A Linearization Method for Determining the Effect of Loads, Shunts and System Uncertainties on Line Protection with Distance Relays

Short circuit calculations usually performed for determining the setting of line protection relays neglect factors such as loads and shunts, and assume that all network parameters, such as line impedances, are known with perfect precision, which is not the case. This paper describes a technique for assessing the effect of these factors on the voltages and currents activating the relays. The study is centered on distance relays using the principle of impedance determination.