Abstract
AbstractTechnical, economical and ecological aspects lead to untransposed power lines. Full transposition schemes are often to expensive and not applicable to short poly‐circuit lines. Therefore line unsymmetry is of importance with respect to the impedance calculation and the setting of distance‐protection relays. As a consequence of line unsymmetry the short‐circuit impedance depends on the fault type and the measuring loop. As conventional distance protection is based on the model of a symmetrical line, this causes an unsharpness of the tripping area in the complex impedance plane. To avoid wrong tripping, distance‐protection relays must be set with reduced ranges. Consequently, the fault clearing time increases for extended sections at both line ends. Furthermore fault localization ‐ an additional feature of increasing importance ‐ will be as inaccurate as the measured impedance. Improvement of distance measurement by new current‐compensation methods are discussed in this paper. Extensions of the methods to mutual coupled double‐circuit lines are outlined.
Published Version
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