DC dissipation current from elements used for lightning protection on 115 kV transmission lines

The Mississippi Power & Light Company is using different elements in transmission lines and towers to protect the electrical system from direct lightning strokes. According to some theories, the objects to be protected against lightning strokes are better protected by using an element from which the charge dissipation current is enhanced. The authors present the results of an experimental study of DC dissipation current magnitude from elements used for lightning protection. DC dissipation current was measured directly by a voltmeter, using a 1000 Ω resistance connected between the tested object and ground. The dissipation current at proper voltage value was established as an average value. It is shown that DC dissipation current depends very much on the polarity of the energized screen. The dissipation current was higher for all tested objects when the top screen was energized with positive polarity, i.e., when the tested object had negative polarity