Opening lecture
In pursuit of electrical ageing mechanisms in polymeric insulations: Current status and trends for the future
Gilbert Teyssedre, Laplace, Université de Toulouse and CNRS, Toulouse, France
Abstract: The approach to more efficient energy conversion and transmission systems has led to tougher specifications for insulating materials used in power equipment: higher service temperature, higher service field and demand for longlife materials in service. These evolutions have typically led to service fields of the order of 8kV/mm under 320 kV HVAC cables to typically 30 kV/mm for 520 kV HVDC cables representing a huge gain in transmission capacity per cm of insulation thickness. Thin films capacitors work with service field beyond 100 kV/mm. In the field of power electronics, combined local high temperature and high electric field, with diverging geometry are the challenge to go to wide band gap semiconductors. All along progresses in developing materials and exposing them to new stresses, there has been a salient question: do materials deteriorate under electrical stress, how, and how to anticipate their end.
The considered mechanism is the following: due to ageing factors, the material integrity evolves and its cohesion weakens, leading to embrittlement to a point it cannot oppose to the propagation of treeing. Then, the cause roots of material evolution need to be found. While it is relatively straightforward identifying it in hydrolytic or oxidative environment, processes under pure electric stress are more difficult to demonstrate. My purpose in this lecture will be to review current knowledge in this field, particularly as regards the access to the cascade of events that lead to a loss of dielectric strength in insulations.
Gilbert Teyssedre (Senior Member, IEEE) earned an engineering degree in materials physics and a master’s degree in solid-state physics from the National Institute of Applied Sciences (INSA) in Toulouse in 1989, followed by a PhD from the Solid-State Physics Laboratory at Paul Sabatier University in Toulouse in 1993, for a work on ferroelectric polymers. He joined the French National Centre for Scientific Research (CNRS) in 1995 and has since worked at the Laboratory of Electrical Engineering (now Laplace – Laboratory of Plasmas and Energy Conversion), a joint research unit between the CNRS and the University of Toulouse. His research interests include the development of luminescence techniques in insulating polymers, with a focus on chemical and physical structure, degradation phenomena, space charge, and transport properties. He is currently a senior researcher at CNRS. He led the Solid Dielectrics and Reliability Group at Laplace from 2004 to 2015. Dr. Teyssedre has served in the Scientific Committee of several conference series, including CEIDP, ICD, ICEMPE, ISEIM and JiCable. He was conference chair of ICD 2024. He has been an associate editor of the IEEE Transactions on Dielectrics and Electrical Insulation since 2021.
e-mail: [email protected]