Gas protection of the hottest transformer

2022-08-01
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Gas protection of transformer

during the operation of transformer, due to internal faults, sometimes we can not identify and take measures in time, which is easy to cause some accidents. After adopting gas relay protection, similar events can be avoided to a certain extent

1 scope of transformer gas protection

scope of gas protection is polyphase short circuit inside the transformer; Turn to turn short circuit, turn to turn short circuit with iron core or sheath; Core failure (heating and burning); Oil level drops or leaks; Poor contact of tap switch or poor welding of wire

the advantage of gas protection is that it can not only reflect various faults inside the transformer oil tank, but also reflect minor inter turn short circuit and core fault that the differential protection can not reflect. In addition, it is also reflected when air enters the transformer. Therefore, it is a protection with high sensitivity, simple structure and rapid action

its disadvantage is that it can not reflect the external faults of the transformer (bushing and precision lead screw pair drive; 2 is the ordinary belt drive outgoing line), so the gas protection can not be the only protection for various faults of the transformer. The performance of gas protection against external interference is poor. For example, it is easy to misoperate in case of severe vibration. If the problem of oil prevention is not well solved when installing the gas relay or the gas relay is not well waterproof, oil leakage may corrode the cable insulation or the relay may cause malfunction due to water ingress

2 operating principle of gas relay

in case of internal fault of transformer, the generated gas will gather at the upper part of gas relay to reduce the oil level. When the oil level is reduced to a certain extent, the upper pontoon will sink to connect the mercury contact and send a signal. If it is a serious fault, the oil flow will impact the baffle, which is generally called high-strength bolt to make it deflect, drive the linkage rod behind the baffle to rotate upward, stir up the linkage ring connected with the mercury contact snap ring to make the mercury contact rotate to both sides perpendicular to the oil flow, and the two mercury contacts are connected at the same time to trip the switch or send a signal

there are two commonly used gas relays: one is float type; The second is baffle type. Baffle type gas relay changes the lower float of float type into baffle structure. The difference between the two is that the baffle structure does not act with the oil level falling, but only when the oil flow rate reaches 0.6 ~ 1.0m/s. Therefore, when the baffle gas relay encounters the oil level falling or serious oil shortage, it will not cause the heavy gas to trip by mistake

3 gas relay collects gas to judge the fault

after the gas relay acts, if it is not clear whether it is caused by the internal fault of the transformer, the gas accumulated in the dislocation density increaser of the gas relay shall be collected immediately, and further judgment shall be made by identifying the nature of the gas

generally, the special glass bottle is inverted to make the bottle mouth close to the vent valve of the gas relay to collect gas. If the collected gas is colorless, tasteless and cannot be ignited, it indicates that the gas relay action is caused by the air discharged from the oil. If the collected gas is yellow and difficult to ignite, it indicates that the wooden part of the transformer has failed; If the collected gas is light yellow with strong odor and can be burned, it indicates that the paper part is faulty; If the gas is gray or black flammable gas, it is insulation oil fault

when judging whether the gas is combustible, for a transformer that has written a lot about the history of Chinese carbon fiber materials outdoors, the vent valve of the gas relay can be directly opened to ignite the gas discharged from the vent valve. If it is combustible, a bright flame will be seen along the airflow direction. During the test, it should be noted that in order to ensure safety, the air release valve must be closed in time before the oil begins to overflow

the gas collected from the indoor transformer shall be placed in a safe place for ignition test. When judging the color of gas, the action must be rapid, otherwise the color will soon disappear, and the correct results will not be obtained

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