ISSN (Print) : 2320 – 3765
ISSN (Online): 2278 – 8875
International Journal of Advanced Research in Electrical,
Electronics and Instrumentation Engineering
(ISO 3297: 2007 Certified Organization)
Vol. 2, Issue 8, August 2013
Copyright to IJAREEIE www.ijareeie.com 4022
margin of system w.r.t voltage collapse point is shown in table III. When min voltage limit is considered, voltage
violation at different loading point for all the buses can be observed in Fig. 3 and Fig 4.When we examined Fig. 3 and
Fig 4 most reduction in bus voltage at 14
th
no bus. This is the weakest bus of the system. It is decided by bus voltage
sensitivity factor. This is same as finding the bus with the greatest ratio | / |value.
The ratio | / | is taken as bus voltage sensitivity factor where and are respectively total active load
change and per unit voltage change in bus in the system. Since the denominators in this ratio are the same for all
buses, the differential change in bus voltages can be taken as voltage stability sensitivity factor. Table.4 shows the bus
voltage sensitivity factor. From table 4 rank of most three weakest buses according to VSF is 14, 10 and 7, while bus
no. 8 and 9 have lowest VSF. This result helps to place reactive power sources to improve voltage stability. When any
contingency like line outage 4 occurs in the system affects bus no 14 and bus no 7 is shown in Fig. 6 and Fig.7
respectively. It can see voltage collapse point reduced with contingency. It is 1.462 times current operating point. In
case of contingency line outage 9 (2-4) , maximum loading point is 1.29 times base load point. Thus system approaches
near to voltage collapse. It can also say that available transfer capacity of the system is 218 Mw more than current
operating point. Maximum loading point lambda is reduced for contingency n-1, here is one transmission line outage.
Here line outage between bus no.1and bus no.8 is considered to examine the effect. It can observe from Fig. 6 and 7
when one transmission line is opened, system maximum loading parameter lambda is reduced from 1.8436 to 1.462.
Voltage at that point is 0.6107 p.u. for normal condition and 0.6093 p.u for TL outage condition for bus no.7 and
voltage is 0.551p.u. for normal condition and 0.566 p.u. for TL outage condition for bus no.14 at maximum loading
point. These results say that VSF is different for different contingencies and Rank of weakest bus is also changed.
Table IV shows VSF of PQ buses for contingency of one line outage. At the time of contingency case line outage (3-8)
rank of most three weakest buses is changed, while for other contingency it remains same .Bus no. 14 is most weakest
bus in all contingencies cases.
V.CONCLUSION
Above all results shows that voltage stability margin can be found easily by CPF. And P-V curve and max. loading
point can access. Only collapse point is not enough for voltage stability assessment .So, using tangent vector sensitivity
analysis can be done. From voltage sensitivity factor weakest bus can identify. The Weakest bus identification is done
by without excessive calculation. Placement of reactive power sources such as Fact devices, capacitor bank is known.
This result is same accurate as to find Bus participation factor using QV modal analysis. This CPF method is more
accurate and simple for Voltage stability analysis.
REFERENCES
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2006926216 , Iowa State University ,Department of Electrical and Computer Engineering . 1122 Coover Hall ,Ames Iowa 50011, U.S.A.
[2] Varun Togiti ―Pattern Recognition of Power System Voltage Stability using Statistical and Algorithmic Methods‖ University of New Orleans
ScholarWorks@UNO University of New Orleans . 5-18-2012
[3] B. Gao, G. K. Morison, and P. Kundur, ―Voltage stability evaluation using modal analysis,‖ IEEE Trans. on Power Systems, vol. 7, no. 4,pp. 1529–1542, Nov. 1992
[4] P. A. Lof, T. Smed, G. Anderson, and D. J. Hill, ―Fast calculation of a voltage stability index,‖ IEEE Trans. on Power Systems, vol. 7, no. 1,pp. 54–64, Feb.
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[5] L. Bao, Z. Huang, and W. Xu, ―On-line voltage stability monitoring using var reserves,‖ IEEE Trans. Power Syst., vol. 18, no. 4, pp.1461–1469, Nov. 2003.
[6] Satish Joshi , ―A Thesis on Voltage stability and contingency selection studies in electrical power system‖, Department of electrical engineering. Indian institute of
technology Kanpur . December 1995.
[7] P. Kundur, ―Power System Stability and Control‖ McGraw-Hilll, 1994.
[8] J. Paserba, V. Ajjarapu, G. Andersson, A. Bose, C. Canizares, N. Hatziargyriou, D. Hill, A. Stankovic, C. Taylor, T. Van Cutsem, V. Vittal
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BIOGRAPHY
Parul A. Upadhyay. Education Qualification: M.E.( Electrical)(Student- M.S university ,Vadodara, Gujarat,
India. Experience : 14 years in Technical Education Department, Gujarat, India.
Dharmesh D. Patel. Education Qualification: M.E.(Electrical)S.P.University,Vallabh Vidhyanagar,Gujarat,
India. Experience : 09 years in Technical Education Department, Gujarat, India.