Calibration method of dielectric strength tester for insulat

In power system, insulating oil is an insulating medium widely used in high voltage electrical equipment。 In the long run, the quality of the insulating oil will gradually change, causing the insulation performance of the equipment to decrease continuously。 In order to ensure the safe operation of electrical equipment, the electrical strength of insulating oil shall be tested regularly。 "Breakdown voltage" is an important index to characterize the dielectric strength of insulating oil。 The insulation oil dielectric strength tester (oil pressure tester) is the test instrument for testing the voltage resistance strength of insulation oil in the power system。

At present, the domestic production of various types of oil pressure gauge, but there is lack of related standards about this kind of instrument calibration, and due to its electrical structure and the particularity of calibration method, these instruments are not able to accurately calibrated。 This paper designs a set of insulation oil dielectric strength tester calibration device with vector measuring function, which can be calibrated to the oil pressure gauge with the accuracy of 0~ 100kV。

At present, there are two kinds of calibration methods for oil pressure tester in China:

1) single-ended method: open the instrument of the cap, take the next one electrode support and insulating casing, leaving only the fastening end of the electrode, the high voltage side in ac high voltage testing line in the electrode is fastening, the grounding end of the ac high voltage table and the ground terminal of the instrument with reliable grounding terminal is connected to the laboratory。 Raise the voltage to the right size and remain the same。

Record the readings of the instrument and the readings of the high pressure gauge. 2 times the high pressure gauge reading is the standard reading for the output voltage.

2) dual output measurement method: remove the support of two electrodes and insulating casing, communicate in two high pressure table, respectively, to the high end of the connection on the two electrodes of the fasteners, two high pressure table ground end and instrument grounding end with reliable grounding terminal is connected to the laboratory。 The sum of the two high pressure readings is the standard output voltage。

Because the high voltage output of the oil pressure gauge is neutral and grounded, the single-end measurement method is only to calibrate the voltage of one of the high voltage terminals。 Intermediate tap the purpose is to reduce the oil pressure gauge of the output of voltage grade, thereby lowering the ground insulation class, but the intermediate tap hard completely symmetrical, so in order to reduce the error, dual output simultaneously measure the oil pressure gauge measuring method with the two high voltage output terminal of the voltage, but due to the calibration results rather than by the method of algebra and vector measurement, will inevitably bring additional error calibration data。

In addition, due to the small power of most testers, the input impedance of the ordinary high voltage divider is much larger than its rated power, so the calibration process is likely to have a voltage drop phenomenon. When the oil pressure gauge is calibrated, it adopts the substitution method, and the oil cup is removed when calibrated, and the calibration device of the same size is placed, so that it happens to be inserted into the fastening end of the electrode. The readings pass through the analog pointer to indicate that the calibration device was designed with the load effect considered, but limited to volume, with only 3% accuracy, and only applicable to oil pressure gauges below level 10.

The zec-503 insulated oil dielectric strength tester, produced by wuhan zhongke xinyi power technology co., LTD., contact number: 400-068-3818, 027-82818935

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