Gas quality limits in emergency situations
National Grid Gas Transmission
David Lavender, box.GT.firstname.lastname@example.org
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Network Innovation Allowance
Gas Transmission Networks
Previously it was understood that only small volumes of Schedule 3 Part II gas would be available for delivery to the National Transmission System (NTS) and that it would be possible to blend this gas within the NTS before it was delivered to a Distribution
Network (DN) offtake. This would ensure that gas conforming to the expected quality as determined in Schedule 3 Part I of GS(M)R would always be supplied to industrial and domestic consumers.
A number of new NTS system entry points that have been commissioned since GS(M)R came into effect in 1996. These entry points either rely on nitrogen ballasting to control gas quality or could import high calorific value (CV) gas from continental Europe. Thus, there is potential for greater volumes of Schedule 3 Part II gas to be made available for delivery to the NTS if required by the NEC.
This increases the risk that Schedule 3 Part II gas could be supplied to a Distribution Network. Before the NEC could authorise the admission of Part II gas they would require sufficient evidence to show the safety benefits are not compromised by permitting this gas to enter the NTS to avert or minimising the consequences of a network supply emergency.
This research programme forms the basis of the assessment process developed to provide the NEC with the required evidence for them to be able to authorise the admission of greater quantities of Schedule 3 Part II gas into the network in accordance with their statutory responsibilities.
An increased understanding of the potential of effects of wider specifications of gas entering the Transmission System which will improve National Grid’s ability to maintain security of supply.