The basic ground potential rise (GPR) study
gives the necessary information for a power company to provide to a telco in
order to provision communications services within the high voltage corridor
(substations, generation facilities, and power transmission towers).
The data necessary for the GPR studies includes
a field trip to the site to gather the resistivity measurements for the
substation being studied. The soil resistivity is simplified to a two-layer
model, which then is used in the CDEGS software, which will calculate the
resistance of the grid. With this information as well as the fault data
provided by the power company, the telco can then determine the zone of
influence (ZOI) of the worst-case fault condition at the substation, thus
giving the telco the information necessary to determine where to place the CFJ
More elaborate and detailed studies are
available for those who have need to see the more specific data involved with
the study. This would include the raw data, charts, graphs, and
explanations of how the study is derived. The basic or Mini-GPR study
would perform the same analysis, but the product would be limited to providing
the telco’s particular HVI form.
The GPR study that is normally provided by an
average engineering firm is a calculated value based on a number of variables,
which have been compromised a bit due to necessary simplification of the
analysis. The use of the Smart Ground Multimeter (SGM) to provide a measured value of resistance as
opposed to merely calculating that value is a tremendous advantage if you are
looking for improved accuracy.