Sequence theory [1] is one of the most important tool for power system engineers. In fact, both in planning and operating activities, power flow and short circuit studies are always based on the knowledge of the sequence impedances. Consequently, positive, negative and zero sequence impedances are the first step for power flow and short circuit analyses and are also necessary for setting the distance relays. Notwithstanding, it is also true that by considering the physical reality of the power networks, it can be questionable to assume purely three-phase configurations and perfectly symmetrical ones, so to use sequence theory based modelling. It is worth remembering that the use of zero, positive-negative sequence impedances Z0, Z1, Z2, is only exact if the system is symmetric since the application of voltage phasors of a sequence causes the circulation of current phasors only of the same sequence so that it is possible to compute the ratios between voltage and current phasors. The paper presents three meaningful examples of sequence theory use limitations.
Some meaningful examples of sequence theory use limitation
Benato, R.
;Dambone Sessa, S.
2016
Abstract
Sequence theory [1] is one of the most important tool for power system engineers. In fact, both in planning and operating activities, power flow and short circuit studies are always based on the knowledge of the sequence impedances. Consequently, positive, negative and zero sequence impedances are the first step for power flow and short circuit analyses and are also necessary for setting the distance relays. Notwithstanding, it is also true that by considering the physical reality of the power networks, it can be questionable to assume purely three-phase configurations and perfectly symmetrical ones, so to use sequence theory based modelling. It is worth remembering that the use of zero, positive-negative sequence impedances Z0, Z1, Z2, is only exact if the system is symmetric since the application of voltage phasors of a sequence causes the circulation of current phasors only of the same sequence so that it is possible to compute the ratios between voltage and current phasors. The paper presents three meaningful examples of sequence theory use limitations.Pubblicazioni consigliate
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