Ramp test technique for D.C. partial discharge

Abstract

There is a relatively little published work [1,2,3,4] on dc partial discharge (P.D.) measurements on practical insulation systems. Compared to the much used technique of ac testing, the number of P.D. pulses are very few, even considerably above inception voltage. The dc inception voltage itself is difficult to determine, consisting of only a very few pulses/minute, and it will only be correct for a fresh, completely discharged dielectric specimen, into which space charge has not yet been injected. For dc partial discharge the quantity φ/ε is the cogent material property factor where φ is the conductivity and ε is the permittivity of the dielectric containing the voids or grain boundaries. This factor represents the inverse of the time constant for charge distribution due to dielectric conductivity [3].