Electric field distribution in glass and porcelain pin insulators

Distribution grid reliability depends heavily on insulation coordination of medium voltage overhead lines (OHL). Adequate knowledge of OHL insulators is needed to improve distribution grid performance. This paper discusses the distribution of electrical fields in 24 kV pin-type porcelain and glass insulators. To visualize the electric fields affecting the insulators, computer simulations were conducted. The simulations results were compared to previously conducted lightning impulse puncture withstand tests. The comparison showed that the electric stress in the insulators was not sufficient to cause puncturing, but in the laboratory tests, puncture did occur in some insulators.