Frequency analysis of fault currents in LFAC power transmission system

The demands for an interconnection and transmission from long-distant sources and renewable energy sources have been increasing, and HVDC and HVAC power transmission systems have become the effective solutions. HVAC is well-proven technology with high reliability, but the transmission cost increases dramatically as the distance grows. HVDC transmission system has the economic advantage for the long-distance power system, but there are still number of problems with the high converter station cost and the interruption of short circuit current. Recently, LFAC (Low Frequency AC) transmission system has been suggested as a potential alternative to HVDC and HVAC for the connection of long distant and renewable energy sources in terms of power loss, reliability and economy. Moreover, HVAC 50Hz and 60Hz technologies can be applied to LFAC system directly except transformers and circuit breakers. Especially, the interruption of short circuit current is the main issues to decrease the grid frequency, similar to HVDC. The objectives of this paper is to evaluate and analyze the fault current characteristics as the change of transmission frequencies in LFAC power system.