Practical techniques for measuring partial discharges in operating equipment

Several viable online partial-discharge (PD) tests have been developed for monitoring the condition of the solid dielectric insulation in high voltage equipment. The main requirement for on-line tests is the ability to reduce or eliminate noise. Such noise can create false indications that the insulation is failing, which in turn destroys the test´s credibility. Several methods have been developed to reduce or eliminate noise. Methods include pattern recognition, frequency and pulse characterization, and pulse propagation effects. The PD detection and noise elimination methods used take advantage of the characteristics of the PD and noise in each type of equipment being monitored. Thus an on-line measuring system for one type of equipment will probably be suitable for another type of equipment. The greatest success with on-line PD measurements has occurred in generators, where the PDA test for hydrogenerators is now routinely used around the world. There has been less success with substation equipment monitoring