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International Journal of Electrical Power & Energy Systems Volume 24, Issue 5, June 2002, Pages 379-386 |
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Copyright © 2002 Elsevier Science Ltd. All rights reserved.
Accepted 16 April 2001
Abstract
There is a growing trend towards the use of sophisticated relays like frequency trend relays for the purpose of automatic load shedding to avert the major system collapses due to integrated operation of modern power system. Accurate load shedding saves loss of revenue to power utility in addition to avoiding unnecessary disruption of vital feeders. Face values of MW capacities of generation outages are normally used for estimating the system overloading and consequent quantum of load shed to recover the system to safe workable frequency. Inherent dependence of transmission line parameters upon the system frequency affects the line performance in terms of its reduced output during under-frequency condition. The paper has attempted to present a modified load shedding scheme incorporating the relieving effect of transmission network and showed the advantages over the conventional method.
Author Keywords: Under-frequency; Revised load-shedding; Transmission line
- List of symbols
- f
- power frequency (50 Hz)
- f′
- sub-normal frequency
- VR
- receiving end voltage phase value at 50 Hz
- VR′
- receiving end voltage phase value at f′ with phase angle θ
- Vs
- sending end voltage phase value at 50 Hz
- Is
- sending end current at 50 Hz
- IR
- load current in amperes at 50 Hz at receiving end
- IR′
- load current in amperes at f′ at receiving end
- PR
- active power delivered by the line at receiving end at 50 Hz
- PR′
- active power delivered by the line at receiving end at f′ Hz
- QR
- reactive power delivered by the line at receiving end at 50 Hz
- QR′
- reactive power delivered by the line at receiving end at f′ Hz
- ABCD
- generalized circuit constants at 50 Hz (complex)
- A′B′C′D′
- generalized circuit constants at f′ Hz (complex)
- α
- phase angle of A
- α′
- phase angle of A′
- β
- phase angle of B
- β′
- phase angle of B′
Article Outline
- Nomenclature
- 1. Introduction
- 2. Low frequency system operation
- 2.1. Causes for low frequency and load shedding schemes
- 2.2. Need for modification in load shedding formulation
- 2.3. Relieving effect of sub-normal frequency performance of long transmission line
- 2.4. Basis for mathematical analysis
- 3. Study of practical application of new approach
- 4. Conclusions
- Appendix A
- References
Corresponding author; email: nisha_c2000@yahoo.com
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International Journal of Electrical Power & Energy Systems Volume 24, Issue 5, June 2002, Pages 379-386 |
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