Accurate fault location estimation in a partially coupled circuit line using Takagi method

In the event of a Single Line to Ground (SLG) fault, the zero-sequence current associated with the faulty line provides sufficient input for the distance relay to calculate the fault location within a single-circuit line. However, the mutual coupling effect within a double circuit line causes the relay protection algorithm to become more complex. Consequently, the relay utilizes zero sequence currents from both the faulty and healthy lines to overcome the challenges related to under reach and over reach scenarios. The Takagi method and its modified variation is suitably framed to predict the magnitude and phase angle of the zero sequence current in the adjacent healthy line. This information enables the proposed scheme to iteratively and precisely determine the fault location. The method is equally effective for both fully coupled and partially coupled lines operating independently of any communication infrastructure. In the proposed scheme, the fault location error remains under 1% even incases of high resistance faults. PSCAD simulations are conducted across different circuit configurations and the results have been satisfactory. Moreover, by employing an angle correction technique, this method extends its capability to deliver favourable outcomes for non-homogeneous circuits. Furthermore, the effectiveness of the proposed scheme is ascertained by testing the algorithm in a mutually coupled transmission line prototype established in the laboratory.