I-GARD Gemini Instruction Manual
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2 ) The conductor connecting the neutral grounding device to the neutral point of the transformer,
generator, or grounding transformer shall not be grounded.
3 ) The conductor connecting the neutral grounding device to the system grounding electrode shall be:
a ) A copper conductor which shall be permitted to be insulated or bare; and
b ) Identified green if insulated; and
c ) Sized to conduct the rated current of the neutral grounding device, and in no case less than
No. 8 AWG in size; and
d ) Installed in accordance with other appropriate Rules in this Code
Can/CSa M421-93 use of electricity in Mines
Pg. 26
neutral-grounding Devices
The neutral grounding device shall be continuously monitored by a device that will trip the supply if an
open circuit in the neutral grounding device occurs.
Pg. 29
4.7.3.4.1 Resistance Grounding
Where on-board three-phase, isolation power transformers larger than 20 kV
•
A and operating at voltages in
excess of 300 V are used, the following requirements shall apply:
a ) Except as permitted by item ( g ), either a direct or derived neutral shall be grounded through a
resistor at the power source to limit the prospective ground-fault current to 25 A or less.
b ) A grounding circuit shall originate at the grounded side of the resistor and extend along with the
power conductors to ground the frames of all electrical apparatus supplied from the circuit, except
where the steel structure provides the ground-return path as permitted by clause 4.7.5 ( b ).
c ) The size of the grounding conductors may be reduced provided the ampacity exceeds the
prospective ground-fault current.
d ) Neutral-grounding resistors shall be isolated by elevation or guarded in accordance with
Clause 4.7.4.1.
e ) Neutral-grounding resistors shall be rated and protected in accordance with Clause 3.6.2.
f ) Ground-fault protection with a minimum tripping ratio of 5 shall be provided, except as permitted
by items ( g ) and ( h ).
g ) Acceptable ungrounded systems with ground-fault detection may be used for specialized
drive circuits.
h ) Ground-fault detection, which alerts the operator to the ground fault, may be used instead of
ground-fault protection where de-energizing a circuit can create a machine-operation hazard.
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ADDITIONAl INfORMATION
If you require more information or experience problems with your equipment that persist after taking the steps
identified in this manual, contact I-Gard customer service.
