Ice melting on a power line while in service

ONE OF THE most serious problems that confronts a system operator is the effects of a dreaded ice storm. Angular displacement of the voltages applied to the extremities of a power line for the purpose of circulating sufficient current to heat the conductors will assist in solving this problem. When this displacement does not exceed 60 degrees, reasonable service for all customers supplied by the line ordinarily can be maintained while the ice is being melted. The method holds a great deal of promise for those long, lightly loaded lines in the moderate-and low-voltage class which so often fall prey to these storms. By choice of line length this circulating current plus load current can be made sufficient either to melt the ice or prevent its formation. The driving voltage Ec which produces the circulating current, varies with the angle between the normal and the displaced source. For a given driving voltage the circulating current Ic is determined by the impedance of the circulating current path, and the angle between Ec and Ic is determined by the circuit characteristics of this path.