Nifty electrical work reduces energy losses

The Darfield Dryer 2 in Canterbury, opened in 2013, produces 30.5 tonnes of whole milk powder per hour.

Schneider Electric’s general manager partner projects, power solutions and industry, Steven Gallagher, says large users of electricity often generate energy-sapping harmonics that compromise the performance of the very network on which they depend. 

Fonterra’s Darfield plant could have been a culprit if not for harmonic filtering equipment supplied by Schneider Electric, he says.

Unlike a traditional system, the set-up at Darfield now reduces heat losses by about 20kW/hour.

“The new system has been very successful, and exceeded all expectations and targets for the project,” Gallagher told Dairy News.

At the Darfield site most motors are controlled by variable speed drives, essential for precisely matching AC motors to process requirements but with much less energy consumption, especially by pumps and fans. 

Gallagher says as a side effect they also represent a non-linear load, contributing to harmonic distortion in the electricity supply. 

“Harmonics cause transmission losses across New Zealand’s national grid, wasting energy by generating excessive heat. This in turn requires electricity suppliers to build more, bigger power stations with higher-capacity power lines and much larger electrical equipment to offset the losses. 

“Eliminating harmonics not only greatly improves power quality and the grid’s efficiency, it also helps to contain the overall cost of electricity.”

A conventional harmonic filtering solution for Dryer 2 (twice the size of Darfield Dryer 1) would have doubled the cost, Gallagher says.

“But between Fonterra and our Schneider Electric designers we developed a much more cost-effective option using phase-shifting transformers. 

“Despite the slightly more expensive phase-shift transformers and the cost of relocating the filters from Dryer 1, the capital expenditure for Dryer 2’s harmonic mitigation came in at less than 10% of the Dryer 1 spend.”

 The new system exceeds all expectations and targets of the project, he says.

Fonterra group manager electrical engineering Glenn Sullivan says a single-provider approach with Schneider Electric allowed the engineers and designers to view the overall project as a whole and select the most appropriate equipment.

“ Schneider Electric’s clean power specialist, Marc Marchal, did an exceptional job to help design a harmonics solution.

“Harmonics can be trimmed by smarter, improved designs for our plants,” says Sullivan.

“While design alone won’t entirely eliminate the issue, it can reduce harmonics to a point where the filtering solution won’t be as expensive. Darfield is an excellent example.”