Evaluation of surface- and corona discharges at DC voltage

Abstract

Due to the rising number of DC transmission systems there is an increasing interest in partial discharge (PD) diagnostics at DC voltage. Under AC stress there are several established instruments to get evidence of the type and the location of the defect, most important the phase angle histogram. Under DC stress there are no such methods available up to now and therefore new interpretation techniques have to be developed. In this paper two typical types of PD are generated and analyzed on the basis of various parameters to identify characteristics which allow a founded differentiation of these two types of defect. The results are discussed on the basis of the physical processes which are involved in the discharge process.

About the influence of temperature and humidity level on pulse shape parameters of positive DC corona discharges in air

“…The rise time, the pulse width and the fall time as primary parameters are considered as well as About the influence of temperature and humidity level on pulse shape parameters of positive DC corona discharges in air Ulrich Lühring, Daniel Wienold and Frank Jenau P secondary parameters such as the coefficient of variation, the kurtosis or the skewness. A comparative analysis of these parameters, gained from PDs of idealized and artificial defects under DC voltage stress, outlines the possibility to differentiate between different types of fault [10] and defects in varying insulating media [11], [12]. Extensive experimental investigations and statistical evaluations, presented in [6], verify that the time domain analysis of PDs enables a precise defect classification.…”