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Transformer DC leakage measurement test

time:2022/1/17   source:华天电力  reading:366 time

Transformer DC leakage measurement test, test instrumentation: DC high voltage generator

Preparation before the test and use of the instrument

The DC high voltage generator consists of two parts, the control box and the voltage doubler rectifier. Use a dedicated wire to connect the two parts together. The grounding terminals of the two instruments are reliably grounded with special grounding wires, and the discharge rods are also reliably grounded. All grounding wires should be connected to the ground of the tested object, and the overvoltage protection should be set to 1.1 times the test voltage to prevent overvoltage. When there is an electric field interference environment test (such as in a substation), a shielded wire is used to connect the test equipment and the test object. Wiring requirements are the same as insulation resistance measurement.

DC Hipot Tester.png

The instrument uses a 220V power supply.

After the DC high voltage generator is connected to the power supply and preheated for 1 minute, turn on the high voltage switch and turn the boost knob to boost the voltage. After the test, first disconnect the high-voltage switch, and use the discharge rod to discharge the test object.

DC high voltage generator

Test process and analysis and judgment

The test voltage is as follows:

Winding rated voltage (kV) 220, test voltage DC (kV) 40; winding rated voltage (kV) 110, test voltage DC (kV) 40; winding rated voltage (kV) 35, test voltage DC (kV) 20; winding rated voltage (kV) 35 Voltage (kV)≤20, test voltage DC (kV) 10;

The test voltage is carried out according to the above table.

The boosting speed should be different according to the capacitance of the tested product, and the current of the main control microammeter should not be too large. After the voltage rises, hold it for 1 minute, read the current value and make a record.

In case of abnormal conditions (such as discharge sound and loud corona sound) during the boosting process, the high-voltage power supply should be disconnected immediately, and the test object should be grounded and discharged to check the wiring.

In order to reduce the leakage current increase caused by corona, sharp corners and burrs should be reduced in the wiring of high-voltage lines.

When the leakage current is large in summer, a bare copper wire can be wound around the middle of the surface of the casing porcelain bottle to connect the shielded wire of the high-voltage generator.

If the above measures are taken and the leakage current is still very large, a comprehensive analysis should be carried out in combination with the measurement of insulation resistance and dielectric loss.

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