Evaluation of the onset of space charge and electroluminescence as a marker for cross linked polyethylene ageing

The aim of the “ARTEMIS” project is to investigate the ageing mechanisms for cross-linked polyethylene under thermo-electrical stress and to identify ageing markers, which can be used to carry out diagnostic procedures. A carefully selected set of techniques which can give cross-correlated information on space charge phenomenology and material degradation were used to investigate specimens peeled from reference and aged cables. The paper shows that ageing induces a change in the density and depth of trapping levels, and an increase in the number and size of mesovoids. Interpretation of these results is discussed in terms of physico-chemical modifications, which can affect trap distribution and microstructure

Behavior of Space Charge in Polyimide and the Influence on Power Semiconductor Device Reliability

Polyimide is widely used in film form as a passivation material for power semiconductor devices such as Si, SiC, and GaN. The magnitude of the electric field at the edge termination area of these semiconductor devices is becoming higher due to the increase of operational voltage and/or demand for shrinking the edge termination area to increase device active area. Hence, it is concerned that the accumulation of space charge in the encapsulation and passivation material may affect the insulation performance of these devices, for example, the degradation of withstand voltage due to distortion of the internal electric field caused by space charge accumulation. To design space charge resistance of semiconductor devices, it is important to understand the space charge behavior in polyimide films with a thickness of several to several tens of micrometers. This chapter addresses practical implementation, specifications, and issues on space charge in polyimide insulation on power semiconductor devices focusing on the space charge measurements in thin polyimide films using the latest developed LIMM method and DC conductivity measurements

Assessment of a Charge Transport Model for LDPE through Conduction Current Measurement

Conduction current measurements have been widely used to characterize charge transport behavior in insulating materials. However, the interpretation of transport mechanisms and more generally of non-linear processes from current measurements alone is not straightforward. For this reason, space charge measurements, on the one hand, and models of charge transport encompassing charge generation, trapping and transport have been developed. The completeness and accuracy of a model can be assessed only if a substantial range of stress conditions, being field and temperature for the current topics, is available. The purpose of this communication is to enrich the investigation of low density polyethylene - LDPE insulation material characteristic using conduction current measurement. Measurements were conducted on 250 μm thick LDPE samples, for DC fields in the range 2 to 50 kV/mm and for temperatures from 20 to 70°C. Experimental data, i.e. transient current in charge/discharge and quasi-steady state currents are compared to the prediction of a bipolar transport model that has been developed over the last years and fitted to the case of LDPE. The deviation of model results is substantial, with essentially an overestimation of the non-linearity of the current-field dependence. These differences are discussed along with prospects from improving the model. Aside from these modelling approaches, we show that thermal preconditioning of samples appears to be influential in the measured apparent conductivity

Matériaux en Génie Electrique

National audienc

Simulation du transport électrique dans un polyéthylène pour câble d'énergie par un modèle de conduction bipolaire avec distribution exponentielle de pièges

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Evidence of hot electron-induced chemical degradation in electroluminescence spectra of polyethylene

International audienc

Evidence of Exciton Formation in Thin Polypropylene Films under AC and DC Fields and Relationship to Electrical Degradation

International audienc