200506 Safety Monitors

1
2005/06 Safety Monitors

• Presentation to Gas Transmission Workstream,
• 5 January 2006

2
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

3
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

4
GS(M)R Safety Monitors

• The GS(M)R Safety monitor arrangements form part
  of National Grids 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

5
Safety Monitors methodology
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

• 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
• gt5860 MWh NDM
• 2196-5860 MWh NDM
• 732-2196 MWh NDM
• 73-732 MWh NDM
• 0-73 MWh NDM

6
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

7
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)

8

• Supply / demand component loads protected by
  monitor

9
1 in 50 Firm load
Baseload supplies underpins storage requirements
(96 of supply)
10
1 in 50 demands by load type
11
1 in 50 load protected by isolation
Isolation 1300 GWh (120 mcm/d)
Monitor (Supply / Demand)
12
1 in 50 load protected by monitor
13
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

14

• Non - supply / demand component load protected
  by isolation

15
Safety Monitors Protected by Isolation
16
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

17
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

18

• Monitor profiles

19
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 (CWVs)
• Latest dates in a winter when such temperatures
  could occur

20
Day Number / Temperature Relationship
Long isolation
Long supply / demand
21
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

22
Latest occurrence of cold (isolation)
23
Long safety monitor profile
Monitor
Isolation