Improvement of Transmission Capacity by FACTS devices in Central East Europe power system

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IFAC-PapersOnLine 49-27 (2016) Improvement of Transmission Capacity by 376–381 FACTS devices in Central East Europe Improvement FACTS powerby system Improvement of of Transmission Transmission Capacity Capacity by FACTS devices devices in in Central Central East East Europe Europe Michal Kolcun*. Zsolt Čonka*, Ľubomír Beňa*, Martin Kanálik*,Dušan Medveď* power system power system

 Michal Kolcun*. Zsolt Čonka*, Ľubomír Beňa*, Martin Kanálik*,Dušan Medveď* Michal Kolcun*. Zsolt Čonka*, Ľubomír Beňa*, Martin Kanálik*,Dušan Medveď* * Department of Electric Power Engineering, Technical University of Košice, Košice, Slovakia  (e-mail: [email protected], [email protected], [email protected], [email protected], * Department of Electric Power Engineering, Technical University of Košice, Košice, Slovakia * Department of Electric Power Engineering, Technical University of Košice, Košice, Slovakia [email protected]) (e-mail: [email protected], [email protected], [email protected], [email protected], (e-mail: [email protected], [email protected], [email protected], [email protected], [email protected]) [email protected])

Abstract: The increased demand for power transfer in combination with environmental and economic issues which setincreased constraints to building new lines, force implementation of new technologies into the Abstract: The demand for power transfer in the combination with environmental and economic Abstract: The increased demand for power transfer in combination with environmental andofeconomic existing system in order to improve its power capability. This paper investigates the use specific issues which set constraints to building new lines, force the implementation of new technologies into the issues which set constraints to building lines, force the transfer implementation of new technologies into FACTS andorder WAMS systemsitsnew topower maximize total capability generally defined as the existing devices system in to improve capability. This paper investigates the use of specific existing system intransfer order totransaction improve itsin power capability. Thispower paper system. investigates the use of specific maximum power Central-East-Europe Optimal allocation FACTS devices and WAMS systems to maximize total transfer capability generally defined as and the FACTSofdevices and WAMS to maximize total transfer capability defined as the control willtransaction besystems very important for TSO or other power market generally regulators. Effectiveness, maximum these powerdevices transfer in Central-East-Europe power system. Optimal allocation and maximum power transfer transaction in Central-East-Europe system. Optimaltypes allocation and optimal allocation and utilization of important phasor measurement units power (PMUs) for different of FACTS control of these devices will be very for TSO or other power market regulators. Effectiveness, control of these devices will be very important for TSO or other power market regulators. Effectiveness, devices flow control andmeasurement increasing transfer capacity for were investigated. Paper also optimal designed allocationfor andpower utilization of phasor units (PMUs) different types of FACTS optimal allocation and utilization of phasor measurement units (PMUs) for different types of FACTS compares the economic aspects of control these devices. devices designed for power flow and increasing transfer capacity were investigated. Paper also devices designed for power flow control and increasing transfer capacity were investigated. Paper also compares the economic aspects of these devices. © 2016, IFAC (International Federation ofdevices. Automatic Control)PMU Hosting by Elsevier Ltd. All rights reserved. Keywords: WAMS, FACTS, power flow, transfer capacity, compares the economic aspects of these Keywords: WAMS, FACTS, power flow, transfer capacity, PMU  Keywords: WAMS, FACTS, power flow, transfer capacity, PMU occurring in the system. Moreover, both these control  1. INTRODUCTION  schemes timesystem. synchronized. occurringareinnotthe Moreover, both these control INTRODUCTION occurring in the system. Moreover, both these control By1. liberalization of the electricity market we have gained schemes are not time synchronized. 1. INTRODUCTION schemes are not time synchronized. 2. WIDE-AREA MONITORING SYSTEM newByopportunities possibilities for electricity liberalizationand of the electricity market we have market gained By liberalization of the electricity market we have gained participants. On the other hand, liberalization also causes 2. WIDE-AREA MONITORING new opportunities and possibilities for electricity market First PMU (GPS based) wasSYSTEM invented in 1988. 2. WIDE-AREA MONITORING SYSTEM new opportunities andfor possibilities fortransmission electricity market considerable problems operators of system participants. On the other hand, liberalization also causes Synchrophasor technology has developed for the last few First PMU (GPS based) was invented in 1988. participants. On the other hand, liberalization also causes operators (TSO). Unsolved problem our time is the considerable problems for operators of of transmission system First PMU (GPSit was based) was and invented in 1988. During this time, implemented by Synchrophasor technology hasdesigned developed for the last few considerable problems number for operators of transmission system years. constantly increasing of unpredictable renewable operators (TSO). Unsolved problem of our time is the advice Synchrophasor technology has developed forthe thewide-area last few promising new concepts, such as operators (TSO). Europe Unsolved of power our time is the years. During this time, it was designed and implemented by energy in northern andproblem insufficient generation constantly increasing number of unpredictable renewable measurement years. During /this time, it was designed and implemented by monitoring system (WAMS). huge advice promising new concepts, such as It thebrings wide-area constantly increasing number of flow, unpredictable renewable in south. Due to unplanned power the security criterion energy in northern Europe and insufficient power generation advice promising new concepts, such as the wide-area for / monitoring the modernization of the Itmanagement, measurement system (WAMS). brings huge energy northern Europe insufficientofpower generation potential N-1 is in unfulfilled cause ofand overloading interconnecting in south. Due to unplanned power flow, the security criterion measurement / monitoring system (WAMS). It brings huge operation, supervision and protection of potential for the modernization ofenergy the systems. management, in south. Due lines. to unplanned power flow,operation the security criterion transmission This facts brings of existing N-1 is unfulfilled cause of overloading of interconnecting potential for the modernization of the management, supervision and protection of energy systems. N-1 is unfulfilled cause oftooverloading oflimits. interconnecting operation, transmission systems closer their physical WAMS (Wide Area Monitoring System) systems is transmission lines. This facts brings operation of existing operation, supervision and protection of energy systems. transmission lines. This facts brings operation of existing synchronous measurements of phasors and mainly used in the transmission systems closer to their physical limits. WAMS (Wide Area Monitoring System) systems is One of the opportunities this problems was transmission systems closer to for theirsolving physical limits. WAMS lines. (Wide Area Monitoring System) systems is transmission synchronous measurements of phasors and mainly used in the building of the newopportunities power transmission lines effectiveness One of for solving thisorproblems was synchronous measurements of phasors and mainly used in the transmission lines. One of the opportunities for solving this problems was utilizationof ofnewexisting transmission lines system capacity by transmission Furthermore building power transmission or effectiveness lines.the surface monitoring and visualization of building ofofnew power transmission or effectiveness utilization such lines as flexible alternating in realthe time or consequential off-line analysis of of utilization ofspecialized existing systems transmission system capacity by the network Furthermore surface monitoring and visualization utilization of transmission existing transmission system capacity by the operating current (AC) systems special Furthermore the surface monitoring andarevisualization of situations These subsystems used also for utilization of specialized systems such(FACTS). as flexibleThis alternating the network in real time or consequential off-line analysis of utilizationcan of specialized such as flexible alternating devices perfectly systems control power flow across monitoring the network of in system real timestability, or consequential off-line analysis of operational management current (AC) transmission systemsthe(FACTS). This special the operating situations These subsystems are used also for current (AC) lines transmission systems (FACTS). This special transmission and helps operators to maintaining stable the operating situations These subsystems are used also for networkof and earlystability, warningoperational systems. management Application of devices can perfectly control the power flow across monitoring system of devices canof perfectly control theIn power flow across operation power systems. combination with monitoring of system stability, operational management of WAMS systems canearly also warning be found systems. in distribution networks, transmission lines and helps operators to maintaining stable the network and Application of transmission lines andsystems helps operators to this maintaining sophisticated it can solve problem. stable network and earlymanagement warning systems. Application of for example in can the ofdistribution distributed energy operation ofWAMS power systems. In combination with the WAMS systems also be found in networks, operation of power systems. In combination with WAMS systems can also be found in distribution networks, resources. Synchronous measurement error generally sophisticated WAMS systems it can solve this power problem. example in the management of distributed energy Transmission system operators of each systems for sophisticated WAMS systems it can solve this problem. for example in the management ofanddistributed energy decreases in subsequent calculations control generally systems, resources. measurement error talkTransmission about the needsystem of increase of theofreliability and safety of resources. Synchronous operators each power systems Synchronous measurement errormanagement generally resulting in an improvement of dispatching Transmission system operators of each power systems decreases in subsequent calculations and control systems, the system. operators talkpower about the needTransmission of increase ofsystem the reliability andsometimes safety of decreases in subsequent calculations and control systems, resulting in an improvement of dispatching management talk about the need ofpower increase of thetoreliability and safety of network. have to manage the system its safety operational the power system. Transmission system operators sometimes resulting in an improvement of dispatching management the power system. in Transmission system operators sometimes limits. some cases, may occur a large network. have toMoreover, manage the power systemit to its also safety operational network. have to manage theout), power system to its safety operational area outages (Black that have negative consequences for limits. Moreover, in some cases, it may also occur a large limits. Moreover, in some cases, it the maymonitoring also occurofapower large society as a whole. the facts, area outages (Black Due out),tothat have negative consequences for area outages (Black out), that have negative consequences for systemsasare made through a SCADA society a whole. Due to the facts, the(Supervisory monitoring ofControl power society as a whole. Due to the facts, the monitoring of power and Data Acquisition) EMS (Energy systems are made through asystems SCADA and (Supervisory Control systems are made through a SCADA (Supervisory Control Management Systems), which do not work real time and and Data Acquisition) systems and in EMS (Energy and Data Acquisition) systems andtransient EMS processes (Energy thus the results are not applicable for fast Management Systems), which do not work in real time and Management Systems), which do not work in real time and thus the results are not applicable for fast transient processes thus the results are not applicable for fast transient processes

Copyright © 2016 IFAC 376 2405-8963 © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Copyright 2016 IFAC 376 Control. Peer review© under responsibility of International Federation of Automatic Copyright © 2016 IFAC 376 10.1016/j.ifacol.2016.10.756

2016 IFAC CTDSG October 11-13, 2016. Prague, Czech Republic Michal Kolcun et al. / IFAC-PapersOnLine 49-27 (2016) 376–381

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Fig. 3. Simplified scheme of PST Key parameters for any transmission line, determine the line impedance, power flow: phase angle between the starting and receiving nodes and terminal bus voltages. U1 and U2 are magnitudes of the bus voltages at both ends of the line with the angle δ = δ1 - δ2 among them. The impedance of the line is marked as X12. In this case, the expression for active power flow across transmission line is: (1)

Fig. 1. PST control scheme with WAMS Use of PMU for data acquisition for regulation of FACTS devices can bring new possibilities for further development of the network control. Measurement of phasors at different part of the power system, can be used for optimization of power flow, minimize power loses or to maximize transmission capacity between various TSO. Example of utilization of WAMS for control of phase shift transformer is shown on Fig 2.

P12 

U1 U 2 X 12

(1)

 sin  1   2 

If the PST is inserted in to outgoing feeder, the transferred power flow by transmission line is given: U1 U 2 P12  P12   P   sin  1   2    X line   X



(2)

where: –kadditional power flow due to PST regulation, –kadditional reactance in PST outgoing feeder,   –kangle between primary and secondary voltage P X

of PST. In case, when the phase shift between primary and secondary winding equals zero (    0  ), the power flow across the line with PST is limited only by its own reactance  X . Without PST, the loading angle is 5   10  . The maximum regulation range of Phase shift transformer is    30   40  . Control angle of phase shift transformer has a significant impact on the power flow across transmission line. Function sin  1   2     can be considered as linear in operation

Fig. 2. Slovak power system with PMUs and PST. 3. PHASE SHIFT TRANSFORMER

area. Hence, the regulation angle   is proportional to tap setting, the resulting flow of active power influenced by regulation of taps will be in proportion with tap setting of PST.

Phase shift transformer is mainly used for active power flow control at the interface between two large independent power systems. Phase-shifting transformers are mainly used to control the active power flow in related networks or to control the active power flow at the profiles between two large and independently controlled power systems. PST transformer principle is based on the use of adjustable angle ratio of the transformer. Winding of the serial unit is connected directly into HV level (e.g. 400 kV), in which the phase angle is controlled. It means, that the overall voltage is consists of primary voltage and phase shifted (additional) voltage. Regulating transformer with tap changer is supplied from serial unit (Fig. 3).

Impact of PST on power flow can be simply demonstrated on a power flow analysis in simply case of parallel lines according to the following figure.

Fig. 4. Network with parallel lines

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The current in node 2 is divided according to the proportion of impedances of parallel lines as follows: I X X 1  I1  X 2  I 2  1  2 I2 X1

Fig. 7. Phasor diagram of voltage and currents for direct axis voltage regulation If additional voltageais in upright to basic voltage ( = 90°), it is called quadraturekvoltage control. Because only network reactance’s are considered, additional current is delayed by 90° of additional voltage and has active character.

Fig. 5. Phasor diagram of voltage and currents (without PST) This distribution depends on reactance of each lines, which may be in some cases undesirable (e.g. overloading of one line). If the resistance and line shunt admittance are neglected, then currents I 1 and I 2 have the same phase shift (Fig. 5). The current distribution among lines can be caused by connection of PST to the network, according to Fig. 6.

Fig. 8. Phasor diagram of voltage and currents for quadrature voltage regulation Resulting distribution of currents shows the phasor diagram, Fig. 8. It is clear, that quadrature voltage regulation influences flows of active power (regulation is changing real component of currents I 1 , I 2 ).

Fig. 6. Network with PST Voltage difference,  U add  U 1 '  U 1 , called additional voltage, will cause circulating current '

 I add 

U1  U1 j X 1  X 2 

 j

 U add

Phase shift transformer for power flow control is one of the solutions to increase transfer capacity of interconnections between neighbours TSO.

,

X1  X 2

4. TRANSFER CAPACITY CALCULATION

which is added to the initial current. Consequently currents in the two parallel lines are '

I 1  I 1   I add

;

Maximum feasible power exchange, which can be transmitted between two meshed power systems reliably and without disturbances of the system stability criterion is represented by Total Transfer Capacity (TTC). To determine how much electricity can be transmitted by interconnecting lines there are necessary essential tasks as: modelling and simulation of the effects of energy exchanges between the two interconnected electricity networks. This is achieved by a suitable simulation model. Based on the expected net configuration, cross-border trade scenarios of consumption and production of electricity, generated energy is pushed between the two systems to activate other cross-border flows, by increasing production in one system and reducing production in the second power system.

'

I 2  I 2   I add

If difference between primary voltage angle and additional voltage equals zero (α = 0°), then there is a direct axis regulation. Because only network reactances are considered, additional current is delayed by 90° of additional voltage and has inductive character (Fig. 7). From the above it is clear, that it is possible to influence mainly active power flow (the reactive part of currents is changing I 1 , I 2 ).

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Electricity consumption in both systems remains unchanged. The profile charged to until they reach the safety limits [3], [4], [7], [9]. The resulting TTC value represents the maximum expected amount of power flow that can be safety transferred through the interconnection between this two systems.

Table 1 below shows the results of calculations for the basic engagement network. The basic model does not include PST transformer. Calculations were made of regard to compliance with the security criteria N-1 and respecting the maximum possible overload capacity of devices. For maximize the power flow between Slovakia and Hungary there was decreased the power generation in Croatia and Romania and increasing power generation in the north part of power system (North Germany, North Poland). Increasing the power flow has been stopped, once the N-1 criterion is not met. The limit element for this case was the line V 448 (VE Gabčíkovo - Gyӧr) when line V449 (Levice - Gӧd) was switched off.

NTC is given by the following equation: NTC = TTC – TRM

(3)

Transmission reliability margin (TRM) covers the inaccuracy of estimated power flow at cross-border interconnection due to uncertain information’s from market players and unexpected real time events. Information from the merchants is imperfect when transmission capacity must be notified. This comes in addition to the precariousness on some power system parameters, as well as the uncertainty of tie-line flows due to unexpected real time events, which are always possible. In this article we consider the value of TRM at 200 MW

Table 1. Transfer capacity for variant SK-HU I. Branch 448 (GabčíkovoGyör) 449 (Levice-Göd)

Line loads [MW] 1077,2

TTC [MW]

NTC [MW]

Limit element (N-1)

1928,4

1728,4

448 (449)

851,2

4.2 Variant SK-HU II. Table 2 below shows the results of calculations for the basic engagement network. In this variant has been installed PST on line V 449 (Levice - Gӧd). Calculations were made of regard to compliance with the security criteria N-1 and respecting the maximum possible overload capacity of devices. For maximize the power flow between Slovakia and Hungary there was decreased the power generation in Croatia and Romania and increasing power generation in the north part of power system (North Germany, North Poland). Increasing the power flow has been stopped, once the N-1 criterion is not met. The limit element for this case was the line V 490 (EMO - Levice) when line V491 (EMO - Levice) was switched off.

Fig. 9. PST placements in Slovak power system Calculation of maximal transfer capacity between Slovakia - Hungary and Slovakia - Czech Republic was provided by simulation program. In the simulation program there was constructed model of Central East Europe power system, with all lines, transformers, generators and with other necessary elements of power system. Total transfer capacity calculation was realised by maintaining of N-1 safety criterion in whole power system. For maximize the power flow between Slovakia and Hungary there was decreased the power generation in south part of CEE power system (Romania, Croatia) and increasing power generation in the north part of power system (North Germany, North Poland).

Table 2. Transfer capacity for variant SK-HU II. Branch 448 (GabčíkovoGyör) 449 (Levice-Göd)

The simulation below contains The simulation below consist of four variants of TTC calculation on Slovakia - Czech Republic interconnection and three variants of Slovakia - Hungary interconnection.

Line loads [MW] 1085,8 1296,9

TTC [MW]

NTC [MW

Limit element (N-1)

2382,8

2182,8

490 (491)

4.3 Variant SK-HU III.

4.1 Variant SK-HU I.

Table 3 below shows the results of calculations for the basic engagement network. In this variant has been installed PST on line V 448 (VE Gabčíkovo - Gyӧr). Calculations were made of regard to compliance with the security criteria N-1 and respecting the maximum possible overload capacity of devices. For maximize the power flow between Slovakia and 379

2016 IFAC CTDSG 380 Michal Kolcun et al. / IFAC-PapersOnLine 49-27 (2016) 376–381 October 11-13, 2016. Prague, Czech Republic

Hungary there was decreased the power generation in Croatia and Romania and increasing power generation in the north part of power system (North Germany, North Poland). Increasing the power flow has been stopped, once the N-1 criterion is not met. The limit element for this case was the line V 440 (Lemešany - Mukačevo) when line V449 (Levice - Gӧd) was switched off.

Table 5. Transfer capacity for variant SK-CZ II. Branch 404 (Nošovice – Varín) 424 (Sokolnice – Križovany) 497 (Sokolnice – Stupava) 280 (Sokolnice – Senica) 270 (Liskovec – P. Bystrica)

Table 3. Transfer capacity for variant SK-HU III. Branch 448 (GabčíkovoGyör) 449 (Levice-Göd)

Line loads [MW] 1317,8

TTC [MW]

2512

NTC [MW] 2312

Limit element (N-1) 440 (449)

1194,2

4.4 Variant SK-CZ I.

Line loads [MW]

TTC [MW]

NTC [MW]

Limit element (N-1)

2677,5

2477,5

280 (497)

-1340,2 -336,9 -661,3 -242 -97,1

4.6 Variant SK-CZ III.

Table 4 below shows the results of calculations for the basic engagement network. The basic model does not include PST transformer. For maximize the power flow between Slovak and Czech republic there was decreased the power generation in Hungary and increasing power generation in the north part of power system (North Germany, North Poland). Increasing the power flow has been stopped, once the N-1 criterion is not met. The limit element for this case was the line V 270 (Liskovec – P. Bystrica), when line V 404 (Nošovice – Varín) was turned off.

Table 6 below shows the results of calculations for the basic engagement network. In this variant has been installed PST on line V 424 (Križovany - Sokolnice). For maximize the power flow between Slovak and Czech republic there was decreased the power generation in Hungary and increasing power generation in the north part of power system (North Germany, North Poland). Increasing the power flow has been stopped, once the N-1 criterion is not met. The limit element for this case was the line V 270 (P. Bystrica - Lískovec) when line V404 (Varín - Nošovice) was switched off.

Table 4. Transfer capacity for variant SK-CZ I. Branch 404 (Nošovice – Varín) 424 (Sokolnice – Križovany) 497 (Sokolnice – Stupava) 280 (Sokolnice – Senica) 270 (Liskovec – P. Bystrica)

Line loads [MW]

TTC [MW]

NTC [MW]

Table 6. Transfer capacity for variant SK-CZ III.

Limit element (N-1)

Branch

Line loads [MW]

404 (Nošovice – Varín)

-586,8

424 (Sokolnice – Križovany)

-1336,3

497 (Sokolnice – Stupava)

-492,1

280 (Sokolnice – Senica)

-172,2

270 (Liskovec – P. Bystrica)

-151,1

-889 -532,2 -910,1

2545,7

2345,7

270 (404)

-101,2 -113,4

4.5 Variant SK-CZ II. Table 5 below shows the results of calculations for the basic engagement network. In this variant has been installed PST on line V 404 (Varín - Nošovice). For maximize the power flow between Slovak and Czech republic there was decreased the power generation in Hungary and increasing power generation in the north part of power system (North Germany, North Poland). Increasing the power flow has been stopped, once the N-1 criterion is not met. The limit element for this case was the line V 280 (Senica - Sokolnice) when line V497 (Stupava - Sokolnice) was switched off.

TTC [MW]

NTC [MW]

Limit element (N-1)

2738,5

2538,5

270 (404)

4.7 Variant SK-CZ IV. Table 7 below shows the results of calculations for the basic engagement network. In this variant has been installed PST on line V 497 (Sokolnice – Stupava). For maximize the power flow between Slovak and Czech republic there was decreased the power generation in Hungary and increasing power generation in the north part of power system (North Germany, North Poland). Increasing the power flow has been stopped, once the N-1 criterion is not met. The limit element for this case was the line V 270 (P. Bystrica - Lískovec) when line V404 (Varín - Nošovice) was switched off. 380

2016 IFAC CTDSG Michal Kolcun et al. / IFAC-PapersOnLine 49-27 (2016) 376–381 October 11-13, 2016. Prague, Czech Republic

TTC [MW]

NTC [MW

Limit element (N-1)

The most suitable location installing a phase shift transformer on inter-connection between Slovakia and Hungary was on line 448 (Gabčíkovo-Györ). The value of total transfer capacity with a phase shift transformer installed on line 448 (Gabčíkovo-Györ) was 2511 MW. The total transfer capacity with PST installed on line 449 (Levice-Göd) was 2394 MW.

2741,9

2541,9

270 (404)

The most suitable place for installation of PMU measurement units in Slovak power system is Lemešany, Križovany, Sučany, Levice and Stupava power stations.

Table 7. Transfer capacity for variant SK-CZ IV.

Branch 404 (Nošovice – Varín) 424 (Sokolnice – Križovany) 497 (Sokolnice – Stupava) 280 (Sokolnice – Senica) 270 (Liskovec – P. Bystrica)

Line loads [MW] -682 -352,2 -1335,1

381

-217,4 -155,2

REFERENCES Kolcun, M., Beňa Ľ., (2011). Využitie špecializovaných zariadení na reguláciu tokov výkonov v elektrizačných sústavách, 50-57, TUKE, Košice Jakubčak R., Beňa Ľ., Kmec, M.,: (2013) Possibilities of Using Facts Devices In Power System. Acta Electrotechnica et Informatica. Vol. 13, page. 8-11. ISSN 1335-8243 ETSO, (2000) Net Transfer Capacities (NTC) and Available Transfer Capacities (ATC) in the Internal Market of Electricity in Europe (IEM), March 2000. Definitions of Transfer capacities in liberalised Electricity Markets online Dobson I., Green S., Rajaraman R., DeMarco Ch. L., Alvarado F.L., Zimmerman R.,: (2001) Electric Power transfer capacity: Concepts, Applications, Sensitivity, Uncertainty, Power System Engineering Research Center November (2001), online http://www.pserc.cornell.edu/ttc/tutorial/TTC_Tutorial.p df ENTSO-E, (2012), Network Code on Capacity Allocation and Congestion Management, Setember 2012 ENTSO-E, (2013). Network Code on Forward Capacity Allocation, October 2013 Z. Čonka, M. Kolcun: Impact of TCSC on the Transient Stability In: Acta Electrotechnica et Informatica. Roč. 13, č. 2 (2013), s. 50-54. - ISSN 1335-8243 Available on internet :www.versita.com/aei. (2013) Calculation methods online [12.05.2015] http://www.elia.be/en/products-and-services/crossborder-mechanisms/transmission-capacity-atborders/calculation-methods Ministry of Economy of Slovak Republic: Návrh Energetickej politiky Slovenskej republiky, May 2014 Online: cit.[19. feb. 2015] http://www.rokovania.sk/File.aspx/ViewDocumentHtml/ Mater-Dokum-165253?prefixFile=m_ FAQ CEPS, a.s. online [19. Feb. 2015] http://www.ceps.cz/ENG/Media/Pages/FAQ.aspx

5. ECONOMIC ASPECTS On the final price of PST have the greatest impact, two main parameters of the transformer - Rated power [MVA] and control capability of PST (regulatory angle of PST). These two characteristics of the transformer, especially for large transmitted power is significant for economical solution. The investment for PST transformer with the same parameters according to experience, reaching about 160% of the standard transformer price, there can therefore be considered with a value of € 19,000 to 1 MVA of installed capacity. For presupposition maximal current limitation 2000 A corresponds circa 1400 MW PST transformer. Install of PST requires the construction of specialized fields in substations. Field for PST must be equipped compared to standard outlets (eg. for line or transformer) - a measure, protected and especially on a full field equipment by-pass (In contrast with conventional fields are fields with PST featured by 2 or 3 circuit breaker and with an appropriate number of isolators). Price of one average field in substation of 400 kV is approximately 3.0 million €. Price of field with PST is approximately 4.5 million €. 5. CONCLUSIONS The results of the simulations suggest new possibilities for increasing the transmission capacity between transmission systems using a PMU and WAMS systems. Properly designed control system PST transformers using time-synchronized measured data from the PMU can increase the transmission capacity of existing lines. Finding a suitable location for both PST transformer and PMU devices, we can increase transmission capacity and also the efficiency and usability of these devices. The results show that the most suitable location of a phase shift transformer. The best place for installing a PST transformer on cross-border connection between Slovakia and Czech Republic is on line V 497 (Sokolnice – Stupava). Total transfer capacity with PST installed on line V 497 (Sokolnice – Stupava) was 2727,1 MW. The total transfer capacity with PST installed on line 424 (Sokolnice – Križovany) was 2698,4 MW, and the TTC with phase shift transformer on line 404 (Nošovice – Varín) was 2681,4 MW. 381