Electrical resistivity‐temperature characteristics enhancement of insulating cross‐linked polyethylene composites by incorporating positive temperature coefficient particles with different Curie temperatures

Abstract

Incorporating positive temperature coefficient (PTC) ceramic particles into polymers provides a prospective alternative solution for suppressing severe electric field distortions caused by negative temperature coefficient (NTC) of electrical resistivity within polymer insulation in high voltage direct current cable. The effect of the Curie temperature of PTC particles on the inhibition of the NTC effect of cross-linked polyethylene (XLPE) is investigated in this study. Positive temperature coefficient particles with varied Curie temperatures are surface-modified and melt blending with XLPE. The modified particles are dispersed on averagely in the matrix. The electrical resistivity, space charge behaviour, and direct current (DC) electrical breakdown strength of the samples are investigated at different temperatures, exploring the effect of the Curie temperature of PTC particles on suppressing the NTC effect of XLPE. It is demonstrated that the reduction in Curie temperature can further suppress the NTC effect of XLPE, enhance the DC strength at elevated temperatures, and inhibit the internal space charge accumulation. The reduction in the Curie temperatures means that the initiation of the PTC effect advances, exhibiting a higher potential barrier and inhibiting the NTC effect more effectively. This work may give a reference for improving the temperature stability of DC properties for XLPE cable insulation.

Improved direct current electrical properties of XLPE modified by graftable antioxidant and crosslinking coagent at a wide temperature range

“…For HVDC cables, the electric field distribution in the insulation layer is inversely proportional to the electrical conductivity, and the conductivity increases significantly with the increase of temperature. During the operation of HVDC cables, the higher temperature conductor core and the lower temperature sheath will cause the temperature gradient in the insulation, which can lead to the electric field inversion under the electric field-temperature gradient coupling field [1,7,8]. Therefore, it is urgent to reduce the temperature sensitivity of conductivity of XLPE in a wide temperature range.…”

“…With the widespread use of an ultra-high voltage direct current (UHVDC) power system, UHVDC cables will become a more economical and convenient solution for power lines crossing rivers and circling cities. Unlike submarine applications, due to the cross-regional nature of the application environment, the increased temperature range for wider applications will result in more significant electric field reversal distribution forms in cable insulation, making it a crucial factor for DC cable application [6][7][8]. For example, when the cable is laid in severe cold area, the surrounding medium is at cryogenic temperatures, and a larger temperature difference will be generated between the inner and outer insulation layer, which leads to more intense electric field reversal.…”