Improved Electric Field Distribution Within Bushing Insulation by EP/GO Nanocomposites With Reduced Temperature Coefficient of Conductivity

Boxue Du,Jin Li,Wei Yang,Hanlei Sun,Xiaoxiao Kong

doi:10.1109/access.2020.3026391

Boxue Du, Jin Li + Show 3 more

Open Access

https://doi.org/10.1109/access.2020.3026391

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Abstract

Field grading within the dry-type bushing insulation presents a major challenge for DC applications due to the highly temperature-dependent conductivity of the epoxy resin insulation. An electric field regulation method based on the epoxy/graphene oxide (EP/GO) nanocomposites with the reduced temperature coefficient of conductivity is proposed and investigated in this paper. DC conductivity of EP/GO nanocomposites with different loadings of 0, 0.05, 0.1 and 0.5 wt% at various temperature are investigated. Trap level distributions are characterized by the isothermal discharge current (IDC) method to clarify the conduction mechanism. Obtained results show that more shallower traps are introduced and the thermal activation energies of the nanocomposites are reduced by the GO nanoparticles, indicating that the temperature coefficient of conductivity of the nanocomposites is reduced. The improvement of electric field distribution within the bushing insulation under operating voltage is verified when the EP/GO nanocomposite with an appropriate content is employed, based on an established ±800 kV valve-side bushing for a converter transformer. However, more defects will be introduced by the GO fillers with excessive content (0.5 wt%), resulting in an obvious reduction of the DC breakdown strength.

Highlights

The valve-side bushing for a converter transformer is one of the key HV equipment in the high voltage direct current (HVDC) system, and the performance of which is closely associated with the safe and stable operation of the HVDC system [1], [2]
When the concentration is increased to 0.5 wt%, many river-shape stripes could be observed and which often starts from the particle as shown in Figure. 2d
It is obvious that the graphene oxide (GO) fillers are homogeneously dispersed in the resin, and the sizes are about 5 μm in diameter and consistent with the parameters provided by the supplier

Summary

INTRODUCTION

The valve-side bushing for a converter transformer is one of the key HV equipment in the high voltage direct current (HVDC) system, and the performance of which is closely associated with the safe and stable operation of the HVDC system [1], [2]. IDC tests are employed to obtain the trap level distribution of nanocomposites with different filler contents. It is found that, compared with the neat epoxy, the density of the shallower traps of the EP/GO nanocomposites increases with the increase of the filler content. The deeper trap density of the EP/GO-0.5 is nearly equal to that of the neat epoxy, and which may be attributed by the more interfacial regions produced by the GO particle since the GO has a large specific surface area with a high aspect ratio as evidenced by Figure 2d

DISCUSSIONS

SIMULATION ANALYIS

CONCLUSION