Abstract

Accumulation of interfacial charges is an inherent feature of HVDC insulation based on solid and gaseous media. The collected surface charges can alter the geometrical electric field leading to undesirable phenomena such as partial discharges and even unexpected flashovers. In the present paper, surface potential decay on silicone rubber samples is analyzed at reduced pressures of ambient air that allows for elimination of surface charge neutralization by gas ions. Thus, influences imposed by bulk and surface conduction in the solid material are studied by means of computer simulations and experimental measurements. The results allow for identifying levels of bulk and surface conductivities above which the corresponding charge decay mechanism becomes dominant. It is shown that with a negligible space charge effect and significant surface leakage, there exists a notable spread of charge along gas-solid interface yielding visible crossover phenomenon in charge decay characteristics. It is also demonstrated that the effect of space charge in the material bulk on surface potential decay can only be significant within layers of material finer than ca. 100 μm.

Highlights

  • Accumulation of interfacial charges is an inherent feature of HVDC insulation based on solid and gaseous media

  • High voltage polymeric insulators usually operate under high electric stresses which may initiate electrical discharges in surrounding air leading to generation of charged species and their deposition on gas-solid interfaces

  • The needle is mounted on a wooden arm and it is connected to an external HVDC generator through a high-voltage bushing of the chamber

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Summary

Introduction

Accumulation of interfacial charges is an inherent feature of HVDC insulation based on solid and gaseous media. The measurements of the surface potential distributions were repeated at different instants after charging and the obtained profiles were further utilized to deduce surface potential decay characteristics.

Results
Conclusion
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