Water treeing in service aged cables, experience and evaluation procedure

Water treeing problems encountered in the Netherlands in some medium-voltage cables prompted in the authors to develop a test with which the degradation of the insulation of extruded cable could be characterized. The test method developed was demonstrated to be effective. It revealed that 20% of the network cables examined were defective and needed replacement. In evaluating the results, it was shown that the water tree susceptibility of some cables can be correlated with specific manufacturers or unknown parameters in their production process. However, it was not possible to attribute the cause of this susceptibility to the cross-linking process, conductor shields, or wet soils alone