Towards a Framework for Managing Active Networks based on paper TFS_Openshaw_B1

1Dave Openshaw UK Alpha 4 – Block 2

Barcelona 12-15 May 2003

Towards a Framework for Managing Active Networks

based on paper TFS_Openshaw_B1



UK Overview

• Kyoto Protocol targets for UK– 10% renewables generation by 2010 (currently 3%)

– plus 10GW CHP by 2010 (current level - 4.8GWe)

– (UK demand - winter max 50GW / summer min 20GW)

• UK Government Energy White Paper– recommends doubling of these targets by 2020

– most of this generation will be embedded within UK distribution networks



LE Group UK Networks Branch165,000 km network14.6 GW demand7.7m customers

b



Three Important Areas

• Technical

• Commercial

• Regulatory



Technical Aspects

• Key challenges for Network Operators– Voltage regulation and management– Fault levels– Transient stability

• Probable impact of these factors– Network design / operational policy changes – Capital investment



Voltage RegulationExample - 33kV rural network East England



Voltage Regulation

• Generator connected to weak 11kV rural network– Simple line drop compensation unable to compensate for

voltage rise at remote connected generator (typically operating at unity p.f.)

33/11kV

AVC / LDC

AG

P+QP-Q



Voltage Regulation

• Possible solutions:– curtailment (no. generators / size / output)– reinforce network– in-line voltage regulators– reactive power import / compensation– co-ordinated voltage control

• real-time measurement

• state estimation



Fault Level Contribution

(I+I’+I’’)

SGAG

I3+I3’+I3’’I2’’

I = sustained fault current

I’ = transient fault current

I’’ = subtransient fault current

33/11kV

IMI1’’

X

IM = induction motor

AG = asynchronous generator

SG = synchronous generator

X

3

1



Fault Level Contribution

• Possible Solutions:– reinforce network (higher switchgear ratings)– series reactors– run with open bus-sections - in conjunction with

auto-close scheme

– super-conducting fault current limiters– a.c. / d.c. / a.c. interface - e.g. voltage-sourced

converter



Transient StabilityTransmission network connected generators

– high fault levels

– high inertia

– high-speed protection

high transient stability

low transient stability

Distribution network connected generators

– low fault levels

– low inertia

– slow-speed protection



Transient Stability

-60

0

60

120

-500 0 500 1000 1500 2000Time from network fault ms

0

2000

4000

6000

8000

10000

12000

RM

S V

olta

ge

Current Angle Voltage

Po

le S

lip

So

urc

e T

rip

Ne

two

rk F

au

lt

Ph

ase

An

gle

(+Le

ad

- L

ag)

Ge

ne

rato

r T

rip

Case study: 5MW 11kV generator - pole slip initiated by voltage dip



• Possible Solutions:– reinforce network (higher fault ratings)– faster / unit protection

• Secondary benefits of higher fault levels– improved power quality• reduced voltage step effects

• better protection co-ordination

Transient Stability



Commercial Aspects

• Connection / Use of System charges for distributed generators

• Contracts for distribution network support services– voltage support– security support– constraining-on contracts



Connection Charges

Shallowish

x

x

33/11kV

LV/11kV

Shallow

x

x

33/11kV

11kV

LV/11kV

11kV

Deep

x

x

33/11kV

11kV

LV/11kV



Contractual Framework

• Voltage / Capacity / Security support

– N-1 conditions– peak demand support– may obviate need for network reinforcement

SG

x

33/11kV



Regulatory Aspects

+

+ +

x OpeningValue

-

Investment

DepreciationDepreciation

AssetValue

WACC

RegulatoryReturn

OperatingCosts

AllowedRevenue

UK regulatory model



Regulatory Aspects

• Network Operator requirements (options)– Generator Use-of-System charges

– Protection from stranded costs

– Higher risk rates of return

– Appropriate depreciation periods

– Fully expensed provisions

– Protection of Regulatory Asset Base



Power Zones

CLACTON

SIZEWELL

CLIFFQUAY

IPSWICHBRAMFORD

STOWMARKET

WICKHAMMARKET

ABBERTON

LAWFORDCOLCHESTER

BURYST EDMUNDS

BELCHAMP

THETFORD DISSHALESWORTH

BRADWELLCHELMSFORD

NORTH

BRAINTREE

THAXTED

UGLEYPELHAM

SALL

GT.YARMOUTH

GORLESTON

LOWESTOFT

EARLHAMNORWICHTHORPENORWICH TROWSE

NORWICHMAIN

LYNN

WALSOKEN

HUNTINGDON

WALPOLE

MARCH

KINGS

HEMPTON

SWAFFHAM

HISTON

FULBOURNLT BARFORDR.A.E.

A.R.A.

EDISONROADBEDFORDAUSTIN CANONS MELBOURN

BISHOP'S STORTFORDSTEVENAGE

LUTON S

LUTON NSUNDON

HOUGHTONREGIS

AYLESBURY EASTILMER

BURWELL

CELLBARNES

HATFIELD

WELWYN

PICOTTS END

RYEHOUSE WEST

HARLOW

EPPING GRID CHELMSFORD EAST MALDON

EATONSOCON

MILTON

KINGS LYNNSOUTH

PETERBOROUGH

PETERBOROUGHCENTRAL

NORTH

BRETTONPETERBOROUGH

PETERBOROUGHPOWER STATION

EAST

MARCHWEST

WYMONDLEY

LETCHW'TH

KINGS LYNNPOWER STATION

ILKETSHALL

OP.AT 33kV

GT.YARMOUTHpower stn.

RUMBURGH

TO GRENDON

TO STAMFORD

0 MW/km2 12

Proposed offshore wind farm - 100MW

Proposed offshore wind farm - 70MW



Conclusion

• Active Networks will require– more sophisticated voltage management– faster / co-ordinated protection systems– some investment in reinforcement

• Network Operators will require– new commercial contracts with generators– Regulatory incentives and/or protection– Power Zone concept

Towards a Framework for Managing Active Networks based on paper TFS_Openshaw_B1

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