Short Circuit Analysis of EHT Network and Solutions for De-Rated Equipment

Abstract

In any power system, load growth occurs due to increase in various activities including industrial expansion, infrastructure development, population growth etc. To meet power demand, the electrical network of utility company required addition in transmission lines, grid stations and power generation. The heavy current that flows due to short circuits causes different types of internal and external faults on the power system which may damage the equipment in the grid station if the fault is not cleared in time. The equipment in the grid station must have the capability to withstand the heavy short circuit level. If unusually high currents exceed the capability of protective devices in the power system, a short-circuit can cause the devices to explode like a bomb, which may ultimately result in collapse of entire system leading to brown out or black out. All these expansion leads to increase in short circuit levels. The short circuit current passes the high voltage, network equipment including circuit breakers, disconnectors, current transformers, potential transformers, surge arresters etc. The high voltage equipment’s need to be check due to increase in short circuit current due to addition in power plants, auto transformers, power transformers and transmission lines. The equipment’s that are already installed are required to withstand short circuit at all time. In the presented work, short circuit levels are calculated by using a software ETAP (Electrical Transient Analysis Program), followed with the analysis of existing equipment’s as whether it can withstand the short circuit level. The proposed period of study is set to be 5 years (till year 2023). Furthermore, three different types of solutions are provided for the derating equipment in the K electric 220V and 132KV transmission lines