¹ H NMR tests on damaged and undamaged XLPE and SiR samples

Abstract

Cross-linked polyethylene (XLPE) and silicone rubber (SiR) samples were subjected to a high-voltage AC stress plane-plane configuration and inclined plane test, respectively. The voltage was applied such that discharge was observed across the surface of the XLPE test sample for several hours and for visible damage to occur on SiR samples also after several hours. Selected stressed samples together with virgin samples from the same manufactured batch were tested using nuclear magnetic resonance (NMR) spectroscopy. Specifically, 1 H NMR spin-lattice (T 1) and spin-spin (T 2) relaxation time measurements were employed to examine potential changes in the chemical bonding of undamaged and damaged XLPE and SiR samples. Preliminary results show that there may be a moderate increase in the T 1 and T 2 values of the damaged samples in comparison with the undamaged ones. This raises the possibility that NMR can be a useful additional experimental tool in characterising material degradation.

Impact of step voltage parameters on accuracy of evaluating XLPE insulation DC voltage endurance coefficient

“…Under the same voltage conditions, the value of t c is mainly a function of the microstructural changes of the XLPE dielectric under electrical stress. The free volume, represented by channels and voids, contributes to the dielectric electrical aging [22,23], which can affect the value of t c . As shown in Figure 15, when the externally applied electric field strength is E > E a , the conditions for the formation of the streamer discharge are reached in the free volume [24].…”

“…Under the same voltage conditions, the value of t c is mainly a function of the microstructural changes of the XLPE dielectric under electrical stress. The free volume, represented by channels and voids, contributes to the dielectric electrical aging [22, 23], which can affect the value of t c .…”

Morphology evolution and breakdown mechanism of cross‐linked polyethylene (XLPE)–silicone rubber (SiR) interface induced by silicone grease diffusion

“…The breakdown between the interface of the cross-linked polyethylene (XLPE) cable insulation and the accessory SiR insulation is the main cause of cable accessory failure [7][8][9]. The interface pressure, surface roughness, interface fillers, and space charge have been shown to be the main factors affecting the breakdown strength of insulating interfaces [10][11][12][13].…”