Diagnosis of the aged XLPE cable using frequency and temperature characteristics of tan /spl delta/ II

The conventional manner of measuring tan δ of cable does not take account of the contribution from the semiconducting layers and the contact resistance. We established the method to separate tan δ component of insulation layer (tan δpe) from tan δ versus frequency characteristics measured in cable configuration. Tan δ pe gives very accurate information about oxidation in insulation layer. Tan δpe takes a maximum value at near -20°C in the aged cables, which is corresponding to "Β" peak in the dielectric dispersion of oxidized PE. These results will be the basis for a new method of the cable diagnosis. Additionally, the application of distorted wave voltage was shown to be effective for field measurement of tan δ - frequency characteristics.