Annual Planning Report 2012 - Transpower

Chapter 6: Grid BackboneFigure 6-4: North Island grid backbone areaUpper NorthIsland areaWairakei Ring areaTaranaki areaCentral NorthIsland areaWellington areaTable 6-2: Grid backbone transmission issuesSectionnumberIssue6.4.1 Upper North Island voltage stability6.4.2 Transmission capacity into Auckland and Northland6.4.3 Wairakei Ring transmission capacity6.4.4 Taranaki transmission capacity6.4.5 Central North Island transmission capacity6.4.6 Wellington area transmission capacity6.4.1 Upper North Island voltage stabilityOverviewThe Upper North Island covers the geographical area north of Huntly, includingGlenbrook, Takanini, Auckland, and the North Isthmus.The transmission capability to supply the Upper North Island load is limited by voltagestability, which in turn is influenced by:generation in Auckland and at Huntlythe reactive power losses due to the transmission system within the Upper NorthIslandthe reactive power losses due to the transmission system supplying the UpperNorth Island area, andthe reactive power demand due to the composition of the load in the area (inparticular the proportion and type of motor load).There are several generator and circuit contingencies that can cause voltage controlproblems. The worst contingencies include the loss of the:462012 Annual Planning Report © Transpower New Zealand Limited 2012. All rights reserved.