Oil-Immersed Transformer Product Introduction

An oil-immersed transformer uses oil as its primary insulation and cooling medium, employing methods such as oil-immersed self-cooling, oil-immersed air cooling, oil-immersed water cooling, and forced oil circulation. The main components include the core, windings, tank, conservator, breather, explosion-proof pipe (pressure relief valve), radiator, insulating bushings, tap changer, gas relay, thermometer, and oil purifier.

Due to long-term immersion in the silicon steel sheets, oil permeates the layers of the transformer, and the elasticity of the transformer oil provides a buffering effect, resulting in lower noise levels. However, the tap changer is located inside the tank, and the contact quality during voltage adjustment is not visible from the outside. If contact is lost, the circuit is open; poor contact can easily burn out the switch under excessive load.

Under specified cooling conditions, oil-immersed transformers can operate according to the nameplate specifications, but the top oil temperature should not exceed 90℃. To prevent insulation aging, the top oil temperature should generally not frequently exceed 85℃, and the alarm setting should be set at 80℃.

Cooling Methods for Oil-Immersed Transformers

(1) Oil-immersed transformers typically employ three cooling methods: oil-immersed self-cooling, oil-immersed air-cooling, and forced oil circulation.

(2) Oil-immersed self-cooling relies on the natural convection of the oil to remove heat. Oil-immersed air-cooling is based on oil-immersed self-cooling, with the addition of a fan to blow air onto the oil tank and oil pipes to enhance heat dissipation. Forced oil circulation uses an oil pump to draw hot oil from the transformer to the outside for cooling before returning it to the transformer.

Structure and Function

In the main substations of urban rail transit power supply systems, the main transformer is typically a three-phase oil-immersed transformer, as shown in Figure 1. An oil-immersed transformer mainly consists of a core, windings, oil tank, voltage regulating device, radiator, oil conservator, gas relay, insulating bushing, and explosion-proof pipe