linepack ‘park and loan’ quantity - influencing factors

Linepack ‘Park and Loan’ Quantity - Influencing Factors

Review Group 291 – July 2010

Summary

Pre-assessment of available quantity for park and loan is complex.

Competing needs for flexibility and contingency impact on the

operating range of linepack.

This motivates discretionary release, with appropriate incentive.

Operational Range of Linepack Flexibility

Maximum operating pressures

Contractually agreed pressures

Linepack

Flexibility

day

Demand / supply pattern

Flexibility + contingency

NTS set-up

System Flexibility

NTS has historically been built to transport gas efficiently, based on flat

supply and demand, within a range of operating pressures.

System flexibility is inherently a “by-product” of operating the NTS within a

range of pressure limits.

Current “limits” of flexibility entirely dependent on the daily NTS setup and

the supply/demand pattern and therefore quite complex to define and model

outer-boundary and maxima of available flexibility.

National Grid is incentivised to minimise day-on-day linepack changes but

has no incentive on within-day linepack ‘release’ or ‘use’

Flow Pattern Volatility – “Time of flight”

The ability to profile energy within day across a number of entry/exit points

whilst maintaining an energy balance in aggregate across the day.

Supply patterns responding to demand and market changes.

Plant issues and Portfolio balancing.

Price-responsive supplies and demands.

Supply A

Offtake

Supply B

200km50km

Flows from Supply A switch to Supply B. Linepack levels at Offtake will drop due to the inherent lag of flow from Supply B taking time to reach the Offtake

Single Entry/Exit Point Flexibility

The ability to profile an entry or exit flow above and below a flat rate.

DN offtake profiles.

Power station changes driven by electricity market interaction.

Storage and interconnector within-day switching.

Within-day entry flow fluctuations driven by demand changes and nomination changes.

Flo

w

Time

Removing Linepack from

NTS

Replenishing Linepack to

NTS

Average flow (1/24th rate)

Example: DN Offtake Flows vary within day due to domestic demand

(2) NTS Flow, Pressure & Flexibility

Time

Flo

w

Average flow (1/24th rate)

Pre

ssur

e

Time

Max Daily Pressure

Min Daily Pressure

22:0006:00Start of Day

06:00

Minimum pressure at point where depletion of

linepack ceases

Flow profile varying about the

1/24th rate

Finite limit of flexibility linked to compression/ flow rates required to return to start of day

pressure

Increases the severity of NTS pressure drop

Increasing Linepack

Usage

Replenishing Linepack to

NTS

Removing Linepack from

NTS DN Offtake

Example Day – 9th January (Actual Data)

Within day linepack movement - 9th January 2010

330

335

340

345

350

355

360

06:00

08:00

10:00

12:00

14:00

16:00

18:00

20:00

22:00

00:00

02:00

GM

T

04:00

06:00

mcm




Linepack

Flexibility

Compressor trip risk

day




Linepack

Flexibility

Within-day exit flexibility


day




Linepack

Flexibility



Within day entry flexibility

day

Within-day Linepack Utilisation

Within-day Max-Min Range of NTS Linepack

0

5

10

15

20

25

30

01

/10

/08

01

/11

/08

01

/12

/08

01

/01

/09

01

/02

/09

01

/03

/09

01

/04

/09

01

/05

/09

01

/06

/09

01

/07

/09

01

/08

/09

01

/09

/09

01

/10

/09

01

/11

/09

01

/12

/09

01

/01

/10

01

/02

/10

01

/03

/10

Date

MC

M

30 day rolling average




Linepack

Flexibility




day

Information uncertainty,EOD imbalance

Day-to-day linepack change

Closing Linepack minus Opening Linepack, 01-Apr-08 to 06-Jun-10

-12

-9

-6

-3

0

3

6

9

12

01/0

4/20

08

01/0

6/20

08

01/0

8/20

08

01/1

0/20

08

01/1

2/20

08

01/0

2/20

09

01/0

4/20

09

01/0

6/20

09

01/0

8/20

09

01/1

0/20

09

01/1

2/20

09

01/0

2/20

10

01/0

4/20

10

01/0

6/20

10

mcm

Within-day PCLP swings

Predicted Closing Linepack (PCLP)Daily Range of Hourly PCLP: Monthly Maximum and Average

0

10

20

30

40

50

60

70

80

Apr

-06

Jun-

06

Aug

-06

Oct

-06

Dec

-06

Feb

-07

Apr

-07

Jun-

07

Aug

-07

Oct

-07

Dec

-07

Feb

-08

Apr

-08

Jun-

08

Aug

-08

Oct

-08

Dec

-08

Feb

-09

Apr

-09

Jun-

09

Aug

-09

Oct

-09

Dec

-09

Feb

-10

Apr

-10

mcm

monthly maximum monthly average

PCLP = Opening linepack+ System Inputs (Daily Flow Nominations and Storage Flow Nominations)– System Demand (Offtake Profile Notifications)

This graph shows ranges of hourly PCLP values during the gas day.




Linepack

Flexibility




day


Supply loss risk

Example Day – 4th January (Supply Loss)


315

320

325

330

335

340

345

350

06:0

008

:00

10:0

012

:00

14:0

016

:00

18:0

020

:00

22:0

000

:00

02:0

0 GM

T04

:00

06:0

0

mcm

4th January - Continued


315

320

325

330

335

340

345

350

06:00

08:00

10:00

12:00

14:00

16:00

18:00

20:00

22:00

00:00

02:00

GM

T

04:00

06:00

mcm

Actual Linepack Linepack based on a Average profile

Within-day entry flexibility




Linepack

Flexibility



Inter-Day Linepack ‘park and loan’

day


Supply loss risk

Release volume

Competing requirements for flexibility and contingency, and varying

conditions day to day, determines the release will be discretionary if

the quantity is to be maximised.

The risks and rewards inherent in linepack release leads to an

incentivised regime.

linepack ‘park and loan’ quantity - influencing factors

Documents