Kabelreserve in Oberösterreich - Institut für Elektrische Anlagen

Abstract
Ausbaugrenzen gelöscht betriebener Netze
Title: Expansions limits of earth fault compensated networks
Keywords: residual earth fault current, extension reserve, harmonics, resonances
This thesis deals with the arising problems in connection with increased extension of earthfault-compensated
grids. The grid extension increases the line to earth capacities, so that the
capacitive line to earth current which can be compensated and also the earth fault residual
current rise.
The earth fault current depends on operating voltage, frequency, harmonics and on the
distribution of capacities and inductances in the grid (resonances). The ground fault residual
current depends additionally on detuning, damping, on the saturation of the Petersen coils
and on parallel led systems, which are in opposition to a perfect compensation.
With the help of a grid calculation program the limits of the grid extension are pointed out, as
well as further problems that bring difficulties are shown. Above all the influence of
harmonics und their resonances are examined, in order to avoid arising degradations of the
earth fault clearing ability. Further technical measures are explained, which ensure a future
problem-free grid operation.
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