Neutral grounding transformers in resistance grounding resistor systems protect power transformers and generators from damaging fault currents. Low resistance grounding of the neutral limits the ground fault current to a high level (typically 50 amps or more) in order to operate the protective fault clearing relays and current transformers. These devices are then able to quickly clear the fault, usually within a few seconds. The limited fault current and fast response time also prevent over-heating and mechanical stress on conductors. Low resistance grounding resistors are typically rated up to 400 amps for 10 seconds, and are commonly found on medium voltage systems. Ground fault protection for high voltage transformer and generator grounding applications typically require a grounding transformer to lower the voltage reflected to the neutral grounding resistor. Post Glover's GT product line is designed for applications up to 15kV primary. Secondary voltage is typically 240 V, and resistors are designed according to customer specification. Typical construction is a dry type transformer with a secondary resistor mounted in a common enclosure.
This document covers design, manufacture and testing of low- or medium-voltage Zigzag Grounding Transformers for use with Neutral Grounding Resistors (NGR) for installation indoors or outdoors onto a concrete pad or power transformer.
This document covers installation, inspection, connection and maintenance of Grounding Transformers for use with Neutral Grounding Resistors (NGR) for installation indoors or outdoors onto a concrete pad or power transformer.