2005/06 safety monitors
Post on 04-Jan-2016
42 Views
Preview:
DESCRIPTION
TRANSCRIPT
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
top related