Grid Type Neutral Grounding Resistor

The cast iron grid type NGR designed, developed and supplied by National Resistors is mainly used in power generation plants for earthing applications. It is designed to prevent sparks in the system. Offered in different specifications, this neutral grounding resistor has a high thermal time constant, which permits HV currents to pass through it for a short time duration. The grids in the resistor are made from cast iron. To strengthen the grid's heat resistant and anti-corrosion properties, Heat resistant aluminium paint is sprayed on the grid. During the assembly procedure, tapping can be provided between any adjacent grids to achieve desired sectional resistance values.

Features:
For insulation between MS Tie Rod and Grids, there is Mica tube.
For insulation between alternate grids, Mica Washers are used.
All electrical contact surfaces are ground finished for better contact between grids and to avoid sparking
In case of high voltages, live parts and enclosure are insulated by Porcelain Insulators.
The temperature coefficient of resistance is approx. 0.05% per degree Celsius for cast iron.