How to calibrate the transformer oil bdv test kit?

How often should you test transformer oil?
According to the transformer operating regulations, transformer oil must be tested every year. Depending on the voltage level, the test cycle and items are also different. The test cycle for 66~550kV transformers is 1 year, and the test cycle for transformers of 35kV and below is 3 years. The test items generally include oil dielectric strength test, oil dielectric loss factor tanδ test, simplified test, etc. For transformers of 330kV and above, other test items should be added.

For measurement type instruments, a calibration test is required every 2 years.
Insulating oil is an insulating medium widely used in high-voltage electrical equipment. In the long-term operation of high-voltage electrical equipment, the quality of insulating oil gradually changes, and the insulation performance of the equipment gradually declines. The bdv value of insulating oil must be tested regularly to ensure the safe operation of electrical equipment. "BREAKDOWN VOLTAGE" is an important index that reflects the dielectric strength of insulating oil, and is a standard for measuring the voltage resistance of insulating oil. The portable dielectric oil tester is a measuring instrument for testing the withstand voltage of insulating oil in the power system.

At present, there are many types of oil testing kits produced in China, but there is no official standard for the calibration of these instruments. In view of the particularity of the electrical structure and calibration method, a calibration device for transformer oil bdv test kit with vector measurement function is designed, which can calibrate the oil withstand voltage meter with an accuracy of 0~100kV below 2%.

There are two calibration methods for portable oil dielectric strength tester in China;
1.Single-edged Measurement Method

Open the oil tank's cover of the dielectric oil tester kit, Remove any electrical frame and insulating sleeve, and leave only the fastened end of the electricity. By the test line of the high voltage terminal is connected to the electrical fastener, the grounding end of the AC high voltage table is connected to the ground end of the device to increase the voltage to the appropriate size, and keep unchanged. At the same time record the readings of the instrument and high voltage gauge's, Double the value of the high voltage gauge is the standard value of the output voltage.

2.Double-edged Measurement Method

Remove the two electrical frames and insulating sleeves, and connect the high-voltage terminals of two AC high-voltage gauges to the two electrical connections respectively, and the grounding terminals of the two high-voltage gauges are together with the grounding terminal of the equipment. The sum of the values of the two high-voltage gauges is the standard value of the output voltage.

Since the high-voltage output of the insulating oil withstand voltage tester is symmetrically grounded, the single-edged measurement method only needs to calibrate the ground voltage of one high-voltage terminal. The purpose of the middle tap is to reduce the voltage level to the ground output by the insulating oil withstand voltage measuring instrument and reduce the insulation level to the ground.

However, because the middle tap is difficult to be completely symmetrical, in order to reduce the error, the dual output measurement method measures the insulation at the same time. The voltage to ground of the two high voltage output terminals of the oil withstand voltage tester, but the final result is expressed by algebraic sum instead of vector test, there will be some additional errors.

Moreover, many insulating oil dielectric strength testers have a small power, and the input impedance of ordinary high voltage divider has been much larger than its rated power, so voltage drop is likely to occur during calibration. In foreign countries, when the insulating oil withstand voltage measuring instrument, an alternative method is used, and the oil cup is removed, and the size is properly suitable for the electrical fastener calibration device. The reading is an analog pointer indicating that the calibration device is designed to consider the load effect, but is limited to a volume, its accuracy is 3%, which can only be used for insulating oil withstand voltage measuring instrument below 10.

No.31-7 Center Plaza, Shapingba District, Chongqing, China

Chongqing Assen Power Equipment Co.,Ltd
Email: sales@assenpe.com/ assenoilpurifier@gmail.com
Tel/Fax:+86-2388703683
Mob/Whatsapp:+86-15223801122
https://www.assenpe.com

This release was published on openPR.