English title

A new PMU-based fault detection/location algorithm for multi-terminal transmission lines is proposed in this paper, which works on the basis of synchronized voltage and current phasors received from PMUs installed in various terminals. The Clark transform (for transposed transmission lines), Eigen-values and eigenvectors theory (for un-transposed ones) are used to decouple 3-phase differential equations and to calculate the line parameters, by applying aerial modes (including α and β) to this issue. Distributed-parameters frequency-dependent transmission line model (J-Marti) is used to implement and simulate this algorithm.

The proposed algorithm consists of three main steps, as: 1) Fault detection, 2) Faulty section identification and 3) Fault location determination. The fault detection is done using an index based on differential equations response. The faulty section is identified by comparing the calculated teed point voltages.

Multi-Terminal Transmission Line (MTTL) is reduced to a simple two-terminal faulty line and the fault location is determined by four methods, by considering differential equation response dependency to time and distance. In the first and second methods, two indices are used, which their values are equal to the fault location during faulty condition. In the third and fourth methods, two new indices are defined based on the voltage and current phasors (∆V and ∑I), which the fault location is monitored by using these indices variations. The value of ∆V is minimized in the faulty point, while ∑I is maximized at that point.

To evaluate the proposed algorithm, extensive simulations are performed on a transposed three-terminal double circuit line and an un-transposed five-terminal double circuit line (a section of Iran power transmission grid), while the maximum error of less than 1% (and less than 3% for specific conditions) is achieved. The MTTL cases are simulated in EMTP software and the obtained data are processed in MATLAB software. All effective factors including power sources with different phase angles and various impedances, zero sequence mutual coupling, un-transposed construction, unbalanced loads are regarded to simulate phase to phase, phase to ground, cross-country and simultaneous faults. Also (n-1) PMU contingency is considered in these studies. Finally, the results and the proper indices are introduced by regarding a series of simulations and comparisons.