For multi-panel boards where we have an extensible switchgear configuration => 4 units (switches or circuit breakers), it is not generally possible to replace individual assets on a piecemeal basis and a total replacement is usually required. As a result, we have allowed for the replacement of some units with a HI less than 5. Where at a substation site we have an extensible switchgear configuration <=3 units (switches or a circuit breaker), we have anticipated a Ring Main Unit solution. As with other items of plant, the higher replacement volumes compared to DPCR5 are a consequence of the 1960s peak of installation now coming to the end of their life expectancy. Additionally, there are a number of plant items (eg ROKSS switchgear) where a previously developed refurbishment had been planned but could not be implemented. This has resulted in the need to add them to the asset replacement programme thus increasing the volumes still further. The current issues with the fuse switch units increase the risk for this asset type above the level we would normally expect. The planned resolution of these issues, together with the replacement of 20% of the asset population over the RIIO-Ed1 period results in a 16% improvement in risk from the 2015 position. 7.6
HV Transformers (GM)
These are the assets that transform the voltage from 33kV to 11 or 6.6kV for onward transmission through the HV network.
Population
Planned ÂŁM replacements
Planned ÂŁM refurbishments
Risk ÂŁ/point points delivered
16,765
1,412
-
254,133
18.1
-
721
1,000,000 900,000 800,000 700,000 600,000 500,000
Without
400,000
With
300,000 200,000 100,000 2015
2019
2023
The majority of our ground-mounted transformer replacement volumes have been identified using the CBRM process and our internal policy which details the intervention strategy for specific transformer types. The volumes also includes an assumption for consequential transformer replacements from the associated LV board replacement programme due to engineering and compatibility issues for the modern equivalent transformer replacement to accept the existing LV board. Electricity North West Limited
13
1 July 2013