Live line measurement of untransposed three phase transmission line parameters for relay settings

The purpose of this study is to develop a method to measure untransposed transmission line parameters for protection relay setting. For relaying schemes such as distance relays, current differential relays and fault locators, it is very useful to ascertain the precise setting values in service, without the need for setting calculations prior to installation, and also for the relays to be able to adaptively change their settings as the system configuration changes. This paper describes a method of live line measurement of the parameters of an untransposed three phase one circuit transmission line and untransposed two parallel transmission lines and necessary conditions to measure line parameters. We propose a mathematical approach using synchronous voltages and line currents at both ends of the line in different states, where two models, the equivalent PI circuit and distributed constant line, are employed. For two parallel transmission lines, applying a mode decomposition, we show that two parallel transmission lines can be transformed into double independent three phase circuits. The efficiency and issues are shown using several simulation examples in MATLAB.