Influence of Conductivity on Tangential Electric Field of Composite Interface of HVDC Cable Joint

The silicone rubber(SR) insulated cable joint contains a composite interface between cross-linked polyethylene(XLPE) and SR, which is the weak component of the joint. Conductivity is an important factor affecting the tangential electric field in XLPE/SR interface of HVDC cables by changing the potential distribution in the insulation. Considering that the cable joint consists of two kinds of insulation, the relationship between their conductivity ratio coefficient and tangential electric field of interface is primarily calculated. It is found that reducing the difference of conductivity between XLPE and SR can keep the tangential field strength of the interface at a relative low level. In addition, considering the nonlinear conductivity of the insulation, the tangential electric field of the interface under DC superposition switching impulse voltage is calculated. The results show that the tangential field strength of the interface is the largest when DC superposition positive switching overvoltage at low temperature, which makes the probability of discharge and breakdown in the joint to be highest. And maximum tangential field strength of the interface is larger under DC superimposed both positive and negative switching impulse voltage than that of the steady-state at higher temperature.