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Clients can avail from us a wide range of Wire Grid Resistance that is widely used for earthing applications. It is precisely designed and manufactured with the aid of cutting edge technology from quality approved raw material. Provided product is employed in alternative current distribution networks and limit the restricted earth current to a safe value that flow from the transformer star point without surpassing specified temperature. The offered product is quality tested before delivery to ascertain their durability at clients end. In tune with the variegated requirements of our clients we provide this Wire Grid Resistance in various specifications.
Resistance wire is would on ceramic insulator to form a coil for wire wound.
Tapping can be taken at any place.
These Resistors are economical for low current.
Available in ratings of 1 Amp and above.
Optional Features Provided On Request
Safety Screen for enclosures.
Neutral Grounding Transformer / Excitation Transformer.
Supporting Pedestal structures.
Stand off insulators.
Aluminum enclosure instead of MS.
Hot dip Galvanized enclosures.
Stainless steel hardware.
Earth fault leakage Relay.
Dissipation is negligible & the temperature rise for the resistor element depends on its capacity to store the energy generated in proportion to the mass & specific heat of the material used. Theses NGRS are connected between the neutral point of transformer / generator & the earth.
In Earth fault condition continuous current of 5 % to 10 % of full load current pass through the resistor due to unbalance in systems.
In Earth fault condition the Restricted earth fault current passes through the Metallic Resistor protecting the system till automatic protection takes place by absorbing the earth pressure, protecting the winding etc.
Hence these resistors are designed for allowing maximum heat dissipation
Internal Features Of Resistor Enclosure
Group of Resistance elements are mounted together to form a Bank. Banks are then connected in series or parallel to provide the current and ohmic value required.
All Resistance Bank to Bank interconnections will be done by solid stainless steel / copper.
In case of continuous current ratings for better heat dissipation, perforated sheet / jali with welded GI wire mesh is provided at the bottom.
Foundation channels have welded or bolted to the angle iron structure on two sides with arrangement to fix on foundation by bolts at site.
Terminals are brought through Porcelain bushings of appropriate voltage class or brought down as per requirement of customer.
In case of higher voltage, the banks are placed on stand off insulators housed inside the enclosures, or the enclosures is also insulated from ground by using stand off insulator if asked by customer
(A) Routine Tests: - Following Tests Will Be Conducted.
Visual and Dimensional.
Insulation resistance value measurement by using 500V / 1000V megger before and after dielectric test.
Resistance value measurement with ± 10 % tolerance.
H.V. Test of twice the rated voltage +1000 volts for voltage class below 660 volts or 2.25 times of rated voltage +2000 volts for voltages above 1100 volts.
(B) TYPE TESTS :-
Temperature rise test i.e., Heat run test if required will be conducted by passing equivalent / rated current for rated / equivalent time keeping IT Constant through a part of Resistor.
Line to neutral voltage rate
Normally Full load current rate is same
System Voltage is divided by root3 i.e. 1.732.
Initial current flow through resistors when it is cold
Time length rate for NGR must tolerate rated voltage.
NGR construction includes resistor assembly, internal connections, plus required insulators, etc
Generally temperature rise rating is restricted to 375 deg.c. above ambient temperature as per BS-587. It can be 760 deg.c. as per IEEE-32
Normally 10 % of full load current is require for continuous functioning rate of neutral grounding resistor of 5 % to 10 % of full load current
Such resistor elements material are made from any stainless steel or FeCrAl or Cu-Ni or Ni-Cr or any other resistance material. Normally formed stainless steel element are best
Information To Be Furnished To Us:
Material of Resistor
Duty rating 10 sec.,30 sec.,60 sec., & continuous etc.
If details against and cannot be given then inform details of transformer such as KVA rating, full load current, Primary & Secondary Voltage.
System voltage / operating voltage.
Type of Enclosure and material for enclosure ( protection class as per IS- 12063)
Location: Indoor or outdoor.
Temperature rise allowed over an ambient temperature.
Whether space heater, current transformer , isolating switch on load / off load, manually / motorised, or any other accessories are required. Details of atmospheric conditions at site and height above sea level.
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