In the article the authors propose main and back-up protections of two and three parallel lines controlling ratio of currents in the phases of all connections of open distribution unit of electric station. The main ones protect from all kinds of short circuits, back-up ones - from one-phase short circuits. It is shown that for identification of a damaged line it is sufficient just to compare the currents in the same phases, for example, for correct functioning of the main one it is necessary to compare the currents in the lines with idle current, of the backup - it is necessary to evaluate the value of ratio of combinations of currents on the side of the lowest tension of boost transformers and the direction of power of zero sequence on the lines. The algorithms of functioning in the form of analytical expressions made on the base of verbal formulation of conditions of actuation with the use of logics of algebra. The algorithms take into consideration the necessity of acceleration of back-up protection with one-phase short circuit on the one of the lines. Flow harts of these algorithms are provided. The operation of these types of protection in different modes and their sensitivity are tested. It is shown that behave themselves in a right way even with disconnection of a wire with one-side earth short circuit and their sensitivity is higher than with traditional ones.
|Number of pages||6|
|Journal||World Applied Sciences Journal|
|Publication status||Published - 2013|
- Currents ratio direction of power the lowest voltage power transformer sensitivity
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