Description:

Powerohm Neutral Grounding Resistors are used in industrial power systems for resistance grounding of wye-connected generators and transformers. A neutral grounding resistor limits the fault current to a value which is sufficient enough to operate protective relays, yet prevent unwanted fault damage.

Neutral grounding resistors are rated in line-to-neutral voltage (system voltage divided by 1.732), initial fault current and maximum time on. Powerohm neutral grounding resistors are designed to dissipate the required amount of energy and not exceed the temperature limitations of IEEE Standard 32-1972. As defined in this publication, the time and temperature ratings for neutral grounding resistors are as follows:

Short time: Short time ratings are 10, 30, and 60 seconds. Since short time rated resistors can only withstand rated current for short periods of time, they are usually used with fault clearing relays. The short time temperature rise for the resistive element is 760°C.

Extended time: A time on rating greater than ten minutes which permits temperature rise of resistive elements to become constant, but limited to an average not more than 90 days per year. The extended temperature rise for the resistive element is 610°C.

Continuous: Capable of withstanding rated current for an indefinite period of time. The continuous temperature rise for the resistive element is 385°C.