1. Place your chosen image here. The four corners must just cover the arrow tips. For covers, the three pictures should be the same size and in a straight line. Modification 461 – Changing the UNC Gas Day to Align with the Gas Day in EU Network Codes Transmission Workgroup 4 th July 2013 Hayley Burden

2. Agenda 1.Background & Reasons for Change 2.Moving Forward - Modification 461 3.Modification High Level Development Plan (3 Phases)  Phase 1 – Understanding the Issue  Phase 2 - Workgroup review of UNC and associated docs  Phase 3 – Updating Modification to reflect agreed solution and phase 2 review 4.NG NTS Analysis to Date 5.Phase 1 – Understanding the Issue 6.Workgroup Review of UNC (Example) 7.Estimated Modification Development Timeline

3. Background & Reasons for Change CAM Approved Code (Regulation) (15 th April 2013) Article 3 - Definitions 7. ‘gas day’ means the period from 5:00 to 5:00 UTC the following day for winter time and from 4:00 to 4:00 UTC the following day when daylight saving is applied; (NB. Although CAM only applies to IPs, the definition is applicable to all EU Network Codes and supersedes the existing GB Gas Day of 06:00-06:00) CAM is set to be implemented 1 st November 2015 Change to Gas Day will need to be implemented no later than this date Logical solution to implement the change to the Gas Day on 1 st October 2015 to coincide with the start of the Gas Year?

4. Moving Forward – Modification 461  ‘Bare Bones’ Modification Proposal to encourage industry participants to develop the right solutions for all parties concerned  Documents in scope to be assessed through development of this Modification:  Uniform Network code (UNC)  General  Transportation Principal Document (TPD)  Offtake Arrangements Documents (OAD)  Associated documents (to include as a minimum); Network Code Operations Reporting Manual, Network Code Validation Rules, ECQ Methodology, Measurement Error Notification Guidelines, Energy Balancing Credit Rules, Uniform Network Code Standards of Service and UK Link Manual  Documents out of scope:  Individual licences, contracts and agreements

5. Modification 461 High Level Development Plan Phase 1 Understanding the Issue Facilitate workgroup understanding of the layers of the issue:  Gas Day definition change  Time references that define the start/end of the Gas Day  Time references attached to UNC processes (Predominantly D and D-1) NG NTS information sharing: options on potential solutions Phase 2 Workgrou p Review of UNC and associated document s Section by section review of UNC, alongside analysis shared by NG NTS As workgroup progress the review of the UNC, decision to be made about which solution to develop Associated documents to be reviewed using same method Phase 3 Updating Mod with agreed solution and Phase 2 review Develop Modification Proposal and legal text to reflect agreed solution and review of UNC and associated documents Obtain appropriate cost assessments for any IS system changes Submit workgroup report to Panel Estimated timescales (To be progressed quicker if feasible) 1–2 months Up to 6 months Up to 3 months

6. NG NTS Analysis to date… NG NTS Internal Analysis UNC Line by Line Review UNC Process Impact Analysis Impact Analysis NG IS Systems Change Order Request Submitted to Xoserve Response to Ofgem’s Open Letter Updates on Gas Day Impacts at Tx Workgroup

7. Phase 1 Understanding the Issue  There are 3 broad strands to understanding the change to the Gas Day; 1) UNC current definition;  General Terms Section C, 2.2.1 (a) "Day" means the period from 06:00 hours on one day until 06:00 hours on the following day;  The EU Network Codes require the Gas Day Definition to Change within the UNC; ‘gas day’ means the period from 5:00 to 5:00 UTC the following day for winter time and from 4:00 to 4:00 UTC the following day when daylight saving is applied 2) UNC times that define the start/end of Gas Day;  These will also require changing in addition to the definition  E.g. UNC Section B System Use & Capacity 2.10  2.10.10 (a) the "offer effective time" is the time on the hour in relation to a daily capacity offer being the later of: (i) 06:00 hours on the Gas Flow Day; and (ii) the time not earlier than 60 minutes after Firm NTS Entry Capacity has been selected pursuant to such bid for surrender;  The 06:00 hours will need to change to 05:00 hours in UNC to coincide with the start time of the new Gas Flow Day

8. Phase 1 Understanding the Issue (Continued) 3) UNC Process times  This is potentially the most complex change associated with the Gas Day  There are a number of process times contained within UNC – many of these occur on D-1 and D  Do these all have to change to accommodate the change to the Gas Day?  NG NTS have conducted some initial process analysis and identified two broad options; Option 1 – Move only the process times that have to move Option 2 – Move all process times forward by an hour To assess feasibility of options; Complete a section by section review of UNC/OAD Categorise changes required Once complete this will assist in informing the preferred solution Throughout this process assess the pros and cons of each option, and consider business risk, and financial and resource implications of each option Decision to be made by workgroup on which option to pursue and Modification Proposal to be developed accordingly The option pursued by the workgroup could influence the Modification development timescale

9. Workgroup Review of UNC  NTS to share results of their section by section review of the UNC (this analysis is ongoing)  NTS to share analysis of potential process impacts and identified interrelationships between processes  Example of UNC category coding used in NTS analysis

10. Workgroup Review – Example Continued Example of Capacity related process times on D-1 and D

11. Estimated Modification Development Timeline