Wind and solar farms in north west Victoria and south-west New South Wales have been warned that they face up to 100 days or more of zero output over the next year because of the need to upgrade the local transmission and distribution networks.

The warning from the Australian Energy Market Operator will affect wind and solar farms as north as Broken Hill in western NSW, and new and existing projects in central west Victoria. The outages have already begun in some cases.

Most of the affected wind and solar farms are based around the so-called “rhombus of regret”, a rhombus-shaped part of the electricity grid linking Mildura, Horsham, Kerang, Ballarat and Bendigo that is struggling to cope with the increase in renewable energy capacity.

The wind and solar farms affected include the Silverton wind farm at Broken Hill, and the neighbouring Broken Hill solar farm. In Victoria, the recently opened Wemen, Karadoc, Gannawarra and Bannerton solar farms are impacted, and to a lesser degree some older installations such as the Waubra, Crowlands and Kiata wind farms.

The worst affected appear to be the Wemen, Karadoc and Broken Hill solar farms, which have been warned they will be curtailed back to zero output for extended periods, and will be affected by nearly all the work to be undertaken over the next 13 months.

That work will be be undertaken on the various 220kV lines linking Red Cliffs, Horsham, Wemen, Crowlands, and Kerang. The biggest impact will come from updating communication infrastructure, with the wind and solar plants warned of up to 76 outages, each lasting half a day to a full day. The exact timetable has yet to be established, and in any case may change.

Another 24 full-day outages will be required for various line and conductor capacity upgrades, and a few other outages will be scheduled to connect some new wind farms such as Neoen’s Bungala and Tilt’s Murra Warra to the grid. The Murray Link connection to South Australia will also be affected.

AEMO says 480MW of wind and solar has been added to the grid in the last year, and with another 900MW of new generation anticipated over the next six months, this will lead to some 1500 MW of new generation located in a very light transmission network.

As a result, a number of necessary upgrades in the next six months will require about 120 outages. The impact of this is that many generators in the region will be constrained downwards, often to zero, during these outages.

Other facilities may be de-rated to less than 5MW output, to ensure system security during the upgrades. (see below for an example).