1. INTRA-DAY TRADING DESIGN Changes required to the MIUN Calculation for SEM Intra-Day Trading 27 March 2012

2. 2 SEM Intra-Day Trading will be implemented in July 2012. SEM Intra-Day Trading (Mod_18_10_v2) requires that: MIUNs are fixed where possible in subsequent MSP Software Runs; Superposition is allowed; and There are three Gate Windows for each Trading Day. These changes to Appendix 2 of Agreed Procedure 2 (where the specific MIUN calculation rules are summarised) are required to align with Mod_18_10_v2. The MIUN Calculator vendor is currently making changes to the MIUN Calculator to deliver this requirement. The changes will be tested by SEMO and delivered prior to the start of Market Trial. The drafting changes in the Modification Proposal are in respect of the approved drafting for Intra-Day Trading. Background

3. 3 Recap: SEM Intra-Day Trading Design Start Overlap Opt’n Period Trading Day - 1Trading Day Gate Window Closure (GWC) EA1 Gate Window Opening (GWO) e.g. as per current GWC EA2 GWO GWC WD1 GWO GATE WINDOW 10:00 TD-29 to 09:30 TD-1 GATE WINDOW 09:30 TD-1 to 11:30 TD-1 GATE WINDOW 11:30 TD-1 to 08:00 TD EA1 Trading Window EA2 Trading Window WD1 Trading Window Ending Overlap Opt’n Period Ending Overlap Opt’n Period Ending Overlap Opt’n Period OPTIMISATION TIME HORIZON EA1 Interconnector Unit trades fixed EA1 and EA2 Interconnector Unit trades fixed MIUN Calculator changes deliver this requirement (where possible).

4. 4 Why do the current AP2 rules not deliver the IDT requirements? Do not allow for Superposition IUNs in each direction are capped by the corresponding ATC limit and ACH i.e. sum[IUNs + ]≤ATC + and sum[IUNs - ]≥ATC - Do not allow for multiple Gate Windows Only one Gate Window currently, taking into account Active Capacity Holdings. Currently, the rules would result in zero MIUNs for IUs without Capacity Holdings. Do not fix previously determined MIUNs MIUN Calculator currently does not consider MIUNs previously calculated. MIUN Calculator considers all Units at the same time (there is no ordering to the consideration of IUs).

5. 5 What changes will deliver the IDT requirements? Allow for Superposition Total IUNs are capped by the ATC import and export limits i.e. sum[IUNs all ]≤ATC + and sum[IUNs all ]≥ATC - Allow for multiple Gate Windows Calculate MIUNs following each MSP Software Run or change in ATC. Fix previously determined MIUNs Track MIUNs calculated following the associated MSP Software Run (Original MIUNs). Fix Original MIUNs where possible (in some circumstances MIUNs cannot be fixed). Then consider IUs where there are no previously calculated MIUNs to fix.

6. 6 The changes in the Modification Proposal are summarised as follows: 1.Clarification that the MIUNs as calculated following the relevant MSP Software Run will be fixed in subsequent MIUN calculations where possible. 2.Correction of the explanation of when Interconnector Units are considered to be ramping up or down. (This is currently incorrect in its description of the existing process.) 3.Introduction of Original MIUNs and Original IUNs as defined terms in Agreed Procedure 2, Appendix 2. These terms will enable fixing and make clear which version of the IUNs/MIUNs are used as inputs to the relevant MIUN Calculator run. Summary of Modification Proposal

7. 7 Overview of MIUN Calculation for Intra-Day Trading EA1 MSP Software Run Interconnector Dispatch Schedule Area under the Interconnector Dispatch curve = sum of MIUNs, allocated to EA1 Interconnector Units COD TOD etc Original MIUNs for EA1 Units Input to MIUN Calc MIUN Calculator Original IUNs for EA1 Units EA2 MSP Software Run Interconnector Dispatch Schedule COD TOD etc Original MIUNs for EA2 Units Input to MIUN Calc MIUN Calculator Original IUNs for EA1, EA2 Units Area under the Interconnector Dispatch curve = sum of MIUNs, allocated to Interconnector Units (EA1 allocated first) WD1 MSP Software Run Interconnector Dispatch Schedule COD TOD etc Original MIUNs for WD1 Units MIUN Calculator Original IUNs for EA1, EA2, WD1 Units Area under the Interconnector Dispatch curve = sum of MIUNs, allocated to Interconnector Units (EA1, EA2, then WD1) Input to MIUN Calc

8. 8 Overview of MIUN Calculation for Intra-Day Trading Ex-Ante One MSP Software: Calculate EA1 Original IUNs. MIUN Calculator Produce feasible Interconnector profile. Calculate EA1 Original MIUNs. If ATC changes, attempt to meet all Original MIUNs if possible. Ex-Ante Two MSP Software: Calculate EA2 Original IUNs. MIUN Calculator Produce feasible Interconnector profile. Fix EA1 Original MIUNs. Calculate EA2 Original MIUNs. If ATC changes, attempt to meet all Original MIUNs if possible. Within Day One MSP Software: Calculate WD1 Original IUNs. MIUN Calculator Produce feasible Interconnector profile. Fix EA1 and EA2 Original MIUNs. Calculate WD1 Original MIUNs. If ATC changes, attempt to meet all Original MIUNs if possible.

9. 9 Correction of definition of Ramping Up/Down

10. 10 Questions and Discussion