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Proper ground fault protection is required
by the National Electrical Code, yet about
15% of ground fault protection systems
tested by NETA (InterNational Electrical
Testing Association) are improperly
installed, contain defective components or
don’t work correctly.
What is grounding?
Grounding or earthing of electrical
equipment serves several purposes. The first
reason is to ensure safety from overvoltages,
faults and lightning. Grounding also
provides stability of system voltages by
providing a solid reference to earth and
establishing a reference to control
electrical “noise” that might interfere with
the proper operation of electronic
equipment.
Why is ground fault
protection important?
A low level arcing ground fault can destroy
switchgear in seconds, before the main
service overcurrent protection kicks in.
That’s because a 480/277 volt solidly
grounded system has enough voltage to
maintain an arc between one phase and a
ground, but not enough current to cause a
large main breaker or fuse to quickly clear
the fault. The resulting arc is like an
electric weld, consuming large amounts of
metal in the seconds it takes the breaker or
fuse to operate.
A properly installed and operating ground
fault protection system will detect and
clear the fault in milliseconds, fast enough
to limit damage to acceptable levels.
HVM can conduct a study of your
grounding system to determine its
effectiveness. Our Grounding Study analysis
can detect problems such as:
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Neutral grounded downstream. Neutral bonded
to ground in wrong location. Causes false
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or
inadequate tripping.
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Incorrect current sensor installation and
wrong polarity. Causes false tripping.
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Inadequate control power or connections.
Causes lack of trip of the protective
device.
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Failure to trip within manufacturer’s
tolerances. Causes inadequate protection.
To ensure the safety of your people and
equipment, call on HVM to perform a
grounding study today.
Features & Benefits
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Limits equipment damage
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Ensures safety of personnel
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Extends equipment life
Scope
Ground fault protection is required by the
National Electrical Code and is usually
installed only on larger circuits and
services of 480/277V 1000 amps and larger.
If your system meets these specifications,
contact HVM to get your system
evaluated. The following tests are typically
performed:
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Field acceptance testing
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Neutral main bonding connection inspection
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Verification of proper installation of
sensor(s) and grounding connections
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Current injection test to verify pickup and
timing characteristics of the relay
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Test to verify operation with control
voltage supply reduced to 277 instead of 480
volts
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Verification of operation of special
features like zone interlocks, etc. |
