UNC Modification 0050 – Storage Monitor Adjustment

Purpose of Modification Proposal

Proposal raised to resolve potential discrepancy between obligations placed on Transco NTS by GS(M)R to review & amend the Safety Monitor when necessary, and its rights under the UNC to do so.

UNC Rights & Obligations

By 1 October Transco NTS is required to notify Users of the Safety Monitor and Firm Gas Monitor for each day in the coming Winter Period.

Paragraph 5.2.5 of UNC Section Q requires Transco NTS to keep under review information previously notified to the Users.

Under certain circumstances the UNC allows aggregate levels of Monitors to be changed;

reallocate the Safety Monitor and/or the Firm Gas Monitor between Storage Facility Types in order to enhance the security provided by current storage stocks;

reduce a Safety Monitor and/or a Firm Gas Monitor to reflect longer-term demand forecasts (for example, during the later Days of the Winter Period); and

adjust a Safety Monitor and/or a Firm Gas Monitor to reflect the occurrence of severe weather.

Increasing the aggregate level of the monitors is currently not an available option.

GS(M)R Obligations

GS(M)R regulations require that no person shall convey gas in a network unless; he has prepared a safety case … and, where any other person is conveying gas in that network, there is a sole

Network Emergency Coordinator (NEC) for the network. The NEC is responsible for coordinating actions across the affected parts of

the network to take action to prevent as far as possible, a supply emergency developing, …

The safe operation of all end-users in a 1:50 severe winter is achieved by protecting gas consumers by allocating them to either a protected by isolation or a protected by monitor category. The primary transporter will determine the arrangements and the classification of all end users into each category.

The NEC safety case states that all conveyers are required to demonstrate the arrangements they have put in place to minimise the risk of a supply emergency occurring.

Safety Monitors are a requirement of Transco’s safety case providing a trigger mechanism for taking direct action to avoid a gas supply emergency.

GS(M)R Obligations (cont..)

If Monitor Levels are breached or are set at too low a level there will be insufficient gas in storage to underpin the safe operation of the system in a 1 in 50 winter. It is therefore imperative that the Safety Monitors are set at the correct level and reviewed regularly.

Transco NTS are therefore obliged to review and amend the levels of the safety monitors in light of any changes to the information available to them in respect of inputs to or offtakes from the total system.

Current UNC Code

“5.2.5

Transco NTS will keep under review the information previously notified pursuant to paragraphs 5.2.1, 5.2.2 and/or 5.2.3, and may:

a) reallocate the Safety Monitor and/or the Firm Gas Monitor between Storage Facility Types in order to enhance the security provided by current storage stocks;

b) reduce a Safety Monitor and/or a Firm Gas Monitor to reflect longer-term demand forecasts (for example, during the later Days of the Winter Period);and

c) adjust a Safety Monitor and/or a Firm Gas Monitor to reflect the occurrence of severe weather.

Proposed UNC Code Change

“5.2.5

Transco NTS will keep under review the information previously notified pursuant to paragraphs 5.2.1, 5.2.2 and/or 5.2.3, together with any information available to Transco NTS in respect of its estimates of expected deliveries to or offtakes from the Total System, and may:

a) reallocate the Safety Monitor and/or the Firm Gas Monitor between Storage Facility Types in order to enhance the security provided by current storage stocks;

b) reduce a Safety Monitor and/or a Firm Gas Monitor to reflect longer-term demand forecasts (for example, during the later Days of the Winter Period); and

c) adjust a Safety Monitor and/or a Firm Gas Monitor to reflect the occurrence of severe weather; and

d) increase or reduce (as the case may be) a Safety Monitor and/or a Firm Gas Monitor to reflect any change in Transco NTS’s estimates of expected deliveries to or offtakes from the Total System.”