Study and modeling of water treeing in solid insulation of power cables

A study of the phenomena of water treeing (W.T) in h.v. solid insulation is presented in this paper. Laboratory made specimens were used to grow vented W.Ts under accelerated conditions. The behavior of W.Ts were studied and recorded by specially designed video camera attached to a high magnification microscope. The observations were interfaced to a microcomputer where they were analysed. Experiments revealed that W.Ts can grow in some dielectrics while it can not grow in certain types of epoxy resins under the same varying conditions of frequency, voltage, applied field and electrolytic solutions. Novel computer techniques were developed using the Finite Differences Method (FDM) to calculate the equipotential distribution in the point-plane electrode system which simulates the W.T growth and initiation model. Polymeric materials were investigated using different permittivities for W.Ts. The electric field concentration and some other random factors were used to control the W.Ts initiation and propagation in the model. The mechanism of W.T in h.v. cables insulation is discussed and explained on the light of the experimental and simulation results.