A TIME-DOMAIN DIFFERENTIAL-EQUATION APPROACH USING DISTRIBUTED-PARAMETER LINE MODEL FOR TRANSMISSION-LINE FAULT LOCATION ALGORITHM

The objective of this work is to develop an algorithm which can provid e both a fast relaying time (1/4-1/2 cycles) and an accurate fault loc ation (error within 1% of the total line length). The proposed algorit hm combines the strengths of the two distinct approaches, namely, the steady-state phasor approaches (SSPA) and the differential equation ap proaches (DEA). In the proposed algorithm, a distributed line model is used, which is suitable for the short, the long, the transposed and t he untransposed lines. The DEA is used to calculate the fault location and is implemented using the Laplace and the Z-transform techniques. There are several advantages in this proposed algorithm ever the exist ing ones: (a) the variations in the line parameters with the frequency are considered; (b) the fault location estimate is less sensitive to the selection of the sampling rate, the fault inception angle, the sig nal spectrum and the equivalent sources behind both bus bars; and (c) the relay performance is greatly improved offering both the desired hi gh accuracy and the speed at the same time. (C) 1998 Published by Else vier Science S.A. All rights reserved.