January 2012 Capital Investment - National Grid

Exhibit ___ (EIOP-19)Page 42 of 684also scheduled for conductor testing to determine if a more comprehensive project isneeded, Gardenville-Depew 54 (C28706) and the Clay-Dewitt 3 (C28709) project 14 .Drivers:A significant driver of this strategy is enhanced reliability of the transmission system.Shield wire serves as a grounding element deflecting the lightning strikes away fromenergized conductors and conveying it to ground without permitting flashover to occur. Awell grounded shield wire system significantly reduces the likelihood of an outage due toa lightning strike.In addition to lightning protection, the shield wire provides critical structural supportagainst imbalance caused by heavy wind, conductor drop or failure, splice failure,localized wind shear, ice loading and other related elements. 15 These imbalances occurmore often than originally suspected and as long as the shield wire system is intact, theycan go unnoticed. An intact shield wire will help minimize structural related outages.Safety is also a major factor in the shield wire strategy. A dropped shield wire that goesunnoticed (no outage) creates a public safety concern if the line remains energized.Customer Benefits:The Shield Wire program targets reliability improvements of the 115kV transmissionsystem. There will also be a benefit in the improvement in the performance of eachcircuit. Even those shield wire failures that do not result in an unplanned outagegenerally require a scheduled outage for repairs. Consequently, the reliability of thecircuit suffers, as does service to customers.2011 to 2012 Variance:Capital spending commenced in FY10 on the LaFarge project (C38125) which will befinished by January 2012. Mountain-Lockport (C28681) and Huntley-Lockport (C28707)shield wire replacement projects are underway. The next project to be completed will beHuntley-Gardenville (C28676).Additional lines that have been identified as shield wire candidates are Gardenville-Buffalo River, Gardenville-Depew and, all of which are in the preliminary design phase.The difference between the two Plans below is largely due to a drop off of the $7.6malready spent in FY12 on shield wire projects. Also, some shield wire projects have beenabsorbed into the asset condition based Overhead Line Refurbishment program such asGardenville-Homer Hill 151 and 152 (southern portion) and Lockport-Mortimer 111.14 The Clay-Dewitt 3 line is being studied in the near future for system capacity needs as part ofthe Syracuse Area Reconductoring project described above. If the line is identified forreconductoring the shield wire will be replaced as part of that project.15 The Company will consider the installation of Optical Ground wire (OPGW) during replacementof shield wire where cost beneficial.II-2543