1. Flow Variations at Entry Transmission Workstream Martin Watson 1 st November 2007

2. © NGG Transmission Workstream 1 st November 2007 2 of 18 Objectives Overview of Flow Variations at Entry Rates of Delivery as defined by UNC Example of within day Flow Variations Frontloading/Backloading Flow Variations at Entry Oct 2006 – Sept 2007

3. © NGG Transmission Workstream 1 st November 2007 3 of 18 Flow Variations at Entry 22.00 06.00 End of Day Measurement = 240 Gwh 5 0 Extent of Backloading = 80 Gwh Flow Variation = (EOD/24 * 16) - (Sum of 06.00 to 22.00 Hourly Volumes) = ( 240 x 16) - ( 5 x 16) 24 = 160 - 80 = 80 Gwh 06.00 10 20 16 hours

4. © NGG Transmission Workstream 1 st November 2007 4 of 18 Rates of Delivery Start of day nomination – 1/24 th rate of 1.2 mcm/hr Re-nomination to increase flow to 1.6 mcm/hr Re-nomination to increase flow to 1.8 mcm/hr Re-nomination to decrease flow to 0.6 mcm/hr UNC Section I 3.10 - Rates of Delivery 3.10.1 Each User shall use all reasonable endeavours to secure that the requirements of paragraph 3.10.2 are complied with……… 3.10.2 (a) The rate at which it delivers gas to the Total system at a System Entry Point changes only with effect from the start of the day and (within the day) with effect from the Re-nomination Effective Time of a Re-nomination in respect of that point.

5. Example of within day flow variation 20 th July 2007

6. © NGG Transmission Workstream 1 st November 2007 6 of 18 20 th July 2007 - Demand and Supply

7. © NGG Transmission Workstream 1 st November 2007 7 of 18 20 th July 2007 – NTS Actual Linepack Linepack depletion 16.2 mcm Linepack depleting at up to 2mcm/hr

8. Impact on Capacity Release of Backloading/Frontloading

9. © NGG Transmission Workstream 1 st November 2007 9 of 18 Backloading Maximum capability 1/24 th flow rate Capacity that may not be released due to profiling NG less likely to release additional capacity if flows are being profiled or there is an expectation, based on past experience of large within day flow variations Actual flow profile

10. © NGG Transmission Workstream 1 st November 2007 10 of 18 Frontloading Maximum capability 1/24 th flow rate Capacity that may not be released due to profiling NG less likely to release additional capacity if flows are being profiled or there is an expectation, based on past experience of large within day flow variations Actual flow profile

11. Flow Variations October 2006 – September 2007

12. © NGG Transmission Workstream 1 st November 2007 12 of 18 Teesside Backloading +ve Net Input flows in period 06.00 to 22.00 BELOW average flows for the day Frontloading -ve Net Input flows in period 06.00 to 22.00 ABOVE average flows for the day

13. © NGG Transmission Workstream 1 st November 2007 13 of 18 Barrow

14. © NGG Transmission Workstream 1 st November 2007 14 of 18 Bacton

15. © NGG Transmission Workstream 1 st November 2007 15 of 18 St Fergus

16. © NGG Transmission Workstream 1 st November 2007 16 of 18 Easington Backloading +ve Net Input flows in period 06.00 to 22.00 BELOW average flows for the day Frontloading -ve Net Input flows in period 06.00 to 22.00 ABOVE average flows for the day

17. Conclusions

18. © NGG Transmission Workstream 1 st November 2007 18 of 18 Conclusions UNC obligations require Shippers to flow at a uniform rate, signalling any changes via the re-nomination process. When Shippers do not flow at a uniform rate, it effects the operational efficiency of the NTS and the ability to maximise the release of additional capacity e.g. discretionary interruptible. NGG and Shippers need to work together to minimise flow variations. However, if Entry Terminals consistently demonstrate behaviours that compromise the safe and efficient operation of the NTS, NGG will look to bring forward timely measures to address this issue.

19. End