1. Modification Proposal 0222 - Amendment of IUK’s Minimum Wobbe Limit
Transmission Workstream 4th September 08

2. Background
The Wobbe Index of a unit of gas provides a measure of the energy released during combustion
GS(M)R limits the range of Wobbe Index that National Grid can accept into the NTS to between and MJ/m3 for safety reasons
Site specific limits to Wobbe Index are detailed in Network Exit/Entry Provisions
The Wobbe Limits set out in IUK’s Network Entry & Exit Provisions are more stringent than the GS(M)R limits
IUK have raised concerns that this is constraining the amount of gas that can enter or exit the NTS at the continental interconnector

3. Modification Proposal 0222
Proposal 0222 seeks to lower the minimum Wobbe Limit set out in IUK’s Network Entry & Exit Provisions to the GS(M)R limit of MJ/m3
Benefits:
A wider selection of gas would be available from Europe
Security of supply would be enhanced
Competition between ASEPs would be increased
Analysis shows that CV shrinkage would not be impacted
No UNC text modifications would be required