Technical report

NEMLink: augmenting the Australian National Electricity Market transmission grid to facilitate increased wind turbine generation and its effect on transmission congestion

31 Dec 2015





This report compares the effect of increasing the number of wind turbine generators on transmission line congestion in the Australian National Electricity Market’s (NEM) under the existing transmission grid and an augmented version of the transmission grid called NEMLink. The comparison is made from 2014 to 2025.

We use a sensitivity analysis to compare the effect of five different levels of wind penetration on transmission congestion in the original NEM grid and NEMLink augmented grid.  The five levels of wind penetration span Scenarios A to E where Scenario A represents ‘no wind’ and Scenario E includes all the existing and planned wind power sufficient to meet Australia’s original 2020 41TWh Large Renewable Energy Target (LRET).  We also use sensitivity analysis to evaluate the effect on transmission congestion of growth in electricity demand over the projections years 2014 to 2025 and weather over the years 2010 to 2012.  The sensitivity analysis uses simulations from the ‘Australian National Electricity Market (ANEM) model version 1.10’.

Without NEMLink, we find congestion on only 14 of the 68 transmission lines using the ANEM Model.  Notably, these 14 congested transmission lines include 6 of the NEM’s interstate interconnectors and 8 of the intrastate transmission lines although only three of the intrastate transmission lines exhibited any significant degree of congestion.  In comparison, with NEMLink, there is congestion on 12 of the 68 transmission lines.  The 12 congested lines include 4 interstate interconnectors and 8 of the intrastate transmission lines.  The congestion on the on the intrastate lines varies between tiny and small.

NEMLink has an uneven effect on congestion but on most lines reduces congestion.  The two Queensland (QLD) to New South Wales (NSW) interconnectors QNI and DirectLink exhibit a complementary pattern under increasing wind power that increases congestion on DirectLink but decreases congestion on QNI.  NEMLink exacerbates this complimentary pattern by eliminating congestion on QNI and increasing congestion on DirectLink.  Similarly, BassLink, the interconnector that links Victoria (VIC) and Tasmania (TAS), and the Tarraleah-Waddamana line in TAS also exhibit a complementary pattern under increasing wind power.  However, this complementary pattern reverses in the highest wind power penetrations scenario E.  This BassLink complimentary pattern persists under NEMLink but NEMLink increases congestion on BassLink and reduces congestion on the Tarraleah-Waddamana line.  In contrast, NEMLink eliminates congestion on the interconnector Regional VIC-Tumut NSW that shows volatility with increasing wind power penetration but introduces an unremarkable amount of congestion on the Dederang VIC-Tumut NSW line.  Finally, the VIC to South Australia (SA) interconnector MurrayLink shows the greatest percentage increase in congestion with increase in wind power, which NEMLink eliminates.  However, NEMLink exacerbates congestion on Heywood that is the other VIC-SA interconnector.

Under increasing wind power, the augmentation of DirectLink is required with or without NEMLink.  Under increasing wind power and the existing NEMLink proposal, BassLink requires reconsidering for augmentation.  Possibly cheaper alternatives to augmenting BassLink include pump storage in Tasmania and relocatable energy storage.  The Australian Energy Regulator has already scheduled augmentation of the Heywood interconnector that should address the increase in congestion discussed.




Peer Reviewed: