Partial Discharge characteristics of mineral oil using needle — Plane and needle — Sphere electrode configuration base on pulse current measurement

The aim of this paper is to describe the study of the Partial Discharge (PD) characteristics of mineral oil obtained from Partial Discharge Inception Voltage(PDIV) testing using the needle - plane and needle - sphere electrode configurations. This paper represents the experimental investigation of the PD characteristics of the mineral oil, Nynas 4000x, with the water content not more than 10 ppm at the PDIV level using various tip radii of needle - plane and needle - sphere electrode arrangements. The tungsten needle electrodes with the tip radius of 10μm, 20μm, and 40μm respectively were used as the high voltage electrode while the brass plane electrode with a diameter of 50 mm was connected to ground via the shunt resistor of 50 ohm. The gap distance of the electrode system was set up at 50 mm. The test experiment, conventional PD measurement, was set up according to IEC 60270. The test procedure was performed in accordance with IEC 61294 under room temperature. PD activities at the PDIV and 1.1 PDIV test level were recorded. Additionally, PD currents were also detected and recorded by a high quality oscilloscope. Furthermore, the brass plane electrode with 75 mm diameter and the sphere electrodes with the diameter of 50.8 mm and 76.2 mm respectively were used also as the grounded electrode tested with the mentioned needles as high voltage electrode. The average PDIV value, the phase - resolved PD characteristics of mineral oil and PD pulse currents of the tested electrode systems are analyzed and presented in this paper. From the test results, we will gain the knowledge of PD characteristics of mineral oil testing by needle - plane and needle - sphere electrode system and we also found that the PD pulse current measurement can be used as an alternative indicator of the mineral oil degradation.