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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)
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Towards a Framework for Managing Active Networksbased 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
165,000 km network 14.6 GW demand 7.7m customers b LE Group UK Networks Branch
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 Regulation Example - 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.) AVC / LDC 33/11kV P-Q P+Q AG
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 = sustained fault current 33/11kV I’ = transient fault current I’’ = subtransient fault current IM = induction motor AG = asynchronous generator 3 å (I+I’+I’’) I ’’ 1 SG = synchronous generator 1 IM X X I +I ’+I ’’ I ’’ 3 3 3 2 AG SG
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
Transmission network connected generators • high fault levels • high inertia • high-speed protection high transient stability • Distribution network connected generators • low fault levels • low inertia • slow-speed protection low transient stability Transient Stability
Transient Stability Case study: 5MW 11kV generator - pole slip initiated by voltage dip Current Angle Voltage 120 12000 Pole Slip 10000 60 8000 Network Fault Source Trip RMS Voltage Phase Angle (+Lead - Lag) 6000 0 4000 Generator Trip 2000 -60 0 -500 0 500 1000 1500 2000 Time from network fault ms
Transient Stability • 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
Commercial Aspects • Connection / Use of System charges for distributed generators • Contracts for distribution network support services • voltage support • security support • constraining-on contracts
Deep Shallowish Shallow 33/11kV 33/11kV 33/11kV x x x 11kV 11kV 11kV x x x LV/11kV LV/11kV LV/11kV Connection Charges
x SG Contractual Framework • Voltage / Capacity / Security support • N-1 conditions • peak demand support • may obviate need for network reinforcement 33/11kV
Regulatory Aspects UK regulatory model WACC Regulatory Opening x Return Value Asset + + Value Allowed Operating Investment Revenue Costs + - Depreciation Depreciation
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
KINGS LYNN SOUTH HEMPTON SALL KINGS WALPOLE LYNN PETERBOROUGH EAST PETERBOROUGH EARLHAM KINGS LYNN NORWICH BRETTON POWER STATION POWER STATION WALSOKEN THORPE TO STAMFORD SWAFFHAM PETERBOROUGH GT.YARMOUTH NORWICH TROWSE NORTH GT.YARMOUTH WEST PETERBOROUGH power stn. CENTRAL MARCH NORWICH GORLESTON MAIN MARCH LOWESTOFT ILKETSHALL RUMBURGH DISS THETFORD HALESWORTH HUNTINGDON BURWELL BURY ST EDMUNDS HISTON SIZEWELL EATON WICKHAM SOCON MARKET MILTON R.A.E. LT BARFORD A.R.A. TO GRENDON STOWMARKET FULBOURN EDISON BRAMFORD BEDFORD ROAD BELCHAMP IPSWICH AUSTIN CANONS MELBOURN LETCHW'TH CLIFF QUAY THAXTED WYMONDLEY LAWFORD SUNDON UGLEY LUTON N PELHAM COLCHESTER BRAINTREE HOUGHTON BISHOP'S STORTFORD LUTON S ABBERTON REGIS STEVENAGE CLACTON OP. AYLESBURY EAST AT 33kV CHELMSFORD HARLOW RYE ILMER WEST WELWYN HOUSE NORTH CELL BRADWELL HATFIELD BARNES PICOTTS END EPPING GRID MALDON CHELMSFORD EAST 12 0 MW/km2 Power Zones 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