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On-load Tap Changer System for Oil-immersed Transformers

The oil-immersed transformer has several separate oil systems isolated from each other. During the operation of oil-immersed transformer, the oil in these independent oil systems is not interlinked with each other, and the oil quality and operating conditions are also different. Therefore, gas chromatographic analysis of the oil should be carried out to determine whether there are potential faults. The on-load tap changer system for on-load oil immersed transformers is described below.

On-load oil immersed transformer with on-load tap switch oil in switching chamber. This part of the oil has its own protection system, named flow relay, oil storage tank, pressure relief valve. The oil in this switch room insulates and extinguishes the current. The oil will go into the oil when the switch cuts off the load current. The oil system should have a good sealing performance, even if the arc pressure is generated during the switching process to protect the sealing performance.
On-load tap-changer switch indoor oil is from the main part in oil, but when filling in a vacuum, to avoid breaking the switch room seal, should with the principal part of oil inside the vacuum oil at the same time, when filling in a vacuum, make the two systems with the same vacuum, when it is necessary, also the system of oil storage tank should be isolated in a vacuum. For the convenience of the structure, the oil storage tank of the main part and the switching switch room is designed as an isolated whole.

When carrying out various insulation tests on the on-load oil immersed transformer, the first step is to release gas, which may be stored through the release plug. The presence of potential faults can be predicted by analyzing gas chromatography in the oil of each system. Each oil system should meet the requirements of operation, such as the change of oil volume when absorbing oil expansion and contraction, the isolation valve between the oil drain valve, gas plug, cooler and radiator and the main oil tank. Each oil system has good sealing performance. The oil in the switching room of on-load tap switch should be replaced independently without releasing the oil in the main body. The oil in the main body can be released during transportation and filled with dry nitrogen.

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