Neutral earthing resistors (ner)
Neutral-earthing resistors (NERs) are used to ground the neutral point in a (medium) voltage grid. The resistors limit the fault current in the case of a phase-to-ground short circuit. A NER limits damage, resulting in shorter and fewer downtimes. The main advantages of NERs over alternative grounding methods is that they limit fault currents, allow simple fault-detection and do not produce over-voltages.
Our NERs are Achilles REPRO certified, so they can be installed at facilities of of the main energy companies of Southern Europe and LATAM.
NERs are selected based on voltage, fault current and duration-of-fault-current. Normally the resistors is chosen based on the energy [E] in joules that can be absorbed by the elements without exceeding the maximum element temperature, energy being power integrated over time, where typical fault-times last 10 to 30 seconds. The power will vary slightly, depending on the resistance’s temperature coefficient. At the start of the fault, the current will be higher due to the resistor’s lower ohmic value but as the element heat up, the fault current will drop