Oil-filled substation transformers 2.5–150 MVA, up to 161 kV

Description

Substation transformers are three-phase oil-filled distribution and power transformers rated from 2500 to 150 000 kVA. High voltage ranges from 2400 V to 161 kV, low voltage from 208Y/120 V to 69 kV. They are used in industrial, commercial and utility networks, at renewable energy facilities and in energy storage systems, and to power EV charging infrastructure. Production is a full cycle, from machining and tank fabrication to coil winding and electrical assembly. The electrical equipment is tested up to 150 kV.

Windings are copper–copper or aluminium–aluminium, with power limitations. The insulating liquid can be mineral oil, a biodegradable natural ester FR3 based on vegetable oils with a higher flash point, or a synthetic ester. Cooling is natural or forced (ONAN/ONAF), with a temperature rise of 65 °C, 55/65 °C or 65/75 °C. The bushings are porcelain. Voltage is adjusted by off-circuit tap changing (DETC) or on-load tap changing (OLTC). A nitrogen cushion or a conservator is provided.

The cover is bolted or welded, with lifting lugs and jacking pads. The ATC cable compartment is available in full or half height. Earthing pads are made of stainless steel to NEMA, the transformer stands on skid rails, and the radiators are panel or corrugated. Versions with a K-factor for non-linear loads and step-up transformers are available. The equipment includes a liquid level indicator, a combined pressure-vacuum gauge, a dial thermometer, a pressure relief valve and a winding temperature indicator, all with optional contacts. There is also a sudden pressure relay, a Buchholz gas relay, a drain valve with sampling point, top filling and vacuum valves, and a terminal box. Connection schemes are delta–wye, wye with grounded neutral–wye, delta–delta, wye–wye and wye–delta. The finish is ANSI-61 light grey, or to order.

Acceptance and routine tests are carried out to ANSI C57.90. They check winding resistance, transformation ratio, polarity and vector group, no-load losses and current, short-circuit losses and voltage, insulation resistance, and all devices. Applied voltage and leak tests are available. Special tests cover zero-sequence resistance, temperature rise, lightning impulse, noise level, loss tangent, partial discharge, dissolved gas analysis (DGA) and frequency response analysis (SFRA).

Technical specifications

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