Online Calibration of Inner Capacitive Coupling Sensor for XLPE Cables

During factory test and off-line test in field, the apparent charge quantity is expressed in picocoulomb(pC). A novel online calibration method based on the simulation of inner capacitive coupling equivalent circuits is proposed, to convert the measured results into the form of the quantity of the apparent charge for the comparison with the results obtained from the off-line tests. The online calibration method is performed in laboratory on a 35 kV XLPE cable along with two other online calibration methods, and compared with the terminal calibration method according to IEC 60270: 2000 standard. By taking the stray capacitance C_s into consideration, the results prove that the scale factor obtained by the proposed novel method has good fit with that obtained by the standard method better.