Method-hybridization for preventing capacitive current based false trips in Turkish cable dense distribution networks

Abstract

Modern distribution networks have constantly evolved to meet different requirements. Basically, increasing energy demand and supply security are the main motivation for these changes. In order to meet the increasing energy need, there are many parallel outgoing feeders in the distribution substations, and there is an intense use of underground cables to increase supply security. During single line to earth fault, zero sequence currents circulate in the system due to cable capacitive currents of underground cables. These capacitive charging currents may cause false trips in healthy sections of the network. Metropolitan distribution networks draw particular attention with distinguishing topological features which are; the usage of long-length underground cables and high number of parallel outgoing feeders. In addition, different types of earthing methods are applied. This situation eliminates the applicability of simple, unique and universal relay settings for all types of networks. As a result, the requirement of feeder-based protection hybridization, specifically tailored to the distribution network topology is inevitable. In this study, feeder-based hybrid protection methods and optimum setting values of these methods are proposed for different network topologies and different neutral earthing methods. The method-hybridization is applied to the 62-busbar distribution network to demonstrate the applicability of the proposed method.