High frequency AC characteristics of 132kV power cable

Tangent Delta is an analytical method to determine cables insulation strength. It is a robust method to analyse aging of cables. Ideally the insulation (XLPE) acts as a perfect capacitor, the voltage and current are phase shifted 90°. Current through the insulation are purely capacitive (IC) with current leading voltage (V). Defects like contamination, scotching and void will add impurities in the insulation resulting in decrease of resistance of the insulation. This causes the increase in resistive current (IR) through the insulation making it no longer a perfect capacitor. A phase shift between the leading capacitive current (IC) and the voltage is utilized to determine the tangent delta (tan δ). Defects such as void in the insulation play a role in the electric field distribution in a cable. Simulation using Electromagnetic Computer Simulation Technology Studio (CST EM) displays a change in the electric field distribution and localization of the electric field. The changes in the Tan Delta, due to the presence of voids are then verified using HF Tangent Delta measurement method. Other cables with defects like scotching and contamination in the insulation (XLPE) will also be measured. The High Frequency AC setup utilizes a small testing environment due to the use of small length cables. This change will result in the reduction of total capacitance of the cable but this is overcome using High Frequency which is sufficient to create high electric stress on XLPE layer thus inducing measureable dielectric current. Tangent delta is obtained using the phase shift between leading current and applied voltage.