Electric field method is one of most efficient
method to defect composite insulator. But it is not be
used widely on porcelain insulator. In this paper,
research of using the electric field method on porcelain
insulators was made. A space electric field probe
measured the distribution of electric field around the
insulators. Several faulty insulators were place on the
insulator string at every position. The relationship
between the resistance of faulty insulators and the
electric field distribution was studied. We found that
the electric field distribution curve will appear descent
at the position of faulty insulator. But the position and
resistance of faulty insulators decided the extent of the
distortion. According to the experiments at laboratory,
we found that faulty insulator above 1OOMQ can't be
detected by the electric field probe.