PD patterns for LDPE with needle-plane electrode

Partial Discharges (PD) cause the degradation of insulating materials and govern the lifetime of high-voltage power apparatus and cables. Therefore, it is important to understand the PD behaviors in the ageing process. In this paper, partial discharges of low-density polyethylene (LDPE) specimens with needle-plane electrode system were investigated. One specimen had a small air gap between the needle electrode and LDPE, and the other had no air gap between them. The change in PD φ-q-n pattern with ageing time was quite different between LDPE specimens with and without a small air gap. These results were also compared with the result for LDPE specimens with a small void. Based on the above experimental results, the mechanisms of PD degradation and the applications to insulation diagnosis were discussed