New French-Spanish VSC link

Transcription

1 21, rue d Artois, F PARIS B4-110 CIGRE 2012 http : // New French-Spanish VSC link Patricia Labra Francos 1 Silvia Sanz Verdugo 2 Red Eléctrica de España Red Eléctrica de España Spain Spain Sylvain Guyomarch Réseau de transport d électricité France SUMMARY Since 2001 the Spanish and French Governments have the compromise of increasing the transfer capacity between both countries. In addition, reinforcing the transmission network between France and Spain will provide a greater security of supply, improved quality and reliability of the electrical system as well as it allowing higher integration of renewable energies in the Iberian Peninsula and fosters the integration of the Iberian Electricity Market (MIBEL) in the Internal European Electricity Market. By 2014, the future interconnection will be in commercial operation between France and Spain with Voltage Source Converter technology. It will consist of two identical but independent links between a future substation in Spain (Santa Llogaia) and an existing substation in France (Baixas), with a nominal active power of MW each (2 x 1000 MW) and a rated DC voltage of ±320 kv. The cost of the project is 700 M and it is assumed equally by French and Spanish TSOs. The project will represent the largest investment in one single project (based on power electronics) carried out by Red Eléctrica de España. This project is Europe s first DC onshore interconnection integrated in the synchronous AC grid. As it will be embedded in a meshed AC grid, it will require a special operation to improve the system security under normal and special conditions, in addition to minimizing the system losses and maximize the commercial transfer capacity. The paper will summarize the most important characteristics of the future HVDC interconnection between France and Spain, the reasons that have led to the implementation of VSC technology, and the conclusions obtained from various network studies realized to determine the future exchange capacities, the most suitable control strategies and the behaviour and operation of the DC link embedded in an AC network. KEYWORDS HVDC, interconnection, VSC, Spain, France, underground, embedded, INELFE. 1 plabra@ree.es 2 sisanz@ree.es

2 1. INTRODUCTION The first interconnection that will be commissioned in more than 25 years between France and Spain will be an important milestone for both countries involved and for the rest of Europe, due to the importance of increasing the exchange capacity in this border for the achievement of the European Energy objectives. In addition, the technologies chosen for the new HVDC interconnection line between France and Spain, both for the cable system and the converter stations represent an innovation at the levels of voltage and active/reactive power required in the Voltage Source Converter (VSC) link. In addition, as the project has the peculiarity of being an HVDC link embedded in an AC network, a special operation is necessary, different from that of the usual HVDC links. Therefore, the active power set-point will be highly influenced by the generation and demand situations in the surrounding area, and the power flow through the AC interconnection lines between both countries. Not taking into account this issue, can lead to inefficient operation points. Additionally, the functional operation point will be established aiming to maximize the benefits offered by the self-commutated VSC technology such as the voltage control, a better dynamic behaviour during disturbances in the system, the possibility of black-start, the fast power reversal, etc., that will enable a much more flexible and safe network management. 2. BACKGROUND Only four transmission cross-border lines connect Spain and France, two lines at 400 kv and two lines at 220 kv: SPAIN-FRANCE AC INTERCONNECTION LINES VOLTAGE LEVELS COMMISSIONING DATE Sabinánigo (Biescas)-Pragneres 220 kv 1955 Rubí (Vic)-Gaudière (Baixas) 400 kv 1964 Hernani-Cantegrit (Argia) 400 kv 1970 Arkale-Mouguerre (Argia) 220 kv 1982 These lines have a special importance for the Iberian Peninsula (Spain and Portugal) as they are the only connection to the rest of the European system. Another two cross-border lines Irún-Errondenia 132 kv and Benos-Lac d Oo 150 kv are just for local support. This interconnection network presently provides a cross-border capacity of MW from France to Spain, and MW from Spain to France. Figure 1. Transmission network in the French-Spanish border 1

3 In 1982 the last transmission line existing today was commissioned between Spain and France (Arkale-Argia 220 kv). Since then, the necessity of increasing the transfer capacity has become more and more important due to the increase of demand of both systems, due to the liberalization of the electricity market and the ambition of the European Union about an European Electricity Market in the 90s, and more recently due to the European Energy Objectives known as objectives (20% RES share in gross energy consumption, 20% reduction of GHG, and 20% increase in energy efficiency). However no new line has been commissioned since then, in spite of several unsuccessful attempts. This situation causes Spain and the Iberian Peninsula to be considered in practice as an electric island. The ratio between the import exchange capacity and the installed capacity is around 3-4%, one of the lowest of Europe and far from the objective recommended by the EU Council in March 2002 (every Member State should have at least a ratio of 10%). Figure 2. Interconnection ratio in different EU countries After some attempts in the 90s rejected for political reasons, in 2001 the French and Spanish Governments committed to reinforce the capacity of interconnection between their countries, establishing two objectives for the exchange capacity, MW in the short term and MW in the long term. This objective was reaffirmed several times by both Governments. As a result of this agreement, RTE and REE, the French and Spanish Transmission System Operators started to work together again and proposed a new project: a new 400 kv double circuit in the Eastern Pyrenees, along the High Speed Train (TAV-TGV) railway line on the Perpignan-Barcelona project. In this period, the European Commission supported the project with subventions for the preliminary studies, and in the Trans-European Energy Networks (TEN-E Guidelines) of 2003 a new interconnection through the Pyrenees between France and Spain was declared as one of the 12 Projects of Common Interest : EL.3: France-Spain-Portugal. In 2006, this priority was reaffirmed for a specific route (TEN-E Guidelines) [1] "Line Sentmenat (SP) - Bescanó (SP) - Baixas (FR)". Moreover, this project appeared in the National Development Transmission Plans published by the Spanish Ministry of Industry in 2002, 2006 and 2008 [2]. However, none of these actions resulted in the realization of the project. The project had important delays due to the lack of clear agreement on the location of the cross-border point, 2

4 but overall due to the strong social opposition, with the greatest opposition being the Public Debate celebrated in France in With the project being on stand by for a long time, in the Gerona summit of November 2006, the Spanish and French Governments asked for the intervention of Brussels in this project, due to its slow progress but its importance for the European network. Therefore, in the framework of the Strategic Energy Review - An Energy Policy for Europe and the Priority Interconnection Plan [5] where the existence of delays in the construction of the eastern reinforcement was confirmed, the European Commission appointed on the 12 th of September 2007 Professor Mario Monti as European Coordinator for the France-Spain interconnection. His objective was to impel the electrical interconnection between Spain and France, to analyze the existing obstacles at all levels, and to look for solutions to undertake the project in the shortest possible time. After meeting all the affected stakeholders and working with the help of an independent consultant, the European coordinator recommended in a first step: A greater transparency in the communication on the justification of the project, the global vision of electrical interconnections needs in the Pyrenees for the future, etc. A common structure in charge of the development of the project. The possibility of applying technical options that today are still exceptional - like the partial underground laying of the line, taking into account the exceptional character of the project. The final recommendation of the European Coordinator of the Spain-France interconnection published at the end of June of 2008, consisted of a solution in HVDC, totally underground laying of the cross-border section of the interconnection (Baixas-Santa Llogaia), with a terrestrial drawing up, and using as far as possible existing infrastructures within a determined area [3]. Both governments accepted this recommendation, and the joint venture INELFE (INterconexión ELéctrica Francia-España) with a respective 50% of participation of the French and the Spanish Transmission System Operators (TSO) was created for the implementation of the project. Due to the social inacceptance of an overhead line in the area, and the results of the Public Debate in France in 2003, only an undergrounded solution is feasible. Having assumed the underground laying, the more suitable technical-economic solution is with direct current technology or HVDC (High Voltage Direct Current), instead of AC, whose breakeven point is around km for underground solutions. In addition, a terrestrial route has much less impact than a submarine solution in this area, due to posseidonia banks and archeological sites. Therefore, this exceptional solution that implies underground laying represents, according to the European Coordinator, the best technical, economic and environmental commitment, considering the expectations of the local populations, and discards the option of AC voltage since this solution only allows the underground laying in limited sections. Therefore this alternative is for the moment the only feasible one for the development of the Spanish- French interconnection by the eastern Pyrenees. 3. DECISION ON HVDC TECHNOLOGY The DC technology and the underground laying consideration had a very great impact on the project, because both factors are not as usual and well-known as the overhead lines in alternative current. Therefore, not only internal studies from the steady-state and dynamic 3

5 point of view, but also new common coordinated analysis between the Spanish and the French TSOs, using the same database, cases and dynamic models were carried out. Figure 3. Two technology possibilities for the new DC link The objective of these studies was to define the capacity and technology for the new HVDC link between the both available technologies, LCC (Line Commutated Converter) and VSC (Voltage Source Converter), and make sure that the exchange capacity objectives for the midterm set by both governments as well as the security of the system was deemed acceptable. One of the main requirements for the new technology was an automatic control of reactive power in the area near the border as there some contingency situations were detected with low voltages and others with high voltages. In addition, there was a necessity to guarantee the security of supply in the border area, mainly in Gerona (Spain). This place is today an increasing demand area, with very few generation plants and fed from the transmission network by some remote points and a 220 kv double circuit line in Juia, which in case of failure would produce an important energy not supplied. On the other hand, the Perpignan area which is a high import region, would have a good enhancement of its security in supply with a new connection for support in case of the double circuit to Narbonne (400 kv Baixas- Gaudiere). FRANCE SPAIN Figure 4. Regional transmission network in Perpignan (France) and Gerona (Spain) 4

6 VSC technology allows an independent control of active and reactive power, and continuous and precise voltage control, which fulfils the requirement stated above. The black start capability was highly appreciated in case of failure of the AC lines for recovering the system. In addition the possibility to feed a passive network and no minimum active power control allows securing of the cross-border security of supply. Moreover having no minimum short circuit power requirement does not limit the transfer flow as it would with the LCC technology. Having no minimum active power is another advantage. On the other hand, the power flow reversal without polarity reversal of voltage in a very short time (since the current is able to be bidirectional through IGBTs in parallel to the diode) can be useful not only for the local and national support but also improving the dynamic performance during contingencies. Finally, harmonics are less problematic than in LCC technology so AC filters are not required, and regarding network security the VSC technology is able to dampen power oscillations in an improved way and allows a better frequency control, disabled under normal conditions, that keeps the frequency within a defined range adjusting the active power. Both are very useful for the network stability. From the engineering point of view, less space is required for the VSC converter station and the cables are lighter and easier to install as the joints are prefabricated. The conclusion of the studies showed that certain features of the VSC technology were indispensable for a better and flexible operation of the DC link in the French-Spanish network. The results regarding the steady-state and the dynamic analysis, necessary to check the consistency of the new technology solution, showed that the behaviour of the network system is correct, and the exchange capacity objectives are reached maintaining the security of the network. After the technical and economical analysis of the manufactures offers, VSC MMC (Modular Multilevel Converter) was selected. The total active and reactive power in this project presents currently the world`s highest power rating of an HVDC link using VSC technology. Figure 5. Main scheme of a MMC converter 5

7 The main concept and basic design of this technology are illustrated in Figure 5, Figure 6 and Figure 7 [8]. Each submodule (SM) consists of two blocks of IGBT/diodes in parallel with a capacitor. Depending on the functional states of the IGBT (driving or blocked), the capacitor voltage (V C ) can appear in the terminals of the SM (V SM ), changing the total voltage V d. Figure 6 shows the commonly use control states of a submodule. State IGBT1 IGBT2 i V SM 1 OFF OFF > 0 V C < ON OFF OFF ON > 0 V C < 0 V C > 0 0 < 0 0 Figure 6. Detail of the different possible states of each submodule The DC voltage (V d ) is given by the sum of the voltages of each submodule in each phase unit which build up the voltage source. The AC voltage (V AC ) is obtained by the combination of the voltage of both arms (upper and lower) as are expressed in the following equations adn shown in Figure 7. V d: DC voltage : submodule voltage (upper and lower, respectively) : inductance voltage Figure 7. AC voltage controlled by MMC topology This type of connection can lead to a voltage between two different levels, and. Considering the converter behaviour as an inverter, to achieve the required output voltage (V AC ) is necessary to activate a defined number of SM in the lower arm, in the upper one, or in both simultaneously. 6

8 4. GENERAL DESCRIPTION OF THE PROJECT The analysis concluded to propose the new interconnection between France and Spain as two independent 1000 MW links (bipole or symmetrical monopole configuration), implemented with VSC technology and ±320 kvdc. The design must achieve a maximum common failure loss of 1000 MW (one link). The requirement related to reactive power capacity for each converter demanded in the functional specification results in ±300 Mvar. The converter stations in France and Spain will be connected respectively to the AC 400 kv 50 Hz nodes of Baixas (in Roussillon, France) and Santa Llogaia (in Alt Empordá, Spain) as shown in Figure 8. Baixas is an existing node in the area of Perpignan while Santa Llogaia is a new node considered in the official Spanish Master Plan and whose expected commissioned date is This last substation will be connected to the 132 kv network and will also supply the High Speed Train. GAUDIERE BAIXAS HVDC STA LLOGAIA RAMIS VIC BESCANO RIUDARENES Figure 8. Location and configuration of the Baixas-Santa Llogaia HVDC interconnection The length around 64.5 km between the two nodes will be carried out by Prysmian with 2 cables per HVDC link (258 km in total). The cables, with a cross section of mm2, will be extruded, copper cable with dry insulation and aluminium tube screen. The DC voltage level is the highest ever used for a buried cable application. The general configuration of the cable system is depicted in the Figure 9: Conductor: round copper section. Inner semiconductor screen: Semiconductor layer extruded jointly with the insulation. Insulation: Cross-linked polyethylene (XLPE) super clean. Outer semiconductor screen: Semiconductor layer extruded jointly with the insulation. Longitudinal water barrier: Swelling tape placed before the screen. Metallic screen and radial water barrier: Aluminium laminated welded. Outer sheath (glued with the metallic screen). o Installation in pipe: polyethylene sheath with outer semiconductor layer extruded jointly with de sheath. o Installation in tunnel: Polyolefin sheath with outer semiconductor layer extruded jointly with the sheath. Figure 9. Dry insulation cooper cable with aluminium tube screen 7

9 In the cross-border section, around 8,5 km have to be layed in a dedicated tunnel through the Eastern Pyrenees as the slopes of the terrain were not adequate for a normal cable layout. The tunnel, as represented in Figure 10, has a 3,5 m diameter and a depth of between 80 and 300m. It has the particularity that visits are not allowed. A consortium leadered by Eiffage TP and Dragados will build the tunnel. Eastern Pyrenees Figure 10. Tunnel: Longitudinal section and cross section The rest of the route will be layed with 2 independent trenches, that require a permanent occupation between 4-7 m, taking into account also security lengths and access to the route. Only grass is allowed to grow in the affected area (moreover a graded aggregate path will be built in the Spanish side) in order to avoid roots damaging the cables. Gravel Buoy Figure 11. Trenches: Cross section. Spanish trench on the left, French trench on the right In order to minimize the environmental and social impact, the reinforcement will try to be far enough away from urban areas and high density population areas, natural protected areas, forests and places of interest. The new interconnection takes advantage, as far as possible of the route of highspeed road and highspeed train. In order to reduce visual and environmental impact also certain directional drillings are planned to avoid roads, railways and rivers. The route through both countries is depicted in Figure 12. Figure 12. VSC project route in France and Spain. 8

10 5. CONTROL SYSTEM The design of the control system complies with the dynamic performance requirements in order to allow a better dynamic behaviour during disturbances in the system. Any severe incident in the Spanish or French network has an important impact on the interconnection between both countries regarding power flows and voltage oscillations. In this sense, both the French and Spanish TSOs have identified several control functions which should be implemented in the HVDC link. In the functional specification of the converter stations, published in December 2009, INELFE required that the HVDC system comprised a certain number of controls that ensure the stable behaviour of the VSC link embedded in the existing AC network. At this stage of the project, INELFE is still studying which is the most suitable operational management and therefore which controls should be implemented to obtain the best response of the link in the steady-state and under contingencies. In any case, the impact of these controls in the power system will be also analyzed by the converter stations manufacturer. As the new VSC link is embedded in a meshed AC grid, parallel to the 400 kv Vic-Baixas line (Figure 1), the active power flow through the AC line is highly sensitive to possible changes in the DC active power set-point. In fact, in a normal operational situation with a preset Net Transfer Capacity and taking into account the location of the VSC link, changes in the DC active power set-point will modify the distribution of active power flow through the AC interconnection lines but will not change the active power flow transferred between both countries. To illustrate the previous idea, Figure 13 outlines the set of the four AC interconnection lines between both countries and the DC link. The scenario selected considers an active power flow interchanged of MW from France to Spain; half of them through the VSC link. If under a generation-load balance situation the DC active power setpoint is reduced to 700 MW, the rest of the AC interconnection lines will increase its active power flow to compensate the decrease in the DC active power set-point. Despite the fact that all the AC interconnection lines increase their active power flow, the 400 kv Vic-Baixas line raises its active power in 70% of the power reduced in the VSC link, while the remaining 30% is distributed among the rest of the AC interconnection lines. Figure 13. Vic-Baixas line s sensitivity to an increase in the DC active power set-point 9

11 Therefore, and considering the significant response of the AC interconnection 400 kv Vic- Baixas line, an adaptable control strategy can achieve a balance between losses and system-security considerations. Regarding losses considerations, setting a certain DC active power set-point (P VSC ) as a function of the active power flow through the Baixas-Vic line (P BAIXAS-VIC ), the losses of the whole corridor (interconnection system formed by both VSC links in parallel to Baixas-Vic line) could be minimized at the same time that the transmission efficiency could be increased. Corridor losses can be expressed in terms of P VSC just considering all the elements in the transmission system: Converters losses: Rectifier and inverter losses are approximately represented by a quadratic function (in accordance with preliminary information). DC cable losses: Baixas-Vic line losses: Figure 14 shows the corridor losses as a function of P VSC. In the analysis it has been assumed three levels of active power through the whole corridor (P CORRIDOR ) MW MW Corridor losses (W) MW P VSC (W) Figure 14. Corridor losses analysis in terms of P VSC Setting a DC active power set-point in the whole VSC system between 60 and 70% of the total active power to be transmitted by the corridor (P HVDC 60-70%P CORRIDOR ), the total losses of this interconnection system reaches its minimum value. 10

12 Regarding system-security considerations, controls susceptible to be implemented in the HVDC can be classified as those controls which manage the DC active power flow, those controls which are related to voltage control and those which improve the dynamic performance of the system. Next, there are described the main aspects and features of some of the most representative controls included in this VSC link. Controls that manage the VSC active power flow: 1. Active power control depending on an established active power set-point An active power control based on a previously established set-point allows the system operator to fix the active power order in each VSC link. However, it implies a previous operation schedule, so the VSC link would not respond automatically to the continuous changes in the power system, in contrast with the automatic behaviour of other controls presented in the following. 2. Control to emulate the behaviour of an AC line A control that emulates the behaviour of an AC line, from the point of view of the active power flow, can be implemented by means of different procedures, two of them are summarized in the following: The first method modifies the DC link active power flow as a function of the amount of active power which is transmitted by a parallel AC line, for example, the Vic-Baixas line. The second method emulates the behaviour of an AC line increasing/decreasing the VSC link active power flow as a function of the difference of the angles of both HVDC sides. This type of control manages the DC active power flow automatically without a prior operation schedule and without the intervention of the system operator, as well as providing the embedded VSC link with a large capacity of response during severe contingencies in the AC network, improving the performance of the transmission system in the post-disturbance period. 3. Active power control in case of a trip of one link Given a possible trip of one of the VSC links, it will be required that the link in service will increase its active power to assume the loss of power in the other link. This function is extremely useful due to its ability to prevent the rest of the AC lines to take over the active power flow lost by the unavailable link. 4. Possibility of decreasing/increasing (runback/runup) the active power transported by the HVDC link (including fast power reversal) as a consequence of an external event The control order increases/decreases the VSC active power flow in an automatic and controlled way whether different events happen. An event is defined as a sudden change in the AC network close to the DC link. Controls that manage the VSC reactive power flow can contribute to the maintenance of the network voltage in the steady state and in the transient state, improving the network voltage stability and supporting the voltage recovery by means of the variations of active and reactive power. 11

13 Also, when the HVDC cables are out of service, the converter station will be used as a STATCOM in order to participate actively in the voltage control in the AC system. Controls that improve the dynamic performance of the network include power oscillations damping control (POD), sub-synchronous damping oscillations control, power system improvement in case of a large disturbances, frequency control if the AC interconnection lines between France and Spain are out of service or in case of feeding a passive network, etc. 6. COSTS AND BENEFITS The total budget of this project is around 700 M, between 8 and 10 times higher than the original cost of the project as an overhead line in AC technology. The new reinforcement will allow the increase in the commercial transfer capacity up to MW from France to Spain and up to MW from Spain to France. Studies performed in the ENTSOE (European Network of Transmission System Operator for Electricity) framework with the forecast of the future generation and demand in Europe based in the NREAPS (National Renewable Energy Action PlanS), allow simulation of the behaviour of this interconnection, and to obtain the savings in variable production cost, in CO 2 emissions, in renewable spillage and the potential reduction of energy not supplied. Therefore, the expected benefits show that the investment will be profitable for the society in less than 10 years, mainly as it allows using more efficient and therefore cheaper generation plants. Other qualitative benefits of the new reinforcement are that it improves the quality and reliability of the electrical system, it provides greater security of supply and a greater stability in the Spanish system, it reduces the consideration of the Iberian Peninsula (Portugal and Spain) as an electrical island, born from the existing low exchange capacity with the rest of Europe, and allows higher integration of renewable energies. It also fosters the Integration of the Iberian Electricity Market in the Internal European Electricity Market. Regarding financing, the project has an important support from the European entities. It obtained a 225 M grant in the framework of the European Energy Program for Recovery (EEPR). In addition, the European Investment Bank (EIB) has undertaken to participate in financing the France-Spain interconnector with a EUR 350 M loan. 7. CONCLUSIONS The first interconnection that will be commissioned in more than 25 years between France and Spain will finally be in service in 2014 and will allow the doubling of the exchange capacity between both countries. It will consist of two identical but independent VSC links between Santa Llogaia (Spain) and Baixas (France), with a nominal active power of MW each and a rated DC voltage of ±320 kv. This project is a great challenge for the technology suppliers as the technologies chosen for the new HVDC interconnection line between France and Spain, both for the cable system and the converter stations, represent an innovation at the levels of voltage and active/reactive power required in the Voltage Source Converter (VSC) link. It is also a challenge for the TSOs as the project has the peculiarity of being an HVDC link embedded in an AC network. A special operation is necessary different from that of the usual HVDC links. 12

14 The advantages of the development of the France-Spain interconnection have been widely spread and are completely in line with the European Energy objectives. These advantages go from the improvement in the conditions of quality and security of the electrical system, making possible at the same time a greater integration of the renewable energies, to the extension of the commercial capacity between both countries, reducing the present situations of congestion, allowing the use of more efficient and cheaper generation, and benefiting the progress to the Internal market. However this is only the first step: there is a governmental agreement for reaching a exchange capacity of MW at this border that is not fulfilled with this reinforcement, the interconnection ratio with this line will be around 5%, still far away from the recommendation of the European Union, and moreover, important congestions are still expected. The studies from the European Commission detect the need of at least MW [10] between France and Spain, and consider the French-Spanish border as one of the four european priorities in electricity [11]. Therefore, in order to get away from the consideration of «electric island» for the Iberian Peninsula, Spain and France are already working on a new interconnection. 13

15 BIBLIOGRAPHY [1] Decision Nº 1364/2006/EC of the European Parliament and of the Council of 6 th September 2006, laying down guidelines for TransEuropean Energy Networks (TEN- E Guidelines) and decision Nº 1229/2003/EC. [2] Spanish Ministry of Industry Planificación de los Sectores de Electricidad y Gas , May de [3] Studies of the European Coordinator M.Monti: [4] French Law Démocratie de Proximité of 27 th February 2002 (law Nº ) and French Decree Nº , of 22 th October 2002, related to the organization of public debates. [5] CIGRÉ Working Group B4.37, VSC Transmission, May [6] Marquardt R. Lesnicar A, New Concept for High Voltage-Modular Multilevel Converter, IEEE PESC 2004 conference, Aachen, Germany. [7] Don J., Huang H., Retzmann D., A new Multilevel Voltage-Sourced Converter Topology for HVDC Applications, Cigré Session, B4-304, 2008, Paris, France. [8] Pérez de Andrés J.M., Dorn J., Retzmann D., Soerangr D., Zenker A., Prospects of VSC Converters for Transmission System Enhancement, Power Grid Europe, Feria de Madrid, Junio 2007, Madrid, Spain. [9] Siemens, HVDC Systems and their planning. [10] M. Supponen, Which role does congestion management play in the Commission s view in the European electricity market?, Energidagene [11] European Commision, COM(2010) 677/4 Energy infrastructure priorities for 2020 and beyond -A Blueprint for an integrated European energy network, November [12] 14