Techniques to increase Surge Impedance Loading level of EHV AC transmission lines for improving power transfer capability

The amount of power that a given EHV AC transmission line can transmit safely depends on various limits. These limits can be categorized into two types viz. thermal and stability/SIL (Surge Impedance Loading) limits. In case of long EHV AC lines the efficiency of transmission is below its thermal limit and restricted by angular and voltage stability limits which restricts line loadability upto it's SIL (Surge Impedance Loading) level due to large inductance. Also decrease in line inductance and surge impedance shall increase the SIL and transmission capacity. SIL depends on various factors like spacing between conductors, bundle spacing, tower configuration, conductor size, etc.. This paper discusses the methods to improve SIL of EHV AC transmission line with various single circuit configurations. The sensitivity of SIL on various parameters has been analyzed with the help of mathematical programming in Matlab software and the results are presented. This paper also evaluates which configuration is best and effective for power transmission with single circuits considering other major aspects for transmission like R.O.W (Right of Way).

I. Introduction

According to most updated statistics India's power system is facing a load growth of approx. 8.62% per year [1]. It is also known that in last 7 years the load demand has increased approx. 62.2% and comparative to that our India's I.C. has raised approx. 77.11% from March 2008 to Aug 2014. In India there is large demand of power in the western and southern region compared to other. Gujarat is a power surplus state among all other states. The most power deficit states in India are Andhra Pradesh, Tamil Nadu, Uttar Pradesh, Maharashtra, Bihar and Assam.