Calibration Method of Power Cable Dielectric Loss Measuring Instrument under 0.1Hz AC Voltage

Abstract

Measuring the dielectric loss under 0.1Hz AC voltage can effectively reflect the aging of power cables, water trees and other defects. With the increasing number and age of power cables, 0.1Hz AC voltage dielectric loss measuring instruments have been widely equipped in China. It is necessary to calibrate these instruments. However, there is no generally accepted method of calibration. This paper proposes a calibration method and establishes a test platform for calibrating the dielectric loss measuring instrument under 0.1Hz AC voltage. This method uses a resistor and capacitor in parallel as standard equipment, and the instrument is calibrated by comparing the measured value with the theoretical value. This theoretical value is calculated by measuring the capacitance value of the capacitor and the resistance value of the resistor using 50Hz standard equipment. Polypropylene film capacitors and non-inductive glass glaze resistors are used to reduce the influence of test frequency and temperature on calibration results. Different capacitance and resistance values were selected, and standard instruments with different theoretical dielectric loss values were prepared, and measured with a 0.1Hz dielectric loss measuring instrument to obtain the test values. The results show that the minimum relative deviation between the theoretical value and the tested value is about 1%. When the capacitance value is constant, the deviation between the theoretical value and the test value increases with the increase of the resistance value. This paper compares and analyzes the reasons for the deviation between the theoretical value and the test value, and proposes the corresponding correction method. The errors of the corrected standard devices are all within 2%, which can meet the general calibration requirements.