How to detect the fault of low-frequency transformer and its fault classification and causes

author: MagTop
The Power transformer, low-frequency transformer
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The fault probability varies from plant to site. A multimeter can be used to distinguish and measure the quality of the low-frequency transformer, which can be directly detected by capacitance and detected by resistance.

1. Use the capacitor file for direct detection

Some digital multimeters have the function of measuring capacitance, its range is divided into 2000p, 20n, 200n, 2μ and 20μ five levels.
When measuring, the discharged capacitor two pins can be directly inserted into the Cx jack on the table board, and the data can be read and judged after the appropriate range is selected.

2. Test with resistance

The charging process of the capacitor can also be investigated using a digital multimeter, which is actually a discrete digital amount to reflect the change of the charging voltage.
If the measurement rate of the digital multimeter is n times/second, n independent and sequentially increasing readings can be seen every second during the charging process of the investigation capacitor.
According to this feature of digital multimeter, the quality of capacitor can be detected and the capacitance can be estimated.

Note: The detection principle and method are the same whether it is a high-frequency transformer or a low-frequency transformer.

Classification and causes of common transformer faults

1The Power transformer itself factory when the problems exist.
Such as loose end, loose pad, poor welding, poor core insulation, short circuit resistance strength.

2. Line disturbance.
Line disturbance is the most important element in the formation of transformer trouble.
The first includes: overvoltage during closing, voltage peak during low load phase, line fault, due to flashover and other abnormal phenomena.
This kind of fault occupies a large share in transformer fault.
Therefore, it is necessary to regularly carry out impact protection experiments on transformers to test the strength of transformers against inrush current.

3. Due to improper use, the aging of transformer insulation is accelerated.
The average life of a general transformer is only 17 or 8 years, much lower than the expected life of 35 to 40 years.

4. Overvoltage caused by lightning strike.

5. Overload.
Over-load refers to the transformer that is in the working state of exceeding the nameplate power for a long time.
Overload is often generated in the power plant continues to slowly increase the load, the cooling device is not running normally, the transformer internal fault and so on, eventually forming the transformer overload operation.
The resulting high temperature will lead to premature aging of insulation, when the transformer insulation board aging, paper strength is reduced.
Therefore, the impact of external faults may lead to insulation damage, resulting in failure.

6. Damp: such as flood, pipe leakage, top cover leakage, water intrusion into the tank along the casing or fittings, and moisture in the insulation oil.

7. Not properly protected.