EXPECTED SOIL RESISTIVITIES
Humus and Loam
Sand Below Ground-Water Level
Broken Stone Mixed with Loam
(e) Oil circuit breakers require two grounds.
(f) Station fences require complete perimeter ground cables, located three feet outside
the fences, and are connected to the station grid. Ground spacing should not exceed 75 feet.
Fences require a fabric ground for approximately every 75 feet and a post ground for every third
(g) All station gates require connection to both gate posts and copper braid to connect
the hinge posts to the gate.
188.8.131.52 Measurement of Soil Resistivity. An earth resistivity measurement of the soil is
important and should be carried out upon installation of the ground grid to assure accuracy of the
grid placement and to assure no loose ends or bad connections exist. The most common method
used to measure the soil resistivity is the four pin method.
3.8.2 Cable Placement. After the above ground connections are completed, the underground
cable, connecting cable, and ground rods should be placed. Cables should be laid in parallel lines
with reasonable spacing to connect these points. Ground rods should be placed at crossings and