Condition monitoring of HV electrical rotating plant-on-line partial discharge techniques

As reliability of strategic plant becomes more cost conscious, pressures on improved reliability and the need to reduce maintenance costs, results in the greater need for adopting effective "on-line" condition monitoring strategies. This is even more important for electrical rotating plant-generators and HV motors-which in service impose on the HV stator insulation a combination of stresses-electrical, mechanical and thermal. These can, if their effects are not identified in the early stage of initiation, result in rapid and premature failure of the HV stator insulation. This paper considers three techniques and gives examples of comparative sensitivity tests which were carried out to assess their effectiveness in detecting electrical partial discharges (PD) generated in service, in the HV stator insulation of HV motors and generators. The paper discusses radiofrequency current transformer, Rogowski coils, and permanent capacitor couplers.