Study of magnetic field shielding roof of cabin electricity authority resulting in operators working

Monitoring, maintenance and repairing works of electric power transmission systems are main functions of power engineers in their daily schedule. Provincial Electric Authority of Thailand (PEA), state own organization in which regional power transmission systems and rural electric power distribution systems are its major services. For economic purposes, two or more circuits are normally hung on the same towers. Typically, a circuit of higher voltage is on the top of the tower. A practice of this configuration is a combination of a 115-kV power transmission line and a 22-kV distribution feeder. Safety of operators working in this circumstance depends on carefulness of all possible risks. Even when one circuit is disconnected from the supply source, magnetic induction becomes a serious issue where two or more circuits are located close enough to each other. This paper proposes a set of mathematical model of magnetic fields caused by high voltage conductors of electric power transmission systems by using a set of second-order partial differential equations. Computer-based simulation utilizing the three-dimensional finite element method (3D-FEM) is exploited as a tool for visualizing magnetic fields distribution around a power transmission line. In addition, magnetic shielding devices are investigated in order to reduce the magnetic induction on the nearby circuit. The configurations of a crane's cabin roof is studied and reported. Moreover, comparison of magnetic field distributions with and without the shielding roof is illustrated.

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