Neutral Earthing Resistor

The system voltage is the starting point for every NER design.

Typical system voltages include:

The resistor is designed for the phase-to-neutral voltage rather than the line-to-line voltage.

Specify the maximum earth fault current that the NER must limit.

The selected current must satisfy both equipment protection requirements and protection relay coordination.

Most neutral earthing resistors are rated for:

A 10-second rating is widely used because it provides sufficient time for fault detection and clearing while maintaining a practical resistor size.

Many NERs are intended only for intermittent fault conditions. If the resistor must carry current continuously, this must be specified during the quotation stage. Continuous current requirements typically affect resistor size, material selection, and pricing.

Resistance is usually determined from:

The resistance value directly controls fault current magnitude and protection performance.

Environmental conditions play a major role in NER design.

The most frequently specified ingress protection ratings are:

Suitable for many indoor and sheltered outdoor installations where ventilation is required.

Provides increased protection against dust and water ingress for harsher outdoor environments.

When requesting a quote, clearly indicate whether the installation will be:

Most industrial customers specify:

For corrosive environments, 316 stainless steel may also be considered. Stainless steel enclosures provide excellent durability and corrosion resistance.

Manufacturers often offer custom powder-coated finishes.

Common requests include:

Including the preferred colour in the RFQ helps avoid delays and variation costs.

Usually around 45-50°C.

Consider to specify a sunshield for outdoor particularly where equipment is installed in direct sunlight. Australia's high solar radiation and ambient temperatures can significantly increase internal enclosure temperatures beyond the nominal ambient design temperature.