Application Note

Why test
grounding systems?
Over time, corrosive soils with high mois-
ture content, high salt content, and high
temperatures can degrade ground rods and
their connections. So although the ground
system, when initially installed, had low earth
ground resistance values, the resistance of the
grounding system can increase if the ground
rods are eaten away.
Grounding testers, like the Fluke 1623-2 and
1625-2, are indispensable troubleshooting tools
to help you maintain uptime. With frustrating,
intermittent electrical problems, the problem
could be related to poor grounding or poor
power quality.
That is why it is highly recommended that all
grounds and ground connections are checked
at least annually as a part of your normal Pre-
dictive Maintenance plan. During these periodic
checks, if an increase in resistance of more
than 20 % is measured, the technician should
investigate the source of the problem, and
make the correction to lower the resistance, by
replacing or adding ground rods to the ground
system.
What is a ground
and what does it do?
The NEC, National Electrical Code, Article 100
defines a ground as: “a conducting connection,
whether intentional or accidental between an
electrical circuit or equipment and the earth, or
to some conducting body that serves in place of
the earth.” When talking about grounding, it is
actually two different subjects: earth grounding
and equipment grounding. Earth grounding is an
intentional connection from a circuit conductor,
usually the neutral, to a ground electrode placed
in the earth. Equipment grounding ensures that
operating equipment within a structure is prop-
erly grounded. These two grounding systems are
required to be kept separate except for a con-
nection between the two systems. This prevents
differences in voltage potential from a possible
flashover from lightning strikes. The purpose of a
ground besides the protection of people, plants
and equipment is to provide a safe path for the
dissipation of fault currents, lightning strikes,
static discharges, EMI and RFI signals and inter-
ference.
Why ground, why test?
2
Why ground?
Poor grounding not only contributes to
unnecessary downtime, but a lack of good
grounding is also dangerous and increases
the risk of equipment failure.
Without an effective grounding system,
we could be exposed to the risk of electric
shock, not to mention instrumentation errors,
harmonic distortion issues, power factor
problems and a host of possible intermittent
dilemmas. If fault currents have no path to
the ground through a properly designed and
maintained grounding system, they will find
unintended paths that could include people.
The following organizations have recom-
mendations and/or standards for grounding
to ensure safety:
• OSHA (Occupational Safety Health
Administration)
• NFPA (National Fire Protection Association)
• ANSI/ISA (American National Standards
Institute and Instrument Society of America)
• TIA (Telecommunications Industry
Association)
• IEC (International Electrotechnical
Commission)
• CENELEC (European Committee for
Electrotechnical Standardization)
• IEEE (Institute of Electrical and Electronics
Engineers)
However, good grounding isn’t only for
safety; it is also used to prevent damage to
industrial plants and equipment. A good
grounding system will improve the reliability
of equipment and reduce the likelihood of
damage due to lightning or fault currents.
Billions are lost each year in the workplace
due to electrical fires. This does not account
for related litigation costs and loss of per-
sonal and corporate productivity.