Analysis of Void Defects in DC TP Cables Based on Partial Discharge Measurements

The demand for DC power grids is increasing due to the growing need for renewable energy and advancements in technology. Consequently, there is a rising necessity for DC cables capable of transmitting large-capacity power over long distances. TP cables offer superior power transmission performance compared to conventional DC cables and have the added advantage of being environmentally friendly due to their recyclability. As a result, they are anticipated as an eco-friendly alternative to high-performance XLPE cables for DC applications. Despite the outstanding dielectric strength characteristics of TP cables, cable defects can lead to electrical and chemical degradation, which eventually causes severe damage to the cable due to dielectric breakdown. One of the primary defects that occur in cables is voids; therefore, research on void defects is essential to prevent dielectric breakdown. However, DC research in Korea remains in its early phases, and studies on DC partial discharge analysis for various power equipment are still scarce. In addition, there is a complete lack of prior research on DC void measurement and analysis for TP insulating materials. Also, there is a significant lack of prior research on DC void measurement and analysis for TP insulating materials. Therefore, in this paper, defects were created in specimens to measure and analyze partial discharge related to void defects in DC TP cables. Therefore, in this paper, defects were fabricated in specimens to measure and analyze partial discharge related to void defects in DC TP cables. Based on the IEC-60270 standard, void defects were measured using an HFCT sensor. Pulse waveforms, TF, and PSA were utilized to analyze the characteristics of the measured DC partial discharges. The experimental results showed that, initially, the repetition rate of void discharges was low. However, as the measurement time continued, the discharge repetition rate increased, and the discharge magnitude grew larger. The characteristics of void discharge pulses were analyzed according to their positions on the TF map. Additionally, PSA patterns were formed by parameters to analyze the unique PSA characteristics of void discharges. Based on the analysis results, it is anticipated that void defects in DC TP cables can be effectively identified.