Lightning Investigation on a Wood Pole Transmission Line

The purpose of this paper is to report the results of an investigation made on a wood pole line. The entire line was originally very highly insulated. The splintering of the structures by lightning indicated that excessively high voltages were appearing quite frequently. Because of the high insulation a cathode ray oscillograph station was installed on the line. A total of 38 significant surges was recorded, two of these being a five million and a four and one-half million-volt surge. Analysis shows that these high surges were the results of lightning bolts striking the lines causing faults between conductors but not to ground. The data also indicate that harmful effects are caused only by direct strokes. These and current measuring records indicate that currents varying from very low values to 100,000 amperes may readily be obtained. Two methods of protection are dealt with, one utilizes a fuse, the other an expulsion lightning discharge device. The new device operated eight times, all of these operations being successful.