Page 9 - excerpts ELP

WORKING ON LINES AND EQUIPMENT
2.6
GROUND SOURCES
46
NORTHWEST LINEMAN COLLEGE
The selection of the best available ground source is critical to the objectives of personal protective grounding.
The selection of the best available ground source is critical to the objectives of personal protective grounding. The path of least resistance will help
limit the current ow through the lineworker, and also, provide the best opportunity for protective devices to clear the fault as soon as possible.
In most cases, the choice depends upon the type of line or piece of equipment being cleared and the location.
Substation ground grid
Substation Ground Grid
Ground rods
Stranded copper
The substation ground grid is available for work inside the substation and is a well-designed ground system that is typically tested to ensure a low value of resistance. It has adequate capacity to carry any fault current that may ow.
System Neutral
This conductor is typically a part of a four-wire distribution circuit and runs the entire length of the circuit and provides a solid path from the supply transformer(s) to the end of the line. The National Electric Safety Code requires that it be grounded a minimum of four times per mile. It must also be large enough to handle the available fault current. The system neutral can be viewed as an extension of the station ground grid that extends throughout the system.
System neutral
Station ground grid
The system neutral is an extension of the ground grid.