LC DC Circuit Breaker based on Precharged Capacitor Commutation

Dragan Jovcic* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


To overcome limitations of the peak DC fault current with previous LC DC Circuit Breakers, this paper studies using a pre-charged capacitor in the auxiliary branch which enables rapid commutation of the fault current from the disconnector in the main branch. The analysis on the theoretical model concludes that the pre-charged capacitor should ideally have high capacitance and low voltage. The design for the practical test case of 5 kV, 2 kA LC DC Circuit Breaker is presented and shows that the pre-charged capacitor voltage requirement is low, at 10% of the DC CB rating. Both, film and electrolytic (lower size and cost) pre-charged capacitor are considered, and the experimental
tests demonstrate successful DC current commutation of 2 kA at 5 kV. Successful breaking is also demonstrated on hardware for negative DC fault current and for very low currents, which represent difficult operating conditions. The experimental study further evaluates robustness to the change of
timing of the current injection and the pre-charged capacitor voltage. The mechanical LC DC CB commutates DC fault current in very short time of 320 µs, and the use of pre-charged capacitor makes this topology good candidate for applications in medium voltage DC systems
Original languageEnglish
Article number107896
Number of pages7
JournalElectric Power Systems Research
Early online date11 Mar 2022
Publication statusPublished - 1 Jul 2022

Bibliographical note

This project is funded by SFC COVID 19 grant. The author is thankful to Mr Richard Osborne, technician from University of Aberdeen for the experimental studies.


  • DC switchgear
  • HVDC protection
  • DC Circuit Breakers


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