A New Approach to Partial Discharge Measurements for Testing Electrical Insulation Systems

Partial discharges (PD) are essentially small "sparks" within a high voltage insulation system that are a sign of future material failure. Detecting partial discharge (PD) activity is an effective method for establishing the quality and reliability of the insulation systems used to transmit and distribute electrical power. Failures can have serious consequences: power cuts for domestic consumers, disruption to transport networks such as railways, and loss of data and/or production in industry. In addition, the electricity industry is continually striving to minimise its environmental impact and ensure the highest levels of safety for its personnel. Both of these aims can be hampered by sudden and unexpected failure of equipment. In its collaborating partners, the research project brought together two very different approaches to the measurement and analysis of PD activity. Conventional measurements to the international standard IEC60270 quantify the amount of electrical charge involved in a "spark", while radio frequency (RF) techniques respond to its acceleration (motion). Both methods respond in different ways to the characteristics of both the PD pulse and the equipment in which it occurs. Our research led to the development of techniques for combining the two methods to produce a prototype diagnostic tool capable of providing high quality information about the location and severity of a PD, even when several different PD sources are simultaneously active in a single component. This measurement system will be used to allow manufacturers to increase automation of high voltage testing and utility companies to employ new and more reliable diagnostic tests in evaluating the condition of in-service plant. In addition, fundamental studies of the relationship between the two methods of measurement have advanced our understanding of the physical processes and will inform international standards concerned with the detection of PD using RF methods.