What is NGR?
- Resistance grounding has been used in three-phase industrial applications for many years and it resolves many of the problems associated with solidly grounded and ungrounded systems. Resistance Grounding Systems limits the phase-to ground fault currents.
- The main reasons for limiting the phase to ground fault current by resistance grounding are:
- To reduce burning and melting effects in faulted electrical equipment like switchgear, transformers, cables, and Rotating machines.
- To reduce mechanical stresses in circuits/Equipments carrying fault currents.
- To reduce electrical-shock hazards to personnel caused by stray ground fault.
- To reduce the arc blast or flash hazard.
- To reduce the momentary line-voltage dip.
- To secure control of the transient over-voltages while at the same time.
- To improve the detection of the earth fault in a power system.
- Grounding Resistors are generally connected between ground and neutral of transformers, generators and grounding transformers to limit maximum fault current as per Ohms Law to a value which will not damage the equipment in the power system and allow sufficient flow of fault current to detect and operate Earth protective relays to clear the fault. Although it is possible to limit fault currents with high resistance Neutral grounding Resistors, earth 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 to approximately rated current of transformer and / or generator. In addition, limiting fault currents to predetermined maximum values permits the designer to selectively coordinate the operation of protective devices, which minimizes system disruption and allows for quick location of the fault.
- There are two categories of resistance grounding:
- Low resistance Grounding
- High resistance Grounding
Features of PAARSUN NGR’s:
PAARSUN Neutral Grounding Resistors:
- are designed and manufactured for voltages up to 63kV, Current rating up to 5000 Amps with rated times from a few seconds to continuous.
- an extensive range of resistor elements allows selection of the most efficient and cost effective solution for any required duty.
- the change in resistance with temperature during operation is predictable. (is depend on resistor material)
- are compact and do not require site calibration or auxiliary power supplies.
- are ease of installation and maintenance.
- maintenance can be limited to periodic inspection and cleaning only.