The deregulation of the power market causes a strong tendency towards separating generation from transmission. The utilities responsible for operation the networks are losing control over the placement and scheduling of generation. A consequence of this development is that in certain parts of power networks the short circuit currents approach, or even exceed, the allowable values based on equipment
rating, primarily circuit breaker interrupting capability. There are clear indications for a growing interest in fault current limiting devices rated for applications in the high voltage system. The answers of a survey among worldwide utilities, conducted by CIGRE WG A3.16, show an increase in the need for fault current limitation in medium voltage (MV) systems (below 72 kV) and especially at the high voltage (HV) level between 110 kV and 145 kV.
System protection is an indispensable part of each power system. It must fulfill the requirements of “sensitivity”,“ selectivity”,“rapidity” and “reliability” in order to neither affect the electrical system performance during normal system operation nor to submit the electrical equipment to failure during the occurrence of abnormal conditions (faults). Protection coordination studies are performed routinely to confirm the accomplishment of such requirements even under adverse influence from other network devices. Without this confirmation, or without a properly tested and fully operational protection system, a power system will never be energized. Thus to support the acceptance of fault current limiters (FCL) as new substation equipment possible interactions between fault current limiters and protection systems have to be investigated and understood.
H. Chmitt, J. Amon, D. Braun, G. C. Damstra, K. H. Hartung, N. Higuchi, J. Jager, J. Kida, L. Martini, M. Steurer, X. Waymel, CIGRE WG A3.16, Electra, No 236