Electrical aging phenomena of medium voltage EPR cable energized by ac voltage with switching impulses superimposed

Abstract

Electrical aging of polymer insulated power cables has been an important subject of investigation in the last several decades. Cable insulation is placed under heavy electrical stress due to overvoltages occurring during switching operations taking place in the power system. Transients overriding the normal ac operation voltage are some of the most hazardous conditions for cable insulation life. Although a good understanding of aging mechanisms under single stress has been achieved, more research work is needed to fully grasp the phenomena taking place under multi-stress conditions. In this study, the electrical aging of 15 kV Ethylene Propylene Rubber (EPR) power cables was undertaken by ac voltage with switching impulses superimposed in wet condition. The experiments aimed at providing a better understanding of the electrical aging phenomenon of EPR cable insulation in wet condition. It also helped to assess the reliability of EPR cables used under such circumstances.

Accelerated electrical aging of medium voltage EPR cables energized by elevated AC voltage with switching impulses superimposed

“…Then the inception voltages start to increase. The similar trend was observed for PD measurements of EPR cable samples aged by switching impulses [18] and by rated ac voltage with switching impulses superimposed [5]. The fluctuation of PD inception voltages appears again at the aging time between 650 and 800 hrs.…”

“…In the past, the aging study of EPR cables under many different conditions has been carried out [5,16]. Tab.…”

“…All of these stresses can influence the aging individually or synergically [5] [6]. The failures of polymer cable insulation under service conditions are rather the results of the combined effects of the multiple stresses.…”

Tools and dielectric requirements for the design of marine cabling systems

“…Moreover, past studies [8] revealed that perfectly manufactured EPR material would not have significant aging under the ac electrical field stress that was less than 20 kV/mm. Under some extreme conditions, such as lightning surges and switching transient conditions in power systems, the local electric field stress could be over ten times the operational field stress [15][16][17]. The majority of the commercially available EPR cables have a maximum working temperature of 105°C.…”

“…Among all of these stresses, the switching surges are treated as one of the most hazardous sources. Yet the detailed information regarding the aging mechanism caused by switching impulses is not fully understood, especially those regarding the long term behaviors of the polymeric cables [15][16][17].…”