Single-ended limiting inductor voltage-ratio-derivative protection scheme for VSC-HVDC grids

Single-ended protection systems present the characteristics needed to fulfil restrictive speed requirement related high voltage direct current grids. This paper proposes a novel single-ended algorithm based on DC across limiting inductors placed at each link end. Voltage measurements are taken both terminals of inductors. The ratio between link- and bus-side voltages enables fault discrimination forward backward conditions while providing directionality. Moreover, derivative voltage-ratio is calculated in order enable fast detection. combined operation these two algorithms avoids nuisance operations against fluctuations close-up external faults. A trip signal only issued circuit breakers when individual criteria simultaneously fulfilled. According this, scheme developed, which covers primary backup as well busbar protections. performance proposed evaluated through simulations four-terminal grid. selective, sensitive accurate demonstrated faults up 250 Ω employing local measurements, common inductor sizes relatively low sampling frequency. Thus, overcomes sensitivity limitations high-resistance detection presented derivative-based algorithms. Its proper under noise disturbances also demonstrated.