A study of treeing phenomena in the development of insulation for 500 kV XLPE cables

Factors influencing electrical treeing in XLPE insulation

“…During the service of the cable, some of the peroxide decomposition products may diffuse out, thereby affecting the treeing inception stress. Ishibashi et al [8] have shown experimentally that when high level of decomposition products are present in XLPE cables, the treeing inception stress can increase from 25% to 70% depending upon the defect's tip radius. Generally, the smaller the tip radius, the greater is the effect of decomposition byproducts.…”

“…The values of the AC inception stress for electrical treeing versus defect tip radius of curvature in XLPE insulation have been reported in References [8,[14][15][16]. Figure 1 shows the experimental data of several researches for the Laplacian field at the defect tip calculated without considering the space charge effects as a function of the defect tip radius of curvature.…”

Study on electrical characteristics of XLPE insulation of high voltage cable

“…Based on these two studies, Newton-Raphson method is applied to determine the intrinsic permittivity of materials of XLPE cable. voltage of extruded transmission power cables has increased to 500 kV [34,35].…”

“…Further, it becomes clear that the onset points of breakdown in XLPE cables are still the small defects in XLPE insulation, although the exhaustive elimination of defects has improved performance. Therefore, the study of electrical treeing phenomena from the defects is important to improve the insulating performance of XLPE cables [35]. In field study, many techniques for on-line condition monitoring and off-line field testing have been developed.…”

“…There are some possibilities to initiate electrical treeing: (1) localized heating and thermal decomposition; (2) internal mechanical stress from manufacturing process [47]; (3) fatigue cracking from polarity changes; (4) small voids; (5) air inclusions around contaminants; and (6) electron injection. The evaluation of tree inception stress by experiment using XLPE block samples has been conducted elsewhere [35]. Voltage profile [48,49] and temperature [50] have influences on the growths of electrical trees in XLPE cable.…”