How to detect the failure of low frequency transformer and its fault classification and cause

author: MagTop
14/11/2022
custom transformer, power transformer

The fault probability varies according to the plant location. The low-frequency transformer can be distinguished and measured by a multimeter, which can be detected directly by capacitance level and detected by resistance level respectively.

1. Use capacitor file for direct detection

Some digital multimeters have the function of measuring capacitance, its range is 2000p, 20n, 200n, 2μm and 20μm five grades.
When measuring, the discharged capacitor two pins can be directly inserted into the Cx jack on the table board. After selecting the appropriate range, the display data can be read and the transformer can be judged.

2. Use resistance to detect

A digital multimeter can also be used to investigate the charging process of the capacitor, which actually reflects the change of charging voltage in discrete digital quantities.
If the measurement rate of a digital multimeter is set at n times per second, n independent and successively increasing readings can be seen per second during the investigation of the charging process of the capacitor.
According to the characteristic of digital multimeter, the capacitor can be detected and the capacitance can be estimated.

Note: Whether it is a high-frequency transformer or a low-frequency transformer, the principle and method of detection are the same.

Transformer common fault phenomenon classification and causes

1. The problems existed when the transformer itself left the factory.
Such as end loose, pad loose, poor welding, poor insulation of the core, short circuit strength lack.

2. Line interference.
Line disturbance is one of the most important factors in the formation of transformer trouble.
The primary includes: overvoltage generated during closing, voltage peak in the low load stage, line failure, due to flashover and other abnormal phenomena.
This kind of fault accounts for a large share of transformer failures.
Therefore, it is necessary to carry out shock protection experiment regularly to detect the strength of transformer against inrush current.

3. The aging speed of transformer insulation is accelerated due to improper use.
The average life of the general transformer as long as seventeen, eight years, much lower than the expected life of 35 to 40 years.

4. Overvoltage caused by lightning strikes.

5. Overload.
Overload refers to the power transformer under the condition that the power of the transformer exceeds the nameplate for a long time.
Overload often results in the condition that the power plant continues to slowly increase the load, the abnormal operation of the cooling device, the internal failure of the transformer and so on, eventually forming the overload operation of the transformer.
The resulting high temperature will lead to premature aging of insulation, when the transformer insulation board aging, paper strength is reduced.
Therefore, the impact force of external failure may cause insulation damage, resulting in failure.



6. Damp: such as flood, pipeline leakage, top cap leakage, water along the casing or fittings into the oil tank and water in the insulation oil.



7. Not using proper protection.