The impact of HVDC links on transmission system collapse

Modern power systems are continually being expanded, are required to carry more power and are being increasingly interconnected. All of these increase the risk of wide area blackout. 2003 North America Blackout and 2006 Europe Blackout demonstrated that a HVDC link provides a `firewall' against the system collapse propagating through a network. However, distance relay response to overload or power swing conditions rather than true line fault which indeed contributing to voltage collapse. The objectives of the paper are to investigate contributions that integrate HVDC interconnection into AC network and the influence that HVDC link would bring to distance relay. The simulation studies were performed using MATLAB/SIMULINK.