New Zealand Waste Disposal Company Chooses S&C’s System VI™ Switchgear.

As part of the consent requirement to operate their landfill, a waste disposal firm in New Zealand was required to extract and destroy the methane created during anaerobic decomposition of the organic waste material. This landfill, located north of Auckland, is the largest in New Zealand and processes approximately 2000 tons of waste a day. Covering 175 acres, the site has a capacity of 20 million cubic meters.

Two 415-volt, 1080-kVA methane-powered generators would meet the requirement. But the waste disposal firm realized that they could sell the excess electricity generated at the site to the local utility, thus creating additional revenue. The problem was making the interconnection.

In working with the utility, it was determined that two 415-volt/33-kV step-up transformers, along with appropriate switchgear, would be needed at the landfill generator site. And additional switchgear would be needed at the utility’s interconnection point, 3 km away.

S&C System VI Switchgear was specified for the application. The 38-kV gear features a modular arrangement of SF6-insulated S&C Vista® Underground Distribution Switchgear in combination with air-insulated S&C Metal-Enclosed Switchgear. The former contains load-interrupter switches and fault interrupters, which protect the transformers. The latter contains circuit breakers, protective relays, voltage and current transformers, metering, a remote terminal unit, and communication equipment. This arrangement provides maximum flexibility and gives the waste disposal firm the ability to add additional generators in the future.

The S&C System VI Switchgear was delivered on time, in early February 2004. Using the two new generators plus two existing generators, the waste disposal firm now generates more than 4 megawatts of “recycled” electricity from the methane derived at the site.

The waste disposal firm plans to install 11 more generators, for a total capacity of over 16 MVA. Additional S&C System VI Switchgear will likely be procured to protect these generators.