The AC Corrosion Performance of Copper Earth Return Electrodes

The U.S. Navy has operated an Extremely Low Frequency (ELF) test facility, which includes four extensive earth electrodes, in northern Wisconsin since 1969. An integral component of this complex are the four earth electrodes. The electrodes, composed of 4/0 stranded copper cable, have a combined total length of approximately 38 000 feet and are buried at a nominal depth of 60 in. During the late summer and early fail of 1977 an examination of the electrodes was performed to determine their physical condition after nine years and more than four million amperehours of operations. This study was undertaken at the suggestion of the National Academy of Sciences because of their expressed concerns over safety and how it might be compromised by the possible corrosion of an ELF ground terminal. The results of this investigation, although limited, indicate that corrosion is not occurring along the terminal facilities.