Studies of partial discharges in HV machines: initial considerations for a PD specification

The search for a low attenuation region for discharge measurements, which is fundamental to setting a discharge acceptance level for machine stators, is promising. One uncertainty is over winding resonance effects and it is proposed to undertake a major investigation over a wide range of machine sizes to assess this effect. Calibration of the discharge measuring arrangement in terms of apparent discharge magnitude is critical to obtaining comparable and repeatable results. The IEC method has been examined experimentally to determine the effects of calibration source impedance and has been found to be satisfactory. No significant high frequency magnetic coupling of discharge pulses was observed. Radiation effects can be significant and must be reduced to an acceptable level so accurate measurements can be made