Measurements and calculations of critical thermal and electrical stress conditions for HVDC bushings

Summary

Insulation materials in high voltage systems have to withstand high electrical and thermal stresses. New applications of HVDC and new technologies as well as modified stress-profiles require further research on the combined thermal and electrical characteristics of HV components like cables, transformers or bushings. For DC insulation systems it is quite important to understand how the electrical conductivity and hence the field distribution inside the dielectric is influenced by temperature. Thermal gradients and thermal transients can cause severe field migrations inside the dielectric. The focus of this contribution is a newly developed measurement setup for the investigation of these effects on real bushing test objects and a comparison with FEM simulations. It is shown that the temperature gradients and transients strongly influence the electrical field distribution inside the dielectrics. Different scenarios were investigated, e.g. a voltage step during a constant temperature gradient or a temperature step while the voltage is constantly applied. Another tested scenario was the polarity reversal. Furthermore, FEM simulations were performed to verify the measurements and to get a better understanding of the dielectric behaviour of HVDC bushings.

Additional informations

Authors

N. HESSDORFER, M. ZINK, A. KUCHLER, A. LANGENS, F. BERGER

Keywords

HVDC, Bushing, DC-field measurement