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Showing papers on "Islanding published in 1992"


01 Aug 1992
TL;DR: In this article, a new approach based on fuzzy set theory is developed for contingency ranking of Taiwan power system, and each post-contingent quantity is assigned a degree of severity according to the potential damage that could be imposed on the power system by the quantity, should the contingency occurs.
Abstract: In this paper, a new approach based on fuzzy set theory is developed for contingency ranking of Taiwan power system. To examine whether a power system can remain in a secure and reliable operating state under contingency conditions, those contingency cases that will result in loss-of-load, loss-of generation, or islanding are first identified. Then 1P-1Q iteration of fast decoupled load flow is preformed to estimate post-contingent quantities (line flows, bus voltages) for other contingency cases. Based on system operators' past experience, each post-contingent quantity is assigned a degree of severity according to the potential damage that could be imposed on the power system by the quantity, should the contingency occurs. An approach based on fuzzy set theory is developed to deal with the imprecision of linguistic terms.

67 citations


Journal ArticleDOI
TL;DR: In this article, a typical application procedure for a coordinated load shedding scheme using both frequency trend relays and normal discrete underfrequency relays is described, and the strategy for islanding such industrial power systems from the grid during grid disturbances is described.
Abstract: A typical application procedure for a coordinated load shedding scheme using both frequency trend relays and normal discrete underfrequency relays is described. By using such a combination of relays it is possible to develop comprehensive protection against frequency disturbances, both sudden and gradual. It is emphasized that in a system where the causes of frequency disturbances are quite varied and complex, a fully automatic scheme may not be the ideal solution and manual load shedding as a backup may be necessary. A typical procedure for a captive power plant system operating in parallel with the grid is described as applicable to a continuous process plant industry. The strategy for islanding such industrial power systems from the grid during grid disturbances is described. >

17 citations


Patent
22 Oct 1992
TL;DR: In this paper, the authors proposed a method to surely stop the electric current of a power supply line in an islanding state by a method wherein a frequency abnormality, a frequency change-rate abnormality and a voltage abnormality are detected and a system-interconnection inverter is released from a system.
Abstract: PURPOSE: To surely stop the electric current of a power supply line in an islanding state by a method wherein a frequency abnormality, a frequency change-rate abnormality and a voltage abnormality are detected and a system- interconnection inverter is released from a system. CONSTITUTION: An electric current always at a definite power factor is output from an inverter 2 over the wide range of the frequency (at which a frequency relay 18 is actuated surely) of an AC power supply 8 by a PLL circuit 22. A slight change in a system is caught by a voltage abnormality relay 25, a frequency abnormality relay 26, a frequency change-rate abnormality relay 27 and the like, an abnormality is found out, the electric current of the inverter 2 fluctuates and becomes out of balance, it is detected that a frequency and a voltage fluctuate largely, and the inverter 2 is released from the system. Thereby, it is possible to surely stop the electric current of a power-supply line in an islanding operation. COPYRIGHT: (C)1994,JPO&Japio

6 citations