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19. Determining optimal neutral reactor to limit overvoltages and duration of secondary arc of transmission lines.

Author

Mohammadi, Abolfazl, Abedini, Moein, and Davarpanah, Mahdi

Subjects
ELECTRIC lines, OVERVOLTAGE, SHUNT electric reactors, ELECTRIC transients, POWER system simulation, FAULT currents
Abstract

Even though shunt compensation of transmission lines (TLs) is a common practice to limit the overvoltages stemming from the Ferranti effect, it may cause transient and steady‐state resonant overvoltages when one phase is left open due to the single‐pole‐open condition following the temporary phase‐to‐ground (Ph‐g) fault. Furthermore, the existing shunt reactors potentially increase the duration of the secondary arc current at the fault point and hence prevent offering fast single‐pole reclosing. To exploit the mentioned issues, in recent studies, a neutral reactor is introduced, which is installed in the neutral point of the shunt reactors; nonetheless, obtaining the appropriate amount of it is remarkably challenging. In this paper, an optimal neutral reactor (ONR) is determined based on an optimization problem, which minimizes the neutral reactor cost subject to limiting both resonant overvoltages and the duration of the secondary arc current. In modelling, the Laplace domain is employed rather than the phasor domain to consider both transient and steady‐state conditions since this technique allows having better control over transient overvoltages as well as transient secondary arc. [ABSTRACT FROM AUTHOR]

Published
2023
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23. Fast and reliable CT saturation detection using a combined method

Author

Dashti, Hamed, Pasand, Majid Sanaye, and Davarpanah, Mahdi

Subjects
Electric transformers -- Design and construction, Electric fault location -- Methods, Electric power transmission -- Research, Algorithms -- Usage, Algorithm, Business, Computers, Electronics, Electronics and electrical industries
Abstract

Busbar differential relays may operate incorrectly for external faults due to current-transformer (CT) saturation. In this paper, two different techniques are suggested to detect CT saturation. The first proposed technique is based on the fact that the waveshape of the CT secondary current changes significantly at the instant of the saturation. Based on this feature, an algorithm which uses the second derivative of CT output current is developed. It uses an adaptive threshold to detect CT saturation fast. The second proposed technique utilizes two criteria based on the zero crossing principle. Utilizing the combination of the second derivative and zero crossing techniques results in a powerful and reliable scheme which is able to detect various CT saturation cases correctly and quite fast. The proposed method is able to detect even small CT saturation events. A real 400-kV busbar is simulated using PSCAD/EMTDC for evaluating the performance of the proposed algorithm. The obtained results demonstrate precise operation of the proposed algorithm in different conditions. Index Terms--Busbar differential protection, current-transformer (CT) saturation detection, second derivative, zero crossing.

Published
2009

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