Optimal Phase Arrangements of Underground Transmission Lines Installed by Metropolitan Electricity Authority of Thailand

Abstract

This paper investigates the magnetic field generated by underground transmission lines, which are practically installed by Metropolitan Electricity Authority (MEA) of Thailand. Specifically, various phase arrangements for duck bank (4×6) and pipe-jacking (21 ducts) of the MEA underground transmission lines were analyzed and simulated by analytical approach based on Biot-Savart Law using MATLAB program. To assure the accuracy of the simulated results, they were compared to the measured results under the same conditions where the test cite was at the tunnel link between Lad-Phrao and Vibhavadi substations, about 8 km, and the tunnel depth was at 15 m from the ground surface. In addition, the magnetic field was simulated from the measured RMS current, recorded every 30 seconds for 16 hrs. By aforementioned setting conditions, the optimal phase arrangements of MEA underground transmission lines in terms of minimized magnetic field for duck bank (4×6) and pipe-jacking (21 ducts) were proposed. Finally, from the simulated results, it shows that the magnetic field generated by underground transmission lines with proposed optimal phase arrangement techniques is not greater than the maximum exposure limits given by the World Health Organization and International Commission on Non-Ionizing Radiation Protection.