Distribution Transformer And Power Transformer Fault Analysis

The common failures of distribution transformer and power transformer in operation include failures of windings, bushings, tap changers, iron cores, oil tanks and other accessories.

Winding fault

Mainly include inter-turn short circuit, winding grounding, interphase short circuit, disconnection and open welding of joints, etc.

Casing failure

The fouling of the transformer bushing will cause pollution flashover in heavy fog or light rain, which will cause single-phase grounding or short-circuit between phases on the high-voltage side of the distribution transformer and power transformer.

Serious leak

The oil leakage of the distribution transformer and power transformer is serious or continues to overflow from the damaged part so that the oil level can no longer be seen on the oil level gauge. At this time, the transformer should be stopped immediately to repair the leakage and refuel. The cause of the oil leakage of the transformer is weld cracking or sealing Parts fail, and the fuel tank is severely corroded and damaged by vibration and external force during operation.

Tap changer

Common faults include poor contact or inaccurate position of the tap changer, melting and burning of the contact surface, and discharge of interphase contacts or discharge of each tap.

Overvoltage

When a distribution transformer and power transformer in operation is struck by lightning, due to the high potential of lightning, it will cause external overvoltage of the transformer. When some parameters of the power system change, due to electromagnetic oscillation, it will cause internal overvoltage of the transformer. Most of the transformer damage caused by such overvoltage is the breakdown of the main insulation of the winding, resulting in transformer failure.

Iron core

Most of the failures of the iron core are caused by the insulation damage of the core screw or the clamping screw of the iron core.

Oil leak

If the oil level of the distribution transformer and power transformer oil is too low, the bushing lead wire and the tap changer will be exposed to the air, and the insulation level will be greatly reduced, so it is easy to cause breakdown discharge.