How to calibrate and maintain high-voltage test transformers

1. Periodic test contents of high voltage test include:

① Performance indicators such as pressure resistance, impurities and other performance indicators of oil sample testing are performed once every three lines. The period of long-term full-load or overload operation of the transformer can be shortened.

② The high and low voltage insulation resistance is not less than 70% (10MΩ) of the original factory value, and the DC resistance of the winding at the same temperature, the difference between the three-phase average value should not be greater than 2%, and it is not compared with the result of the previous measurement. Should be greater than 2%.

③ The grounding resistance value of the high-voltage test transformer is measured once every two years.

④ The cycle of cleaning and inspection after power failure is determined according to the surrounding environment and load conditions, generally once half a year to once a year; the main content includes the removal of defects found during inspections, cleaning of the porcelain casing, cracked or aged rubber pad replacement, and connection points Check the tightening, lack of oil and replenish oil, check and replace the silica gel of the respirator.

2. The daily maintenance methods for high-voltage test transformers are:

①, the grounding of the transformer

② The housing of the transformer should be grounded reliably, the working neutral wire and neutral grounding wire should be laid separately, and the working neutral wire should not be buried in the ground.

③ The neutral ground loop of the high-voltage test transformer should be made of detachable connecting bolts near the transformer. Bus processing machine

④ The grounding of transformers equipped with valve arresters should meet the requirements of the trinity; that is, the neutral point of the transformer, the transformer shell, and the grounding of the arrester should be connected at one place and grounded together.

⑤ The grounding resistance should be less than 4 ohms. Generally, high-voltage test transformers are dead oil-immersed. Routine inspections mainly check for oil leakage and check the oil chromatogram and DC resistance. Use a megohmmeter to check the insulation resistance, and the calibration is mainly carried out with a voltage divider.