Oil system must have good sealing performance
Jun 08, 2018

Oil-immersed transformers have several isolated oil systems that are isolated from one another. During the operation of the oil-immersed transformers, the oils in these independent oil systems are mutually exclusive, and the oil quality and operating conditions are also different. It is necessary to perform oil gas chromatographic analysis in order to determine whether there is any potential fault.

(1) The main body oil system. The oil system that communicates with the oil around the windings is an in-body system that includes the oil in the cooler or radiator, the oil in the conservator, and the internal oil in the oil-injection casing of 35kV and below.

When filling the oil, the gas bleeder plug stored in the oil system must be released. Generally speaking, the above components should have their own bleeder plugs. The oil in the main body mainly acts as insulation and cooling. Oil can also increase the electrical strength of insulating paper or insulating paperboard. When vacuum filling, if some parts can not bear the same vacuum strength as the main tank can withstand, apply temporary brake isolation, such as the gate valve between the oil storage tank and the main tank. The head of the submersible pump on the cooler should be sufficient to avoid inhaling air due to negative pressure. This oil system should have a pressure relief device protection system to eliminate the pressure generated when the body is in failure.

(2) The on-load tap-changer switches the oil in the switch chamber. This part of the oil has its own protection system, that is, flow relays, oil conservators, and pressure relief valves. The oil in the switch chamber acts as an insulating and extinguishing current. The oil will go in the oil produced when the switch cuts off the load current. This oil system should have good sealing performance and should protect the sealing performance even if arc pressure is generated during the switching process.

a. The oil-immersed transformer low-voltage winding adopts a cylindrical structure with copper foil winding in addition to the small-capacity copper conductor; the high-voltage winding adopts a multi-layered cylinder structure, which makes the distribution of the ampere turns balanced and magnetic flux leakage. Small, high mechanical strength, strong resistance to short circuit.

b. The iron core and the winding are individually tightened. The fasteners, such as the height of the device and the low-voltage leads, are provided with self-locking locknuts. They are designed to withstand the shock of transport.

c. The coils and cores are vacuum-dried. Transformer oil is vacuum filtered and filled with oil to minimize the moisture inside the transformer.

d. The fuel tank uses corrugated sheets. It has a breathing function to compensate for changes in the volume of the oil caused by temperature changes. Therefore, the product does not have an oil storage cabinet, which obviously reduces the height of the transformer.

e. Since the corrugated sheet replaces the oil conservator, the transformer oil is isolated from the outside, so that the entry of oxygen and moisture is effectively prevented and the insulation performance is reduced.

f. Based on the above five characteristics, it ensures that the oil-immersed transformer does not require oil change during normal operation, which greatly reduces the maintenance cost of the transformer and extends the service life of the transformer.

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