![International Journal of Applied Power Engineering (IJAPE)
Vol. 3, No. 2, August 2014, pp. 124~129
ISSN: 2252-8792 124
Journal homepage: http://iaesjournal.com/online/index.php/IJAPE
Influence of Static Var Compensator for Undervoltage Load
Shedding To Avoid Voltage Instability
ReshmaRajan, B.VenkateswaraRao, G.V.Nagesh Kumar
Department of Electrical and Electronics Engineering, GITAM University, Visakhapatnam, India
Article Info ABSTRACT
Article history:
Received Mar 2, 2014
Revised Jul 10, 2014
Accepted Jul 23, 2014
In the recent years, operation of power systems at lower stability margins has
increased the importance of system protection methods that protect the
system stability against various disturbances. Among these methods, the load
shedding serves as an effective and last-resort tool to prevent system
frequency/voltage instability. For major combinational disturbances, the
active power deficit is usually accompanied by reactive power deficit. Under
frequency load shedding schemes have been widely used, to restore
powersystem stability post major disturbances. However, the analysis of
recent blackouts suggests that voltage collapse and voltage-related problems
are also important concerns in maintaining system stability. For this reason,
voltage also needs to be taken into account in load shedding schemes. This
paper considers both parameters in designing a load shedding scheme to
determine the amount of load to be shed and its appropriate location .The
amount of load to be shed from each bus is decided using the fixed step size
method and it’s location has been identified by using voltage collapse
proximity index method. Static VAR Compensator (SVC) is shunt
connected FACTS device used to improve the voltage profile of the system.
In this paper impact of SVC on load shedding for IEEE 14 bus system has
been presented and analyzed.
Keyword:
FACT Devices
Load Shedding
Static Var Compensator
Under Voltage Load Shedding
Voltage Stability
Copyright © 2014 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
B.VenkateswaraRao ,
Departement of Electrical and Electronics Engineering,
GITAM Institute Of Technology,GITAM University,
Visakhapatnam, India
Email:bvrao.eee@gmail.com
1. INTRODUCTION
The requirement for improved efficiency whilst maintaining system security necessitates the
development of improved system analysis approaches and the development of advanced emergency control
technologies. Load shedding is a type of emergency control that is designed to ensure system stability by
curtailing system load to match generation supply. Here a new adaptive load shedding scheme that provides
emergency protection against excess voltage decline, whilst minimizing the risk of line overloading. When a
sudden loss of generation is occurred, there will be a mismatch between energy supplied and energy
demanded which will lead to system frequency drop or voltage drop .If governor action cannot activate the
available spinning reserve from generating units quickly enough to restore the system to its normal operating
value the system will collapse, which will lead to a large scale loss of load. So, a suitable corrective control
action should be applied to restore the system to a new steady-state operating condition .Load shedding is an
effective corrective control action in which a part of the system loads are disconnected according to certain
priority in order to steer the power system from the existing potential dangers with the least probability of
disconnecting the important loads. Load shedding is considered as the last resort tool for use in that extreme
situation and usually the less preferred action to be adopted, but in this kind of problem it is vital to prevent
the system from collapsing [1]. Therefore, load shedding becomes a common practice for electric utilities](https://image.slidesharecdn.com/1329-4376-1-pb-201208075244/85/Influence-of-Static-VAR-Compensator-for-Undervoltage-Load-Shedding-to-Avoid-Voltage-Instability-1-320.jpg)
![IJAPE ISSN: 2252-8792
Influence of Static Var Compensator for Undervoltage Load Shedding To… (B.VenkateswaraRao)
125
proposed load shedding scheme uses the local voltage rate information to adapt the load shedding behaviour
to suit the size and location of the experienced disturbance. In a power system disturbance, the deviation of
frequency and voltage quantities are related to each other. Hence, it is more logical to consider combinational
load shedding methods, which are dependent on both frequency and voltage, instead of designing two
independent under-frequency and under-voltage load shed schemes [2]. In proposed combinational methods,
load shedding decisions are based on the combination of measured frequency and voltage at relay locations
[3]. In these methods, load shedding is selected as a function of the disturbance location, either directly or
indirectly. Since the load shedding decision is made locally based on local measured quantities, no
communication link is required for implementing these methods. It should be noted that this paper’s objective
is not focused on selecting the most economical location for load shedding amounts. The objective is to
rescue the system during severe combinational events.A power system can experience blackout for various
reasonssuch as frequency instability, voltage instability[4].The FACTS device performance depends upon its
location and parameter setting.The power electronic based flexible AC transmission systems introduced in
1980’s,provided a highly efficient and economical means to control the power transfer in interconnected AC
transmission systems.A FACTS device in a power system improves voltage stability,reduces the power
losses and also improves the security of the system[5].Flexible AC transmission system is akin to high
voltage dc and related thyristors developed designed to overcome the limitations of the present mechanically
controlled ac power transmission system.
The SVC is most commonly used FACT devices which is shunt connected providing simultaneous
control of voltage magnitude and reactive power flows.StaticVar Compensator (SVC) The SVC uses
conventional thyristors to achieve fast control of shunt-connected capacitors and reactors. Among the FACTS
devices, the Static VAR compensator is a versatile device that controls the reactive power injection at a bus
using power electronic switching components [6]. The reactive source is usually a combination of reactors
and capacitors. SVC state variables are combined with the nodal voltage magnitudes and angles of the
network in a single frame of reference for unified, iterative solutions using the Newton-Raphson method [7].
In this paper Voltage Collapse Proximity Indicator has been used to identify the best location for
load shedding. SVC incorporated in Newton Raphson Power flow to observe the impact of SVC on load
shedding. Amount of load to shed at a particular location is based on fixed step size method.This paper
proposes a new use of SVC to reduce load shedding. IEEE 14 bus system results are presented and analyzed.
2. VOLTAGE COLLAPSE PROXIMITY INDICATOR FOR OPTIMAL LOCATION FOR LOAD
SHEDDING
Here we look at a method based on the sensitivity of the total change in generator reactive power for
a change in real power demand at particular bus is one method. It is called voltage collapse proximity
indicator (V C P I). The voltage collapse proximity indicator for each load bus, considering reactive power
only, is:
igPi P/)Q(VCPI (1)
Where ∆Qg is the change in reactive power output at generators for a change in real load at bus i.
The bus with the highest value of VCPIPiis the most suitable location for Load shedding. In this
study 10% of the real load increased in respective load buses and compute the VCPIPi. The Table I indicates
the VCPIPi calculated the bus number and its index for IEEE 14 bus system. From this table it is also
observed that the bus no 14 has highest VCPIPi compared to all other load buses. So the bus no 14 is the most
suitable location for Load shedding.
Table I. Weak Buses Ordering In IEEE 14 Bus Systems
Rank VCPIPi Bus Index VCPIPi
1 14 39.2751
2 10 33.5
3 13 33.133
4 9 33.040](https://image.slidesharecdn.com/1329-4376-1-pb-201208075244/85/Influence-of-Static-VAR-Compensator-for-Undervoltage-Load-Shedding-to-Avoid-Voltage-Instability-2-320.jpg)
![ ISSN: 2252-8792
IJAPE Vol. 3, No. 2, August 2014 : 124 – 129
126
5 12 31.786
6 11 31
7 4 24.548
8 5 20.052
3. STATIC VAR COMPENSATOR
Static VAR Compensator (SVC) is a shunt connected FACTS controller used to regulate the voltage
at a given bus by modulating its equivalent reactance. SVC normally includes a combination of mechanically
controlled and thyristor controlled shunt capacitors and reactors. The most popular configuration for
continuously controlled SVC is the combination of fixed capacitor and thyristor controlled reactor. The SVC
is taken to be a continuous, variable susceptance, which is adjusted in order to achieve a specified voltage
magnitude while satisfying constraint conditions. SVC total susceptance model represents a changing
susceptance [8, 9]. The SVC (Static Var Compensator) may have inductive or capacitive, respectively to
absorb or provide reactive power. It may take values characterized by the reactive power Qsvc injected or
absorbed at the voltage of 1 p.u. The variable susceptance model and its equivalent circuit is shown in Fig 1.
SVC can be represented as an adjustable reactance [10].
Figure 1. Variable shunt Susceptance
In general, the transfer admittance equation for the variable shunt compensator is
kjBVI (2)
And the reactive power equation is,
BVQ kk
2
(3)
The current drawn by the SVC is
ksvcsvc VjBI (4)
Reactive power drawn by the SVC, which is also reactive power injected at bus k, is
SVCksvc BVQ 2
(5)
The linearised equation of the SVC is given by the following equation where the total
susceptanceBsvc is taken to be the state variable.](https://image.slidesharecdn.com/1329-4376-1-pb-201208075244/85/Influence-of-Static-VAR-Compensator-for-Undervoltage-Load-Shedding-to-Avoid-Voltage-Instability-3-320.jpg)
![ ISSN: 2252-8792
IJAPE Vol. 3, No. 2, August 2014 : 124 – 129
128
Table 4. Comparision of Voltage Profiles before, after load shedding with SVC at Bus No-13
Before Load Shedding After Load Shedding
V VA V VA
1.06 0 1.0600 0
1.0450 -3.6955 1.0450 -0.0627
1.0100 -9.0156 1.0100 -0.1543
1.0126 -6.4066 1.0136 -0.1080
1.0202 -5.4020 1.0211 -0.0907
1.00 -7.584 1.000 -0.1235
0.9909 -6.0235 0.9927 -0.0983
1.0 -1.9459 1.0000 -0.0272
0.9763 -8.4213 0.9794 -0.1382
0.9724 -8.6004 0.9750 -0.1413
0.9822 -8.2376 0.9836 -0.1350
0.9956 -8.7763 0.9953 -0.1431
1.00 -9.3408 1.0000 -0.1517
0.9673 -9.9635 0.9793 -0.1602
Table 5. Amount of Load Shedding By Placing SVC at Different Bus Locations
Before Load Shedding After Load Shedding
SVC
location
Total Real
Power
Generation
Initial
Losses
Total Real
Power
Generation
Final
Losses
Amount of
load shed at
bus no 14
13 266.0092 7.0092 261.2278 6.5278 0.0430
12 266.0205 7.0205 257.8252 6.2252 0.0740
11 265.9552 6.9552 260.2896 .3896 0.0510
10 265.8758 6.8758 262.8703 6.5703 0.0270
9 265.8120 6.8120 264.7004 6.7004 0.0100
8 265.9654 6.9654 256.6988 6.0988 0.0840
4. CONCLUSION
The load-shedding system has undoubtedly benefited in terms of reliability and minimizing
production losses.By finding out the VCPI at each bus location we came to know the suitable location for the
load shedding and by placing the static var compensator the voltage profiles have been improved and thereby
reducing the real power losses by shedding minimum percentage of loads at that particular bus.The results
show that incoperating the svc in the IEEE 14 bus system can reduce the real powerlosses,improves the
voltage profiles and enhances the system stability.
REFERENCES
[1] Y. Wang, I.R. Pordanjani W. Li, W. Xu, E. Vaahedi, ”Strategy to minimise the load shedding amount for voltage
collapse prevention”, IET Gener. Transm. Distrib., 2011, Vol.5, Iss 3, 307-313.
[2] Hridya Pradeep, N. Venugopalan “A Study of Voltage Collapse Detection for Power System” ,(ISSN 2250-2459,
ISO 9001:2008 Certified Journal, Volume 3, Issue 1, January 2013).
[3] Taylor, C.W., "Concepts of Undervoltage Load Shedding for Voltage Stability" IEEE Transactions on Power
Delivery, Volt 7, No 2, April 1992.
[4] J. Jung, C. C. Liu, S. L. Tanimoto, and V. Vittal, “Adaptation in load shedding under vulnerable operating
conditions,” IEEE Trans. PowerSyst., vol. 17, no. 4, pp. 1199–1205, Nov. 2002.
[5] K. Palaniswamy, J. Sharma, and K. Misra, “Optimum load-shedding taking into account of voltage and frequency
characteristics of loads,”IEEE Trans. Power App. Syst., vol. PAS-104, no. 6, pp. 1342–1348, Jun1985.
[6] E. D. Tuglie, M. Dicorato, M. L. Scala, and P. Scarpellini, “A correctivecontrol for angle and voltage stability
enhancement on the transient timescale,”IEEE Trans. Power Syst., vol. 15, no. 4, pp. 1345–1353, Nov.2000.
[7] D. Xu and A. Girgis, “Optimal load shedding strategy in power systems with distributed generation,” in Proc.
IEEE Power Eng. Soc. WinterMeeting, vol. 2, Columbus, OH, Jan. 2001.
[8] N. G. Hingorani and L. Gyugyi, “Understanding FACTS: Concepts and Technology of Flexible AC Transmission
System”, IEEE Press, 2000. IEEE/CIGRÉ, “FACTS Overview”, catalogue number 95TP108, 1995.
[9] Y.H. Song and A.T. Johns, eds, Flexible AC Transmission Systems (FACTS), IEE Press, U.K., 1999 Acha E.,
Fuerte-Esquivel C, Ambriz-Perez H and Angeles C., “FACTS: Modelling and Simulation in Power Networks”.
John Wiley & Sons, 2004.](https://image.slidesharecdn.com/1329-4376-1-pb-201208075244/85/Influence-of-Static-VAR-Compensator-for-Undervoltage-Load-Shedding-to-Avoid-Voltage-Instability-5-320.jpg)
![IJAPE ISSN: 2252-8792
Influence of Static Var Compensator for Undervoltage Load Shedding To… (B.VenkateswaraRao)
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[10] FACTS Modelling and Simulation in Power Networks (Book) by Enrique Acha, Claudio R. Fuerte-Esquivel, Hugo
Ambriz-Perez, Cesar Angeles-Camacho.
BIOGRAPHIES OF AUTHORS
ReshmaRajanwas born in Thrissur, India in 1990.She received her Bachelor’s degree in
Electrical and Electronics Engineering from Avanthi Institute Of Engineering And Technology,
Vizianagram in 2012.She is pursuing her Master’s Degreee in Power Systems And Automation
at GITAM University.
B.Venkateswararaowas born in Ramabhadrapuram, India in 1978. He received his Bachelor
degree in Electrical and Electronics Engineering from College of Engineering, Gandhi Institute
of Technology And Management (GITAM), Visakhapatnam, India in 2000, and the Master
degree in Electrical Power Engineering from the College of Engineering, JNTU, and Hyderabad
in 2007. He is presently working as Assistant Professor in the Department of Electrical and
Electronics Engineering, GITAM University, Visakhapatnam and he is pursuingPh.Dfrom
Jawaharlal Nehru Technological University, Hyderabad. His research interests are Power system
stability analysis, FACTS devices, Power system control. He has published several research
papers in national and international conferences.
Dr. G.V. Nagesh Kumar was born in Visakhapatnam, India in 1977. He graduated College of
Engineering, Gandhi Institute of Technology and Management, Visakhapatnam, India in 2000,
Masters Degree from the College of Engineering, Andhra University, Visakhapatnam, in 2002.
He received his Doctoral degree from Jawaharlal Nehru Technological University, Hyderabad in
2008. He is presently working as Associate Professor in the Department of Electrical and
Electronics Engineering, GITAM University, Visakhapatnam. His research interests include gas
insulated substations, FACTS devices, Power System Stability analysis, fuzzy logic and neural
network applications, distributed generation, Partial Discharge Studies and Bearing less drives.
He has published 92 research papers in national and international conferences and journals. He
received “Sastra Award” , “Best Paper Award” and “Best Researcher Award”. He is a member
of various societies, ISTE, IEEE, IE and System Society of India. He is also a reviewer for IEEE
Transactions on Dielectrics and Electrical Insulation, Power Systems and a member on Board of
several conferences and journals.](https://image.slidesharecdn.com/1329-4376-1-pb-201208075244/85/Influence-of-Static-VAR-Compensator-for-Undervoltage-Load-Shedding-to-Avoid-Voltage-Instability-6-320.jpg)
Influence of Static VAR Compensator for Undervoltage Load Shedding to Avoid Voltage Instability
- 1. International Journal of Applied Power Engineering (IJAPE) Vol. 3, No. 2, August 2014, pp. 124~129 ISSN: 2252-8792 124 Journal homepage: http://iaesjournal.com/online/index.php/IJAPE Influence of Static Var Compensator for Undervoltage Load Shedding To Avoid Voltage Instability ReshmaRajan, B.VenkateswaraRao, G.V.Nagesh Kumar Department of Electrical and Electronics Engineering, GITAM University, Visakhapatnam, India Article Info ABSTRACT Article history: Received Mar 2, 2014 Revised Jul 10, 2014 Accepted Jul 23, 2014 In the recent years, operation of power systems at lower stability margins has increased the importance of system protection methods that protect the system stability against various disturbances. Among these methods, the load shedding serves as an effective and last-resort tool to prevent system frequency/voltage instability. For major combinational disturbances, the active power deficit is usually accompanied by reactive power deficit. Under frequency load shedding schemes have been widely used, to restore powersystem stability post major disturbances. However, the analysis of recent blackouts suggests that voltage collapse and voltage-related problems are also important concerns in maintaining system stability. For this reason, voltage also needs to be taken into account in load shedding schemes. This paper considers both parameters in designing a load shedding scheme to determine the amount of load to be shed and its appropriate location .The amount of load to be shed from each bus is decided using the fixed step size method and it’s location has been identified by using voltage collapse proximity index method. Static VAR Compensator (SVC) is shunt connected FACTS device used to improve the voltage profile of the system. In this paper impact of SVC on load shedding for IEEE 14 bus system has been presented and analyzed. Keyword: FACT Devices Load Shedding Static Var Compensator Under Voltage Load Shedding Voltage Stability Copyright © 2014 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: B.VenkateswaraRao , Departement of Electrical and Electronics Engineering, GITAM Institute Of Technology,GITAM University, Visakhapatnam, India Email:[email protected] 1. INTRODUCTION The requirement for improved efficiency whilst maintaining system security necessitates the development of improved system analysis approaches and the development of advanced emergency control technologies. Load shedding is a type of emergency control that is designed to ensure system stability by curtailing system load to match generation supply. Here a new adaptive load shedding scheme that provides emergency protection against excess voltage decline, whilst minimizing the risk of line overloading. When a sudden loss of generation is occurred, there will be a mismatch between energy supplied and energy demanded which will lead to system frequency drop or voltage drop .If governor action cannot activate the available spinning reserve from generating units quickly enough to restore the system to its normal operating value the system will collapse, which will lead to a large scale loss of load. So, a suitable corrective control action should be applied to restore the system to a new steady-state operating condition .Load shedding is an effective corrective control action in which a part of the system loads are disconnected according to certain priority in order to steer the power system from the existing potential dangers with the least probability of disconnecting the important loads. Load shedding is considered as the last resort tool for use in that extreme situation and usually the less preferred action to be adopted, but in this kind of problem it is vital to prevent the system from collapsing [1]. Therefore, load shedding becomes a common practice for electric utilities
- 2. IJAPE ISSN: 2252-8792 Influence of Static Var Compensator for Undervoltage Load Shedding To… (B.VenkateswaraRao) 125 proposed load shedding scheme uses the local voltage rate information to adapt the load shedding behaviour to suit the size and location of the experienced disturbance. In a power system disturbance, the deviation of frequency and voltage quantities are related to each other. Hence, it is more logical to consider combinational load shedding methods, which are dependent on both frequency and voltage, instead of designing two independent under-frequency and under-voltage load shed schemes [2]. In proposed combinational methods, load shedding decisions are based on the combination of measured frequency and voltage at relay locations [3]. In these methods, load shedding is selected as a function of the disturbance location, either directly or indirectly. Since the load shedding decision is made locally based on local measured quantities, no communication link is required for implementing these methods. It should be noted that this paper’s objective is not focused on selecting the most economical location for load shedding amounts. The objective is to rescue the system during severe combinational events.A power system can experience blackout for various reasonssuch as frequency instability, voltage instability[4].The FACTS device performance depends upon its location and parameter setting.The power electronic based flexible AC transmission systems introduced in 1980’s,provided a highly efficient and economical means to control the power transfer in interconnected AC transmission systems.A FACTS device in a power system improves voltage stability,reduces the power losses and also improves the security of the system[5].Flexible AC transmission system is akin to high voltage dc and related thyristors developed designed to overcome the limitations of the present mechanically controlled ac power transmission system. The SVC is most commonly used FACT devices which is shunt connected providing simultaneous control of voltage magnitude and reactive power flows.StaticVar Compensator (SVC) The SVC uses conventional thyristors to achieve fast control of shunt-connected capacitors and reactors. Among the FACTS devices, the Static VAR compensator is a versatile device that controls the reactive power injection at a bus using power electronic switching components [6]. The reactive source is usually a combination of reactors and capacitors. SVC state variables are combined with the nodal voltage magnitudes and angles of the network in a single frame of reference for unified, iterative solutions using the Newton-Raphson method [7]. In this paper Voltage Collapse Proximity Indicator has been used to identify the best location for load shedding. SVC incorporated in Newton Raphson Power flow to observe the impact of SVC on load shedding. Amount of load to shed at a particular location is based on fixed step size method.This paper proposes a new use of SVC to reduce load shedding. IEEE 14 bus system results are presented and analyzed. 2. VOLTAGE COLLAPSE PROXIMITY INDICATOR FOR OPTIMAL LOCATION FOR LOAD SHEDDING Here we look at a method based on the sensitivity of the total change in generator reactive power for a change in real power demand at particular bus is one method. It is called voltage collapse proximity indicator (V C P I). The voltage collapse proximity indicator for each load bus, considering reactive power only, is: igPi P/)Q(VCPI (1) Where ∆Qg is the change in reactive power output at generators for a change in real load at bus i. The bus with the highest value of VCPIPiis the most suitable location for Load shedding. In this study 10% of the real load increased in respective load buses and compute the VCPIPi. The Table I indicates the VCPIPi calculated the bus number and its index for IEEE 14 bus system. From this table it is also observed that the bus no 14 has highest VCPIPi compared to all other load buses. So the bus no 14 is the most suitable location for Load shedding. Table I. Weak Buses Ordering In IEEE 14 Bus Systems Rank VCPIPi Bus Index VCPIPi 1 14 39.2751 2 10 33.5 3 13 33.133 4 9 33.040
- 3. ISSN: 2252-8792 IJAPE Vol. 3, No. 2, August 2014 : 124 – 129 126 5 12 31.786 6 11 31 7 4 24.548 8 5 20.052 3. STATIC VAR COMPENSATOR Static VAR Compensator (SVC) is a shunt connected FACTS controller used to regulate the voltage at a given bus by modulating its equivalent reactance. SVC normally includes a combination of mechanically controlled and thyristor controlled shunt capacitors and reactors. The most popular configuration for continuously controlled SVC is the combination of fixed capacitor and thyristor controlled reactor. The SVC is taken to be a continuous, variable susceptance, which is adjusted in order to achieve a specified voltage magnitude while satisfying constraint conditions. SVC total susceptance model represents a changing susceptance [8, 9]. The SVC (Static Var Compensator) may have inductive or capacitive, respectively to absorb or provide reactive power. It may take values characterized by the reactive power Qsvc injected or absorbed at the voltage of 1 p.u. The variable susceptance model and its equivalent circuit is shown in Fig 1. SVC can be represented as an adjustable reactance [10]. Figure 1. Variable shunt Susceptance In general, the transfer admittance equation for the variable shunt compensator is kjBVI (2) And the reactive power equation is, BVQ kk 2 (3) The current drawn by the SVC is ksvcsvc VjBI (4) Reactive power drawn by the SVC, which is also reactive power injected at bus k, is SVCksvc BVQ 2 (5) The linearised equation of the SVC is given by the following equation where the total susceptanceBsvc is taken to be the state variable.
- 4. IJAPE ISSN: 2252-8792 Influence of Static Var Compensator for Undervoltage Load Shedding To… (B.VenkateswaraRao) 127 i svcsvc k i k i k k BBQQ P /0 00 (6) At the end of iteration i, the variable shunt susceptanceBsvc updated according to the equation given below; svc i i svc svcsvc i svc i B B B BB )1()1( (7) The changing susceptance represents the total SVC susceptance necessary to maintain the nodal voltage magnitude at the specified value that is 1.0pu. 4. RESULTS AND ANALYSIS In IEEE 14 bus system bus no 1 is considered as a slack bus and bus no’s 2,3,6,8 are considered as a PV buses all other buses are considered as load buses.This system has 20 interconnected lines. A MATLAB program is coded for the test system and results have been presented and analyzed.Table II represents the voltage profiles without the placement of SVCat 14-bus. Table-III indicates the initial and final losses without SVC and the amount of load to be shed is 0.0840.Table-IV indicates the voltage profiles with the placement of SVC at bus 13. Table-V shows the SVC at different bus locations and the minimum amount of load to be shedded is found at bus no-9. The voltage profiles have been improved and brought in to limits. Table 2. Comparision of Voltage Profiles Before, After Load Shedding Without SVC Before Load Shedding After Load Shedding V VA V VA 1.06 0 1.06 0 1.0450 -3.6948 1.0450 -0.0610 1.0100 -9.0156 1.0100 -0.1515 1.0120 -6.3917 1.0142 -0.1044 1.0198 -5.3960 1.0216 -0.0874 1.0 -7.6116 1.0 -0.1156 0.9889 -5.9851 0.9928 -0.0914 1.0 -1.8991 1.0 0.0203 0.9722 -8.3857 0.9794 -0.1296 0.9690 -8.5755 0.9751 -0.1328 0.9805 -8.2361 0.9836 -0.1268 0.9831 -8.5997 0.9861 -0.1315 0.9770 -8.6772 0.9834 -0.1327 0.9548 -9.6838 0.9815 -0.1438 Table 3. Initial and Final Losses With out SVC Before Load Shedding After Load Shedding Total Real Power Generation Initial Losses Total Real Power Generation Final Losses Amount of load shed at bus no 14 265.9654 6.9654 256.6988 6.0988 0.0840
- 5. ISSN: 2252-8792 IJAPE Vol. 3, No. 2, August 2014 : 124 – 129 128 Table 4. Comparision of Voltage Profiles before, after load shedding with SVC at Bus No-13 Before Load Shedding After Load Shedding V VA V VA 1.06 0 1.0600 0 1.0450 -3.6955 1.0450 -0.0627 1.0100 -9.0156 1.0100 -0.1543 1.0126 -6.4066 1.0136 -0.1080 1.0202 -5.4020 1.0211 -0.0907 1.00 -7.584 1.000 -0.1235 0.9909 -6.0235 0.9927 -0.0983 1.0 -1.9459 1.0000 -0.0272 0.9763 -8.4213 0.9794 -0.1382 0.9724 -8.6004 0.9750 -0.1413 0.9822 -8.2376 0.9836 -0.1350 0.9956 -8.7763 0.9953 -0.1431 1.00 -9.3408 1.0000 -0.1517 0.9673 -9.9635 0.9793 -0.1602 Table 5. Amount of Load Shedding By Placing SVC at Different Bus Locations Before Load Shedding After Load Shedding SVC location Total Real Power Generation Initial Losses Total Real Power Generation Final Losses Amount of load shed at bus no 14 13 266.0092 7.0092 261.2278 6.5278 0.0430 12 266.0205 7.0205 257.8252 6.2252 0.0740 11 265.9552 6.9552 260.2896 .3896 0.0510 10 265.8758 6.8758 262.8703 6.5703 0.0270 9 265.8120 6.8120 264.7004 6.7004 0.0100 8 265.9654 6.9654 256.6988 6.0988 0.0840 4. CONCLUSION The load-shedding system has undoubtedly benefited in terms of reliability and minimizing production losses.By finding out the VCPI at each bus location we came to know the suitable location for the load shedding and by placing the static var compensator the voltage profiles have been improved and thereby reducing the real power losses by shedding minimum percentage of loads at that particular bus.The results show that incoperating the svc in the IEEE 14 bus system can reduce the real powerlosses,improves the voltage profiles and enhances the system stability. REFERENCES [1] Y. Wang, I.R. Pordanjani W. Li, W. Xu, E. Vaahedi, ”Strategy to minimise the load shedding amount for voltage collapse prevention”, IET Gener. Transm. Distrib., 2011, Vol.5, Iss 3, 307-313. [2] Hridya Pradeep, N. Venugopalan “A Study of Voltage Collapse Detection for Power System” ,(ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 1, January 2013). [3] Taylor, C.W., "Concepts of Undervoltage Load Shedding for Voltage Stability" IEEE Transactions on Power Delivery, Volt 7, No 2, April 1992. [4] J. Jung, C. C. Liu, S. L. Tanimoto, and V. Vittal, “Adaptation in load shedding under vulnerable operating conditions,” IEEE Trans. PowerSyst., vol. 17, no. 4, pp. 1199–1205, Nov. 2002. [5] K. Palaniswamy, J. Sharma, and K. Misra, “Optimum load-shedding taking into account of voltage and frequency characteristics of loads,”IEEE Trans. Power App. Syst., vol. PAS-104, no. 6, pp. 1342–1348, Jun1985. [6] E. D. Tuglie, M. Dicorato, M. L. Scala, and P. Scarpellini, “A correctivecontrol for angle and voltage stability enhancement on the transient timescale,”IEEE Trans. Power Syst., vol. 15, no. 4, pp. 1345–1353, Nov.2000. [7] D. Xu and A. Girgis, “Optimal load shedding strategy in power systems with distributed generation,” in Proc. IEEE Power Eng. Soc. WinterMeeting, vol. 2, Columbus, OH, Jan. 2001. [8] N. G. Hingorani and L. Gyugyi, “Understanding FACTS: Concepts and Technology of Flexible AC Transmission System”, IEEE Press, 2000. IEEE/CIGRÉ, “FACTS Overview”, catalogue number 95TP108, 1995. [9] Y.H. Song and A.T. Johns, eds, Flexible AC Transmission Systems (FACTS), IEE Press, U.K., 1999 Acha E., Fuerte-Esquivel C, Ambriz-Perez H and Angeles C., “FACTS: Modelling and Simulation in Power Networks”. John Wiley & Sons, 2004.
- 6. IJAPE ISSN: 2252-8792 Influence of Static Var Compensator for Undervoltage Load Shedding To… (B.VenkateswaraRao) 129 [10] FACTS Modelling and Simulation in Power Networks (Book) by Enrique Acha, Claudio R. Fuerte-Esquivel, Hugo Ambriz-Perez, Cesar Angeles-Camacho. BIOGRAPHIES OF AUTHORS ReshmaRajanwas born in Thrissur, India in 1990.She received her Bachelor’s degree in Electrical and Electronics Engineering from Avanthi Institute Of Engineering And Technology, Vizianagram in 2012.She is pursuing her Master’s Degreee in Power Systems And Automation at GITAM University. B.Venkateswararaowas born in Ramabhadrapuram, India in 1978. He received his Bachelor degree in Electrical and Electronics Engineering from College of Engineering, Gandhi Institute of Technology And Management (GITAM), Visakhapatnam, India in 2000, and the Master degree in Electrical Power Engineering from the College of Engineering, JNTU, and Hyderabad in 2007. He is presently working as Assistant Professor in the Department of Electrical and Electronics Engineering, GITAM University, Visakhapatnam and he is pursuingPh.Dfrom Jawaharlal Nehru Technological University, Hyderabad. His research interests are Power system stability analysis, FACTS devices, Power system control. He has published several research papers in national and international conferences. Dr. G.V. Nagesh Kumar was born in Visakhapatnam, India in 1977. He graduated College of Engineering, Gandhi Institute of Technology and Management, Visakhapatnam, India in 2000, Masters Degree from the College of Engineering, Andhra University, Visakhapatnam, in 2002. He received his Doctoral degree from Jawaharlal Nehru Technological University, Hyderabad in 2008. He is presently working as Associate Professor in the Department of Electrical and Electronics Engineering, GITAM University, Visakhapatnam. His research interests include gas insulated substations, FACTS devices, Power System Stability analysis, fuzzy logic and neural network applications, distributed generation, Partial Discharge Studies and Bearing less drives. He has published 92 research papers in national and international conferences and journals. He received “Sastra Award” , “Best Paper Award” and “Best Researcher Award”. He is a member of various societies, ISTE, IEEE, IE and System Society of India. He is also a reviewer for IEEE Transactions on Dielectrics and Electrical Insulation, Power Systems and a member on Board of several conferences and journals.