Optimization - and Model - Based Methods for Protection of Power Lines
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Date
2020
Publication Type
Doctoral Thesis
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yes
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Abstract
Constantly growing power demand and increasing penetration of renewable energy sources (RES) are pushing power grids to their limits. Due to importance of protection for reliable and safe operation of these grids, changes in their operating conditions necessitate the improvement of existing and development of new protection algorithms. This work aims at addressing several challenges faced by protection of modern power grids. First, it focuses on improving performance of the first zone of conventional distance protection, which is widely used for transmission lines. In particular, the work tackles two shortcomings of this zone: limited coverage of internal faults due to the design of the zone characteristic, and further reduction of coverage in case of installed series compensation devices (SCDs). This is accomplished by proposing an optimization-based algorithm for constructing an optimal first zone characteristic of distance protection for lines with and without SCDs. The proposed algorithm ensures that the first zone has the maximum possible coverage of internal faults without compromising its security. Second, this work proposes a communication-assisted protection algorithm for medium-voltage lines that does not rely on any user-defined set-points, in contrast to other existing protection algorithms. Lack of set-points simplifies the algorithm’s application, reduces the risk of human errors, and improves reliability as the algorithm is not affected by sub-optimally selected set-points. In addition, the algorithm inherently combines protection, fault location and fault type identification functionalities, which enables the unification of these closely related functions. Lastly, this work proposes a protection algorithm that addresses the challenge of enabling economically efficient yet reliable protection of medium-voltage lines in grids with RES. It relies only on local measurements and enables simultaneous protection of all medium-voltage lines at a substation, which makes it a low-cost solution. Moreover, the algorithm has high speed and is unaffected by the operation modes of RES as it is based on the traveling wave theory. Extensive simulation results demonstrate that the algorithms proposed in this work can potentially provide reliable protection of power lines in modern grids.
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Examiner : Hug, Gabriela
Examiner : Andersson, Göran
Examiner : Razzaghi, Reza
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Publisher
ETH Zurich
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Subject
RELAY PROTECTION + SELECTIVE PROTECTION + DISTANCE PROTECTIVE SYSTEMS PROTECTION (ELECTRICAL PROTECTIVE DEVICES); Optimization algorithms; Power lines
Organisational unit
09481 - Hug, Gabriela / Hug, Gabriela