Home > Archives > IJSRST151328

A Quantitative Evaluation of Security Indices for Nigerian National Grid System

Authors(2) :-Ganiyu A. Ajenikoko, Samuel O. Okeniyi

Security of a power system is the degree of risk and ability to survive imminent disturbances (contingencies) without interruption of continuous service. Security indices are parametric variables used to represent the degree of operation or malfunction of power system before the system faces interruption of service or the element faces outage or malfunction. A concept opposite to security is vulnerability concept. An element or a system is vulnerable if contingencies lead to an interruption of service at a point or the entire element or system. Vulnerability index (VI) and Margin index (MI) are quantitative security indices that provide comprehensive information about the individual parts and the whole system.

This paper presents a quantitative evaluation of security indices for the Nigerian national grid Mathematical models were formulated for the two prominent security indices. Twenty four generators, Twenty four buses and Twenty four branches were selected as case studies on the Nigerian national grid system while their impacts on the vulnerability and margin indices were stressed. The vulnerability indices increased as more generators were added while the margin indices also decreased proportionately as the number of generators increase. The average value for the vulnerability index was 0.0275 per generator while the average margin index was 0.8073 per generator. The vulnerability indices increased as more buses were added into the system while the margin index between 6 and 7 buses remained constant at 1.0 suggesting that the buses appeared to be at optimum even though, as the number of buses increased, the margin indices decreased. The average vulnerability and margin indices for the buses were 9.921 per bus and 14.0495 per bus respectively. The vulnerability indices for the branches increased with increase in branches while the margin indices decreased as more branches were included in the system. The average vulnerability and margin indices for the branches were 0.1906 and 0.4640 per branch respectively.

The results from this work will assist power system engineers and utility staff in safe-guarding various contingencies emanating from violation of the power system operational limits.

Ganiyu A. Ajenikoko, Samuel O. Okeniyi
Security, Vulnerability Index, Margin Index, Static Security, Dynamic Security, Transient Stability, Contingency.
1. Bruch M, Muuch V, Aichinger M, Kuhu M, Weymann M and Schmid G (2011): "Power blackout risk: Risksmanagement options, emerging risk initiative – position paper," Pp 22-28.
2. Carreras B.A, Newman D.E and Dobson I (2012): "Determining the vulnerability of the power transmission system," In Proceedings of the 45thHawali International conference on system sciences, (HICSS 112), Pp 2044 – 2053.
3. Chan G, Dong Z.Y, Hill D.J, Zhung G.H and Hua K.Q (2010): "Attack Structural vulnerability of power grids: A hybrid approach based on complex network," Physical A, Vol 389, No 3, Pp 595 – 603.
4. Chen J, Thorp J.S and Dobson I. (2005): "Cascading dynamics and mitigation assessment in power system disturbances via a sudden failure model," International Journal of Electrical Power and Energy System, Vol. 27, No. 4, Pp. 318-326.
5. Dobson I (2012): "Estimating the propagation and extent of cascading failure line outages from utility data with a branching process," IEEE Transmissions on power systems, Vol. 27, No. 4, Pp 2146 – 2155.
6. Dobson I, McCalley. J and Liu C.C (2010): "FACTS Simulation, Monitoring and Mitigation of Carcading Failures," Power Systems Engineering Research Centre, Pp 34-45.
7. Grigg C and Wong P (1999): "The IEEE reliability transmission system – A report prepared by the reliability transmission system task force of the applications of probability methods subcommittee," IEEE Transmission on power systems, Vol 14, No 3, Pp 1010 – 1029.
8. Salim N.A, Othman M.M, Musirin I and Servan M.S (2011): "Cascading Collapses assessment considering hidden failure," In proceedings of the 1st International Conference on Information and Computational intelligence (ICI ‘11), Pp 318 – 328.
9. Shi Z, Shi L, Ni L, Yao L and Bazargan M (2011): "Identifying Chains of events during power system cascading failure," In proceedings of the Asia-Pacific Power and Energy Engineering Conference (APPEEC’ 11), Pp 34-51.
10. Valman M, Ben K, Chan A.T (2012): "Risk assessment of cascading outages: Methodologies and Challenges," IEEE Transactions on power systems, Vol. 27, No 2, Pp 631 –641.
11. Wang A, Luo Y, Tu G and Liu P (2011): "Vulnerability assessment scheme for power system transmission networks based on the fault chain theory". IEEE Transactions on power systems, Vol. 26, No 1, Pp 442 – 450.
###### Publication Details
Published in : Volume 1 | Issue 4 | September-October 2015
Date of Publication : 2015-10-25