Experimental study of polymeric cable insulation under DC-superimposed long temporary overvoltage and lightning impulse voltage stress

Materials Research Express, vol. 13, pp. 116301

Abstract

Abstract Fault events in high-voltage direct current (DC) cable systems can generate DC-superimposed long temporary overvoltages (DC-LTOVs), same-polarity impulses that create stress conditions different from those in conventional superimposed lightning impulse (DC-LI) testing. The impact of such overvoltages on dielectric withstand strength and erosion processes in cable insulation under combined electrical and thermal stress conditions remains insufficiently understood, as previous research predominantly uses simplified specimens that lack cylindrical geometries or waveform-dependent erosion analysis. This work presents an experimental investigation on electro-thermally conditioned cross-linked polyethylene model cables subjected to DC bias with superimposed same-polarity impulses, evaluating withstand strength, breakdown time, and post-breakdown tree morphology across different waveforms and polarities. Within the investigated dataset, comparable withstand levels are obtained for DC-LTOV and DC-LI, while a pronounced polarity dependence of tree morphology is observed and a reduction of effective DC withstand is indicated when impulses are present. The findings suggest that waveform and polarity govern the observed erosion-dominated breakdown behavior, whereas the influence of impulse duration on withstand strength appears limited within the investigated parameter range and sample size. The study underscores the necessity for further investigation of space-charge dynamics and electrical-treeing phenomena in cable insulation, supported by increased statistical repetition.

Authors 7

1. Robert Gerlach corresponding Aachen

   RWTH Aachen University

   Affiliation as printed

   IAEW at RWTH Aachen University

2. Till Scholz corresponding Aachen

   RWTH Aachen University

   Affiliation as printed

   IAEW at RWTH Aachen University

3. Willem Leterme corresponding Aachen

   RWTH Aachen University

   Affiliation as printed

   IAEW at RWTH Aachen University

4. Bastian Soppe corresponding
   Affiliation as printed

   TenneT TSO GmbH

5. Tanumay Karmokar corresponding
   Affiliation as printed

   TenneT TSO GmbH

6. Isabella Nett corresponding
   Affiliation as printed

   TenneT TSO GmbH

7. Dominik Haring corresponding
   Affiliation as printed

   Südkabel GmbH