Network gas supply emergencies (NGSE)
A network gas supply emergency (NGSE) may be caused by unforeseen circumstances, such as pipeline or equipment failure, or where system demand exceeds either total supply or planned system capacity. On this page you will find more about our emergency arrangements and the processes relating to emergency curtailment quantities (ECQ), storage curtailment compensation arrangements, and post-emergency claims.
Exercise Zeus (2018)
Exercise Zeus took place on Wednesday 3rd and Thursday 4th October 2018.
Exercise Zeus was the NEC industry exercise for 2018 and took place Wednesday 3rd and Thursday 4th October, during normal business hours.
The NEC Post Exercise Report is currently being authored, expected for publication in January 2019 following review by the HSE.
Should you have any queries or feedback regarding any aspect of Exercise Zeus, please get in touch with the Gas Emergency and Incident Framework Team.
To subscribe to updates on the NEC and emergency exercises click the link below (Note: The NEC Mailing list is not the route for receiving operational communications).
Exercise Yield (2017)
Exercise Yield took place on Wednesday 4th and Thursday 5th October 2017.
The post exercise report has now been published.
Should you have any queries or require further information regarding any aspect of Exercise Yeild, please get in touch with the Gas Emergency Planning Team.
Under normal operating conditions supplies of gas entering the National Transmission System (NTS) are matched to the demand for gas leaving the system and pressures within the system remain within an acceptable range.
As operator of the NTS, we are responsible for ensuring that a supply – demand balance on the NTS is achieved. We have a range of system balancing tools to match supply and demand.
A network gas supply emergency (NGSE) occurs when we are unable to maintain a supply – demand balance on the NTS using our normal system balancing tools. As a consequence of the imbalance between supply and demand, pressures in the system fall and it may not be possible to safely maintain gas supplies to industrial and domestic gas consumers who are supplied with gas either directly or indirectly from the NTS.
A NGSE could be caused by a major loss of supplies to the system as a result of the failure of a gas terminal or as the result of damage to an NTS pipeline affecting the ability of the system to transport gas to consumers.
If we were unable to maintain a supply – demand balance on the NTS using our normal system balancing tools, we would request the network emergency coordinator (NEC) to declare a NGSE.
The declaration of a NGSE would provide us with access to additional balancing tools for use in restoring a supply – demand balance. These emergency tools include requesting additional gas supplies be delivered to the NTS, or requiring gas consumers, starting with the largest industrial consumers, to stop using gas. These tools will be used, under the authorisation of the NEC, to try to maintain supplies to domestic gas consumers as long as possible.
The cooperation of gas industry participants, including gas terminal operators, gas shipping companies, gas transportation companies and large industrial consumers, is required to successfully implement the emergency system balancing actions. Sufficient emergency balancing actions will be undertaken to restore a supply-demand balance on the NTS and minimise the safety consequences of the emergency to gas consumers.
Once a supply – demand balance has been achieved and the safe operation of the system ensured, supplies will be restored to consumers a soon as practicable. Once supplies have been restored to all consumers who are supplied with gas directly from the NTS, the end of the NGSE will be declared by the NEC.
You can find a more detailed breakdown of the process in the Procedure for Network Gas Supply Emergency (T/PM/E/1) document.
There has, to date, never been a network gas supply emergency.
The NEC is responsible for coordinating actions to prevent a supply emergency developing or, where it cannot be prevented, to take timely decisions in order to minimise safety consequences.
There is a legal requirement for there to be an NEC when there is more than one gas transportation company operating on the UK gas network.
The NEC is responsible for coordinating actions across the affected parts of the gas network to take action to prevent, as far as possible, a supply emergency developing, and where it cannot be prevented, to take timely decisions in order to minimise the safety consequences. A 'supply emergency' is defined as an emergency endangering persons and arising from a loss of pressure in a network or any part thereof.
The NEC is independent from any commercial interests of gas industry participants. We currently undertake the role of NEC.
Industry participants such as gas transportation and gas shipping companies have a legal duty to cooperate with the NEC.
The NEC has established support arrangements to assist in discharging its legal duties. Support to the NEC is provided by the National Grid Emergency Planning Team. This support includes organising periodic industry wide emergency exercises to measure the effectiveness of industry’s response to a gas supply emergency.
The NEC is responsible for declaring a network gas supply emergency and for authorising the use of emergency balancing tools to restore a supply - demand balance on the National Transmission System.
The Procedure for Network Gas Supply Emergency (T/PM/E/1) document is produced on behalf of the NEC and made available to all industry participants. It describes the types of NGSE that could be declared by the NEC, the emergency actions that may be authorised, and the communication routes to be used during the emergency.
Interruptions to supplies
This section provides information for industrial users regarding potential reasons for interruptions to supply.
There are no longer any interruptible sites connected to the National Transmission System (NTS), the high-pressure gas transportation system that provides supplies to the distribution networks and a number of very large industrial consumers. From October 2012 new industry arrangements deem all sites as firm.
Industrial consumers may choose to use firm or off-peak capacity products. For further information on how these products may be affected by localised system constraints, please refer to the Constraint management page.
The network emergency coordinator (NEC) is appointed to be an independent body whose responsibility in a major gas supply emergency affecting the NTS is to coordinate actions across the affected parts of the network to minimise the safety consequences of the emergency.
Firm load shedding is the procedure used by transporters to secure a graduated and controlled reduction in demand on all or part of their systems in order to keep the system safely pressurised.
During an emergency, industrial consumers using firm capacity may be contacted by their transporter and requested to stop using gas. Consumers using the off peak capacity product can expect their off peak capacity entitlement to be scaled back prior to the declaration of the emergency.
An emergency may be caused by unforeseen circumstances such as pipeline or equipment failure, or where system demand exceeds either total supply or planned system capacity.
Minimising the safety impacts of emergencies requires the cooperation of everyone. All industrial consumers must be able to stop using gas following a direction notice from their transporter, safely and as quickly as practical. It is a criminal offence to knowingly fail to comply with a direction notice.
The Government has defined a number of categories for priority industrial consumers. Gas supply to these consumers will be maintained until operating conditions require the site to stop using gas to protect gas supplies to domestic consumers. There are currently three categories of priority industrial consumer:
Consumers (using more than 25,000 therms per annum, 732 megawatt hours) on firm supply contracts, where a failure in the supply to their premises could put lives at risk. Examples of such consumers would be hospitals or homes for the elderly and disabled.
Distribution network consumers who would otherwise fall into category "A" but are deemed as interruptible supplies.
Consumers operating major items of capital plant, which require time to be safely shut down and would sustain serious damage (£50 million or more) if gas supplies ceased suddenly. Examples of such consumers would be furnaces and glass works.
If you feel your industrial premises should be classified as a priority consumer please contact your gas supplier in the first instance.
This section provides a brief outline of NEC forms and declarations sent to industry in the event of an NGSE being declared.
NEC Declaration or industry update form: This proforma is issued by the NEC to the industry providing the NEC Declaration of the NGSE or update of the emergency stage, this proforma is used for all emergency classifications (gas deficit emergency/critical transportation constraint and safety monitor breach). This is a two-page proforma that includes the NEC, NEMT and connected transporter contact details for industry use during a NGSE.
NEC Declaration of end of NGSE Form: This proforma is issued by the NEC to the industry providing the NEC Declaration of the end of a NGSE for all emergency classifications (gas deficit emergency/critical transportation constraint and safety monitor breach).
Distribution networks and interconnector forms
Please contact the Emergency Planning Team to discuss any of the following.
Distribution network forms
- NETMAN1 and Minimal Critical Offtake Pressure Form
- Distribution Network Demand Reduction Form
- Distribution Network Additional Gas Requirements Form
- Distribution Network Situation Report Form
- GS(M)R Schedule 3 Part 2 Gas - Information Form
- GS(M)R Schedule 3 Part 2 Gas - Authorisation Form
- GS(M)R Schedule 3 Part 2 Gas - Withdrawal Form
- GS(M)R Schedule 3 Part 2 Gas – Revocation Form
- GNI Demand Breakdown Request Form
- GNI Demand Reduction Notification Form
- GNI Notice of Revocation Form
- I(UK) Demand Reduction Notification Form
- I(UK) Notice of Revocation Form
These are the storage forms to be used in an emergency.
Storage information request form: A request for storage information to the Storage Operators to determine the available supply to meet demand.
Storage injection notification form: A direction to affected storage operators to amend their storage injection flows due to a breach in the safety monitor. Issued in emergency stage 1/2/3/4 of a safety monitor breach emergency. (Injection)
Storage withdrawal curtailment notification form: A direction to affected storage operators to curtail or amend their storage withdrawal flows due to a breach in the safety monitor. Issued in emergency stage 1 of a safety monitor breach emergency. (Withdrawal)
These are the shipper forms to be used in an emergency, including NTS directly connected sites.
Oil and Gas Authority (OGA) gas availability status (G.A.S.) report: A gas availability status report from the UK offshore supply sector over the next 48 hours to determine the available supply to meet demand.
Terminal/LNG flow direction notification form: A direction for amended supply into the NTS for use in emergency stage 2/3/4 of a gas deficit emergency to terminal/LNG operators.
GS(M)R direction notice to NTS directly connected sites (Shipper): Information to shippers informing that GS(M)R direction notices have been issued to NTS directly connected sites to reduce/stop using gas.
GS(M)R revocation notice to NTS directly connected sites (Shipper): Information to shippers informing that GS(M)R direction notices have been issued to NTS directly connected sites to resume using gas.
Market actions (ICE ENDEX forms)
ENDEX suspend National Grid market actions: A proforma to the On the Day Commodity Market (OCM) facilitator to suspend National Grid's participation in the OCM at stage 2 of a gas deficit emergency.
ENDEX reinstate National Grid market actions: A proforma to the On the Day Commodity Market (OCM) facilitator to reinstate National Grid's participation in the OCM at the end of a gas deficit emergency.
Emergency curtailment quantity (ECQ)
The emergency curtailment quantity (ECQ) process relates only to sites (system exit points) curtailed as part of a gas deficit emergency. The ECQ process assigns the quantities of gas associated with emergency curtailment actions undertaken by transporters as a trade nomination between National Grid NTS, as residual system balancer, and each user.
The objective of the ECQ process is to ensure that shippers imbalance positions for the day are unchanged if transporters curtail the offtake of gas at sites as part of a gas deficit emergency.
The calculation of the emergency curtailment quantity (ECQ) is defined within UNC TPD Section Q 6 as "The quantity of gas (in kWh) which the Transporters, in aggregate, reasonably estimate that Users would have offtaken from the Total System at System Exit Points in respect of which Emergency Curtailment has occurred but for the fact that Emergency Curtailment had occurred at those System Exit Points"
For every affected user, the ECQ value is calculated as the aggregate quantity of emergency curtailment which has occurred, less any quantity of user commercial interruption at the relevant sites. See the 'shipper curtailment' information below for further details on commercial interruption.
Details of how ECQ is calculated are contained within the ECQ Methodology which can be found on the Joint Office website.
Post-event information provision
In accordance with UNC, National Grid NTS will notify shippers of the ECQ for each day of curtailment and the proportion of that ECQ which relates to each transporter.
A summary of the process - including communications - can be viewed on the high level overview process flow document. The NTS report is referred to as the 'transporter ECQ report' on the ECQ high level overview document.
Download the Emergency Curtailment High Level Overview document
In addition, where NTS system exit points have been curtailed, National Grid NTS will endeavour to provide relevant users with a site specific report detailing the method used to calculate the ECQ. This is referred to as the 'NTS ECQ report' on the ECQ high level overview.
NTS P70 (curtailment): notify National Grid Transmission of shipper curtailment at directly connected NTS sites.
NTS P71 (restoration): notify National Grid Transmission of shipper restoration at directly connected NTS sites.
DNO P70 (curtailment): notify distribution network owner (DNO) of shipper curtailment at directly connected NTS sites.
DNO P71 (restoration): notify distribution network operator (DNO) of shipper restoration at directly connected NTS sites.
P70 and P71 notices and the emergency curtailment calculation: Q: Should I issue a P70 to the appropriate control room for any commercial relationship I enter into that has the direct effect that a site ceases its consumption of gas? A: Yes, the information will assist control room operations and minimise shipper exposure.
Storage curtailment compensation
Details regarding compensation payments to be made in the event of storage curtailment.
You can find details relating to storage curtailment in the Uniform Network Code (UNC) Transportation Principal Document under Section Q.
The storage curtailment compensation arrangements enable users (who tend to be gas shippers) to be financially neutral if a storage curtailment is undertaken by the Network Emergency Coordinator (NEC). A Storage curtailment occurs where there is a reduction or cessation of delivery of gas to the NTS from a storage facility following either a direct or indirect request to do so by the NEC.
Storage connection point (SCP) and storage curtailment compensation quantity (SCCQ) shipper procedure and submission statement can be downloaded below:
SCP and SCCQ shipper procedure: this is a link to the procedure for registered users to submit their storage curtailment statement.
SCP and SCCQ statement: download the spreadsheet here
Post emergency claims (PEC)
Post emergency claims (PEC) can be made relating to additional gas offered to the UK gas system during a gas deficit emergency (GDE). This web page contains details of the post emergency claims process; including PEC user guidelines, the standard claim form and useful information for claimants.
The post emergency claims rules are detailed in UNC Q4.5.
Process and guidelines
The guidelines provide information regarding the processes and procedures that claimants are required to undertake when seeking to submit an eligible PEC. In addition, the process flow diagram identifies the responsibilities of all parties and the flow of information.
Post emergency claims (PEC) user guidelines: Guidelines for use when submitting Post Emergency Claims.
Post emergency claims (PEC) process flow diagram: High-level flow diagram for the PEC process.
Post Emergency Claims Economic Assessment Guidelines (V2): Guidelines for economic price assessment of post-emergency claims.
Supporting information - OCM process
As the OCM physical market is used to submit offers, for completeness we have provided details of physical renomination process for accepted offers and examples.
Renomination example for turndown: this document provides an example of how renominations would work if physical offers for turn down on the OCM were accepted.
Physical renominations example for turnup: This document gives an example of how renominations would work for a turnup if physical offers on the OCM were accepted.
On the Day Commodity market (OCM) physical renominations on Gemini: Presentation for users of Gemini.
Following receipt of PECs, we will use reasonable endeavours to publish information relating to claims here as detailed in the Uniform Network Code. Example templates for the reports are attached below for information. If required, PEC reports will be published here.
Post emergency claim reporting: An example template which provides a guide to the reports which will be published regarding Post Emergency Claims and includes the timescales for publication as defined by UNC.
Gas balancing and useful documents
We must keep the National Transmission System (NTS) within safe operating limits. To find out more about how we balance the NTS please go to the Gas balancing pages.