Development of Congestion Management Procedures

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consideration regulations of the European Union and ETSO recommendations. ..... methods are being applied, such as 'priority list' (first come first served) or ...
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Development of Congestion Management Procedures in South-east Europe Zoran Ž. Vujasinović Mladen R. Apostolović, Snežana V. Mijailović

Abstract—Countries of the South-east European region are simultaneously progressing in the development of the regional electricity market, especially in the domain of the procedures related to the Congestion Management, while taking in full consideration regulations of the European Union and ETSO recommendations. The paper presents experiences of European countries in implementation of auctions as the market-based method for transmission capacity allocation, whether it is explicit or implicit together with the trade in electric energy. The accent is put on coordinated procedures that are jointly applied by TSOs involved, the aim of which is to find the most efficient solution for the common problem of congestions that occur in transmission networks. Regional approach to this problem in South-east Europe reflects through a common pilot-project of coordinated flow-based explicit auctions, which is soon supposed to begin the dry-run period of implementation. Index Terms—Auction, Capacity, Coordination, Power Exchange, Transmission

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Congestion,

I. INTRODUCTION

ON-DISCRIMINATORY approach to interconnected tie-lines between electric power systems of particular states is one of the preconditions for the smooth operation of the free electricity market. This is why the existing interconnection tie-line capacities must be used in an efficient way and in accordance with market principles. When it is known that interconnection capacities are scarce, one of the most important questions is fair and economically based allocation of such transmission capacities. In the process of definition of rules applied to regional electricity market in South-east Europe, important task is to define procedures for congestion management i.e. transmission capacity allocation. In definition of these procedures, TSOs of southeastern European countries were lead by: 1) the need to establish all aspects of regional market, including the procedures of congestion management, on rules and regulations of EU, which is in accordance with the ”Memorandum of Understanding” [1], for the purpose of harmonization with EU internal electricity market even before the admission of countries in the region in EU. This is why the Regulation of European Commission [2], Z. Ž. Vujasinović is with Electricity Coordinating Center (EKC), Belgrade, Serbia & Montenegro (e-mail: [email protected]). M. R. Apostolović is with Electricity Coordinating Center (EKC), Belgrade, Serbia & Montenegro (e-mail: [email protected]). S. V. Mijailović is with Electricity Coordinating Center (EKC), Belgrade, Serbia & Montenegro (e-mail: [email protected]).

Guidelines for Congestion Management [3] and relevant ЕТSO recommendations are used as the basis for the definition of procedures for Congestion Management, 2) the fact that electric power systems in the region are highly meshed, thus the need for coordination of the process of transmission capacity allocation. Aware of interdependence of electric power systems in the region, and starting from experiences from the European Union in this field, the intention of TSOs of southeastern Europe is to achieve high level of cooperation in transmission capacity allocation. In that respect, special attention is paid to examination of possibilities of application of coordinated flow-based auctions method. European practice has already recognized the need for coordination, that is for regional approach to resolution of congestions in transmission network, and in the beginning of 2005. activities in this field were intensified. It is also clear that auctions are identified as the market-based method that can successfully be applied in elimination of congestions. Depending on the time horizon for allocation of transmission rights to interconnected tie-lines and the level of development of particular markets (existing Power Exchanges or not), application of explicit and/or implicit auctions is possible. Basic feature of explicit auctions is that it involves only the trade in transmission capacities (MW), which means that the obtaining of the rights for the use of transmission capacities is separated from the trade in electric energy (MWh), which naturally precedes such trade and they can be applied to time horizons from day-ahead to year-ahead. Unlikely to explicit auctions, implicit auctions includes both the trade in electric energy and transmission capacity required for the realization of such trade and they naturally apply only to a day-ahead time horizon. Since the implementation of one of the possible explicit auction methods doesn’t impose big requirements related to the organization of national markets, they are imposed as logical solution for implementation in the southeastern European region, while aiming for gradual introduction of economically more efficient implicit auction methods, whenever possible, as particular national markets grow and develop. II. EXPLICIT AUCTIONS In the first half of 2005, the system of explicit auction of transmission capacities was for the first time introduced to

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numerous European borders, and in places where it already existed [4] it has been improved, so that explicit auctions are currently the most applied method for elimination of congestions in the continental Europe. Implementation of this method is in accordance with the European Commission Regulation No. 1228/2003 [2], which anticipates the introduction of market-based methods for congestion elimination, i.e. transmission capacity allocation, and notably underlines explicit auctions, putting the accent on the special part about “guidelines for explicit auctions” within broader “guidelines for management and allocation of available transmission capacities of interconnection tie-lines between national systems”. Explicit auctions of transmission capacities are nondiscriminative, transparent and market-based method, which allocates scarce capacities to such participants in these auctions who offered the highest price. The capacity is distributed to interested players only up to the amount of offered capacity that was previously calculated by TЅOs that organize auctions on their borders. Explicit auction represents the competition of players on electricity market who wish to use transmission capacities between particular states, i.e. their control areas. In their offers, players state the amount of transmission capacity (expressed in active power) that they want to buy as well as the price they are ready to pay for it. Positive result in the auction gives the right to the player to exchange the electric energy between corresponding states/areas, in power that he obtained. The first and the main precondition for implementation of explicit auctions is calculation of transmission capacities between states, determination of the value that will be offered to market players and its publication. Prevailing method of transmission capacity calculation is based on definitions provided by ETSO organization [5]. Since the “contracted path method” is still currently used in Europe for establishment of exchange programmes between particular (control) areas, according to which electricity exchanges are nominated on the border between two neighboring areas, the implementation of these “bilateral” transmission capacities and their offering in auctions is widely spread. If after the ranking of all offers it turns out that required capacity is higher than the one offered at the auction, it is necessary to make a selection of offers in the way that requests are accepted only up to the amount of offered capacity. Next question is how much players will be charged after the auction. There are two possibilities: each player will pay the amount that he offered for the transmission right that he has achieved at the auction (payas-bid) or that all players pay equal “marginal” price (marginal pricing). Charging the player the marginal price is generally accepted because its purpose is to free the player of payments if there are no congestions (no congestion-no payment). Marginal price is the price of the latest offer that was entirely or partially accepted (Fig. 1). The choice between these two pricing methods depends on agreed rules for the auction.

The principle of marginal pricing shows the good side of explicit auctions which give directional economic signals about locations that really require the increase of transmission capacities. Namely, if there are no congestions on some border, it means that interconnecting tie-line capacities are sufficient to support required international trade. And vice versa, if congestions occur on the border, it is necessary to charge for the use of capacity and to route collected money for the increase of transmission capacities on that border.

Price [? /MW] Bid1 Bid2 Marginal price

Offered capacity - ATC

Bid3 Bid4

Requested capacity [MW] Fig. 1. Explicit auctions: marginal pricing

Beside all good points of explicit auctions related to the fact that they are based on sound and well-known economic principles, their ability to adapt to different ways of organization of national electricity markets on both sides of the border (whether it is Power Exchanges or bilateral trade), they also have their bad points, such as when they are limited only to bilateral implementation between two neighboring TЅOs: - they don’t take much in consideration that in meshed transmission networks, electricity exchanges at a certain power between two (neighboring) states/areas can cause considerable parallel load flows (loop flows) through a third country. This implies that bilateral transmission capacities cannot be strictly defined and guaranteed, because they are highly interdependent, - with implementation of still valid method of contracted path, in the contracting of transfers of power through several borders (transit), with auctions on these borders, it is very likely that this virtual path is interrupted because of unsuccessful result of the auction only on one of the borders. In order to overcome these deficiencies, it is necessary to achieve regional cooperation between TЅOs and to apply common mechanisms for allocation of capacities on their borders. Today, there are several examples of regional coordination of procedures of transmission capacity allocation in Europe. III. COORDINATION OF AUCTIONS OF TRANSMISSION CAPACITIES Faced with the above-mentioned problems related to implementation of unbundled (bilateral) allocation methods, TSOs in Europe are more and more recurring to the regional coordination of allocation process. A step in

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that direction is also the most recent initiative of ETSO to organize several regional „mini-fora” that need to approach the problem of congestions at the regional level. The Table I represents the overview of existing methods of coordination of auctions between TЅOs, and their classification is based on “goods” traded in (electric energy, transmission capacity), type and way of recognition of interdependence of restrictions that are limiting transmission capacities, with the remark where is particular method applied in Europe.

TABLE I OVERVIEW OF EXISTING METHODS FOR COORDINATION OF AUCTIONS AMONG TЅOS COORDINATION OF AUCTIONS auctions:

explicit

trade with:

transmission capacity

name: based on: restriction:

Joint auctions

Coordinated auctions

ATC-based exchange program

ETSO coordinated auctioning flow-based physical

restrictions interdependence

unbundled

bundled

bundled

implemented:

The Netherlands, Belgium, Germany

Czech Rep., Poland, Germany

SE Europe – pilot-project

auctions:

implicit

trade with:

electric energy + transmission capacity

name:

Market Splitting

Flow-based Market Coupling

based on:

ATC-based

flow-based

restriction:

exchange program

physical

restrictions interdependence

unbundled

bundled

implemented:

Nordic countries

theoretical

The following text gives the summary explanation of existing examples of coordination of explicit and implicit auctions from European practice, whereas the examination of coordinated flow-based explicit auctions, which is under way in southeastern Europe, is explained in the separate chapter.

Fig. 2. Coordination of the auctions at The Netherlands borders

Auctions are held on yearly, monthly and daily level [6]. For each of directions of possible electricity exchanges, presented on the Fig. 2, available transmission capacities are notably published and there are six separate, individual auctions. Interdependence of these capacities is taken in consideration in their calculation, i.e. they are unbundled for the auction. The price for use of transmission capacities is determined on marginal price principle, i.e. all players who get the capacity pay the same price set by the latest entirely or partially accepted offer. If there are two offers with the same price, and there is not enough capacity to meet them both, remaining capacity will be allocated proportionally to their requirements („pro-rata rationing“). If the interest for transmission rights in some direction is smaller than available capacity, the price equals zero, i.e. players who have allocated capacity can use it free of charge. B. Coordinated explicit ATC-based auctions: CENTREL A step further in recognition of interdependence of use of transmission capacity between the states was made in late 2004 by TЅOs of Czech Republic (ČEPS), Poland (PSE-O) and Germany (VE-T), with the agreement on implementation of joint coordinated explicit auctions of transmission capacities, as of January 2005 on common borders (Fig. 3). During 2005, Slovakian TSO (SEPS) didn’t take part in these coordinated auctions. However, all calculations are made also for the border PSE-O – SEPS, unilaterally for PSE-O side.

A. Unbundled coordination of explicit auctions: Netherlands

VE-T

PL

Bout

PSE-O

Bin

A o ut

DE

A in

t ou

CZ

C

D out E-ON

D in

The first example of coordination of operation of neighboring TЅOs from the aspect of joint auctions of transmission capacities at borders on which capacities are highly interdependent is The Netherlands with its neighbors Belgium and Germany. Dutch (TenneT), Belgian (ELIA) and two German (EoN i RWE) TЅOs have established in spring 2000 a joint auction ofiice called “TSO Auction BV”, with the main office in Arnhem (The Netherlands).

ČEPS

C in

SK

SEPS

Fig. 3. Coordinated auctions between Czech Republic, Poland and Germany

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Auctions for transmission capacities are organized on a yearly and monthly basis and as of April 2005 also on a daily basis [7]. The capacity that remained unallocated on yearly auctions is offered on a monthly level, and subsequently on a daily level. For these auctions, so-called commercial and technical profiles are defined. Commercial profiles are borders between involved TSO (PSE – VET, PSE – ČEPS, VET – ČEPS and PSE – SEPS), whereas technical profiles are groups of borders for which common restriction of transmission capacities is defined, as established by at least one TSO and which includes at least one commercial profile. Technical profiles are represented on the Fig. 3 with (A,B,C,D,E) and defined for both directions, whereas commercially important are: export from Poland (Aout); import to Germany-VET from Poland and Czech Republic (Bin); import to Czech Republic from Poland (Cin); export from Czech Republic to Germany-VET (Dout); import to Slovakia from Poland (Ein). It can be noticed that some of these technical profiles partially overlap, and that limitations defined for them are NTCs calculated according to ETSO procedure. The quantity that players can require in one offer is limited to 50 MW. However, one player can send more than one offer (each not more than 50 MW) but in that case offered prices mustn’t be the same. This partially avoids the problem that can cause “big” players in the market by abusing their dominant position, i.e. „market power”. Offers are submitted on commercial profiles, and exceeding of restrictions (i.e. published ATC) is observed on technical profiles. Offers are ranked by the offered price, from the highest to the lowest, and exceeding of restrictions on all technical profiles is examined simultaneously. If the limit is not exceeded, the capacity is obtained free of charge. If however, the limit is exceeded, the offer with the lowest price, which goes through congested technical profile, is rejected entirely (in yearly and monthly auctions) or partially – up to the level of ATC (in daily auctions). The last accepted offer determines the marginal price, i.e. the price for use of capacities on all commercial profiles that correspond to that congested technical profile. If the congestion occurs on two partially „overlapping” technical profiles, higher of two marginal prices is taken in consideration. C. Coordination of implicit auctions (ATC-based) Considering that implicit auctions include both the trade in electric energy and the trade in transmission capacities, it can be concluded that the model of implicit auctions is more advanced solution compared to explicit auctions, where the player must obtain transmission capacity first and then to participate in electricity market so as to be able to use that capacity. Coordinated implicit auctions are already for fifteen years applied in Scandinavia, under the name of Market Splitting. Problem solving related to congestions that occur between Norway, Sweden, Finland and western Denmark is conferred to the jointly owned Power Exchange

“NordPool”. Basic characteristics of market splitting method are: - complete trade in electric energy (and implicitly in capacity too) between states is carried out over the Power Exchanhe, i.e. bilateral agreements between states are not allowed, - physical trade is agreed only for the following day, and there are corresponding financial markets for long-term contracts (futures, forwards), - restrictions of transmission capacities (ATC) are unbundled because of characteristics of the transmission network in the region (poorly meshed network with low interdependence of transmission capacities). D. Coordination of implicit auctions (Flow-based) Implementation of Market Splitting in continental Europe is at the moment not applicable, primarily for the two following reasons: - absence of Power Exchanges in all states (as the alternative to one common Power Exchange for the whole Europe, which shouldn’t be even considered), - interdependence of transmission capacities in continental Europe cannot be represented in adequate way through unbundled Available Transmission Capacities (ATC). Solution to these two problems could be a sort of development of implicit auctions, as those that exist today in Scandinavia in two ways: - existence of several regional Power Exchanges, as the alternative to only one that exists in Scandinavia, - recognition of interdependence of transmission capacities in continental Europe, through implementation of a flow-based model, that is, through the modeling of physical load flows caused by transactions through Power Transfer Distribution Factors (PTDF). A new theoretic proposal of ETЅO and EuroPEX organizations, called Flow-based market coupling [8], contains these very two qualities. Basic idea was to form regional areas between which there are restrictions to electricity exchange and through the use of Power Exchanges in these areas and distribution factors, to have the best possible use of transmission capacities between these areas. Main deficiency of this proposal is that it is impossible at the moment to implement it widely because of the earlier mentioned fact that electricity Power Exchanges do not exist in all countries that would be involved in this mechanism. IV. SOUTH-EAST EUROPE: CURRENTLY APPLIED METHODS AND PILOT-PROJECT ON COORDINATED EXPLICIT FLOWBASED AUCTIONING

Countries of the South-east Europe are at the moment on different levels of development of allocation procedures, so that in many borders at the moment some non-market methods are being applied, such as ‘priority list’ (first come first served) or pro-rata rationing. On all borders are currently applied bilateral methods of transmission capacity allocation. Currently applied capacity allocation methods in

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SEE region are presented in the Fig. 4 (situation in May 2005) [9]. Through the joint work on the establishment of coordination in calculation and allocation of transmission capacities, the first result was recently introduced monthly exchange of transmission network model used for coordinated calculation of Net Transfer Capacities (NTC) [14]. The need for coordination has already been recognized through NTC calculations not only between individual states, but also between groups of states, where it is necessary. The new approach in the modeling of mutual influence on inter-state transactions of electric energy is applied in South-east Europe through the pilot-project of coordinated flow-based auctions of transmission capacities (Fig. 5). Uneven size of some electric power systems in the region, absence of allocation mechanisms due to the level of deregulation, and especially strong mutual influence between such power systems imply that coordinated and simultaneous capacity allocation that respects load flows is necessary solution for the region of South-east Europe. In this method, defined by ETSO [10], Power Transfer Distribution Factors (PTDF) are calculated for each source and sink (i.e. for each TSO pair), the result of which is the impact of each individual commercial transaction on physical load flows on each interconnection tie-line, or the border. Restriction called “Bottleneck Capacity” (Bottleneck or Border Capacity - BC) is defined for each border, which differs from NTC, because it restricts physical load flows and not exchange programmes.

IT

IA /

/ IA EA

A PL / E

HR P L /P R

BA P L ,P L

PL / E A PL /

PR

PL, P L PL PL,

CG PL, PL IA /

EA

In auctions, players send their offers in which they define required quantity [MW], source/sink TSOs and offered price. The impact of such offers is through PTDF matrix transformed into load flows on borders and observations are made whether Border Capacities are exceeded. Transactions that have the lowest offered price per 1 MW on eventually congested border are rejected. The mechanism of coordinated flow-based auction [13] is basically very similar to the solution applied between the Czech Republic, Germany and Poland, but it is improved with more precise physical representation of particular transactions impact on load flows on interconnection tielines.

IA / EA

PR

SI

PR / EA A nt E Joi

HU / A R E P

L P L, P

/ PR

t) tes EA(

MK PL PL

RO / L P

PL, P PL L, P L

AL

EA – Explicit Auction IA – ImplicitAuction PR – Pro Rata PL – Priority List (first come-first served) No – No method ?? – Missing information

Fig. 5. Coordinated Auctioning Pilot-project in South-east Europe

EA / EA(te st)

SR

AT

P L E A

t)s e t( A E

BG N o

TR

GR

Coordinated among TSOs≡ in all cases NTC shared50% / 50%, except between AT and HU(joint allocation of100% NTCs in both direction) Not coordinated among TSOs - two TSOs applying separate allocation for the same capacity (or no method applied )

Fig. 4. Currently applied allocation methods in SEE region

During the summer of 2004, the first phase of pilotproject was completed, in which technical aspects of eventual implementation of this method in the region was defined (network models, PTDF and BC calculations, comparison of calculated and actual load flows...). Results were presented at the 5th Athens Forum [11], which has after that decided to organize a „dry-run” implementation of coordinated auctions in the southeastern European region, as of the summer 2005, but due to legal reasons at 6th Athens Forum it was agreed to postpone start of „dryrun” period to October 2005. Preparations for the „dry-run“ period are under way, together with the definition of all technical, organizational and legal aspects of implementation of the method in the forthcoming period, and also the cooperation with regulators of countries involved in the process is also initiated, with the aim to find a common solution [9]. V. HYBRID METHODS In the recent literature [12], one of the mentioned possible final solutions of congestion problem at the European level is the implementation of a “hybrid” model

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that anticipates explicit auctions for time horizons longer than the daily level, whereas implicit auctions are proposed for day-ahead trade. Such combination would allow the coexistence of long-term bilateral agreements with the dynamic trade in the day-ahead market. Such solution could be suitable also for the region of South-east Europe, if explicit auctions (on longer time horizons) and implicit auctions (on day-ahead time horizon) were organized with paying full respect to physical load flows through PTDF factors. VI. CONCLUSION Regional cooperation in resolution of problems related to congestions in transmission networks, through correct transmission capacity allocation, is the future of the whole Europe and should overcome all existing problems related to unbundled (bilateral) allocation methods in regions with high interdependence between the electric power systems. Steps in that direction are recently organized „mini-fora” that should help in finding the most favorable methods for elimination of congestions at the regional level. First „minifora” for South-east Europe is anticipated to take place in September 2005. in Athens. Countries of South-east Europe are at the moment trying to find the solution for the method of transmission capacity allocation that would improve described solution applied in the central Europe in the way to recognize physical influence of certain transactions, through the pilot-project and preparations for the „dry-run“ implementation of ETSO’s method of coordinated flow-based auctions. Implicit auctions of electric energy, although naturally limited only to the day-ahead planning, represent for the time being the greatest achievement in the process of congestion management. The most recent theoretic proposal of ETЅO and EuroPEX to introduce implicit coordinated auctions at dayahead level that would also take in consideration the influence of physical load flows, although complicated from the organizational aspect, represents a sort of bettered Market Splitting method, i.e. it is adjusted to regions with high interdependence between the electric power systems. General conclusion is that all solutions related to transmission capacity allocation in Europe converge towards regionalization and implementation of a hybrid model, that is: - coordinated explicit auctions on long-term (yearly, monthly) level, and - coordinated implicit auctions on daily level, so that in both cases the approach of modeling of transmission network for the purpose for transmission capacity allocation based on load flows is applied.

[2]

“Regulation (EC) No 1228/2003 of the European Parliament and of the Council of 26 June 2003 on conditions for access to the network for cross-border exchanges in electricity” [3] “Congestion Management Guidelines”, European Commission, Directorate-General for Energy and Transport, draft, September 2004 [4] “An Overview of Current Cross-border Congestion Management Methods in Europe”, ETSO September 2004 [5] “Definitions of Transfer Capacities in liberalized Electricity Markets”, ETSO April 2001 [6] 2005 Regulations for the auctioning of cross-border electricity transfer capacity on the extra high-voltage Belgium - Netherlands, GermanyNetherlands interconnectors [7] Rules for coordinated auctions of transmission capacity at the common borders of ČEPS, a.s., PSE-Operator S.A., Vattenfall Europe Transmission GmbH for the year 2005 [8] “Flow-based Market Coupling - A Joint ETSO-EuroPEX Proposal for Cross-Border Congestion Management and Integration of Electricity Markets in Europe, Interim Report” ETSO September 2004 [9] “Coordinated Auctions in SEE region – Activity Report (for 6th Athens Forum)”, ETSO, May 2005 [10] “Coordinated Auctioning: A market-based method for transmission capacity allocation in meshed networks”, ETSO, Final Report, April 2001 [11] “Pilot-project on Coordinated Auction of transmission capacity in South-east Europe, 1st phase results (for 5th Athens Forum)”, ETSO October 2004 [12] “Analysis of Cross-Border Congestion Management Methods for the EU Internal Electricity Market”, CONSENTEC, Frontier Economics Limited, Final Report, June 2004

Papers from Conference Proceedings (Published): [13] Mijailovic S., Popovic D., “A NEW COORDINATED AUCTIONING METHOD AS A SOLUTION FOR CONGESTION MANAGEMENT PROBLEM”, VI Bulk Power Systems Dynamics and Control, IREP Symposium 2004, August 22-27, 2004, Cortina D’Ampezzo, Italy, A129 [14] Popovic D. P., Dobrijevic Dj., Mijailovic S., Vujasinovic Z., “AUTOMATIC CROSS-BORDER TRANSMISSION CAPACITY ASSESSMENT IN THE OPEN ELECTRICITY MARKET ENVIRONMENT”, CIGRE, Paris, France, 2004

VIII. BIOGRAPHIES Zoran Vujasinović was born in 1974 in Knin. He graduated in 1999 at the Faculty of Electrical Engineering, Energy Department, Electric Power Systems Section. Since June 2000 he is employed in the Electricity Coordinating Center in Belgrade as the engineer for analyses. His interests are focused on the development and implementation of NTC calculations, congestion forecasts (DACF) and methodologies for congestion management. He is a member of SETSO/SUDEL working group "Access to network, congestion management and load flows", the prime task of which is implementation of the above-mentioned activities in the southeastern European region. He has been working on many Interconnection studies/analyses and he published a number of papers for local and international CIGRE. Mladen Apostolović was born on October 6, 1975, in Belgrade, Serbia and Montenegro. In 2000, he graduated at the Faculty of Electrical Engineering of the University of Belgrade, Serbia and Montenegro. He is currently employed in the Electricity Coordinating Center in Belgrade and he is on postgraduate studies at the University of Belgrade. He is a member of the UCTE Technical Committee for Albania. His research interests include congestion management methods and electricity market organization and functioning. Snežana Mijailović was born in 1965 in Pančevo, Serbia & Montenegro. In 1990 she graduated at the Faculty of Electrical Engineering of the University of Belgrade, Serbia and Montenegro. She worked in Nikola Tesla Institute, and since 1997 she is employed in the Electricity Coordinating Center in Belgrade. She is a member of several UCTE, SETSO and ETSO groups. She became Master degrees on the problems of congestion management methods and electricity market issues.

VII. REFERENCES Technical Reports: [1]

“Memorandum of Understanding on the Regional Energy Market In South East Europe and its Integration into the European Community Internal Energy Market”, Athens, December 8, 2003”

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