CS RESISTORS
(PTY) LTD

Neutral Earthing Resistors (NERs) are designed to limit the current that would flow through the neutral point of a transformer or generator in the event of an earth fault.

Neutral Earthing Resistors (NERs) are used in the electrical distribution system to limit the fault current to values that will not further damage the other electrical equipment involved in the fault and most importantly improving the safety of personnel working close to the fault area.

C S Resistors (Pty) Ltd. has a long and successful record manufacturing Neutral Earthing Resistors (NERs) that started early in the year 2000.

By using its expertise and commitment to customer service, C S Resistors has become the preferred supplier of all major manufacturers of neutral earthing compensators with neutral earthing resistors, earthing transformers, transformers for mine applications, auxiliary transformers as well as electrical substation contractors.

C S Resistors (Pty) Ltd can supply NERs oil insulated (ONAN) and natural air cooled  which are mainly used in electrical distribution systems to cover the range up to 44 000 volts of voltage system, 2000 amps of short time current and a short time of up to 60 seconds.

Also air insulated and natural air cooled to the same limits. The choice of the type between other factors is based on the environmental pollution on the installation site and the fire risk associated with a major failure of the unit or surrounding equipment.

Voltage Systems:

C S Resistors have successfully manufacture (NERs) for voltage systems from 400 Volts and up to 44 000 Volts.

Short time current:

The ranges of short time currents vary from 25 Amps and up to 2000 Amps. The short time currents also vary from 2 seconds and up to 1 minute. Other short time current requirements can be met in consultation.

Continuous current:

The common values of continuous currents are from 2 Amps to 30 Amps nevertheless values of continuous currents out of the above range can be supplied on consultations.

Insulation Voltage levels:

The insulation voltage levels usually agree with the standard values of the voltage of the system therefore it insulation voltage levels between 2.5AC/30LI to 95AC/250LI are supplied.

Material of the resistors:

The standard material of the resistors elements is stainless steel well-proven grade 3CR12 or alike. Stainless steel elements on different grades such as AISI 304 or 316 can also be supplied. Even resistors elements on sophisticated alloys known to have an extremely low-temperature coefficient are possible.

Construction type of the resistors:

Welded grid of stamped resistors elements is the most common type of the construction of the resistors. Wire wounded over a high alumina form can also be supplied. Another very common construction of the resistor is made of shielded elements insulated with MgO.

C S Resistors can supply the Resistor’s elements required by the manufacturers to their specification in order for them to incorporate the resistor in their product.

The standard enclosure material is mild steel plate with an epoxy powder coated finished. Enclosures made out galvanized steel sheet and epoxy powder coated are very common. For corrosive environment enclosures manufactured from stainless steel grades 3CR12, AISI 304 and AISI 316 are often specified and supplied.

For air-cooled resistors, IP23 degree of protection is common due to the protection offered against vermin and the good ventilation of the resistor nevertheless other degrees of protection can be offered after consultation.

When the specifications require the fitting Medium Voltage termination boxes their most common insulation medium is air and the protection degree specified is commonly IP54 or IP55.

Oil insulated / cooled NERs constructions are more varied as also are their specifications. Almost all insulators positions (inside voltage boxes; on the side of the tank; on top of the tanks; etc) are supplied. Totally sealed units (free maintenance) or free breathing are commonly specified.

Other accessories:

Pressure relief valves to avoid the NER tank bursting in case of a sudden failure; Gas relays to detect incipient failures before they disrupt the system; Thermometers with alarm and trip contacts to protect the NER against overload; Air breathers or dryers to keep the water content of the oil under control; Filler plugs, drain valves and oil samplers to maintain the insulating oil in good condition; Steel fabricated plinths to increase the height of the top fitted insulators to be safe to personnel working in the substation and NGMR neutral grounding monitor relays are some of the accessories that can be supplied with the NERs.