Advancing Space Charge Test Techniques: Pulsed Electro-Acoustic Measurement on a 525-kV HVDC Cable

In 2017, the IEEE Dielectrics and Electrical Insulation Technical Committee HVDC Cable Systems introduced a procedure to assess the effect of space charge accumulation in extruded high-voltage DC (HVDC) cables with rated voltages up to 550 kV, which is known as IEEE Standard 1732. In this article, we present the results of a pulsed electro-acoustic (PEA) measurement, which has been carried out in compliance with the IEEE guidelines, for the first time on a full-size cable with a rated voltage, U0, of 525 kV and with more than 100 m in length. The aim is to evaluate the maximum absolute percent variation of the electric field profile, ΔEmax, to determine after how long it takes to stabilize (variation less than 10%). Compliance with this condition is checked at three-hour intervals. Results include both positive (+U0) and negative (−U0) volt-on tests, each followed by a volt-off test. The findings reveal a significant reversal of the electric field profile during the positive and negative volt-on tests, with electric field stabilization reached after a total duration of nine and six hours, respectively. Notably, the reversal of the field is concentrated within the first hour. However, evaluating the ΔEmax at three-hour intervals leads to extending the test duration to a minimum of six hours. Furthermore, the evaluation of ΔEmax based on the profiles acquired at the beginning and end of the interval could make the results overly sensitive to external disturbances. This study demonstrates the reproducibility of the PEA measurement on full-size cables longer than 100 m and the applicability of IEEE Standard 1732.