Application
The best way to ground a power system is to obtain the system neutral through a generator or transformer with a wye-connected winding. However, a system neutral may not be available, particularly in many older low voltage systems and a significant number of existing medium voltage systems. To avoid a high cost of replacing a source transformer, an existing delta-connected system can be grounded using a star/ open delta or star/ delta transformer. During a line-to-ground fault condition, the zero sequence currents can flow into the ground at the point of the fault, and back through the neutral of the grounding transformer, hence providing facility to monitor & limit ground fault current. However Neutral Grounding Resistors are used for system grounding through Neutral Grounding Transformer & generators. A neutral grounding resistor limits the fault current, which is sufficient enough to operate protective relays, yet prevent unwanted fault damage.

Basic Construction
Primary side of the neutral grounding transformer is star/ wye connection and output side is open delta or closed delta, depends on required configuration. The resistor coils consist of a stainless steel element wound around a ceramic core, which is mounted on a stainless steel strip. All other connections are also stainless steel material. This unit is designed to permit the high operating temperatures. Resistors elements are joined by stainless steel connectors, which form the positive electrical path.