I-Gard GCHK-100, Instruction Manual

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I-GARD GCHK-100 Instruction Manual
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introduction
To service the special needs of the mining industry I-Gard developed the GCHK-100 ground fault relay to protect
personnel and equipment in underground or above ground applications.
The GCHK-100 is state of the art protection for mobile, trailing cable equipment, providing superior accuracy
and flexibility to the user. The micro controller based design reduces the likelihood of false tripping. The relay
automatically operates in three distinct modes:
• Ground Fault Detection and control
• Ground resistance checking and control through the use of an auxiliary pilot wire
• Frame touch voltage detection and control
• External remote display with Modbus
Designed for use with resistance grounded systems up to 4160V. It could also be used with any Grounded
System in branch circuit applications.
The relay can also be used with an external remote indicator (mGARD-SYM), capable of remotely displaying
readings and allowing remote RESET and TEST. The mGARD-SYM can monitor up to 50 GCHK-100 relays and
provides an isolated connection to an external Modbus network. Alternatively, a standard LED based remote
indicator (GCHK-DRI) can be used for remote indication.
Ground Fault detection requires the use of current sensors, and the GCHK-100 is designed to operate with
I-Gard TxA type sensors or a wide variety of sensors with ratios of 1000:1, 600:1 and 40:1 (200:5). The sensors
are typically mounted in the substation where the GCHK-100 is installed. Detection of ground faults is important
to prevent arcing faults in equipment where electric shock and fire can occur and cause serious equipment and
personnel hazards.
Operator safety from electrical shock depends to a large extent on the integrity of the grounding of energized
equipment. Therefore, it is vital to know if grounding has been compromised. To do this an auxiliary conductor
(pilot wire) is used in trailing cable to mobile equipment. The GCHK-100 monitors the loop resistance and trips
when it exceeds a preset value.
Additionally the relay detects if the ground loop has been shorted as can happen when the trailing cable is cut
accidentally. For this purpose a pilot wire terminator is connected between the pilot wire and ground. I-Gard
provides a special zener package for this purpose (GCHK-ZT).
In the event of a ground connection failure and internal leakage within the mobile equipment, it is possible for the
frame of the equipment to become live and present a shock hazard to personnel in the vicinity. The GCHK-100
has the capability to monitor and control dangerous frame voltages.