220kV變電站電氣一次系統(tǒng)設(shè)計(jì)（負(fù)荷 唐冉,220kV變電站電氣一次系統(tǒng)設(shè)計(jì)（負(fù)荷,唐冉,kv,變電站,電氣,一次,系統(tǒng),設(shè)計(jì),負(fù)荷 2010 International Conference on Power System Technology Challenges on Integrating Renewables into the Chilean Grid Juan C Araneda Senior Member IEEE Sebastian Mocarquer Member IEEE Rodrigo Moreno Member IEEE Hugh Rudnick Fellow IEEE Abstract The Chilean Electricity Law introduced an obligation to power traders from 2010 to 2014 to certify that at least 5 of the electricity traded comes from renewable sources From 2015 onwards the obligation will increase by 0 5 annually until 10 in 2024 Several challenges need to be addressed to permit efficient access for renewable energies One of these is the natural barrier to entry for new generators originated in the radial characteristic of the transmission systems In the past these systems have essentially developed and adapted economically to conventional generation and demand International experience shows that grid operation and expansion needs to be smarter for allowing renewable power connection In Chile significant challenges have arisen in grid planning and pricing which this paper attempts to address While new wind farms can be installed in 1 5 years transmission infrastructure requires 3 to 6 years to be completed In this framework extensive construction times of new grid developments considering community and environmental approval require a long term vision which in turn provides regulatory signals in order to minimize bottlenecks for the integration of new generation particularly renewable On the pricing side wind farms push large transmission expansions but given regulatory arrangements participate with a small part on transmission toll payments because of the low plant factors of wind generation In addition transmission planning under uncertainty by taking account of different scenarios and the concept of anticipatory investment becomes critical Index Terms Renewable energy transmission planning electricity regulation wind energy I INTRODUCTION Chile has two main interconnected systems SINO Northern Interconnected System and SIC Central Interconnected System nmning along around 2 600 km from north to south The SIC electricity generation matrix has been traditionally composed by large hydro and thermoelectric power plants mainly coal fired and natural gas SINO is a 100 thermoelectric system with coal fired natural gas and diesel plants Recent events concerning energy security and low carbon footprint according to global trends have brought renewable energy to the center of public debate In Chile energy policy is fimded on three main principles security of supply economic efficiency and social and environmental sustainability Thanks to Fondecyt and Transelec for support Juan C Araneda is with Transelec Chile email jcaraneda transelec c Sebastian Mocarquer is with Systep Ingenieria y Diseftos Chile email smocarquer systep c Rodrigo Moreno is with Imperial College London UK email rmoreno imperial ac uk Hugh Rudnick is with Pontificia Universidad Cat6lica de Chile e mail hrudnick ing puc c 978 I 4244 5940 7 1 01 26 00mOI 0 IEEE Although Chile contributes marginally to world s total greenhouse gas emissions the population is becoming progressively more aware of the impact of large hydro power plants and fossil fuel fired plants International non governmental organizations NGO have been watching and opposing projects of those characteristics driven by private investors in the liberalized energy market raising the debate between balancing economic growth via energy supply efficiency and security versus sustainability 1 The Chilean law identifies Non Conventional Renewable Energy NCRE as the generation from non conventional sources connected to the grid such as wind geothermal solar biomass tidal cogeneration and small hydro generation up to 20 MW In this paper the impact of integrating NCRE to the Chilean grid is analyzed identifying the main challenges faced by private investors to develop renewable energy projects transmission grid expansion issues and regulatory signals to be taken into account by the regulator in order to facilitate the NCRE integration and permit a sustainable growth of the Chilean energy market II EVOLUTION OF THE CHILEAN ELECTRICITY MARKET Chile was the world pioneer country deregulating and privatizing the electricity industry after the enactment of the Electricity Law in 1982 The electricity market was restructured in generation and distribution companies that were successively privatized at the end of the 1980 s In 1993 the main transmission company was created also under private ownership The Chilean electricity market consists of three segments generation transmission and distribution According to the law the generation segment is defined as a competitive market with freedom to invest while the transmission and distribution are recognized as monopolistic activities and therefore companies operating in these segments have regulated tariffs Agents in the generation market compete to supply power to consum ers operating under a short nm marginal cost SRMC pool dispatch regime coordinated by the system operator namely CDEC Competition for system development aims on capturing demand growth with the most economic generation plus transmission technology The Electricity Law was amended in March 2004 with the introduction of significant changes to the transmission pricing and expansion procedures Furthermore in May 2005 the law was again amended to introduce improvements on the energy market regarding long term prices applied to the contracts among generation and distribution companies introducing energy contract auctions in a pay as bid scheme Electricity demand is expected to continue growing up linked to the Chilean economy growth Figure 1 presents the SINO and SIC load growth historic and forecast installed capacity and source and main geographic and demographic figures Demand forecast for the period 2010 2020 corresponds to projections of the Chilean energy regulatOlY body the National Energy Commission CNE Main Chilean Interconnected Systems NORTHERN INTERCONNECTED SYSTEM SING Average load growth 1999 2008 Expected annual load growth Inst capacity 1 Max Oem Regulatedl Non Reg Customers Hydro 1 Thermal length Population 7 2 5 3 3 6101 1 816 MW 10 190 1 199 600km 6 CENTRAL INTERCONNECTED SYSTEM SIC Average load growth 1999 2008 5 1 Expected annual load growth 5 3 Inst capacity 1 Max Oem 11 2901 6 240 Regulatedl Non Reg Customers 65 1 35 Hydro 1 Thermal 60 1 40 length 1 800 km Population 93 Figures December 2009 Figure 1 SINO and SIC main power system figures In 2008 a modification was introduced to the Chilean Electricity Law in order to encourage the entry of non conventional renewable energy into the electricity market Thus from 2010 to 2014 power traders that withdraw electricity from the system to supply regulated and non regulated price consumers must certifY monthly that at least 5 of the electricity traded comes from renewable power either self produced or bought from other generators Fro 2015 onwards the obligation will increase by 0 5 annually until reaching 10 in 2024 In order to meet the obligations of the NCRE law significant investment on renewable energy plants is expecte d over the next years Table 1 presents the NCRE generation projects presented to the national environmental impact evaluation system Wind power presents the highest penetration albeit the energy contribution is low due to the low expected plant factor around 25 to 30 Generation Projects of NCRE MW Presented Approved 210 100 0 10 Projects Under 950 qualifying 150 0 73 Announced Not yet Projects submitted 850 200 100 0 Table 1 NCRE projects in Chile Figure 2 shows the expected demand growth and installed capacity of the SIC considering the contribution of NCRE Installed Capacity vs Demand 18 000 16 000 14 000 12 000 10 000 8 000 6 000 4 000 2 000 c J NCRE Hydro c J Coal c J Gas Diesel Average Demand Maximum Demand Figure 2 Expected contribution ofNCRE to the SIC energy matrix III INTEGRA nON OF RENEW ABLES INTO THE GRID Several problems need to be addressed to permit an efficient access for renewable power into the transmission grid e of these is the natural barr ier to entry for new generators ongmated in the radial characteristic of the Chilean transmission systems In the past these were essentially developed and adapted economically to conventional generation and demand 2 However there are areas for instance in the north of SIC where wind power potent ial is high and transmission grid expansions may be required by capacity constraints i e transfer peak wind injections although energy contribution is rather small In Chile transmission expansion and pricing was modified in 2004 into a co operative regulated scheme in order to include the participation of every agent of the electricity market Since then significant challenges have arisen in grid pl ann ing and pricing 4 Three transmission segments were defined by the law trunk subtransmission and additional systems Trunk system assets are those essential for co tition in the energy market and are integrated by facIlitles over 220 k V that are economically efficient and necessary to supply the total demand Subtransmission system assets facilitate access to consumers with regulated and non regulated prices clients of capacity equal or higher than 2 MW Additional transmission systems assets are those exclusively dedicated either to non regulated price consumers or to connect power plants to the system On the expansion pl anning side every fo ur years there is a long term trunk transmission pl anning exercise directed by a multl party comm ittee representing market agents generators transmission companies large consumers and the regulator It defines a schedule of transmission reinforcements and or new installations based on a generation expansion overview provided by the regulator Then evety year the system operator CDEC must revise this trunk expansion plan according to the curren t market conditions particularly demand and effective generation development with a consultation process including all the involved agents Then CDEC rec omm ends the corresponding trunk transmission projects to the CNE Afterwards the CNE has 30 days to release the expansion plan of the trunk system with the projects that must begin construction in the next 12 months Trunk Expansion Revision CDEC SIC Oct Expansion Plan CNE Dic Discrepancies Expert Panel Dic Resolution Expert Panel Feb Decree Energy Ministry Abr Projects tendering and awarding Transmission lines Substations works bigger 30 months Substations works minor l Coal Plant 36 months Biomass Plant 30 months i Small Hydro Plant 24 months I Onshore Wind Plant 18 month Figure 3 Annual revision of the trunk expansion plan While new wind funns can be installed in 18 months needed new transmission lines require at least 42 months to be completed including rights of way negotiations environmental impact study and construction Figure 3 shows the annual trunk expansion plan revision comparing construction terms of different generation technologies and typical transmission projects including substations or lines To speed up the release of new transmission capacity to network users intemational experience shows that present philosophy of grid operation and expansion needs to be significantly changed towards smarter concepts technologies special protection schemes coordinated voltage control techniques wide area monitoring and control systems advanced dynamic security assessment techniques and demand side management and practices for allowing renewable power to connect in a timely fashion For example the massive grid connection of 30 GW of wind power expected in Great Britain by 2020 has triggered a number of procedure reviews covering various aspects of the technical comm ercial and regulato framework transmission access security and quality of supply standards SQSS RPI X regulation anticipato investment proposals and the transmission network charging scheme Particularly the review of the deterministic Supply Quality and Security Standards SQSS for example concerning the best usage ofN k criteria which has been used from 1950 3 IV IMPACT DERIVED FROM THE INTEGRATION OF RENEWABLES The integration of NCRE represents a challenge for a power system largely dominated by conventional generation technologies Particularly wind power in large scale means a big impact on a long radial transmission grid due to the intermittent and unpredictability characteristic of power injections Operational aspects such as voltage stability control and generation reserves for frequency control will become major issues for the system operator Problems also emerge on the transmission pricing side The existing regulation allocates payments of the transmission lines to generators based on line usage over time Wind farms may push large transmission expansions which do not coincide with their small proportion on transmission payments because of the low plant factors of wind generation Therefore existing generators could potentially see toll payments increases and so will oppose to such expansion projects This in tum can potentially affect the connection decision of wind power projects because of the risk of congestion in the transmission grid In order to make decisions in advance to avoid constraints to new NCRE entrance transmission pl ann ing under uncertainty by taking account of different generation plan scenarios along with an anticipato investment regime becomes critical The main issues that challenge the definition of the transmission expansion plan are related to the new generation power plants to be commissioned under a competitive energy market 5 The following questions arise What kind of technology will be used in the new generation plants When will the new plants being connected Where are the new plants going to connect to the grid How much capacity is being connected Under a deregulated scheme there is freedom to answer all this questions and then the investment decision concerning the expansion of the grid takes the form of an expansion strategy instead of an expansion plan This strategy must determine the set of transmission projects that allow the best solution to the energy market participants minimizing the total cost to the users A system operator that only recommends transmission expansions based on firm comm itments from new network users i e full certainty on new generation plants decisions will be always late and will provoke higher operational costs in the short tenn and economic losses on NCRE investors In this framework extensive construction times of new grid developments considering commooity and environmental approval and rights of way negotiations require a long term vision which in turn provides regulatory signals in order to minimize bottlenecks for the integration of new generation particularly renewable energy However in contrast existing generntors exercise market power on new entmnts through lll1derinvestment in some tmnsmission corridors when also trying to minimize toll payments in the short tenn Figure 4 represents the economic evaluation of a new tmnsmission line on a corridor with two tower options single circuit line today and another single line in the future or double circuit today but only one circuit constructed and adding the second circuit cable in the future In power systems with permanent demand growth like Chile the economic evaluation usually arises to the conclusion that the present value of investment is lower for the double circuit option and therefore that is the expansion decision to be made However for generntors that will pay the new line tmnsmission tolls will be higher in the short term due to the higher cost of a double circuit line in comparison with a single circuit line This paradox has meant severnl discussions and oppositions from generntors to new tmnsmission lines although for a sustainable development it is essential to minimize the number of new corridors especially in a narr ow COlll1try TRANSMISSION CAPACITY I NVESTMENT Short term J r J r t vision Ir t Long term vision Figure 4 Long and short term vision in transmission expansion v MAIN CHALLENGES Chile is a developing COlll1try where energy consumpti on growth is strongly correlated with economic growth in spite of recent efforts to increase energy efficiency The discussion arises as NGO s propositions aim on more participation of NCRE in the energy matrix However the COlll1try already has one of the most expensive electricity rntes in Latin America and NGO s alternative means a higher cost of electricity compared to conventional generation sources One important challenge is the improvement of the annual revision process of the trunk expansion plan by CDEC which has been an issue to debate because the agents cannot wait for another year to find a tmnsmission solution when they decide to build a new power plant which is especialJy important for wind furms due to the fast construction times after obtaining the environmental approval Due to the nature of a competitive generntion market projects may change postpone or new ones can appear in a short period of time requiring flexible pl ann ing methods to decide tmnsmission expansions The downside of this flexibility is that the solutions achieved could often be considered incremental solutions which follow the generation market but do not represent the most efficient altematives in the long tenn A way forward for this dilemma may be seeking support in the increasing use of new and smarter network technology such as special protection schemes coordinated voltage control techniques wide area monitoring and control systems advanced dynamic security assessment techniques and demand side management These can actually provide more flexibility by releasing larger network capacity in operational timescales allowing planners to defer transmission construction and wait for the adequate signals in order to build efficient lines more according to a long term vision VI CONCLUSIONS The transmission regulation in Chile tol1 arran gements and expansion procedures included does not facilitate the introduction of large renewable generation parks into the market The lll1certainties of tmnsmission expansion and the short tenn view which arises from curre nt regulation affect both generation and tmnsmission long tenn investments jeopardizing in particular the timely entry of renewables Rtmning for almost thirty years Chilean regulation is fucing another challenging moment to balance economic efficiency and sustainability Difficulties to build up new transmission instal1ations require changes on regulatory signals in order to anticipate tmnsmission investment decisions to provide certainty to new entrants particularly NCRE that open access is real and congestion will be minimized NCRE investors require certainties to evaluate and obtain project financing This is a big issue for a tmnsmission grid that has been developed permanently adapted to generation and demand requirements with probabilistic security of service criteria where there is no spare capacity Another important regulatory signal to be revised relates to the allocation of tolls among users Curre ntly tmnsmission payment allocation depends on the expected energy tmnsported while the effective use that correlates with expansion should address on the users contribution at maximum transportation levels Subsidies that derive from the curr ent allocation scheme could be used by existing generators to oppose tmnsmission expanSIOns VII BIBLIOGRAPHY 1 Rudnick H Barr oso L Mocarquer S and Bezerra B A delicate Balance in South America IEEE Power and Energy Magazine Vol 6 July August 2008 2 Rudnick H and Mocarquer S The insertion of renewables into the Chilean electricity markef IEEE General Meeting 25 29 July 2010 Minneapolis Minnesota USA 3 Moreno R Pudjianto D and Strbac G Future transmission network operntion and design sta