Grid Code Frequency Response Working Group System Inertia Antony - PDF document

Grid Code Frequency Response Working Group System Inertia Antony Johnson, System Technical Performance

Overview � Background to System Inertia � Transmission System need � Future Generation Scenarios � Initial Study Work � International Experience and Manufacturer Capability � Transmission System Issues � Conclusions

Frequency Change � Under steady state the mechanical and electrical energy must be balanced � When the electrical load exceeds the mechanical energy supplied, the system frequency will fall. � The rate of change of frequency fall will be dependant upon the initial Power mismatch and System inertia � The speed change will continue until the mechanical power supplied to the transmission system is equal to the electrical demand.

Why is Inertia Important � Inertia is the stored rotating energy in the system � Following a System loss, the higher the System Inertia (assuming no frequency response) the longer it takes to reach a new steady state operating frequency. � Directly connected synchronous generators and Induction Generators will contribute directly to System Inertia. � Modern Generator technologies such as Wind Turbines or wave and tidal generators which decouple the prime mover from the electrical generator will not necessarily contribute directly to System Inertia � Under the NGET Gone Green Scenario, significant volumes of new generation are unlikely to contribute to System Inertia

What is inertia? � The stored energy is proportional to the speed of rotation squared � 3 types of event cause a change in frequency � Loss of generation (generator, importing HVDC link etc) � Loss of load � Normal variations in load and generator output Loss of Generator on the system Frequency Falls as demand > generation Stored energy delivered to grid as MW

The maths behind inertia H = Inertia constant in MWs / MVA H = Inertia constant in MWs / MVA ½J ω 2 ½J ω 2 J = Moment of inertia in kgm 2 of the rotating mass J = Moment of inertia in kgm 2 of the rotating mass H = H = ω = nominal speed of rotation in rad/s ω = nominal speed of rotation in rad/s MVA MVA MVA = MVA rating of the machine MVA = MVA rating of the machine Typical H for a synchronous generator can range from 2 to 9 seconds (MWs/MVA) ∂ f ∂ f ∆ P ∆ P ∂ f/ ∂ t = Rate of change of frequency ∂ f/ ∂ t = Rate of change of frequency = = ∆ P = MW of load or generation lost ∆ P = MW of load or generation lost ∂ t ∂ t 2H 2H 2H = Two times the system inertia in MWs / MVA 2H = Two times the system inertia in MWs / MVA

Strategic Reinforcements An NGET Future Scenario TRANSMISSION SYSTEM REINFORCEMENTS Dounreay Thurso REINFORCED NETWORK Mybster Stornoway Cassley Dunbeath 400kV Substations 275kV Substations Lairg THE SHETLAND ISLANDS 400kV CIRCUITS Brora 275kV CIRCUITS Shin ‘Gone Green 2020’ Mossford Major Generating Sites Including Pumped Storage Grudie Bridge Alness Conon Elgin Fraserburgh Luichart Orrin Connected at 400kV Ardmore Macduff St. Fergus Dingwall Connected at 275kV Deanie Culligran Keith Keith Strichen Aigas Kilmorack Inverness Nairn Hydro Generation Dunvegan Blackhillock Peterhead Beauly Fasnakyle Dyce Glen Kintore Persley Broadford Morrison Woodhill Willowdale Foyers Ceannacroc Boat of Under Construction or ready to start Fort Augustus Garten Clayhills Tarland Craigiebuckler Construction subject to consents Invergarry Redmoss Quoich � Plant closures Fiddes Fort William Errochty Errochty Power Station Very strong need case Rannoch Clunie Bridge of Dun Tummel Lunanhead Bridge Tealing Cashlie Lochay Dudhope Arbroath � 12GW Coal & oil LCPD Lyndhurst Milton of Craigie Taynuilt Killin Finlarig Charleston Cruachan Dalmally Burghmuir GlenagnesDudhope Strong need case Nant Clachan St. Fillans SCOTTISH HYDRO-ELECTRIC Cupar TRANSMISSION Inveraray � 7.5GW nuclear Glenrothes Sloy Leven Devonside Westfield Redhouse Future requirement, but no strong Whistlefield Stirling Kincardine Glenniston Port Mossmorran Ann Longannet Dunfermline need case to commence Bonnybridge Iverkeithing Dunoon Helensburgh Grangemouth Shrubhill Cockenzie Dunbar Some gas & additional coal Spango Devol Strathleven Telford Rd. Gorgie Portobello Torness at present � Valley Moor Erskine Cumbernauld Bathgate Broxburn Whitehouse Inverkip Lambhill Easterhouse Livingston Kaimes Newarthill Currie Clydes Hunterston Neilston Mill Farm Wishaw Berwick Series Capacitors Hunterston Busby Strathaven Kilwinning Whitelee East Blacklaw Saltcoats Town Kilmarnock Kilbride South Linmill Eccles Carradale Meadowhead Kilmarnock Galashiels Coalburn South Ayr SP TRANSMISSION LTD. Coylton Elvanfoot Hawick � Significant new renewable Maybole NGC Blyth Gretna Auchencrosh Dumfries Ecclefechan Fourstones Newton Tynemouth Stewart Harker � Chapelcross Stella South Shields 29 GW wind (2/3 offshore) West West Boldon Glenluce Tongland Offerton Hawthorne Pit Hart Moor Spennymoor Hartlepool � Some tidal, wave, biomass & solar PV Saltholme Tod Point Grangetown Norton Greystones Lackenby Renewable share of generation grows from 5% to 36% � Hutton Heysham Quernmore Poppleton Osbaldwick Bradford Thornton Stanah West Kirkstall Skelton Creyke Beck Padiham Grange Monk Fryston Saltend North � Significant new non renewable build Penwortham Saltend South Elland Drax Killingholme Eggborough Rochdale Ferrybridge Humber Refinery Keadby South Washway Farm Kearsley Whitegate Templeborough West Thorpe Humber Kirkby Marsh Bank Grimsby Lister South Stalybridge Melton West Wylfa Rainhill Manchester Stocksbridge Pitsmoor West Drive Aldwarke Burton Birkenhead Carrington Bredbury Winco Bank Thurcroft � 3GW of new nuclear Daines Neepsend Fiddlers Sheffield City Ferry Brinsworth Capenhurst Frodsham Jordanthorpe Cottam Norton Lees Pentir Macclesfield Deeside Chesterfield High Dinorwig Marnham 3GW of new supercritical coal (some with CCS) Staythorpe � Legacy Cellarhead Ffestiniog Bicker Fenn Willington Trawsfynydd Ratcliffe Drakelow Walpole 11GW of new gas Rugeley Spalding � North Norwich Ironbridge Main Bushbury Willenhall Bustleholm Shrewsbury Penn Nechells Hams Enderby Hall Ocker Hill Coventry Oldbury Kitwell Berkswell Burwell Sizewell Feckenham Main Bishops Grendon Eaton Wood Socon Patford Bramford � Electricity demand remains flat (approx 60 GW) Bridge East Sundon Claydon Pelham Wymondley Leighton Braintree Rassau Walham Buzzard Rye House Waltham Cross Imperial Brimsdown Park Cowley Pembroke Swansea Watford Elstree Hackney � Reductions from energy efficiency measures North Amersham Main Baglan Cilfynydd Whitson Culham Mill Hill Tottenham Redbridge Warley Rayleigh Main Upper Boat Uskmouth Minety Didcot Bay Margam Iron Acton Willesden Barking West Thurrock Coryton Alpha Steel Iver Ealing Northfleet East Pyle N.Hyde Tilbury Grain Singlewell Seabank City Rd W.Ham Cowbridge St Johns Tremorfa Laleham Wood New Hurst Kingsnorth Cardiff Cross Aberthaw Kemsley � Increases from heat pumps & cars East Melksham Bramley West Chessington Rowdown Littlebrook Weybridge Fleet Beddington Canterbury Wimbledon North Hinkley Point Bridgwater Sellindge Alverdiscott Bolney Taunton Nursling Ninfield E de F Dungeness Marchwood Lovedean Axminster Mannington Fawley Botley Wood Exeter Chickerell Langage Abham Landulph Indian Queens ISSUE B 12-02-09 41/177619 C Collins Bartholomew Ltd 1999

Quantitative Analysis � The effect of System Inertia is being quantitatively analysed through two methods:- � Energy Balance spread sheet approach � Utilising simple predictive output models based on an energy balance � System Study using a Test Network � Utilising Dynamic System Models

Energy Balance Spread Sheet Approach � System Considered � 16.5 GW of Wind, 6.9 GW Nuclear, 1.6 GW Carbon Capture � Load Response 2% per Hz � Assumed loss – 1800MW � System Balanced at t = 0 seconds � Inertia considered in isolation � General Conclusion � The higher the inertia the longer it takes for the steady state frequency to be reached. � See subsequent slides

Energy Balance Spread Sheet – Results Wind Generation with and Without Inertia Variation in Inertia - Low Resolution 50.5 50 49.5 49 Frequency Hz 48.5 48 47.5 47 46.5 46 0 10 20 30 40 50 60 Time (s) H=0 H=3

Energy Balance Spread Sheet – Results Wind Generation with and Without Inertia Variation in Inertia - High Resolution 50.2 50 49.8 49.6 Frequency (Hz) 49.4 49.2 49 48.8 48.6 48.4 48.2 0 1 2 3 4 5 6 Time (s) H=0 H=3