3 phases from the LV and MV generator are combined inside the Generator Neutral & Leads Cubicles to provide a neutral point. This neutral point is connected to the ground through a resistor. The purpose of Neutral Grounding;

  • Limit the ground fault current to prevent any damage to the generator and ensure operation continuity and safety
  • Provide sensing the fault current with the relays by means of current transformer mounted inside the Neutral Grounding Resistor and limiting the fault duration.
  • Send data to the relevant relays with phase current transformers connected to the three phases prior to the neutral point
  • Limit oscillating and non-oscillating transient voltage caused by the interruption of the failure current and so protect the insulation level of system equipment
  • Improve personnel safety by ensuring that the step voltage on the site is maintained at safety levels
  • Prevent overheating and mechanical stress on the equipment subject to failure current
Phase-ground fault current of generators are generally limited to 5 A, 10 A or 20 A. Fault duration is generally set as 10 seconds. This can be up to 30 seconds at plants which do not have any tolerance to sudden power interruptions. At hospitals, data centers, textile plants, cement plants and other facilities that manufacture with injection, fault duration can be continuous unless the fault current do not damage the system to ensure continuity of system and determine the fault point without any power interruption. See “High-Resistance Neutral Grounding System” for detailed information. The following basic parameters and a single-line scheme of the system, if possible, are required for preparing an offer for a generator neutral grounding resistor system.
  • Phase to phase and phase to neutral voltage of the generator which the resistor is connected
  • Fault current level
  • Fault duration
  • Specifications of phase current transformers
Technical Specifications:
  • Suitable up to 17.5/√3 kV
  • Applicable for fault currents up to 5000 A
  • Stainless steel resistance material suitable for extreme ambient conditions, resistant to oxidation and corrosion, (AISI304, AISI310, AISI316, AISI430, CrAl, CrNi)
  • Special mechanical and electrical design to withstand high temperature and extreme current values
  • Internal current transformer detecting failure current
  • Design and tests in accordance with ANSI/IEEE 32 standard and special specifications
Resistor Element:
  • Spring-wound, edge-wound or grid resistor elements with a cross-section suitable for the nominal current
  • Fully-modular, bended and stainless steel bolt connections in order to ensure electrical continuity at high temperature
  • High conductivity for high current with bended and cascaded terminal connectors suitable for serial and/or parallel connections with high cross-section, low contact resistance
  • High internal insulation and high mechanical resistance against to shocks and sagging thanks to the use of large surface satiated bushings and M16 shear connectors
  • Special designed to dissipate the thermal and mechanical effects of overcurrent to the surface grid resistors
Enclosure:
  • Standard IP20 Protection Level suitable for indoor usage and perfect cooling
  • Enclosure with standard paint (RAL7035)
  • Fully-modular, rigid, strong enclosure design with resistor blocks mounted to the frame for safety lifting from the upper or lower side
  • Lockable door with hinges
  • Corrosion-resistant handling rings and connectors
  • Stainless Steel product and warning labels
Options:
  • Requested protection level from IP20 to IP56
  • Hot-dipped galvanized, stainless steel, aluminum enclosure
  • Painting enclosure in desired color code
  • Entry from top or bottom with bushings
  • Additional equipment including voltage transformer, surge arrester, panel heater, analog display etc.
  • Special design for high altitude
Type Size Download Link
General Catalog PDF 1 MB Download
Neutral Grounding Resistors Catalog PDF 1 MB Download
 

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