Specification of Neutral Earting Resistance ( NER )
NEUTRAL GROUNDING RESISTOR (NGR)
Description
NGR is a resistance that is installed serially with a secondary neutral on the transformer before it is connected to ground. The purpose of installing the NGR is to control the amount of fault current flowing from the neutral side to the ground. This is related to the secondary side of the power transformer security pattern (distribution system).
ENCLOSURE
The frame enclosure must be made of structural steel, all corners are welded, or bolted with stainless-steel hardware. The top of the enclosure should be solid, slightly outward and at a slight angle. An eyebolt must be attached for lifting purposes. The front of the enclosure must be ventilated with holes in the form of a grille. The sides of the four sides must be bolted. Nameplate permanently attached to either side shall show the complete manufacturing and rating.
RESISTOR
• Resistive elements must be low temperature coefficient. The stainless steel mass grade resistors are sufficient to withstand the prescribed duty.
• Resistors must be installed in a stainless steel support frame.
• The entire resistor assembly must be mounted on an insulator appropriate to the system voltage.
• All resistor terminals and interconnections between resistor units must be stainless-steel using stainless-steel hardware including lock washers.
