09_Bamji_whitehead_memo - S. S. Bamji et al.: Luminescence...

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S. S. Bamji et al.: Luminescence and Space Charge in Polymeric Dielectrics 1070-9878/09/$25.00 © 2009 IEEE 1376 Whitehead Memorial Lecture (2008) Luminescence and Space Charge in Polymeric Dielectrics S. S. Bamji, A. T. Bulinski and M. Abou-Dakka National Research Council of Canada 1200 Montreal Road, Bldg. M-50 Ottawa, Ontario, Canada, K1A 0R6 ABSTRACT Polymers are extensively used as insulating material in high voltage devices, such as underground power cables, power capacitors and transformers. During normal operation the polymeric insulation of a power device is not only subjected to electrical stresses, but could also be subjected to other stresses that can cause the degradation and ultimately lead to insulation failure. It has been well established that electroluminescence and charge injection, which gives rise to space charge in the polymeric insulation, occur at ac, dc and impulse field above a certain threshold value. Space charge can cause dissipative energetic processes such as photon and phonon emission, increase the local electric field and reduce the withstand voltage of the insulation. This paper describes the characteristics of electroluminescence in polymeric insulation subjected to ac voltage and shows its relevance to space charge injection in the material. It is shown that insulation subjected to high voltage could emit various types of light but electroluminescence emission which is related to space charge injection can be clearly distinguished from these other types of light emission. The electroluminescence technique is a valuable tool to evaluate the dielectric properties of novel insulating materials, such as nanodielectrics. Index Terms Electroluminescence, space charge, dissipation current, phase resolved pulsed electro-acoustic technique. 1 INTRODUCTION DIELECTRIC materials are the backbone of all electrical and electronic devices. These materials not only separate the high voltage from ground potential in power devices, such as generators, motors, transformers, capacitors and cables but also provide the required electrical insulation in electronics for electromagnetic shielding, junction devices, solar cells and others. A vast number of dielectric materials are integrated into complex insulation systems for a host of specialized applications and have become a vital component of high voltage electrical and electronic equipment, a multi-billion dollar annual market. The real test of the suitability of a dielectric material for a specific application is how well it performs in actual use when subjected to the full range of conditions experienced during service. Insulation integrity is extremely important for all electrical power applications, and the lack of it often results in catastrophic breakdowns and power failures with losses of millions of dollars in productivity to the country’s economy. Using dielectric materials that can withstand high electric
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09_Bamji_whitehead_memo - S. S. Bamji et al.: Luminescence...

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