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40220130405021 2

  1. 1. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING & ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME TECHNOLOGY (IJEET) ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), pp. 206-220 © IAEME: www.iaeme.com/ijeet.asp Journal Impact Factor (2013): 5.5028 (Calculated by GISI) www.jifactor.com IJEET ©IAEME AN ASSESSMENT OF TECHNICAL AND ECONOMICAL PROBLEMS BASED ON REACTIVE POWER IN RESTRUCTURED TURKISH POWER SYSTEMS OMER GUL Istanbul Technical University, Department of Electrical Engineering ABSTRACT In electrical energy systems, reactive power is needed to reduce the losses, keep the voltage within acceptable limits, active power flow and reliable operation conditions. In this study, the technical and economical problems based on reactive power are being discussed, which have arisen in the reactive power supply after the Turkish electrical power system has been restructured and unbundled to generation companies, transmission company, and a number of distribution companies. Moreover, it is aimed to contribute to the formation of a reactive energy market by providing suggestions for the reactive power management and reactive power auxiliary service purchase in the Turkish electrical energy market during its deregulation process. Index Terms- Electricity Market, Reactive Power, Restructured Power Systems, Turkey. 1. INTRODUCTION For long years, the electrical energy industry at its vertical organizational structure covering generation, transmission and distribution, was a monopoly structure with the responsibility to serve all consumers. However, in the last two decades, electric utilities around the world are involved in a restructuring process, moving from vertical integrated to competitive market structure. The most important reason for these changes was to increase the productivity at the electrical energy systems and to provide the electrical energy to the customers at lowest cost via enabling competitive conditions in the electricity market [1, 2]. In Turkey, the management inadequacy, high level of losses and also the inadequacy of public resources should also be added to the list of justifications for restructuring. Among these justifications, the most significant for Turkey is the fact that public resources prove to be insufficient in the financing of the electrical energy industry that is growing annually at 7% on the average. Law No. 4628 becoming effective as of March 3, 2001, has been the most significant step towards the establishment of a competition based market in the Turkish electrical energy industry from its day of enforcement until today [3]. The public institutions operating in this sector were 206
  2. 2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME restructured and the market rules to enable liberalization were started to be implemented. Turkish Electrical Energy Sector Reform and Privatization Strategy Instrument, being the short and medium term road map of the electrical energy sector regarding privatization, was published on March 17, 2004 [4]. The formation of a competition based market in the electrical energy sector requires a transition period. This transition period is still continuing in the Turkish electrical energy market where the necessary legal arrangements are almost completed. The National Load Dispatch Directorate under the structure of Turkish Electricity Transmission Inc. Co. (TEIAS), for whom it has been decided to remain as a public company, is performing the role of the independent system operator (ISO) and the created balancing and conciliation system is again operating as bound to TE AS [5]. Today in the deregulated energy systems, the ISO operator has the responsibility to operate in a reliable manner. This responsibility necessitates operation within the transmission line power flow limits and bus voltage limits. Therefore, besides reducing the system losses, the reactive power management has a vital significance for the system operators to ensure that the system can be operated in a reliable manner [6, 7]. In the Turkish electrical energy sector, where the process for the formation of the free market rules is still continuing, reactive power is required to ensure reliable operation conditions. The generation, distribution and consumer responsibilities to provide the required reactive power have been arranged with several regulations. Furthermore, reactive power provision has been perceived as an auxiliary service and it has been put under regulation with the Electricity Market Auxiliary Services Regulation published [8]. After the restructuring, the technical and economic responsibilities of the parties have changed; and certain technical and economical problems are being experienced in the process of adaptation to the changed new situation. In this study, the technical and economical problems are discussed that have arisen with the separation of the electrical energy sector under generation, transmission and distribution with the aim of transition to free energy market and separate identification of the responsibilities for the provision of reactive power. In the conclusion, suggestions are put forwards concerning the reactive power management for the restructured electrical energy system in Turkey and the formation of the reactive power market. 2. RESTRUCTURED ELECTRICAL POWER SYSTEM IN TURKEY With the development of the electrical energy sector in Turkey, a need for an institutional structure come forward and the Turkish Electricity Agency (TEK) was founded in 1970 with the responsibility to serve all the consumers nationwide. The generation, transmission, distribution and supply activities in the electrical energy sector were combined under the public agency TEK. In 1984, Law no. 3096 on the Commissioning of Institutions other than Turkish Electricity Agency for the Generation, Transmission, Distribution and Trade of Electricity. Law no. 3096 provides for the performance of the electrical energy-related services with the facilities of the private sector and the execution of the service for certain periods with the transfer of the operation right. To increase the participation of the private sector furthermore, Turkish Electricity Agency was taken inside the scope of privatization and TEK was separated into two under the names of Turkish Electricity Generation and Transmission Inc. Co. [9]. (TEAS) and Turkish Electricity Distribution Inc. Co. (TEDAS) with the Decision no. 4789 of the Ministers Board of the Republic of Turkey in 1993 to prepare the company for privatization. As can be seen in Figure 1, it is seen that the technical and nontechnical losses rates have increase more as of 1993 when the distribution was made as a separate company [10]. In 2000 years where the technical and nontechnical losses rates have exceeded 20%, the necessity to privatize electricity distribution became more pronounced due to the need for renewal and additional investments 207
  3. 3. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME required by electricity distribution owing to the high amount of failure-related interruptions and periods thereof, voltage fluctuations, etc. poor energy quality problems. Figure 1. Technical and nontechnical losses of the electricity distribution in Turkey Besides the existing problems of the electrical energy sector, the restructuring studies in the energy sector were accelerated with the foresight that the public resources would prove to be insufficient and supply difficulty would be encountered in the future in meeting the additional investment costs to be brought about by the new power plants, transmission and distribution lines to meet the growing electrical energy sector demand at 7% annually on the average as seen in Figure 2 and that is expected to grow more in the future [11]. Figure 2. The electricity consumptions of Turkey as per the years ( ( ) scenarios 208 ) high and ( ) low demand
  4. 4. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME In 2001, Turkish Electricity Inc. Co. (TEAS) was divided into three separate companies as Turkish Electricity Transmission Inc. Co.(TEIAS), Turkish Electricity generation Inc. Co. (EUAS) and Turkish Electricity Trade and Undertaking Inc. Co. (TETAS) with the decision no. 2026 of the Ministers Board. The foundation of the Turkish Energy Market Regulatory Board (EPDK) in 2001 with the Law no. 4628, has been an important milestone in the restructuring process of the Turkish electrical energy industry. This law covers topics such as the separation of generation, transmission and distribution activities, regulation of wholesale and retail sales activities, regulation of the electrical energy sector by EPDK, bringing forth license application, definition of free consumer, benefiting of all users from the transmission and distribution services at equal terms, bilateral agreements among the license holder judicial entities subject to special legal provisions, creating an operating market and complementing thereof with a balancing and conciliation mechanism [12]. The structural change of the electrical energy sector in Turkey is given in Figure 3 and the Energy Market Regulatory Board (EPDK) has been kept responsible for the regulation of the electricity market. Before 1993 1993 2003 Today TEK (Generation, Transmission, Distribution) TEAS (Generation, Transmission) EUAS Generation TEIAS Transmission TEDAS (Distribution) TETAS Wholesale TEDAS (Distribution) 21 Companies Figure 3. Structural change in the Turkish electrical energy sector The Electricity Market Application Guide was published by EPDK and EPDK has put into force nineteen regulations to regulate the electrical energy market from its establishment until today. The “Electrical Energy Sector Reform and Privatization Strategy Instrument” that has been prepared with the agreement of all the parties related with the implementation of the electricity market reform with an integrative approach, was accepted with the March 17, 2004 dated 2004/3 numbered decision of the Higher Planning Board. With the Electrical Energy Sector Reform and Privatization Strategy Instrument, the distribution grid of Turkey was divided into 21 distribution zones by considering geographical proximity, managerial structure, energy demand and other technical/financial factors and TEDAS, possessing 20 of these, were taken in the scope of the privatization program [4]. The consumption and losses rates of these electricity distribution companies according to their subscriber groups are given in Table 1 [10]. In Turkey, that has quickly shaken off the effects of the global economic crisis that has put its mark in the 2008-2009 period, the privatization of the electricity distribution is continuing at high pace towards the creation of a transparent electricity market that can operate in a competitive environment according to special legal provisions, financially sound and stable, and the implementation of a cost based pricing mechanism. A distribution company was founded in each of the 20 zones taken inside the privatization program and these companies with distribution license are shown on a Turkey map in Figure 4. The only distribution zone that is left outside of privatization is Kayseri, of which the operation right was transferred to Kayseri Electricity Distribution Inc. Co., (Kayseri EDAS) in 1990 [13]. Among these distribution companies, Baskent EDAS, Sakarya EDAS and Meram EDAS were privatized in 2009 by the Privatization Department Presidency in the scope of the Privatization Law no. 4046. Aras EDAS, Çoruh EDAS, Yesilirmak EDAS and Osmangazi EDAS are distribution companies whose 209
  5. 5. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME privatization tenders have been completed and are at the approval stage. Van Lake EDAS, Firat EDAS, Camlibel EDAŞ and Uludag EDAS privatization tender announcement has been made. It is expected that the Prime Ministry Privatization Administration Presidency of the Republic of Turkey will announce a privatization tender within the February month of 2010 regarding the “granting of operation right” for 52 Power Plants belonging to EUAS divided into 19 groups. The operation of the Turkish electricity market first of all depends on the privatization of the electricity generation power plants and electricity distribution companies at the hand of the public in the shortest time possible and thereby on the increase the share of the private sector in the electrical energy sector [14]. Agricultural (%) Lighting (%) Other (%) Consumption 15,0 3,7 14,2 5214 64,2 Van lake 39,8 13,6 13,9 7,4 0,8 12,8 11,7 1137 55,9 Aras 44,1 13,8 16,1 7,0 1,0 8,3 9,8 1656 27,2 42,1 15,0 6,0 24,9 0,1 6,4 5,5 2268 10,7 28,9 9,6 17,7 27,8 6,6 4,8 4,6 2145 10,5 29,8 10,0 5,1 37,9 4,2 6,3 6,8 2088 8,8 Toroslar 25,7 11,2 3,7 46,7 3,3 3,3 6,1 13905 8,9 (2) 22,6 10,3 6,7 30,5 23,9 3,7 2,2 5859 8,4 34,6 18,7 13,4 28,0 1,4 2,9 0,9 11161 8,3 Akdeniz 27,5 31,8 9,0 19,0 3,4 3,2 6,2 6049 9,0 Gediz 27,4 12,8 3,7 43,0 4,2 3,2 5,7 13862 6,3 Uludağ 22,2 12,0 2,9 54,4 1,0 1,6 5,8 10941 6,0 Trakya 16,6 6,8 1,9 62,9 1,8 1,4 8,5 5473 7,0 40,5 27,5 2,3 25,3 0,0 1,6 2,7 8672 8,6 Sakarya 18,4 12,6 3,5 59,9 0,1 2,0 3,4 8760 6,3 Osmangazi 22,3 10,3 4,2 48,6 4,7 3,0 6,9 5042 5,2 Boğaziçi 35,8 29,0 3,0 26,2 0,0 1,7 4,3 18948 11,0 Menderes 29,5 20,6 3,6 33,1 2,7 1,6 9,0 3815 4,2 Göksu 15,8 5,4 1,9 65,1 3,3 1,6 6,9 3303 7,3 Aydem 28,0 21,4 5,1 28,0 2,9 1,7 12,8 1811 17,5 23,5 11,0 1,4 52,0 3,3 2,9 6,0 2224 7,0 Çoruh Fırat (1) Çamlıbel (1) Meram Başkent (2) (1) Ayedaş (2) Kayseri (1) The privatization is in the tendering process; 210 (2) Privatized in 2009. Leak (%) Industrial (%) 20,7 (1) Loss Official (%) 8,1 Dicle (GWh) Commercial (%) 9,4 Company 28,9 Distribution Residential (%) Table 1. The consumptions and loss-leak rates in the subscriber groups of the distribution companies in 2008
  6. 6. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME Figure 4. The Turkey map showing the areas of responsibility for the electricity distribution companies 3. REACTIVE POWER MANAGEMENT IN TURKEY In the liberalized power systems, the independent system operators have the responsibility to meet the active power flow and bus voltage limits at the transmission lines. Besides the safe operation of the electricity system, operation of the bus voltages and transmission line loadings within the limiting values, due its importance in terms of minimizing the costs, the reactive power management has a vital importance for the independent system operators. Since sufficient reactive support is required for sufficient active power sales, it is of importance to establish a pricing system for reactive energy in terms of supply safety [15]. Although the financial penalties or incentives brought about on the manufacture, distribution and consumers for reactive power support provide some level of benefit; they prove to be insufficient for reactive power supply and a cost based pricing mechanism is needed [16]. As in the whole world, it is inevitable for to experience economic and technical problems in Turkey regarding the provision of reactive power in the restructured electrical energy sector. With the restructuring of the electricity sector, the operation and control strategies have been altered. In the new state in Turkey, the voltage and frequency control are perceived as auxiliary services and managed separately [8]. For the effective management of the reactive resources in the electricity systems, the market processes have to be defined and a correct economic value has to be assigned to the reactive resources. In the vertical electricity markets, the reactive power support cost is included to the electricity unit prices paid by the electricity distribution customers. Moreover, there is a penalizing system applied in case the reactive energy is not within certain defined limits. However, here the fundamental thing is not the price of the reactive energy but the penalty of the reactive energy. In the horizontal energy markets where the generation, transmission and distribution are separated from each other, it is required to determine the suppliers of the reactive power. Due to the local nature of reactive power supply, the reactive power support can be supplied from several different resources. Consequently, new arrangements are needed to enable for the competition-based reactive power resources to take place within the electricity market. The need for the new arrangements has increased the interest of the researchers towards the studies of reactive power management and establishment of a reactive power market [17-19]. Transmission grid is one of the most important elements of the liberalizing electricity market. As the transmission system provides a play field for transmission grid access to all generators and 211
  7. 7. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME customers, the transmission system operator has to be independent from the market participants. The National Load Dispatch Directorate comprises the central unit under the structure of TEIAS, responsible from the real time balancing of the electrical energy supply and demand and the operation of the system, and managing the Regional Load Dispatch Directorate operating as bound to it. The operation safety principles cover the precautions, measures and operational principles that need to be taken to ensure that the system can be operated under real time conditions without losing its stability within the predetermined limits of the voltage, frequency and power flows. To ensure that system instability is not experienced in the transmission system together with supply capacity loss, unacceptable voltage conditions or inadequate voltage performance, the reactive power requirement of the gird has to be met [19-22]. The responsibilities of the parties determined by the regulations to meet the reactive energy requirement at the Turkish electricity energy sector are given below. According to Article 16 of the Electricity Market Customer Services Regulation, the responsibilities of the customers regarding reactive energy are summarized below. When these responsibilities are not fulfilled, the user will have to make a payment for penalty based on a certain unit price for the reactive energy consumed and given to the grid. • If the ones with an installed power below 50 kVA, consume inductive reactive energy exceeding 33% (thirty three percent) of the active energy amount they draw or consume capacitive reactive energy exceeding 20% (twenty percent) of the active energy amount, • If the ones with an installed power equal to or over 50 kVA, consume inductive reactive energy exceeding 20% (twenty percent) of the active energy amount they draw or give capacitive reactive energy to the system exceeding 15% (fifteen percent) of the active energy amount. They are obliged to pay reactive energy consumption price. The principles and procedures regarding the reactive energy price required to be paid by the customers the exceed both the mentioned limits in terms of their inductive and capacitive energy consumptions or that have not established a mechanism to measure reactive energy despite the fact that they have such an obligation or that have not established such mechanism as compliant with the legislative provisions can be found at the Electricity Market Tariffs Regulation and the tariff recommendations proposed to EPDK in the framework of the related communiqués. The distribution company has the right to monitor whether the reactive power at the connection point of the user remains within the limits indicated at the connection agreement. The distribution company applies the sanctions arranged at the connection agreement in the framework of the provisions of the Electricity Market Customer Service Regulation on the user that exceeds the mentioned connection power limits. According to article 11 of the Electricity Transmission System Supply Reliability and Quality Regulation, the ratio of the inductive reactive energy drawn from the system to the active energy drawn from the system cannot exceed twenty percent (20%) and the ratio of the capacitive reactive energy given to the system to the active energy drawn from the system cannot exceed fifteen percent (15%) for the consumers directly connected to the transmission system and the judicial entities bearing a distribution license, at every measurement point related with the connection to the transmission system and at every conciliation period. The sanctions to be applied to the users in case the ratio stipulated at every measurement point of the transmission system is not complied with are arranged at the connection and system utilization agreements. According to article 20 of the Electricity Market Grid Regulation; the generation facility units should have a capacity to provide the nominal power output between power factors of 0.85 with over-excitation and 0.95 for low excitation, the units operating as synchronized compensators will be able to operate with zero power factor, the thermal power shall be able to give out reactive power up 212
  8. 8. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME to 75% of their nominal power when operated with over-excitation and consume up to 30% of their nominal power when operated with low excitation, the hydroelectric units should have a capacity to give out reactive power up to 75% of their nominal power when operated with over-excitation and consume up to 60% of their nominal power when operated with low excitation, the generation plant based on wind energy shall be operable at every point for the power factors within the limits. As conforming to the supply safety and quality regulation, TEIAS can permit for the change of these capacities without making any discrimination among the users. The reactive power given to or drawn from the system during the operation of the units as a generator or a synchronized compensator is defined as one of the obligatory auxiliary services that the judicial entities with generation activity are responsible from. The reactive power capacity outside the capacity that makes the units to give a nominal output between power factors of 0.85 at over-excitation and 0.95 at low excitation is defined as commercial auxiliary service. According to the reactive power control service supply principles as per the Electricity Market Auxiliary Service Regulation; it is obligatory that all the licensed generation facilities connected to the transmission and distribution system to participate to the reactive power control via automatic voltage regulator between the power factors of 0.85 at over-excitation and 0.95 at low excitation and/or in line with the instructions of the transmission or distribution system operator and the generation group loading curve. For the generation facilities to provide the reactive power capacity or operate as a synchronized compensator, it is fundamental for there to be an auxiliary service agreement regarding reactive power control between the judicial entity displaying generation activity to whom they are registered to and TEIAS, for the generation facilities connected from the transmission level, or the distribution license owner judicial entity, for the generation facilities connected from the distribution level. The transmission or distribution system operator has to select the generation facilities to provide the related services among the generation facilities to provide reactive energy related with reactive power control by considering the system limitations and as to minimize the cost of total reactive power control supply. The reactive power management in the Turkish electrical energy sector is under the responsibility of the National Load Dispatch Directorate (MYTM) being a subsidiary of TEIAS. MYTM determine the reactive power requirement of the electricity grid in terms of regions and has to meet the reactive power demand from the generation facilities in line with the system requirements. The instruction related with drawing reactive power from the system via the generation facilities operating as a generator or synchronized compensator with the aim of regulating the system voltage in real time have to be obtained from the generation facilities. To control the reactive power of a unit or block party to the balancing system committed as per the connection fundamentals, TE AŞ can monitor the voltage of the unit of block at the connection point to see whether it remains within the range indicated at the balancing fundamentals and can request for a reactive power test. 4. AN ASSESSMENT OF TECHNICAL AND ECONOMICAL PROBLEMS BASED ON REACTIVE POWER For the provision of the reactive power needed by the restructured electrical energy system, the responsibilities of the generation, transmission, distribution and consumers have been revalorize with regulations and the changes made have been summarized briefly in part 3. In this part, the technical and economic problems are discussed arising in the provision of the reactive power while the parties are fulfilling their responsibilities and suggestions are proposed towards reactive power management and establishment of a reactive energy market. 213
  9. 9. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME The energy efficiency law enforced in Turkey makes it obligatory to take precautions by the transmission, distribution systems and consumers to reduce the energy losses. Furthermore, the limits related with the quality of the electrical energy have been defined at the regulation prepared by EPDK. It is known that, while fulfilling the compensation responsibilities in the restructured electrical energy sector, it would be to the benefit of the parties to handle the energy efficiency and energy quality improvement works simultaneously. For long years, the reactive power compensation responsibility in the electrical energy market was left to the end user and the residences and the subscribers below 9 kW power were kept exempt from compensation. It is estimated that the consumption kept exempt from reactive energy compensation corresponds to about 40% of the whole consumption. Although a significant portion of the electricity subscribers had low voltage problems and the losses rates were very high, as a result of the electricity distribution grid being operated for long years by a monopoly public company, the reactive compensation was not paid attention; almost no compensation was made at the low voltage and medium voltage distribution grid. The only thing done by the electricity distribution systems are the compensation made at the low voltage side to meet the losses of the distribution transformers at vacancy. It was expected from the consumers with reactive power compensation responsibility to fulfill their compensation duties, and the penalties taken from the ones failing to do so have become an important source of income for the distribution companies. Before the restructuring, the responsibility of the electricity distribution companies towards the transmission grid is not to consume reactive energy above 50% of the consumed active energy on a city basis. The compensation made by the customers with a compensation responsibility within these limits has proven to be sufficient. Transmission grid operators meet the required reactive energy first of all from the power plants to keep the grid voltage within certain limits and to safely operate the grid. However since reactive energy has a problem of transportation, the reactive energy need of the transmission grid at the points far from the power plants are met by the help of the capacitors installed at the distribution side of the transformers present at the reducer centers. The application of a penalty system instead of a cost based tariff for the reactive energy is causing several problems. In the penalty system, the consumers with a compensation responsibility are made to pay the reactive penalty calculated with a certain unit price for all the consumed reactive energy as a penalty in case they exceed the predefined limits. In this case, it is not a fair application when the consumers with high reactive consumption, meeting the target power factor limits pay nothing although they consume much more reactive power than the small strong customers, but the small strong consumers exceeding the limit values paying reactive energy fee although they consume much less reactive energy as compared to the big strong customers. With the free consumer regulation that has been commenced to be implemented without lowering the high losses rates at the Electricity Distribution Grid, as the other firms prefer lower cost electricity of other companies that the electricity distribution companies financing a high losses at the rate of 20% cannot compete with, these companies have started to lose a significant portion of their customers. Due to the weakening economic power of the distribution companies owing to the loss of customers, the investments cannot be made and thus the amount of interruptions due to failure and the period of failure are continuing to increase. In the application, the subscribers of the low voltage electricity distribution system can generally be in an unstable structure. The former reactive power limits were able to be met by the activation and deactivation of the three phase balanced compensation units with measurement made from single phase. The strong subscribers above 50 kW are implementing inductive consumption as 20% of the active power and 15% of the capacitive reactive active consumption as of 1.1.2008. The compensation made with balanced three phase capacitor as a result of the calculation of the three phase reactive energy via separate measurement of the reactive power of each phase by the digital three phase reactive power counters, is causing for the imbalanced consumers to be burdened with 214
  10. 10. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME reactive penalty application. For this reason, it becomes necessary for the unbalanced load consumers to establish a compensation system separately for each phase and make much more expense on the compensation facility. Furthermore, as a result of the fact that the constriction of the reactive limits was not announced sufficiently, several subscribers had to pay reactive penalty. Among these subscribers paying penalty, there are ones that require new investment since their compensation facility is insufficient and there are others whose compensation facilities are sufficient and that could have avoided this penalty only with the adjustment of the compensation relay. It is thought the fact the reactive penalties being a significant earning means for the distribution companies had an effect on the insufficient announcement of the change of the reactive rates to the subscribers. Since a high majority of the low voltage subscribers are residential units and consumers below 9 kW, significant amount of reactive energy is drawn from their distribution transformers. There is need to establish compensation systems to reduce the reactive consumption arising from load other than the fixed compensation used for losses at vacancy at the distribution transformers. However, at a system with thousands of distribution transformers, it is almost impossible to operate a compensation system unless a widespread SCADA system is built. And the cost of building such a system would be very high. For long years, the residences do not have reactive energy compensation responsibility assuming that they do not fall below the target power factor. However, the target power factor in the electrical energy sector of Turkey started with 0.90 and then rose to 0.95, which was then elevated to 0.98. Moreover, although the real power factor of the vast majority of the residences utilizing about 25% of the electrical energy used in Turkey is below 0.98, no reactive power price is paid for these residences. While the energy consumption of the residences rise, the additional losses caused by the reactive load on the electricity distribution systems, bring about additional costs to the electricity distribution companies. Today, the use of devices consuming reactive energy in the residences have become more widespread associated with the increase in the per capita electricity consumption and per capita national income, the incandescent wired lighting tools consuming active power have been replaced with the energy saver lighting tools with reactive energy consumption. The increase of the electrical energy consumption in the residence by the years is given in Figure 5. The number of subscribers within the subscriber groups presents at the Turkish electricity distribution grid as of 2008 and their energy consumption rates are given in Figure 6. Figure 5. The increase of the electrical energy consumption at the residence by the years (Source: TEDAS) 215
  11. 11. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME Resitential Resitential Commercial Commercial Official Authority Official Authority Industry Industry Irrigation Irrigation Lighting Lighting Other Other Figure 6. The number of subscribers within the subscriber groups present in Turkey A detailed study is needed related with the reactive consumption of the residences that are thought to increase the distribution system losses, occupying the transformer and cable capacities and to cause the occurrence of new investment costs. The following suggestions have been proposed to reduce the losses at the low and medium voltage electricity distribution systems caused by the reactive consumption of the residences and the pricing of the consumer reactive energy amount. • Reactive energy price can be taken as a certain percentage of the price of the active energy consumed in the residences; and thus, they will not be requested to make compensation. By installing compensation systems adjusted at suitable places at the secondary distribution or low voltage distribution system, the transformer and low voltage line losses can be decreased while the distribution transformer capacity increases; moreover, this situation shall also have contribution towards the reduction of the medium voltage grid losses. • A second option might be bringing about the obligation to make joint compensation to the residences at apartments with a certain quantity of flats (at the apartments with a contracted power above 50 kW). In terms of monitoring the reactive power consumption, digital counters recording active and reactive consumption can be placed to the building entrances and a price can be taken for the reactive energy measured with these counters. • Thirdly, a reactive power price can be requested from the residential consumers that is proportional with the active power amount. For the residential consumers, by taking 0, 75 fold (cos ϕ = 0,8), 0,50 fold (cos ϕ = 0,90) or 0,20 fold (cos ϕ = 0,98) of the active power, the reactive power amount can be determined. A comprehensive study is needed to categorize the residential consumers and to determine a coefficient for these groups. At the medium voltage distribution grids, it is being passed to cable grid in a fast manner at the cities where the land price and the illegal consumption rate is high. It is expected that the cable grid will have significant reactive power contribution. With the arrangements made at the reactive ratios, it is expected that the compensation to be made by the customers and the reactive amount drawn from the medium voltage gird of the cable grid to decrease. Requesting the fulfillment of the reactive power responsibility of the distribution at the joint connection point of the transmission and distribution grid without the finalization of the expectation to create a significant decrease at the reactive consumption drawn from the medium voltage, cannot be deemed as correct in terms of the timing of the compensation investments. It will be fit for the responsibility of the distribution companies to commence a few years after the commencing of the compensation responsibility of the customers. Furthermore, the common problem of the electricity distribution companies in Turkey is the lack of data. Since there are no daily load curves prepared for the different periods of the year related with the joint connection points where compensation is to be made, there are uncertainties in the 216
  12. 12. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME design of the compensation systems. At a compensation system made with limited data, making bank addition or removal, bank options with different powers and flexible solution techniques with a modular structure will aid in overcoming the uncertainties caused by the lack of data. The compensation made at the joint connection points so that the distribution grids can fulfill their responsibilities brought about by the regulation, does not have any contribution to the distribution grid in terms of energy efficiency and quality. Instead of at the joint connection point, compensation has to be made at the suitable points in the medium voltage line determined after optimization. However, the space problem is an important difficulty in the metropolitan cities like Istanbul. Especially where the land cost is high, the technical solution does not prove to be the practicable solution. In the studies, the technical and economic evaluation has to be made simultaneously. Before making an optimization study for the place of compensation at the medium voltage line, it would be a better solution to first make place determination and then make an optimization among the practicable solutions. In other words, while minimizing the technical losses at the distribution, the economic costs should be minimized as well. Due to new limit values at the joint connection point, the resonance frequency gets smaller as the compensation power increases. Since the harmonic amplitudes are higher at lower frequencies, the resonance becomes more dangerous. In the recent years, the harmonic ratio in the electrical energy sector is continuously increasing. In the addition of a capacitor, the resonance risk should be taken into consideration. Still, most of the electrical engineers working in the market, do not have sufficient information regarding the harmonics. In the recent 4-5 years in some universities of Turkey, the harmonics subject is being given as an optional course in the graduate education. There is a significant amount of need of education in the harmonics subject. The resonance problem is valid at both the joint connection point among the transmission and distribution, and the joint connection point of the electricity distribution low voltage customer. At the limited amount of electrical energy quality measurements made on Bosporus Electricity Distribution Inc. Co. (BEDAS), it has been determined that there were customers operating at resonance conditions. It has been decided to privatize 21 distribution companies. In the current state, 15 electricity distribution companies are still operated by the public. Due to the responsibility of the power coefficient values that need to be met at the transmission system joint connection points by the distribution companies after restructuring, big-scale investments were made. Due to the inadequacy of the public resources, the restructured system is becoming a burden to the public. Moreover, it could have been a better approach to make the compensation investments, made at the joint connection points, at the low voltage and medium voltage distribution grid by observing the energy efficiency and energy quality. Although the compensation made at the transmission grid joint connection point meets the reactive requirement, it does not contribute to the reduction of the high rate losses at the electricity distribution grids. The sped up schedule of the restructuring process and the fact that the power correction range has been narrowed has caused the distribution grid decision makers to put the energy quality and efficiency concepts in the back ground and the compensation investments at the points of measurement were made with limited information. At the 154/35kV substation, there are multiple transformers and there are measurement circuits at each transformer. With the maneuvers made at the operational conditions, the limit values are being exceeded with load transfer and change of the load characteristic of the transformers, and thus penalization occurs. Before restructuring, high amount of reactive power was being drawn from the transmission system and the transmission grid generally met its reactive power requirement from the synchronized power plants. The power plants were fulfilling their responsibilities brought about by the regulations. Moreover, at the places where the grid is weak, there were shunt compensation capacitors activating at the times when the voltage drops were much. The reason for the use of these compensation 217
  13. 13. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME capacitors is to keep the voltage within suitable limits rather than to reduce the losses. When the grid’s reactive power requirement could not be met despite all these, the backup power plants of the public were taken into operation as dynamic compensators and the reactive need was being met in this manner. At metropolitan cities like Istanbul, with the commencement of using 154 kV and 380 kV underground cables, it will be possible to reduce the need for dynamic compensators after the significant amount of reactive power contribution of the cables to the transmission grid. Before the restructuring, the electricity distribution companies had to meet a power coefficient of 0,9 in terms of local region. In the new status, the electricity distribution system has the responsibility to meet an inductive power factor of 0,98 and a capacitive power factor of 0,99 at the joint connection point with the electricity transmission system. The electricity distribution companies are installing very high MVAr capacitors at the joint connection point to meet this responsibility. Again, the same regulation permits the transmission system to install reactive power capacitors to make voltage control at the same point. There still has not been found any solution to operate compensators by overcoming the technical and economical problems to arise with the connection of the reactive power compensation-purposed capacitors of the distribution and voltage controlpurposed capacitors of the transmission. While the electrical energy generation, transmission and distribution was formerly under the hand of a monopoly public company, the reactive energy generation was made as per the requirement at the suitable place and amount. In the new state, the generation power plants act reluctantly in fulfilling their reactive power generation responsibility coming from the legislative obligation; and when additional reactive is needed for the safe operation of the gird, failing to meet the reactive power demand is threatening the system safety. The most important reason of the problem being experienced is that no price is being paid for reactive energy generation at the power plants that were privatized until 2008. The reactive power facility at the joint connection point necessitates much more expensive static VAR compensators since the classic compensation proves to be inadequate at the variable loads owing to the over-narrowing of the power coefficient band. When sudden reactive power requirement arises at the grid, if the requirement is not met, there might be irregularity at the voltage and collapsing at the grid. Separate reactive reserve is needed in the transmission systems to meet the reactive power demand. To meet this demand a pricing system has to be used and the duties of the players have to be made clearer in terms of the reactive power market. The out of order status occurring at the compensation systems present at the joint connection point between the electricity distribution and transmission system cannot be noticed in time due to the inexistence of a SCADA system; and thus, the distribution company is frequently penalized. By using the daily, seasonal load curves of the distribution grid and the reducer centers’ capacity groups and levels, the reactive energy load curve has to be obtained and the reactive power demand estimates have to be calculated for the transmission system. It should evaluate as to whether this reactive power is met or not from the power plants which are the most important reactive power sources. Moreover, the reactive power requirement of the grid should also be considered in the new 380 kV cable line installation and the aerial line cable transformation planning. Analysis shall be required related with the activation of the compensation investments made by the electricity distribution companies at the joint connection point and the determination of the reactor places to consume inductive power at certain points of the transmission grid with the effect of the additional capacitive power to arise with the transformation of the aerial lines at the transmission system into cable. 218
  14. 14. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 5, September – October (2013), © IAEME 5. CONCLUSIONS The restructuring in the electrical energy sector required well planning, the transition process should be well-monitored and fast solutions have to be generated for the arising problems since it has significant impacts on the economic and social life. In this study, the technical and economical problems were evaluated that have arisen in the reactive power supply after the Turkish electrical power system has been restructured and unbundled to generation companies, transmission company, and a number of distribution companies. In deregulated electrical energy markets, it a very complicated matter to provide reactive power support and to create suitable pricing mechanisms. The suggestions regarding reactive power management and reactive power auxiliary service purchase are given below with the aim of contributing to the formation of the Turkish electrical energy market that is in the process of restructuring. • Due to the problems encountered in the application, it is suggested that the implementation of free-of-charge reactive energy generation and reactive energy consumption within certain limit values be abandoned and transition should be made, as soon as possible, to a cost-based application where the reactive energy producer takes the price of the reactive energy it generated and the reactive energy consuming subscribers pay the price of reactive energy they actually consume. • It is suggested that a two-zone pricing route is following for the generators providing reactive power service. The first is the calculation of the reactive energy price based on the unit price of the reactive energy generation within the limits determined by the legislation and the second is the calculation of the lost opportunity cost, by using the active power unit price, by considering the active power sales loss brought about due to the extra reactive power generation of the generator. • It is suggested that passive, static and dynamic reactive energy generation licenses are granted so that the reactive energy price can be lowered via increasing the competition among the reactive power providers and the grid safety can be increased via providing source diversification. In the supply of the reactive power need at the transmission system, by also considering the transportation difficulty of reactive energy, it is suggested that local reactive power markets be created in order for the reactive power sources to be diversified in economical and technical terms. 6. ACKNOWLEDGEMENT I would like to extend my gratitude to Mr. Erol Türksen, the Trakya Load Distribution Operation director of TE AŞ transmission grid, Mr. Mehmet Gönen the vice manager of BEDAŞ Load Distribution center and Assoc. Prof. Dr. Özcan Kalenderli for their invaluable contributions. 7. REFERENCES [1] [2] [3] [4] Philipson L, Willis HL. Understanding electric utilities and deregulation, Marcel Dekker, Inc., 1999. S. Stoft, Power System Economics: Designing Markets for Electricity. Piscataway, NJ: IEEE Press, 2002. Electricity Market Law, Law No: 4628 Ratification Date: 20.02.2001 Enactment Date: 03.03.2001. High Planning Council, Strategic document on privatization and reform in electric energy industry. Date 17.3.2004, No. 2004/3, 2004. 219
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