Improved Multi-Ended Impedance-Based Fault Locating For Untransposed Transmission Lines
Transmission lines are usually spread over many miles and go through various kinds of terrains. When a fault occurs on a 100-mile transmission line and the fault locator accuracy is within +/– 5 percent, the repair crew must patrol +/– 5 miles from the location provided by the IED. This highlights the need for an accurate fault-locating algorithm to improve the line restoration process.
Impedance-based fault-locating algorithms can be classified as single-ended, multi-ended using remote currents, and multi-ended using remote currents and voltages. The choice of a particular method depends on available signals. While one might expect higher accuracy with more available signals, this hasn’t traditionally been the case. This is because all these methods assume an ideally transposed line, when in fact all transmission lines are either untransposed or not perfectly transposed. The assumption that the lines are transposed, simplifies the mutual coupling between sequence networks, making fault location calculations more straightforward. However, this simplification introduces errors in fault location estimation.
This paper introduces a novel fault-locating algorithm designed to improve accuracy in untransposed transmission lines. The proposed multi-ended fault-locating method makes use of remote currents and voltages. It differs from the traditional multi-ended method in that it doesn’t assume the lines are transposed and includes the mutual coupling between the sequence networks. The sequence coupling parameters, however, are not required to be determined or entered by the user, instead, the algorithm itself estimates these parameters. Additionally, the paper expands the error analysis to parallel lines and introduces an enhanced approach for improving fault location accuracy in these configurations.
This paper illustrates the effectiveness of the proposed approach using simulated power system models. The simulations are conducted under a variety of power system conditions to evaluate fault location accuracy in untransposed lines. These conditions include source impedance ratios, fault location, loading, fault resistance, fault type, and transmission line configurations. The approach is also validated using field events with known fault locations.
In summary, the paper introduces a novel fault-locating algorithm that effectively addresses the challenges posed by untransposed transmission lines for accurate fault location estimation. Through extensive testing, involving simulations and real-world field events, the proposed algorithm proves its efficacy by accurately identifying fault locations.