Review of Partial Discharge Monitoring techniques used in High Voltage Equipment

To ensure economic operation of high voltage equipment, reliable condition evaluation concepts are essential. They enable long-term inspection strategies with regard to a maximized service life of each component. Condition based maintenance (CBM) is therefore desirable and it is already used more and more in practice. Monitoring and diagnostic systems are on the way to get important tools for modern high voltage units or electrical equipment. With the help of modern monitoring techniques, it is possible to record and process significant parameters which is helpful for diagnostics. The quantity and magnitude of partial discharges (PD) are major quality characteristics in the assessment of high voltage equipment. For the PD measurements, different physical effects can be utilized, such as electrical, optical, acoustic, chemical and high-frequency effects. Therefore, in addition to the conventional PD measurements (according to IEC 60270), depending on the electrical equipment, a multiplicity of different alternative methods are currently being used. At the same time a distinction between on-and off-line measurements is possible. For new high voltage equipment, the direct integration of sensors for PD detection during production is practical as this enables the possibility of on-line measurements and furthermore a permanent operation monitoring. This paper deals with different possibilities for on- and off-line PD measurements in variety of electrical equipment. Moreover, new methods to measure and detect PD and the influence of interferences at on-site measurements are discussed.