Oil-immersed distribution transformers of medium and large rating up to 30 MVA, 36 kV

Description

Oil-immersed distribution transformers of medium and large rating are installed at substations near consumers. They receive electricity from the high-voltage grid, step it down and distribute it between consumers or lower-voltage substations, regulating the voltage in the grid. The manufacturer produces such transformers rated up to 30 MVA with primary and secondary voltage up to 36 kV. Each transformer is designed to the customer's requirements, and the list of options is very wide.

The tank is hermetically sealed or has a conservator, with corrugated walls (for ratings up to 3 MVA) or with attached radiators. The core is assembled from high-quality cold-rolled grain-oriented Hi-B steel without holes in the laminations and clamped with heat-treated plastic bands. This reduces no-load losses, magnetizing current, magnetostriction and noise, as well as mass and dimensions. The windings are selected for the purpose: disc windings with high series capacitance for HV, and cylindrical layer windings of transposed conductor or helical windings for LV with high currents. Transposed conductor reduces additional losses and local overheating, so the transformer is lighter and more compact.

The standard equipment of the conservator version includes HV and LV bushings, an off-circuit tap changer, lifting lugs, earthing terminals, a Buchholz gas relay, a dehydrating breather, a pressure relief valve, a dial thermometer, an oil level gauge, a filling pipe, skids, a drain valve and a rating plate. Options include an OLTC, plug-in HV bushings, a galvanized tank, a rubber diaphragm, a dual-voltage version, a winding temperature indicator, cable boxes, wheels, fans and pumps, an oil-water heat exchanger and an oil oxidation protection system.

There are also special designs, namely a transformer combined with GIS, a fully assembled transportable transformer and a low-noise version. The transformers are made at plants in Japan and Thailand. Typical applications are 35/6–10 kV substations of industrial enterprises, power plant auxiliaries, infrastructure facilities and renewable energy sources. The series is an equivalent of ТМН/ТДН oil-immersed transformers up to 35 kV. The choice of options depends on the substation conditions and the customer's requirements. An OLTC is needed where the voltage must be regulated under load, and cooling with fans and pumps is intended for increased load.

Technical specifications

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