In recent years

a number of failures due to discharge on the buffer layer in HV cable systems were reported.Although the conclusions of the failure mechanisms have been controversial

the distorted electric field between the metallic sheath and the buffer layer was believed to be the main reason.Previously published investigations failed to consider the influence of the geometric parameters of the corrugated sheath on the distorted electric field.A numerical simulation model

considering

the impedance of the buffer layer and the sheath geometry of an 110 kV XLPE cable

is established in this paper based on Maxwell equations.The results show that:When the conductivity of the buffer layer is between 10

-6

～10

-9

S/m

the voltage potential is mainly affected by the conductivity.The voltage potential depends on the buffer layer permittivity under the condition that the conductivity is less than 10

-9

S/m.The voltage potential is close to 0 in scenarios where the buffer layer conductivity is greater than 10

-6

S/m.Distribution of the voltage potential in the air gap becomes corrugated due to the shape of the sheath

resulting in high electric field concentrating near the interface.This finding is consistent with previous reports of the discharge area.The voltage potential of the outer surface of the buffer layer decreases when approaching the material interface because of the corrugation

while the inner surface is not influenced by the sheath.Smaller pitch or larger embossing depth of the metallic sheath results in greater electric field in the air gap.