Abstract
Power cables undergo various types of overstressing conditions during their operation that influence the integrity of their insulation systems. This causes accelerated ageing and might lead to their premature failure in severe cases. This paper presents an investigation of the impacts of various dynamic electric fields produced by ripples, polarity reversal and transient switching impulses on partial discharge (PD) activity within solid dielectrics with the aim of considering such phenomena in high voltage direct current (HVDC) cable systems. Appropriate terminal voltages of a generic HVDC converter were reproduced — with different harmonic contaminations — and applied to the test samples. The effects of systematic operational polarity reversal and superimposed switching impulses with the possibility of transient polarity reversal were also studied in this investigation. The experimental results show that the PD is greatly affected by the dynamic changes of electric field represented by polarity reversal, ripples and switching. The findings of this study will assist in understanding the behaviour of PDs under HVDC conditions and would be of interest to asset managers considering the effects of such conditions on the insulation diagnostics.
Highlights
THE introduction of polyethylene in the 1940s initiated a revolutionary progress in the cable industry [1], and since many polymeric materials have been produced and found applications in cable manufacturing owing to their technical and economical advantages
Successful deployment of high voltage direct current (HVDC) projects relying on mass impregnated non-draining (MIND) cables motivated the employment of their polymeric counterparts, of cross-linked polyethylene (XLPE) material in such applications
According to 6b-6d, partial discharges (PD) pulses tend to occur following the fast transitions in the ripples as well as the peak values of the applied voltages
Summary
THE introduction of polyethylene in the 1940s initiated a revolutionary progress in the cable industry [1], and since many polymeric materials have been produced and found applications in cable manufacturing owing to their technical and economical advantages. Successful deployment of high voltage direct current (HVDC) projects relying on mass impregnated non-draining (MIND) cables motivated the employment of their polymeric counterparts, of cross-linked polyethylene (XLPE) material in such applications. The first application of XLPE DC cable was the Gotland project, Sweden, operating at 80 kV in 1998, and since significant developments have taken place in terms of material, rating and characteristics [2].
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