Evaluation of Noise and DC Offset Voltage on Signal Processing for Space Charge Measurement of HVDC Cables

The influences of noise and DC offset voltage on the maximum electric field, root-mean-square error (RMSE) of space charge profile, and RMSE of the electric field profile in insulating materials, such as HVDC cables, are evaluated using a signal processing method and a reference waveform. Also, baseline correction was used to rectify errors. Based on the noise evaluation, the maximum of three-sigma intervals at S/N ratio +20 dB was 19 % for the maximum electric field, 7.5 % for RMSE of the electric field profile, and 10.6 % for RMSE of space charge profile with baseline correction. The maximum electric field is affected twice as much by the noise level, compared to the other parameters. Based on the DC offset voltage evaluation, a DC offset voltage of +/- 1% could introduce a 23 % relative error into the maximum electric field without baseline correction and a 6.6 % relative error in the maximum electric field with baseline correction. Hence, it was found that baseline correction reduces +/- 1% DC offset voltage error by 16 %.