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    01. Neutral Grounding Resistors

    Neutral Grounding Resistors (Neutral Earthing Resistors)  (Request Quote)

    The purpose of a neutral grounding resistor is to limit the ground fault current to a safe level so that all the electrical equipment in the power system is protected. The resistor should be the only current path between the neutral of power transformers or power generators and ground.

    When the neutral of a system is not grounded it is possible for destructive transient overvoltages to appear from line to ground during normal switching of a circuit having a line-to-ground fault. Experience has proved that these overvoltages cause aging and failure of insulation at locations on the system other than at the point of fault. In this way, a relatively unimportant line-to-ground fault on one circuit may result in considerable damage to equipment and interruption of service on other circuits, not to mention the increased difficulty in finding the original location of the problem.

    A neutral grounding resistor is designed to limit the ground fault current to a safe value while at the same time letting enough current to flow to operate the protective relays that will alarm or clear the fault. While the disturbance lasts the resistor must be capable of absorbing and dissipating the energy generated without exceeding the temperature limits established by IEEE-32 Standards. In this way the fault is safely limited, isolated, and the power system is protected against over-voltages.


    Standard Voltages 

    System
     Voltage, V
    Resistor Voltage, V
     400  231
     440  254
     460  266
     480  277
     600  347
     690  398
     2400  1386
     3300  1905
     3450  1992
     4160  2402
     6000  3464
     6300  3637
     6600  3811
     6900  3984
     7200  4157
     10k  5774
     11k  6351
     12.5k  7200
     13.2k  7621
     13.8k  7967
     14.4k  8314
     15k  8660
     20k 11547
     22k  12701
     23k  13279
     24k 13856
     25k 14434
     33k  19053
     34.5k  19919

    Standard Currents:

    Current Limit, A  Time
     2.5  Cont.
     5  Cont.
     10  Cont.
     15  Cont.
     25  Cont.
     50  10 s
    100  10 s
     200  10 s
     250  10 s
     400  10 s
     500  10 s
     800  10 s
    1000  10 s
    1200  10s

    Advantages of using Neutral Grounding Resistors:
    • Reduced operation and maintenance expenses.
    • Fast isolation of the original fault.
    • Reduced transient over-voltages.
    • Reduced physical damage on the equipment at fault.
    • Simplification of ground fault location.
    • Increased life and protection of transformers, generators and related equipment.
    • Reduced frequency of faults.
    • Improved service reliability.
    • Increased protection in the use of lightning arresters.
    • Increased safety for personnel.
    Standard Models:

    (We can also custom manufacture to suit your requirements)

    NGRvoltage-current-time 

    Where voltage is the line-to-neutral rms voltage, current is the limit current and time is the rated time,10s for ten seconds or C for continuous duty, i.e. NGR2400-400-10s or NGR347-5-C.

    Our standard models include NEMA 3R or IP14 galvanized steel enclosures phosphatized and powder coated light gray ANSI 61 for indoor/outdoor use but we also supply custom made resistors and enclosures according to our customer's needs.

    Resistive Elements: 
    Type: Wirewound / Edgewound / Stamped Grid
    Material: Low TCR stainless steel
    Stainless steel hardware

    Enclosure:
    Protection: NEMA 3R (Indoor/Outdoor Ventilated)
    Material: Galvanized steel
    Finish: Epoxy polyester powder coated ANSI 61 gray

    Features:
    Terminal block, compression lugs or NEMA pads
    Bonding bolt or compression lug
    Nameplate
    Warning stickers
    CSA code special inspection and blue sticker


    Optional Features:

    The following suffix codes can be added to the model name to denote special features:

    Bushings
    /TNB: Top Neutral bushing
    /SNB: Side Neutral bushing
    /TGB: Top Ground bushing
    /SGB: Side Ground bushing

    Enclosure Material
    /SS: 304 Stainless steel enclosure
    /316: 316 Stainless steel enclosure
    /AL: Aluminum enclosure
    /HDG: Hot dipped galvanized enclosure

    Enclosure Protection
    /OP: OPEN (No enclosure)
    /N1: NEMA1 (indoor use) enclosure
    /N4: NEMA4 completely closed enclosure
    /N4X: Nema 4X completely closed enclosure
    /IPxx: IEC rated enclosure protection
    /SZ: Seismic zone special bracing
    /TP: Tamper-proof enclosure
    /VC: Ventilated Covers (i.e. Louvered)
    /FL: Ventilated with filters
    /DL: Door with lock

    Instruments and other components
    /SP: Space for customer supplied instruments
    /HT: Heater with thermostat
    /CT: Current transformer
    /PT: Potential transformer
    /ER: Startco sensing resistor
    /DS: Disconnect switch
    /GF: Ground Fault Relay
    /PS: Pulsing System




    Type: N-01:
    Dim: 22"x18"x8.25"H (559x457x210mm)
    Type: N-02:
    Dim: 22"x22"x12.75"H (559x559x324mm)
    Type: N-02-D: 
    Dim: 22"x22"x23.75"H (559x559x603mm)
    Type: N-05: 
    Dim: 34"x36"x33"H (864x914x838mm)
    Type: N-06: 
    Dim: 45"x37"x38.75"H (1143x940x984mm)
    Type: N-06-D: 
    Dim: 45"x37"x72"H (1143x940x1829mm)
    Type: N-07:
    Dim: 53"x27"x61"H (1346x686x1549mm)
    Type: N-09:
    Dim: 45"x50"x39.75"H (1143x1270x1010mm)
    Type: N-09-D:
    Dim: 45"x50"x72"H (1143x1270x1829mm)
    Type: N-10:
    Dim: 45"x62"x50.5"H (1143x1575x1283mm)
    Type: N-12: 
    Dim: 76"x56"x59"H (1930x1422x1499mm)
    Type: N-18: 
    Dim: 81"x61"x73.5"H (2057x1549x1867mm)
    Type: N-20: 
    Dim: 98"x74"x76"H (2489x1880x1930mm)
    Type: N-30:
    Dim: 110"x85"x85"H (2794x2159x2159mm)
    Type: N-40: 
    Dim: 204"x82"x100"H (5182x2083x2540mm)