SD700 Lowers Harmonics On Large Irrigation Scheme

ElectraServe and Terrace Water

  We use Power Electronics VSDs for all of our irrigation pumping. The new active front end SD700 provided us the very latest state of the art low harmonics VSD all in one without the need for mounting up separate filters, cabling etc. Installation and commissioning was so simple Blair Watson, Managing Director, ElectraServe

With the ever increasing tightening of harmonic limits by South Island power authorities, smarter low harmonic VSD solutions are being needed – enter the SD700 active front end range.

Based in Ashburton, ElectraServe is the largest electrical contractor in mid Canterbury and boasts 46 years of service to the irrigation industry. It was ElectraServe’s proven record and constant innovation based on Power Electronics product that secured them the electrical development of the Terrace Water Irrigation Scheme in Tarras.

Terrace Water is an irrigation scheme privately owned by a group of farmers in the Tarras area. The scheme comprises 1360kW of submersible pumps lifting water from the terraces of the Clutha River to a 31377m2 area, 73 million litre storage lake located 7km away. Water is pumped at a rate of 883l/s over a 60m head.

Aurora Energy, the local power authority imposes tight harmonic limits on their network so it was important to provide a low harmonic variable speed drive solution that would meet these limits and would work well on a rural network. Power Electronics has the broadest low harmonic product offer in NZ with options of 12,18,24 pulse, passive filters, active filters and active front end (AFE) technologies. The SD700 FR AFE series drives were selected by Electraserve because they provide a compact all in one offer without the need for external filters that require mounting, cabling etc. Because the project was remote it meant transportation of single units was easier too.

The SD700FR AFE series synchronise to the mains as part of the AFE technology. Initially the SD700FRs were too ’aggressive’ with their synchronisation and with eight 170kW units running at the same time, were able to pull the weak 11kV network around. Fortunately the SD700FRs are very programmable so were ‘softened’ thus dampening the AFE response to a level more suitable to the network conditions. A later local substation upgrade also helped ‘stiffen’ up the network.

The low harmonic performance of <5% THDi, unity displacement power factor at all loads combined with IP54 ratings, ultra-low dV/dT and the hugely powerful on board pump macro have provided Terrace Water the ideal VSD for their irrigation scheme.