Distance Protection Impedance Measurement for Inhomogeneous Multiple-Circuit 400/150 kV: Transmission Lines with Shared Towers

• Published in: 13th International Conference on Development in Power System Protection 2016 (DPSP) p. 6
• Main Authors: Bak, C.L, Sigurbjo¨rnsson, R, Bukh, B.S, Post, R
• Format: Conference Proceeding
• Language: English
• Published: Stevenage, UK IET 2016; The Institution of Engineering & Technology
• Subjects: Circuits; Couplings; Electric potential; Faults; Impedance and admittance measurement; Impedance measurement; Power line supports, insulators and connectors; Power system management, operation and economics; Power system measurement and metering; Power system planning and layout; Power system protection; Power transmission, distribution and supply; Relay; Towers; Transformers and reactors; Transmission lines; Voltage; power transmission lines; power system measurement; complex fault current distribution; fault currents; transformer; transmission line; relay protection; PSCAD simulation; power system interconnection; power transmission faults; power transmission protection; voltage 150 kV; power system CAD; power transformer protection; phase-earth loop; poles and towers; distance relay; phase-phase loop; distance protection impedance measurement; complex R-X plane; powers system inteconnection; shared tower; voltage 400 kV; fault loop impedance measurement; inhomogeneous multiple-circuit; Danish TSO Energinet.dk; electric impedance measurement; mutual coupling
• ISBN: 1785611380; 9781785611384
• DOI: 10.1049/cp.2016.0027

Combined transmission lines where different voltage levels shares same towers are used in transmission systems in order to save way of right. Faults between different voltage levels results in complex fault current distributions due to mutual couplings and the fact that the faulted phases no longer are interconnected in a simple way but via transformers and infeed from remaining parts of the network. Distance relay measured fault loop impedance shows wide ranges of variations for both phase-phase loops as well as phase-earth loops. No simple relations exist. Simulation models can be used to study fault loop impedance for combined faults and thereby shed light on relay trips. This study uses actual fault records, analytical method and PSCAD simulation studies to analyse combined faults in an existing 400 and 150 kV transmission line owned by Danish TSO Energinet.dk. The results clearly show that an accurate modelling followed by fault loop impedance calculation is possible. Selected results show that fault loop impedance can be located in unexpected regions of the complex R-X plane.