Investigation Into the Issues Associated with Closing an Automated Normally Open (N/O) Point on Three Medium Voltage (MV) Networks Where Fault Location, Isolation and Service Restoration (FLISR) is Planned

The design of Medium Voltage (MV) Overhead Lines (OHL) is often radial in nature which makes back-feeding difficult and these networks are often long which increases their exposure to faults. This has resulted in poor network reliability. Customers are mainly affected by faults on the MV network, to which particular attention has to be paid. Permanent faults (involving equipment damage) have negative impact on customers since they experience outages or interruptions while the equipment is repaired or replaced. The impact on customers increases when these outages are long. Customers continue to demand higher levels of uninterrupted supply from the distribution network; therefore it is necessary to implement self-healing Smart Grid technologies. One such technique is Fault Location, Isolation and Service Restoration (FLISR). The main drive towards implementing FLISR is to improve Eskom's network performance, increase electricity sales, improve flexibility and reduce the impact on the economy of outages. This paper discusses various ways to implement FLISR and will also focus on case studies on real distribution networks and look at the issues associated with closing a remotely controlled or automatically operated Normally Open (N/O) point for back-feeding. This paper aims to show how automated service restoration can reduce switching and restoration time from hours to minutes.