Audited Supplier
Powerohm Type NR Neutral Grounding Resistors are used in industrial power systems for resistance grounding of wye connected generators and transformers. A neutral grounding resistor limits the fault current to a value which is sufficient
Δ enough to operate protective relays, yet prevent unwanted fault damage.
Δ Reduced overvoltages.
Δ Reduced equipment damage.
Δ Isolation of faulted circuit.
Δ Increased protection of transformers, generators and auxiliary equipment.
Δ Reduced operation/maintenance expense.
Δ Increase safety.
Δ Improved reliability.
Δ Reduced frequency of faults.
Δ Quicker fault location.
Δ Increased lightning protection.
Δ Low coefficient of resistance and are designed to meet all applicable specifications of ANSI, NEC, NFPA, NEMA, and OSHA
Here are some parameters to consider when choosing and sizing an NGR
Δ Rated Line-to-Line voltage or Line-to-Neutral voltage.
Δ Time duration of the NGR will carry the maximum current.
Δ Short time rating: typically, 10 seconds or 60 seconds.
Δ Continuous rating: normally 5% to 10 % of full load current.
Δ Maximum current when the resistor is cold.
Δ Insulation specified based on line voltage.
Δ The maximum short time temperature rise for the resistive element is 760°C, in accordance with IEEE Standard 32-1972 Δ (Requirements, Terminology and Test Procedure for Neutral Grounding Devices).
Δ Ingress protection IP rating for outdoor or indoor enclosures. Standard enclosures are manufactured having IP10, IP13 or IP23.
Δ Enclosure material can be mild steel, finished in powder coat or hot-dip galvanized, or Stainless-steel.
Δ Auxiliary items: Voltage transformers, off-load isolators, current transformers, or other options.
Our NGRs are made using a Heavy-Duty Resistor Grid from low temperature coefficient Fe-Cr-Al Stainless Steel alloy, that is compliant with the applicable new standard IEEE-C57.32, 2015 "Requirements, Terminology and Test Procedure for Neutral Grounding Devices". These resistor are designed to permit thermal expansion under rated duty with spot-welded stainless-steel jumpers between resistor banks. Ceramic spacers and ANSI Standoffs electrically isolate the resistive elements.
Neutral Earthing Resistors can be supplied with outdoor or indoor enclosures with appropriate ingress protection levels. In the case of an outdoor enclosure, material can be mild steel finished in powder coat or Hot Dip Galvanized. Hot Dip Galvanized enclosures are built according to ISO 1461:1999. This ensures a high degree of protection against corrosion, fabricated from min 14 gauge mild steel (12 gauge for feet &side supports). Our metal parts are galvanized after all sheet metal processing operations (drilling, cutting etc.) are completed and the unit is pre-assembled for quality check and disassembled after approval. This two-stage approval before galvanizing is a key requirement to prevent any uncoated part, which may adversely affect the corrosion performance during service. Other enclosure options are unpainted 14-gauge AISI 304 (EN 1.4301) stainless steel to provide the best outdoor protection available.
PLN Rote 2×3MW power plant Neutral Grounding Resistors system
PLN is the Indonesian National Grid Corporation, responsible for the construction of power stations and power grids in Indonesia. SHME, as a long-term partner of PLN, provides PLN with high and low voltage distribution switchgear and DCS control systems for multiple power stations.
