1. Leakage Model Modification Update
Shrinkage Forum 26 September 2012

2. Leakage Model Modifications
Presented to Shrinkage Forum 6 January 2012
LP Service Modification
Re-baseline service numbers to an estimate of 2010/11 Populations
Incorporate impact of service transfers into leakage calculation
AGI Venting Modification
Assess venting rates for Positioners and Controllers
Estimate steady-state and operational venting

3. LP Service Modification
Formal Consultation by National Grid February 2012 and submitted to Ofgem April 2012.
Ofgem indicated they would need to consult on changes to licence baselines
Ofgem indicated a preference for a common model for all the DNs
National Grid has agreed to defer application of the modification into the next price control period
Ofgem should be able to direct changes to licence baselines then
All DNs should be in a position to make the modification
Modification to apply to the leakage assessment for 2013/14

4. AGI Venting Modification
National Grid has initiated an IFI Project to quantify Venting from control equipment
Key deliverables
Establish relationship between venting rate and control system operating pressure for steady-state venting
Identify levels of venting in operation
Investigate the potential to relate operational venting to telemetered flow and pressure data
The viability of this will be assessed when data is available

5. AGI Venting Modification
Data is to be collected from four sites from August 2012 through to March 2013 to identify any seasonal variances
As with the LP Service Modification, it is intended to apply the modified venting assessment in the first year of RIIO-GD1 for application to the leakage and shrinkage assessment for 2013/14
Data will be shared to enable other DNs to make the modifications at the same time

6. Impact on Key Shrinkage Dates
Neither modification will apply to the current price control period
Shrinkage estimate for 2013/14
Published 31 December 2012
Do we include an estimate of the impact of the two modifications?
Accurate estimate of LP Service impact could be available
Accurate estimate of AGI unlikely

7. Impact on Key Shrinkage Dates
Shrinkage estimate for 2014/15
Published 31 December 2013
Consultation and Ofgem decision on both modifications expected to be complete
2013/14 Leakage and Shrinkage Assessment
Published 31 July 2014

8. Key Dates
Autumn 2012 – Establish relationship between steady-state venting and control system operating pressure
From Autumn 2012 – Model validation with recorded venting rates over winter period
Spring 2013 – Project complete
Spring 2013 – Formulate Consultation and discuss at Shrinkage Forum
Spring 2013 – Formal Consultation
Summer 2013 – Ofgem decision