Guarding your assets. Online monitoring tackles partial discharges

Ensuring a reliable and uninterrupted operation of transmission and distribution equipment poses a key challenge in the area of monitoring and maintenance of power engineering systems. Indeed, monitoring the condition of high voltage (HV) systems and cable networks is becoming increasingly important as ‘production needs’ demand less downtime, higher output from machinery and cables, as well as reduced maintenance and repair costs. Moreover, with unscheduled shutdown of equipment, additional costs are often incurred, which are subsequently found to be way above the cost of the repairs deemed necessary. A satisfactory method of anticipating failure of key components is therefore required so as to attain an economic lifetime extension of high voltage equipment. In determining system reliability, the role of Partial Discharges (PD) is paramount, as they are a serious degradation stress mechanism, the precursor of insulation failure and a symptom of ageing occurring. PD is evident inside HV assets as a result of such defects as insulation impurities or ageing due to thermal, mechanical and electrical stresses. As a high percentage of failures are associated with PD, its testing, therefore, provides excellent information on the integrity of an electrical system. Left unchecked the equipment is likely to ultimately fail with possible catastrophic results. Hence, one of the most useful diagnostic tools for quality assurance during the design, manufacture and life assessment of electrical equipment is PD detection. By understanding and investigating further the activities of PDs occurring in voids or imperfections within the insulation, it is possible to assess the ageing of insulation materials and detect other such imperfections which can occur. An expanded and more reliable database of experimental test results, together with improved detection and noise reduction techniques suitable for continuous on-line monitoring of energized equipment, will enable the design of improved condition monitoring systems.