1. Review of progress and future work SQSS Sub Group 2 August 2006 DTI / OFGEM OFFSHORE TRANSMISSION EXPERTS GROUP

2. Content Review of likely boundary between Offshore Generator and Offshore TO Cost benefit analysis Work plan Data availability and transparency Other issues

3. Offshore Ownership Boundary Reason for review –Need to understand the scope of the offshore transmission system to understand the required scope of the offshore security standards This assessment has taken into account 4 options Each option has been compared to existing onshore arrangements, and existing CUSC, STC and charging methodology definitions. More detailed paper to be made available for wider consultation.

4. Option 1; TO to own up to the transmission voltage busbar clamps on the platform transformer circuit Offshore transmission system 132kV assets Option 4; TO to own up to the individual wind turbine generator transformer. Windfarm electrical system 33kV assets Option 2; TO to own up to the transformer LV disconnectors Option 3; TO to own up to the disconnector on the busbar side of the circuit breaker on the incoming windfarm circuit Windfarm electrical system Single offshore platform Options considered

5. Initial Thoughts Option 3 is recommended as it: –Best facilitates competition in generation –Simplifies ownership of offshore platforms –Allows the offshore TO to provide Users with a consistent level of security Option 1 could be considered but provides less benefits than Option 3 if more than one Offshore Generator is connected Options 2 and 4 are not recommended

6. Initial Thoughts Sub-group intends to develop a detailed paper explaining the recommendation Sub-group has assumed that the default offshore ownership boundary will be as its recommendation (Option 3) Main Impacts: –Transformer circuits will be included within the security standards for offshore transmission –Assumption will require a review of the consequential impact on Grid Code, access rights and charging methodology

7. Cost-Benefit Analysis Concept Scope Example configurations Work progress and key results Proposed format of SQSS for offshore transmission

8. Concept of cost -b enefit analysis Network Capacity and Redundancy Cost Investment &Maintenance Costs Cost of curtailed wind energy and losses Total Cost Optimal network

9. Scope of cost-benefit analysis Offshore networks –Switchgear reliability, installation cost, platform cost, ratings, maintenance requirements –Cable reliability, installation cost, maintenance requirements, ratings, electrical parameters Transmission mode (AC vs DC) –Compensation requirements –Losses Windfarms –Wind resource characteristics –Typical turbine ratings, availability, cost –Windfarm size –Windfarm distances from shore Future value of energy and ROCs Impact on onshore system operation –Additional reserve costs

10. Examples of single AC connections 132 kV 33 kV Onshore network 132 kV 220kV 33 kV 220 kV Onshore network Windfarm electrical system Shoreline

11. Example of a shared AC connections 132 kV 33 kV 400 kV 132 kV Onshore transmission network 400 kV 132 kV 33 kV 132 kV 33 kV

12. 132 kV 33 kV 400 kV 132 kV On-shore transmission network 400 kV 132 kV 33 kV 132 kV 33 kV AC DC DC AC 275 or 400 kV Example of a shared DC connection

13. Progress and key results Methodology for the evaluation of cost and reliability performance of alternative offshore transmission configurations has been developed Key differences between offshore and onshore networks –Significantly higher capex requirements –Technology constraints –Wind generation operates at lower load factors than conventional plant Analysis of a range of connection types suggests that generally lower levels of redundancy can be justified for offshore transmission networks when compared with onshore transmission networks –Justifiable levels of redundancy will be influenced by the size of the wind farm and its distance from shore –Initial analysis suggests significant benefits in providing flexibility at the platform and interconnections between offshore platforms in close proximity

14. Illustrative results Numerical values shown are indicative ONLY. Studies are NOT complete and key assumptions and electrical, reliability and cost data need validation. Comprehensive sensitivity studies are yet to be carried out Wind farm size (MW) 150 300 450 Distance to shore (km) 1050 600 One circuit Two circuits Three circuits

15. Numerical values are indicative ONLY Proposed Table form of SQSS for Offshore Networks/1 Distance from Shore: 10 km Wind Farm Capacity Network Capability to be Restored Range of Power Available Network Capacity Following First Circuit Outage Available Network Capacity Following Second Circuit Outage Up to 150MW 0NIL Between 150MW and 300MW X1NIL Between 300MW and 450MW Y1Z1 Above 450MWU1V1

16. Numerical values are indicative ONLY Proposed Table form of SQSS for Offshore Networks/2 Distance from Shore 50kM Wind Farm Capacity Network Capability to be Restored Range of Power Available Network Capacity Following First Circuit Outage Available Network Capacity Following Second Circuit Outage Up to 300MW 0NIL Between 300MW and 450MW X1NIL Between 450MW and 800MW Y1Z1 Above 800MWU1V1

17. Work plan

18. Work plan and key dates Further develop the cost-benefit evaluation models (by 14 August) –Take account of the impact of losses –Quantify the impact of diversity in the windfarm output –Take account of the impact of reactive power effects –Develop models further and carry out sensitivity analysis Carry out cost-benefit studies and propose Draft Tables and Processes for forming SQSS for offshore transmission networks for review by the sub-group (by 24 August) Submit draft SQSS Generation Connection Criteria for offshore transmission networks to OTEG for consideration (31 August) Carry out detailed sensitivity analysis. Re-assess and refine draft SQSS Generation Connection Criteria for offshore transmission networks (30 September) Proposed workplan discussed at subgroup meeting on 28/07/06

19. Data Availability and Transparency

20. Data availability The study work is conditional on receipt of all data from suppliers and developers The sub-group has defined the data requirements and highlighted the data that has not yet been provided There is risk that the timescales in the work plan will not be met if this data required is not provided –The current work plan is contingent on all data being provided by 14 th August.

21. Transparency of data All results of the cost-benefits evaluations should be re-producible All data used in the analysis should be visible Some of the cost information and wind data is only being provided to the DTI Centre for Distributed Generation and Sustainable Electrical Energy (under confidentiality agreements). –It is hoped that suitable anonymous, generic, representative data can be produced from project specific data Concern is that the sub-group may not be able to make a recommendation based on the results of the analysis work if the input data was not available to them.

22. Other Issues

23. Other issues Offshore TO/DNO/GBSO Interface –Sub-group is concerned by the possible implications on the security of an offshore transmission network connected to the onshore transmission network via a distribution network. –Particular concern relates to differences between the design standards applicable to transmission and distribution networks. –Sub-group will investigate and provide feedback to OTEG HVDC –Sub-group is considering DC connection options as part of the cost benefit analysis work Paralleling main onshore GB transmission network through offshore transmission network –The subgroup is un-aware of any proposed windfarm connection that will parallel any nodes of the GB transmission system. Islands –National Grid currently developing Commercial Charging arrangements for Islands connections. Sub group work to concentrate on establishing optimum offshore network technical solution with any commercial arrangements to follow.