Experimental Investigation of Electrical Stresses on the Main Components of HVDC Circuit Breakers

Abstract

Recently a number HVdc circuit breakers (CBs) based on various dc current interruption principles have been developed and a few are put in operation. However, due to a lack of practical experience, no clearly defined requirements that the HVdc CBs should satisfy exist. To define and refine justified test requirements, a thorough understanding of the interactions between the internal components of the HVdc CB and the stresses on these components under real dc fault current interruption condition is necessary. In this paper, an experimental dc CB based on the active current injection technique is setup in a high-power laboratory to investigate the performances of the main components; namely, the vacuum interrupter (VI) and the metal oxide surge arrester (MOSA). The performances of three different designs VIs are investigated and it is found out that each of the VIs behave completely different. The key parameters having impact on current interruption performance of the VIs are identified and analyzed in detail. Moreover, the performance of a MOSA, designed for HVdc CB application, is also investigated by applying energy per volume ranging between 70-220 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at temperature as high as 250 °C. In order to find out the performance limit of the MOSA for this application, successive high-energy tests are performed until electro-mechanical failures occur in the MO varistors. Various failure modes such as fracturing and puncture are observed. The detailed analysis of these failure mechanisms during destructive tests and the root causes are presented.