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Transformer Riddle No.44 - Power harvesting
I need to harvest power from a high voltage line using the Faraday's law. i.e. whenever current flows in a conductor, magnetic field is produced around the conductor. So I have to use a sensing coil (only have secondary) without touching the power line to generate 9V @ 1A. Is it possible to make this. If possible, how can I proceed.
Author : Kotteeswaran - From: Chennai, Tamil Nadu
Tue, June 1st, 2010 - 17:30
It is impossible and not applicable; indeed the magnetic flux density due to power line current in limited zone, e.g. a wound bobbin is negligible. Applicable calculation and measuring about this subject is related to interference between power line and neighbored parallel pipeline study.
The components of magnetic flux density due to a overhead conductor at (hn,dn) which carries a phase current In  are given in eqn. below.

In case of a three phase system, if all the three phase wires are at equal distances from the axis of the pipeline, voltage induced on the pipeline will be zero. However, this case is seldom met, as most of the time, the asymmetry between the three phase conductors and the pipeline causes the induction of non-zero voltage in the pipeline. The inductive influence problem is severest in the case of faults. The induced electromotive forces (EMF) cause currents circulation on the pipeline and voltages between the pipeline and the surrounding earth. In the normal operating conditions, the balance of the three phase currents causes no substantial effect. In this case, voltage induced is low, due to the geometrical asymmetry of the pipeline from power line. However under faulted conditions, high voltages and currents may be induced in the nearby pipeline, which may result in shock hazards to people or working personnel touching the pipeline or other metallic structures connected to it.
Author : Hamid - From: Iran
Fri, July 23rd, 2010 - 16:45
Normally we gat a higher current and lower voltage owinf to the proximity of a metallic structure with the power line . it does not look possible to generate 1 amp at 9 volt . May be the reverse will be true . 
Author : R K Mohapatra - From: India
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