Radio Interference with the Operation of Static Utility Protective Relays

Controls used in electric power distribution systems are generally tolerant of the high level of interference signals found in that environment. Recently, however, increased power demnds have required a new class of solid state controls which are more sensitive to RFI. In order to delineate the problem this report examines the magnitude and distribution of RF fields in a small power substation during an incident of radio transmission. RF electric field strengths were of the order of 10 V/m. Exposure of cormercial distribution relays to such fields are shown to produce considerable interference with normal operation. Radio frequencies from 20 to 500 MHz were employed