Partial Discharge Measuring Based On Change Of The Charge Density In Oil

Large transformer is one of the most important apparatus in power system. The main insulation of large transformer is always subjected to the thermal, electrical and environmental stress during the long-term operation. So partial discharge takes place in the weak parts, gradually developed and resulted in the aging of insulation. It is very significant for measuring partial discharge (PD) to ensure transformer working safely and reliably. On the base of analyzing transformer PD measuring system home and abroad, one measuring method on charge density in transformer oil was brought forward indirectly judging PD happen in the paper. Self-designed oil-paper insulation pipeline simulating system had been made to simulate static electrification phenomena, and measured leakage current and charge density in oil utilizing absolute charge density sensor and micro-amperemeter. The experiment expressed that the charge density in oil increased obviously with the increasing of external voltage, especially at the condition of PD taking place at the oil-paper insulation pipeline simulating system. It made sure that it is feasible to measure the PD according to change of the charge density. At the same time, as the core of virtual device technology and graphic applied software, the PD data collection and procession system had been developed and completed. The achieved experiment result, namely, the charge density in oil increased with the increasing applied voltage and phenomena was sported suddenly at the PD condition, was explained academically. In addition, virtual device measuring system was discussed in the paper, it may monitor PD online possibly by the method of measuring charge density in oil. So it provided the research direction about intelligentized measuring PD online.