TABLE OF CONTENTS The expansion of electrical power systems by new power stations and new lines (overhead transmission lines and cable circuits) results in an increase of short-circuit currents due to an increase in sources feeding the short-circuit and due to a reduction of system impedance. The improvement of existing installations and the replacement of equipment are necessary, in case the permissible short-circuit current will be exceeded. Measures to limit the short-circuit currents can also be realised which might be more economic than the replacement of equipment and installations. Different measures have to be taken into account such as measures affecting the whole system (higher voltage level), measures concerning installations and substations (separate operation of busbars) and measures related to equipment (Ip-limiter).
All measures have an influence on the system reliability as well, which must be guaranteed under outage conditions of equipment after the measures for limitation of short-circuit currents are in operation. Measures for short-circuit current limitation decrease the voltage stability, increase the reactive power requirement, reduce the dynamic stability and increase the complexity of operation. Furthermore some measures to limit short-circuit currents will contradict requirements for a high short-circuit level, e.g., to reduce flicker in the case of connection of arc-furnace.
The decision on location of power stations is determined beside other criteria by the availability of primary energy (lignite coal fired power stations are build nearby the coal mine), requirement of cooling water (thermal power stations are placed near the sea or at large rivers), geological conditions (hydro...
