Investigation of Electrode Surface Roughness in HVDC GIL by Numerical Simulation

Inhalt:
High-voltage direct current gas insulated lines combine the advantages of high voltage capacity, high efficiency concern-ing losses and compact size. They consist of an insulating gas, a solid insulator to sustain the system and the electrodes, namely the conductor and the grounded shell. Due to manufacturing processes, there is a specific roughness of the elec-trode surface given. Under DC condition, charge accumulation occurs in the gas insulated system, influencing the electric field distribution, which may lead to partial discharge or even system failure. Experiments show that the roughness of the surface of the electrodes has an influence on the charge accumulation, due to the micro-protrusions on the surface. In most works, where the gas insulated system is investigated by numerical simulations, the electrode surface is considered perfectly smooth. This, however, does not represent reality and neglects the effect, which the electrode surface roughness has on charge accumulation and hence on the local electric field distortion. For the ability to investigate gas insulated lines precisely, this work focuses on implementing the electrode surface roughness in an electro-thermal model with the combination of an application of specific electric conductivity models for the insulating materials. Different degrees of roughness are investigated to examine its influence on the electric field distribution. Also, a different simulation approach, namely an ion-drift-diffusion model, is compared to the electro-thermal model with an implementation of the electrode surface roughness.