2005/06 Safety Monitors

Presentation to Gas Transmission Workstream,

5 January 2006

Safety Monitors – background

Define levels of storage that must be maintained through the winter period

Introduced in 2004 to replace ‘Top-up’ ‘Top-up’ focused on maintaining security of supply:

Safety Monitors focus is public safety Requirement of National Grid Gas’ Safety Case

that action is taken to ensure storage stocks do not fall below the Safety Monitor levels - these decay as the winter progress

Gas Safety (Management) Regulations 1996

Requires anyone conveying gas in a network to prepare a Safety Case and for the Safety Case to be accepted by the HSE

The Safety Case must contain particulars which describe arrangements for a number of items listed in Schedule 1

These are high level requirements which must be described in detail in the Safety Case – GS(M)R does not define how a specific requirement is to be met.

The relevant requirement in Schedule 1 is clause 16 16 - Particulars to demonstrate that the duty holder has established

adequate arrangements to minimise the risk of a supply emergency, where a “supply emergency" means an emergency endangering persons and arising from a loss of pressure in a network or any part thereof

GS(M)R Safety Monitors

The GS(M)R Safety monitor arrangements form part of National Grid’s detailed demonstration that it has arrangements in place to minimise the risk of a supply emergency

They address the risk posed by the possibility of insufficient storage being available for a 1 in 50 duration winter

The arrangements have been accepted by the HSE as discharging our responsibility in this area and we have a legal obligation to follow those arrangements

Any change in arrangements would constitute a material change to the Safety Case and National Grid would have to present a case which demonstrated that the new arrangements were at least as safe as the current arrangements

Safety Monitors – methodology

Loads protected by Isolation NTS Interruptibles LDZ Interruptibles NTS Power Firm NTS Industrial Firm DM (excluding priority

customers)

Loads protected by Monitor Priority Firm DM Ireland Firm All NDM

>5860 MWh NDM 2196-5860 MWh NDM 732-2196 MWh NDM 73-732 MWh NDM 0-73 MWh NDM

Concept – sufficient gas held in store to support those customers who can not be physically isolated from the network, requirements include isolation process of large loads All loads categorised into two groups:

Supplies – assumptions (1)

“Baseload” – non storage supplies that are not limited by ‘space’, includes:

Beach Interconnector Grain (LNG Imports)

10 mcm/d supply risk to cover for supply uncertainty, notably import assumptions

Supply (mcm/d) Maximum September Assumptions

December Assumptions

Comments

Beach 327 303 ~303 92.5% max beachGrain 17 13 ~13IC Imports 48 42 ~30 75% new importsSupply Risk -10Baseload Supplies 392 348 348 ~3800 GWh/d

Supplies – assumptions (2)

Storage supplies Long – Rough Medium –

Includes Hornsea and Hatfield Moor deliverabilities only Includes Hornsea, Hatfield Moor, Hole House Farm and Humbly

Grove space (reduced at onset to reflect start-up uncertainty)

Short – 4 LNG storage sites Total storage supply level ~ 110 mcm/d (~1200

GWh) Total storage space ~ 4000 mcm (~ 43,200 GWh)

Supply / demand component – loads protected by monitor

1 in 50 Firm load

3000

3500

4000

4500

5000

5500

6000

6500

1 11 21 31 41 51 61 71 81 91

GW

h

Baseload Long Medium Short 1in 50 F + I 1in 50 F

Baseload supplies underpins

storage requirements (96% of supply)

1 in 50 demands by load type

3000

3500

4000

4500

5000

5500

6000

6500

1 11 21 31 41 51 61 71 81 91

GW

h

NDM DM Firm NTS Firm Interruptible Interconnector

1 in 50 load protected by isolation

3000

3500

4000

4500

5000

5500

6000

6500

1 11 21 31 41 51 61 71 81 91

GW

h

NDM DM Firm NTS Firm Interruptible Interconnector Volume protected by monitor

Isolation ~1300 GWh (120 mcm/d)

Monitor (Supply / Demand)

1 in 50 load protected by monitor

3000

3500

4000

4500

5000

5500

6000

6500

1 11 21 31 41 51 61 71 81 91

Day

GW

h

Baseload Rough MRS LNG Vol protected by monitor Total F + I demand

Supply / demand component

10 mcm/d supply risk included in September analysis to cover for supply uncertainty, notably import assumptions

Supply risk had to be identified at time due to UNC requirements Supply risk located in Long not to unsettle markets & Long considered

lowest risk of monitor breach

(GWh) September Assumptions

Sept with 10 mcm/d

supply risk

Sept with re-allocation of supply risk

December Assumptions

Long 4778 6790 7311 6655

Medium 586 886 586 864

Short 155 376 155 358

Total 5519 8052 8052 7877

Non - supply / demand component – load protected by isolation

Safety Monitors – Protected by Isolation

0

200

400

600

800

1000

1 11 21 31 41 51 61 71Day

GW

h

Long Medium Short

Isolation Component

Supply risk has a lesser impact than in supply / demand Isolation needs established from observed behaviour from winter

exercises (Krakatoa, Moscow) Improved industry response would reduce isolation needs Support for Isolation process is up to 48 hours

All above isolation needs are similar

(GWh) September Assumptions

Sept with 10 mcm/d

supply risk

Sept with re-allocation of supply risk

December Assumptions

Long 910 910 1127 910

Medium 440 440 440 440

Short 459 676 459 651

Total 1809 2026 2026 2001

Total Requirement for December

Final requirement is lower than combined needs of Supply Demand & Isolation due to some reduction for “double counting” i.e. Supply Demand for Day 1 and Isolation for Day 1

(GWh) Supply Demand

Isolation Combined Final Requirement

Final Requirement

Long 6655 910 7565 6987 20.5%

Medium 864 440 1304 1202 16.4%

Short 358 651 1009 700 40.2%

Total 7877 2001 9878 8889 20.6%

Monitor profiles

Monitor Profile Methodology

Storage space and duration requirements are known for all storage types for protected by monitor and protected by isolation

Protected by monitor is a winter long requirement Protected by isolation is a one off requirement Need to develop 2 key relationships:

Demand days and temperatures (CWV’s) Latest dates in a winter when such temperatures could occur

Days on Load Curve

Supply Demand

Isolation

Long 26 62Medium 6 11

Short 2 4

Day Number / Temperature Relationship

Weather Duration Curve

-6

-4

-2

0

2

4

6

8

0 4 9 14 19 24 29 34 39 44 49 54 59 64 69 74 79 84 89 94 99

Day Number

Deg

rees

CW

V

Average

1 in 50

Long isolation

Long supply / demand

Calculation of Profiles

Protected by isolation is a one off requirement Need to identify latest date when isolation could occur A different requirement is calculated for each “Day”

i.e. the Day 1 requirement is much earlier in winter than say Day 62

Protected by monitor is a winter long requirement Need to identify latest requirement Need to identify earlier needs to establish within year

profile – review all previous winters Profiles are then combined

Latest occurrence of cold (isolation)

-6

-5

-4

-3

-2

-1

0

1

2

3

4

01-Nov 01-Dec 01-Jan 01-Feb 01-Mar 01-Apr

De

g C

WV

Cold CWV Coldest since 1928 Cold CWV + 90% diff

Day 11, CWV = -2.16, 23 Feb

Day 4, CWV = -3.46, 16 Feb

Day 62, CWV = 2.23, 3 Apr

Long safety monitor profile

-5

0

5

01/0

1/06

08/0

1/06

15/0

1/06

22/0

1/06

29/0

1/06

05/0

2/06

12/0

2/06

19/0

2/06

26/0

2/06

05/0

3/06

12/0

3/06

19/0

3/06

26/0

3/06

De

gre

es

CW

V

0

1000

2000

3000

4000

5000

6000

7000

8000

GW

h

Long Safety Monitor 1946/47 Long Threshold

Latest date Long threshold tempEarliest date Long

threshold temp

Monitor

Isolation