Surface charge accumulation on the cone-type insulator under DC voltage

Abstract

Surface charge accumulation on cone-type insulators is a remarkable phenomenon in Gas Insulated Line (GIL), especially under DC voltage. It may lead to a considerable reduction of the flashover voltage of insulators. For this respect, this paper focuses on the surface charge distribution on the real insulator after applying DC voltage. In order to study this phenomenon, a set of device for measuring surface voltages on the insulator is designed, base on the electrostatic probe method. After applying different DC voltage amplitudes to the cone-type insulator, the surface voltage distributions, which reflect charge distributions to some extent, are measured by an electrostatic probe in SF 6 gas. Despite of the axial symmetry of the insulator, the measurement results show that the charge distribution is nonaxisymmetrical. The negative charge accumulates mostly under positive DC voltage. On the other hand, no apparent positive charge accumulation is observed on the surface. In areas which are close to electrode, the measured voltage amplitudes are much higher than outer areas.

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“…Below are characteristics of some insulation materials in Table 2. In addressing these issues, a study [7] developed a high-voltage contact-type fiber optic insulator using room temperature vulcanized silicone rubber material [8]. The integral molding structure of this insulator addresses potential sealing defects at the interface between the insulator and the fiber optic, preventing breakdown due to local voltage spikes during high current flow.…”

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“…Until now, very few works have been reported on surface charge measurements of real-size GIS/GIL spacers and the results can be summarized as follow [49,[52][53][54][55][56]: From the measured surface potential, the surface charge density distribution on the spacer is then deduced by using the charge inversion algorithm [48,50] and compared with the calculated surface charge density distribution derived from Equation 14 (transient state) or Equation (15) (steady state).…”

“…Until now, very few works have been reported on surface charge measurements of real-size GIS/GIL spacers and the results can be summarized as follow [49,[52][53][54][55][56]:…”

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“…However, the gas voltage divider SF 6 is not environmentally friendly. Moreover, the gas medium has a certain fluidity and discharge effect, and its voltage dividing stability is weaker than that of the solidstate medium [25][26][27][28].…”