Common Faults and Daily Inspection of Power Transformer

1 Common faults and causes of power transformer1) Short circuit damage accidentThe transformer suffers various short circuit accidents during operation, such as single phase to ground, two phases or two phases to ground and three phases, among which the short circuit at the outlet is the most serious. Daily patrol inspection. During the operation of the transformer, daily patrol inspection shall be carried out. It is mainly to check whether the operation of transformer auxiliary equipment is good and whether the transformer temperature is normal. By measuring with infrared imager, some faults such as overheating and lack of oil in the transformer can be found effectively.

2) Insulation accidentThe insulation damage accident of transformer accounts for about 70% 80% of the total accidents. There are insulation damage caused by mechanical force or overheating, or the insulation strength fails to meet the requirements when leaving the factory, or the insulation is damaged, which reduces the strength and cannot meet the requirements of bearing capacity. The analysis reasons are as follows: Transformer water ingress and moisture

The main problems are loose sealing at the end of the casing, water inflow, water leakage of the water cooler, dew accumulation in the explosion-proof cylinder, ponding in the oil conservator, etc. The existence of moisture will reduce the breakdown strength of transformer insulating oil, resulting in insulation accidents. The most common parts of insulation accidents are windings, leads and screens. The development of creepage leads to inter turn and inter layer short circuits. Foreign matters remaining in the transformerThe residual metal conductor foreign matters and impurities in the transformer body cause insulation breakdown and damage in the event of overvoltage or under normal working voltage due to partial discharge or insulation wear.

Lightning strikeThe low lightning resistance level of lightning protection at the medium and low voltage sides of the transformer and the weak insulation structure of the transformer cause the grounding short circuit accident of the transformer during lightning stroke.3) Overheating fault

There are overheating caused by abnormal current, such as overheating caused by circulating current and eddy current, overheating caused by increased resistance of conductive circuit, overheating caused by blocked heat dissipation, etc.2 Daily patrol inspection, regular test and maintenance of transformer1) On line detection technology

Partial discharge on-line monitoring technology. In case of internal fault or poor operating conditions of transformer, partial discharge will be generated due to high local field strength. In general, the detection of partial discharge can be divided into electrical measurement method and non electrical measurement method. On line analysis technology of gas in oil. For a long time, gas chromatography analysis of gas composition and content in oil immersed transformer oil has been an important means to judge the internal state of transformer. The principle is to infer the cracking conditions of oil or oil paper insulation by using the relative ratio of the collected gas concentration.2) Daily patrol inspection. During the operation of the transformer, daily patrol inspection shall be carried out. It is mainly to check whether the operation of transformer auxiliary equipment is good and whether the transformer temperature is normal. By measuring with infrared imager, some faults such as overheating and lack of oil in the transformer can be found effectively.

3) Periodic test. It is mainly carried out in accordance with the code for handover and preventive test of power equipment. There are 35 items in total, and there are more than 10 routine test items. Adhering to the implementation of some projects can effectively find some faults of transformers and take effective measures in time to avoid the expansion of accidents. It is an effective means in production.