Bespoke IECEx and ATEX approved resistors

NERs are used in medium-voltage AC distribution networks to limit the current that would flow through the neutral point of a generator in the event of an earth fault. The resistors limit fault currents to a value high enough to be detected but low enough to prevent damage to switchgear or generators.

Cressall's IECEx and ATEX approved NERs are tested and approved to operate safely for the specifications of Zone 2, T3 classified locations. Zone 2 locations are defined as areas where ignitable concentrations of flammable gases, vapours or liquids are not likely to exist under normal operating conditions. However, flammable materials are likely to be present in a leak.

Cressall reduced the element temperature of the NERs to meet the requirement of the T3 classification: less than 200°C, but could design to meet other T classifications if required.

Martin Nicholls, Sales Director, Cressall, commented: "As well as adhering to IECEx and ATEX certifications, the enclosure and electrical components had to be compliant with the customer specified requirements. In addition, the unit needed to successfully pass inspection and testing by a certified laboratory to ensure compliance.

"This is not the first time Cressall has successfully designed and manufactured IECEx/ATEX certified equipment, but it was one of the more challenging cases. It is not possible to standardise a range because of the specific requirements customers bring to us. Each project is unique, so we work closely with our customers and partners to make sure we provide the best solution on the market.”