i-GARD Sigma 3 Ground Fault Relay and Neutral Grounding Resistor Monitoring Relay

With over thirty-five years of both domestic and international experience, I-Gard’s full line of neutral grounding resistors, ground fault protection systems and power-resistor based solutions provides world class power protection.


i-Gard’s SIGMA 3 relay is a combination ground fault and monitoring relay with pulsing capability, that fully complies with the requirements of the Canadian Electrical Code 2021 section 10.302 without exception or rating restrictions.

The Sigma 3 monitor relay measures the current through the NGR, the transformer neutral-to-ground voltage, and the NGR resistance. The relay compares the measured values with the field settings of the relay and provides relay outputs and LED indications when an abnormal condition is detected.

The SIGMA 3 is designed for application in High Resistance Grounding systems (systems typically below 5kV where the fault current is limited to 10 amps or less) and the complete range of Low Resistance Grounding systems (systems between 5kV and 69kV where the NGR is time rated).


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Krueger & Associates, LLC. is the factory authorized manufacturers representative for i-GARD in Oklahoma, Arkansas, Kansas, and Western Missouri. For i-GARD customers outside of our service area, click here to locate your local sales and support contacts.