Basic working principle and setting method of gas transformer protection for power transformers - News - Global IC Trade Starts Here Free Join

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

Photocoupler

1. Basic working principle of gas protection When a fault occurs inside the power transformer tank (including a short circuit breaker and a grounding short circuit caused by dielectric breakdown), the transformer oil will be caused by the action of the fault point current and the arc. (usually 25# insulating oil) and other insulating materials are decomposed by local heat to generate gas. Because the gas is relatively light, they will flow from the fuel tank to the upper part of the oil pillow. When the fault is serious, the oil will rapidly expand and generate a large amount of gas. At this time, a strong gas will be mixed with the oil flow to the upper part of the oil pillow, so that the contact of the relay will act, the specified control loop will be turned on, and the signal will be sent in time. Or the automatic removal of the transformer and the protection device that acts in response to the above gas is called gas protection.
Gas relay is the main component that constitutes gas protection. For example, FJ3-80 and QJ series are installed on the connecting pipe between the fuel tank body and the oil pillow. In order to increase the sensitivity and reliability of gas protection, it must be inside the transformer. The gas generated by the fault passes through the gas relay smoothly. Therefore, when installing the transformer, the oil tank body should be inclined 1 to 1.5% toward the oil pillow, and the oil pipe should be inclined 2 to 4% toward the oil pillow.
The old gas relay (float type mercury contact relay) is not stable enough, and its anti-vibration ability is poor. It is easy to cause the mercury flow to cause malfunction due to vibration. The open cup baffle gas relay has high vibration resistance and reliable operation. Therefore, the current popular application in China's power system is the open cup baffle gas relay.
When the relay is in normal operation, its internal part is filled with transformer oil. When the inside of the transformer is slightly faulty, a small amount of gas generated by the transformer rises and accumulates in the air chamber above the gas relay, forcing the oil surface to rotate downward, causing the upper magnetic steel. Close to a pair of dry spring contacts, a light gas fault signal is emitted after the action. If it is a serious fault, a large amount of gas is generated, and at the same time, the oil temperature rises, the hot oil expands, and the pressure inside the tank increases sharply, forming an oil flow rapidly pulsing the lower baffle of the relay, causing the lower magnetic steel to be close to the other pair of reed contacts, acting on Tripped.
2. The setting of the gas relay of the gas relay can be adjusted by the differential pressure flow test or the oil pump type oil speed test equipment. The starting value is set according to the oil flow speed. Generally, the heavy gas is 0.5~1.5m/s. When the transformer has The oil circulation device is used in the range of 1~1.5m/s, and the forced oil circulation device is used in the range of 0.6~1m/s; for the light gas, the volume occupied by the gas in the relay is set, and the range is 250~300cm3. transmit signal.