A. AREAS OF USAGE

  • Reducing single phase fault currents which occur in M.V. electrical networks to prevent damages on transformers and generators
  • Reducing temporary over voltages occurred by braking instantaneous fault current, . Providing long-life for switchgear
  • Reducing step voltages to a harmless level for staff

 

Neutral Grounding Resistors are used for resistance grounding of industrial power system. They are generally connected between ground and neutral of transformers, generators and grounding transformers. Neutral Grounding Resistors are used in order to limit maximum fault current to a value which will not damage the equipment in the power system, yet allow sufficient flow of fault current to operate protective relays to clear the fault. Although it is possible to limit fault currents with high resistance Neutral Grounding Resistors, phase to ground short circuit currents can be extremely reduced. As a result of this fact, protection devices may not sense the fault. Therefore, it is the most common application to limit single phase fault currents with low resistance Neutral Grounding Resistors.

B. FEATURES

 

  • Stainless-steel resistor elements
  • Current transformer included (EN 60044-1)
  • Bolted resistor element connections instead of welded connections in order to be able to assemble spare parts on site immediately
  • Typically, RAL 7032(and others) painted
  • Typically, 2 mm hot dip galvanized steel enclosure
  • High thermal capacity to absorb high currents
  • High altitude ratings
  • Custom made lifting eyes provide secure lifting
  • Rugged shock-resistant construction

 

Kian Tajhiz resistors are designed to absorb a large amount of energy without exceeding temperature limitations defined in IEEE 32. Neutral Grounding Resistors Kian Tajhiz can be used for indoor and outdoor and the neutral point is connected with a porcelain bushing or with a (minimum cross-section = 70 mm2 copper or 95 mm2 aluminum) high voltage (XLPE) cable from the bottom, top or side. The most common protection degree preferred for Neutral Grounding Resistors is IP 23 as it allows the resistor elements to cool easier and they can be used both at sea shores and deserts because the resistor elements are completely stainless steel and does not get affected by extreme conditions. Neutral Grounding Resistors are shipped with maintance and installation guidelines. In maintance and intallation guidelines, recommended relay settings for each Neutral Grounding Resistor are stated as well. Kian Tajhiz provides complete technical assistance in order to meet your specifications or site conditions.

 

B.a. Technical Specifications

 

  • Operation Voltage: Up to 110 kV line to line systems
  • Rated Current (A): Up to 5000
  • Ambient Temprature (ºC): <55
  • Resistance Alloy: Stainless Steel
  • Protection Degree: IP 23(outdoor) and others
  • Standards: IEEE 32, IEC 60137, IEC ISO 1461, IEC 60298, IEC6 0273, IEC 60071, IEC 60060

 

B.b. Enclosure Features

 

  • 2 mm hot dip galvanized steel enclosure
  • Stainless steel or aluminium enclosures are avaible on demand
  • Typically, RAL7032 paint for enclosures (other colors are avaible on demand)
  • Solid top cover sloped to prevent water accumulation
  • Custom made lifting eye bolts for secure lifting
  • Front cover for easy access to connection and inspection doors avaible on demand
  • Corrosion resistant stainless steel nameplate

 

B.c. Options

 

  • Elevated support stands are provided for ground clearance and safety
  • Specially designed units for hazardous and extreme locations
  • Stainless steel or aluminium enclosures on demand
  • Installation of voltage transformers
  • Installation of protection relays
  • Porcelain entrance bushings can be mounted on top or on the side of Neutral Grounding(earthing) Resistors
  • Grounding transformer installation
  • Motorized or manual single pole disconnector switches, load bank switches, surge arresters and heaters in the Neutral Grounding(earthing) Resistors
 

 

C. TESTS

 

C.a. Routine Tests

  • Measurement of insulation resistance between enclosure and resistor
  • Withstand test of dielectric strength at network frequency for one minute
  • Measurement of total DC resistance
  • Insulation test of resistor blocks
  • Galvanization thickness test
  • Paint thickness test

C.b. Type Tests(on demand)

  • Temperature rise test
  • Protection degree test
  • Impulse voltage test (1,2 / 50 µs)
  • Measurement of AC resistance
  • Seismic test
 

 

D. SELECTION DETAILS

  • System Voltage
  • Line to Neutral Voltage
  • Desired Current Rating
  • Desired Resistance Level
  • Maximum Time ON (seconds)
  • Bushing Entry or Cable Entry
  • Current Transformer Ratio (if applicable)
  • Disconnector Switch (if applicable)
  • Special Options (if applicable)