Direct Current Electrical Performances of Cable Accessory Insulation EPDM Modified by Grafting Polar-Group Compound

Area of Science:

• Materials Science
• Electrical Engineering
• Polymer Chemistry

Background:

• Direct current (DC) cable accessories require optimal electrical matching between ethylene-propylene-diene misch-polymere (EPDM) and crosslinked polyethylene (XLPE) insulation.
• Current methods face challenges in achieving desired electrical properties for enhanced performance and longevity.

Purpose of the Study:

• To improve the electrical matching between EPDM and XLPE insulation in DC cable accessories.
• To investigate the effect of glyceryl monooleate (GMO) graft modification on EPDM's electrical properties.
• To elucidate the charge trapping mechanism responsible for improved DC electrical performance.

Main Methods:

• Chemical graft modification of EPDM with glyceryl monooleate (GMO).
• Analysis of charge trap characteristics using thermal stimulation current (TSC) testing.
• First-principles electronic property calculations to verify charge trapping mechanisms.
• Electric field finite-element simulations.

Main Results:

• GMO grafting introduced shallow charge traps in EPDM, leading to nonlinear electric conduction and improved electrical conductance.
• The modified EPDM exhibited enhanced electrical matching with XLPE while maintaining high dielectric breakdown strength.
• Shallow traps captured charge carriers, forming homocharge layers that mitigated breakdown strength reduction.
• Simulations showed homogenized electric fields in DC cable terminals using GMO-grafted EPDM.

Conclusions:

• GMO graft modification is an effective strategy to enhance EPDM insulation for DC cable accessories.
• The introduced shallow charge traps play a crucial role in improving electrical performance and dielectric strength.
• GMO-grafted EPDM offers a viable solution for homogenizing electric fields and improving overall cable accessory reliability.