Recognizing Ability of Local Currents During Two-Side Observation of Transmission Line
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Vol. 54, No. 4, November, 2020
RECOGNIZING ABILITY OF LOCAL CURRENTS DURING TWO-SIDE OBSERVATION OF TRANSMISSION LINE Ivan Kochetov,1 Yu. Ya. Liamets,2 and F. A. Makashkin2 Translated from Élektricheskie stantsii, No. 6, June 2020, pp. 54 – 58.
The article is aimed at analyzing the various information and parameters involved in diagnosing the fault location on the power line and identifying the damaged branch if there are several branches. Relay protection algorithms widely use the separation of the short-circuit current into the previous and emergency components. The latter carries the basic information of the fault location. Recently, it was found that the emergency component can also be divided into two components, namely normal and local. The local component is particularly very important because the ratio of local currents shows a strong dependence on the fault location or on the damaged branch, but does not depend on the fault current and, most importantly, does not on the part of the electrical system external to the observed line. The influence of unobserved branches on the accuracy of determining the damaged location by the proposed measurement is analyzed. Attention is drawn to the correlation between local currents algorithm and the emerging trends in merging or unifying the characteristics of relay protection and automation. Keywords: a transmission line; fault location; two-side observation; fault current components.
sents one of the two-wire channels on the basis of complex quantities. Generally, an asymmetrical multi-wire system will be represented by modal channel, and a three-phase symmetrical transmission line will be by depressed-zero channel that combines the forward and reverse sequences of one phase. When a SC occurs in the system at a certain place xf, the system switches from the previous mode to the current one (Fig. 1a). In the channel model under consideration, the only change that occurs is the appearance of a dependent SC current source If at the point xf. In the passive model of the system, the independent sources are removed from the external module A, so that it becomes passive module P (Fig. 1b), the source If creates a purely emergency mode in the system. Then respective voltages Usem, Urem, and currents Isem, Irem are noted at the connecting terminals of the line model in this virtual mode. The line model, considered autonomously, is activated purely in an emergency mode at three places (s, r, and f). The line mode will be protected if each of these places has a dependent source of voltage or current acting there. Using the superposition method, we distinguish between the character and function of sources acting at places s and r, and a source acting at the SC place f. Here, the first one acting in the model of an intact line is the electromotive force Usem and Urem creating currents of the normal mode Isem, nm and
As the reliability of contemporary communication facilities has increased a lot, the scope of application of two-side observation of a power transmission line is ex
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