Design of distribution sub-station with cascaded protection

Abstract

The main purpose of the substation is to provide continuous and consistent electric power supply to the end consumers connected to the distribution network. In a situation, when a fault occurs in the distribution network, it is essential to interrupt and disconnect the power supply until the fault is removed. For this reason, a distribution substation must have different protective equipments and techniques that can detect and recognize any significant fault emerging in the system and that ultimately forces disconnection of power supply in a very short time interval. In this paper, we emphasize on the load calculation of the current transformers (C.Ts) along with the use of potential transformer (P.Ts) and the protection relays in the proposed distribution substation. We consider a typical protection system consists of two distribution transformer 2000KVA at 11KV/420V and 1250KVA at 11KV/420V in the proposed distribution substation. Moreover, we focus on different parameters that are necessary for the protected system like short circuit, over current, earth faults generated in the line before the transformers. Such a protected distribution substation may fulfill stability, sensitivity, selectively and consistency of the continuous power supply.