Permanent Magnet Biased Fault Current Limiter used for HVDC Systems

This paper presents performance analysis of a novel design of permanent magnet (PM) biased fault current limiter used for high voltage direct current (HVDC) systems using COMSOL Multiphysics package. This cost-effective design overcomes many drawbacks of using PM in fault current limiters and enhances the performances. Results reveal that in comparison to the conventional/rectangular (letters: CI) core configuration (having the same volume of soft magnet, PM, and cross-sectional area of the DC coil), the new delta-shaped design shows an increased capability of fault current clipping ratio by ~34%, slowing of current slope (steepness) to ~65.8, and the peak value of induced transient overvoltage at the instant of fault clearing to 82.6%. In the novel design, it is found that increasing the number of turns and/or the PM height play a crucial role in enhancing the performance in terms of increasing the fault current clipping ratio, decreasing of current slope (steepness), and with a slight increase in the peak value of induced transient overvoltage. Finally, the fault duration, which is determined by the circuit breaker technology, governs the dynamic performance of the fault current limiter. The shorter the fault duration, the higher is current clipping ratio, and the lower is the transient induced overvoltage across the fault current limiter, without any effect on the current steepness.