Generation shift factor and line outage factor
- 1. Security Analysis Prepared by Viren Pandya Ref. Book:- Wood Power Generation, Operation, and Control - Allen J. Wood, Bruce F. Wollenberg
- 2. An Overview of Security Analysis • Study the power system with approximate but very fast algorithms. • Select only the important cases for detailed analysis. • Use a computer system made up of multiple processors or vector processors to gain speed.
- 3. Methods of Security Analysis • The first method has been in use for many years and goes under various names such as “D factor methods,” “linear sensitivity methods,” “DC power flow methods,” etc. • This approach is useful if one only desires an approximate analysis of the effect of each outage. • It has all the imitations attributed to the DC power flow; that is, only branch MW flows are calculated and these are only within about 5% accuracy. • There is no knowledge of MVAR flows or bus voltage magnitudes.
- 4. Linear Sensitivity Factors • The problem of studying thousands of possible outages becomes very difficult to solve if it is desired to present the results quickly. • One of the easiest ways to provide a quick calculation of possible overloads is to use linear sensitivity factors.
- 5. Linear Sensitivity Factors • Generation shift factors. • Line outage distribution factors.
- 7. Linear Sensitivity Factors • It is assumed in this definition that the change in generation ΔPi is exactly compensated by an opposite change in generation at the reference bus and that all other generators remain fixed. • The factor ali then represents the sensitivity of the flow on line l to a change in generation at bus i.
- 8. Linear Sensitivity Factors • Suppose one wanted to study the outage of a large generating unit and it was assumed that all the generation lost would be made up by the reference generation • If the generator was generating P0 MW and it was lost, we would represent ΔPi as ΔPi = - P0 • Such factors can be precalculated and tabulated
- 9. Linear Sensitivity Factors • Using such precalculated generation shift factors, post contingency line flows can be easily obtained quickly as follows: ∧ f l = f l 0 + ( ali ×∆Pi ) for l = 1, 2 ,3....L where ∧ f l = post contingency flow on line l after the generator on bus i fails f l = flow before the failure or contingency 0
- 10. Linear Sensitivity Factors Line outage distribution factor •The line outage distribution factors are used in a similar manner, only they apply to the testing for overloads when transmission circuits are lost.
- 11. Linear Sensitivity Factors • By definition, the line outage distribution factor has the following meaning: ∆ fl dl ,k = 0 fk where dl ,k = line outage distribution factor when monitoring line l after an outage on line k ∆ fl = change in MW flow on line l f k0 = original flow on line k before it was outaged (opened)
- 12. Linear Sensitivity Factors • If one knows the power on line l and line k, the flow on line l with line k out can be determined using "d" factors. ∧ fl = fl + ( dl ,k × f ) 0 0 k where fl 0 , f k0 = preoutage flows on lines l and k respectively ∧ fl = post contingency flow on line l with line k out
- 13. Linear Sensitivity Factors • By precalculating the line outage distribution factors, a very fast procedure can be set up to test all lines in the network for overload for the outage of a particular line. • Furthermore, this procedure can be repeated for the outage of each line in turn, with overloads reported to the operations personnel in the form of alarm messages.
- 14. Contingency analysis (sensitivity factors) – Flowchart