System Ground Study
System Ground Studies
Under ground-fault conditions, the flow of current will result in voltage gradients within and around the substation, not only between structures and nearby earth, but also along the ground surface. In a properly designed system, this gradient should not exceed the limits that can be tolerated by the human body.
The purpose of a ground mat study is to provide for the safety and well-being of anyone that can be exposed to the potential differences that can exist in a station during a severe fault. The general requirements for industrial power system grounding are similar to those of utility systems under similar service conditions. The differences arise from the specific requirements of the manufacturing or process operations.
Some of the factors that are considered in a ground-mat study are the following:
a) Fault-current magnitude and duration
b) Geometry of the grounding system
c) Soil resistivity
d) Probability of contact
e) Human factors such as:
1) Body resistance
2) Standard assumptions on physical conditions of the individual
Ground Mat Analysis is performed to determine the step and touch potential voltages that could be present posing a serious danger to personnel. The analysis is performed to help optimize grid design or reinforce existing grids of any shape.
Compliance: IEEE 399, 142