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The UNC Transmission Workgroup has analyzed the estimated release volume for park and loan services as of February 11, 2011. The National Grid will decide both the volume released and the timing, with a potential range between 2 and 10 mcm. It is estimated that release will occur on 60% to 80% of days, typically within 2 to 6 mcm. While uncertainty exists early in the gas day, it decreases later, allowing for greater operational stability, particularly in closing linepack (CLP) targets, which in 2010 averaged a difference of 2.0 mcm.
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Linepack ‘Park and Loan’ - Estimated Volume UNC Transmission Workgroup, 11 February 2011
Estimated release volume • We previously indicated: • Decision to release and volume released at discretion of National Grid. • Potential range of park and loan between 2 and 10mcm. • After further analysis we now estimate: • Release park and/or loan on 60% to 80% of days. • Most often net volume of release between 2mcmand 6mcm.
Estimated Release Volume (2) • More uncertainty at early release times. • More certainty later in gas day, but limited time for physical rate increase/decrease. • Likely to release both park and loan at same time, depending on operational conditions. • Minority of days with zero release - for example following recent supply loss, and uncertainty over subsequent reliability of this supply.
Uncertainty of physical imbalance • Uncertainty reduces during the gas day. • Current incentive to ensure closing linepack (CLP) is close to opening linepack (OLP), whilst minimising effect on market. Target change = 2.8mcm. • In 2010, achieved average difference of 2.0mcm. • Projected closing linepack (PCLP) is increasingly accurate during gas day, demonstrating increasing certainty of physical imbalance. • Of course late changes can occur. • The following graphs illustrate this.
