Effect of Test Method and Needle Plane Configuration on Partial Discharge Inception Voltage Measurement of Mineral Oil based on Weibull Analysis

Abstract

Abstract The discussion of test method and electrode configuration for Partial Discharge Inception Voltage (PDIV) measurement is continuously developed because the PDIV can be used as indicator to determine condition of insulating liquid. However, many researchers investigate the PDIV using different test method and electrode configurations. This paper discusses the effect of test methods and needle to plane electrode configuration on the PDIV measurement of mineral oil as insulating liquid. The mineral oil that used in experiment test was Nynas Nitro 4000x with water content less than 10 ppm. In experiment, the test circuit was set up according to IEC 60270. The first test method that was carried out in this experiment according to IEC 61294 with ramp rate of test voltage 1 kV/s until PDIV occurred. Meanwhile, a Combine Method as the second test method was used as comparative PDIV test technique for this experiment. With this combine method, the test voltage was applied to the test object with rate 1 kV/s until 70% of the PDIV value obtained from the first test method. Then the test voltage was increased in steps with 1 kV/step with step duration of 1 minute until PDIV obtained with PD charge ≥ 100 pC. The rest time between consecutive tests was 5 minutes. The needle tip radii that used as high voltage electrode were 10 μm and 20 μm, meanwhile brass plane electrode with diameter 50 mm was used as the grounded electrode. In this paper, the electric field stress of the needle to plane electrode was calculated using Finite Element (FEM) simulation with input voltage 100 volt. The test result was analyzed using Weibull distribution to calculate the Cumulative Distribution Function (CDF) and Probability Density Function (PDF) of PDIV value. The calculation results show that the test results agree with Weibull distribution.