Abstract
Variability of the available short-circuit power also implies variation of the fault level, which can potentially cause several protection problems in the electric networks. In this study, a novel protection method that is insensitive to the fault level changes caused by variable short-circuit power is presented. It relies on utilisation of symmetrical components of the short-circuit currents and on communication between the protection relays. The proposed method addresses the single phase to ground (SPG) faults occurring in directly grounded distribution networks, with focus on closed-loop medium voltage (MV) feeders. Case studies are presented, which demonstrate that the proposed protection scheme is capable of effectively detecting the SPG faults in closed-loop feeders with variable short-circuit power.
Highlights
The distribution networks comprise radial feeders supplied from a single utility source [1]
Regardless of the type of feeder involved in a distribution network, its protection system is challenged by variability of the available short-circuit power, as the short-circuit currents are variable in this situation [4]
The newly developed protection scheme has been tested in a closed-loop medium voltage (MV) feeder with variable short-circuit power using PSCAD and the simulation results demonstrate its effectiveness in these conditions
Summary
The distribution networks comprise radial feeders supplied from a single utility source [1] In this arrangement, the current flow is unidirectional and protection against the shortcircuit faults is realised typically by overcurrent (OC) relays [1], but an electric fault could cause a power outage for all loads placed downstream the fault location [2]. In order to mitigate some of the protection problems mentioned above, a new protection scheme is proposed in [5] for radial MV feeders with variable short-circuit currents. This paper presents a new communication-based protection scheme for loop MV feeders with variable short-circuit power. The newly developed protection scheme has been tested in a closed-loop MV feeder with variable short-circuit power using PSCAD and the simulation results demonstrate its effectiveness in these conditions.
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