. By releasing the pressure and part of the oil flow, the pressure relief valve can reduce the temperature and pressure peaks inside the tank, reducing the probability of fire, explosion and other vicious accidents from the source.

6. Compatible with a wide range of transformer types

Applicable to oil-immersed transformers, reactors and other equipment, whether it is a small distribution transformer or a large power transformer, can be selected according to its structure (such as with oil pillows, fully sealed) to adapt the pressure relief valve model, versatility.

7. Auxiliary fault diagnosis

Some of the pressure relief valves are equipped with action signal output devices (such as mechanical indicators, electrical contacts), when the valve action, the signal can be sent to the monitoring system, prompting the operation and maintenance personnel may exist within the transformer fault, to facilitate timely investigation of hidden problems.

8. Excellent oil and aging resistance

Valve body materials (such as cast iron, stainless steel) and seals (such as oil-resistant rubber) have good resistance to corrosion of insulating oil, high temperature aging characteristics, can be in the long-term operation of the transformer in harsh environments (oil temperature changes, oil oxidation) to maintain stable performance, long service life.

9. Easy installation and maintenance

Compact structure design, usually through the flange or thread directly mounted on the top or side of the transformer tank, the installation process is simple; routine maintenance only need to regularly check the sealing status, operational flexibility and signaling device, without complex operation.

10. Compliance with international safety standards

Product design and performance to meet the IEC (International Electrotechnical Commission), GB (national standards) and other relevant norms (such as IEC 60517, GB/T 30141), through the strict verification of the type test, to ensure the reliability of the reliability of the transformer in various types of operating conditions, for the safe operation of the transformer to provide compliance guarantees.
The pressure relief valve becomes an indispensable safety barrier for the transformer through the features of "fast response, precise control, automatic reset, and compatibility", which not only protects the equipment itself, but also indirectly guarantees the stable operation of the power system.

Principle of operation of transformer pressure relief valves

on the basis ofPressure sensing and mechanical linkage controlThe core is to sense the pressure change inside the transformer through the sensitive element, when the pressure exceeds the set threshold, open the valve quickly to release the pressure, and close it automatically when the pressure returns to normal, so as to realize the overpressure protection of the equipment. The specific working process can be divided into the following stages:

I. Normal operating conditions: sealing and standby

During normal operation of the transformer, the internal pressure is in the stabilized range (usually balanced by the oil pillow respiration, the pressure is close to atmospheric pressure). At this time:

 

  • Pressure relief valves forsealing assembly(e.g. rubber gasket) inSpring preloadUnder the action of the valve body, it is tightly pressed onto the sealing port of the valve body to ensure that the oil and gas inside the transformer will not leak.
  • The spring preload is precisely adjusted to correspond to the valve'sAction Pressure Threshold(e.g. 0.05MPa~0.12MPa, set according to the transformer model), to ensure that the valve is always closed and sealed under normal pressure.

Second, overpressure trigger stage: the pressure breaks through the threshold, the valve opens

When the transformer internal failure (such as winding short circuit, core overheating, insulation breakdown, etc.), it will instantly produce a large number of high temperature gases (such as decomposition of oil and gas mixtures), resulting in a sharp rise in pressure in the tank:

 

  1. The elevated pressure acts on the pressure relief valve'sDiaphragm or piston(pressure-sensing element), which produces an upward thrust.
  2. When the thrustExceeding the spring preloadWhen the spring is compressed, the sealing assembly separates from the sealing port and the valve opens quickly (opening time usually ≤ 2ms).
  3. High-pressure gases and part of the oil flow are discharged to the outside of the transformer through the release channel of the valve (e.g. the exhaust port on the side of the valve body), thus quickly reducing the pressure in the tank and avoiding overpressure damage.

III. Pressure recovery phase: automatic shutdown and reset

After troubleshooting, the pressure inside the transformer gradually dropped to the normal range:

 

  • As the pressure drops, the thrust acting on the diaphragm/piston decreases and the spring preload gradually regains its dominance, pushing the seal assembly back together on the seal port.
  • The valve closes automatically to restore the sealing state, ensuring that the transformer's internal oil level and insulation properties are not affected and that normal operation can continue without manual intervention.

IV. Auxiliary signal feedback (some models)

Some pressure relief valves also incorporateMotion indicating device, used to indicate whether the valve has been triggered:

 

  • mechanical indication: When the valve is opened, the linkage mechanism drives the indicator plate to pop up (e.g. "actuated" sign), visualizing the action record.
  • Electrical signalsThe transformer can be operated by a microswitch or a dry contact to transmit an electrical signal to the monitoring system in the control room, alerting the operation and maintenance personnel that there may be internal faults in the transformer that need to be investigated in a timely manner.

 

In short, the operating principle of a pressure relief valve can be summarized as follows:"Spring preloaded seal → overpressure top open valve → spring reset after pressure release"It is an indispensable "safety relief valve" for oil-immersed transformers, which realizes dynamic pressure protection of the transformer through the sensitive response of the mechanical structure.
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