Abstract
Being fast and highly reliable under different conditions, line current differential relays (LCDRs) are high-end protective devices that are deployed to protect DC and critical AC lines. LCDRs, however, are vulnerable to cyber attacks, since this type of relay is dependent on communication infrastructure and the global positioning system (GPS). This susceptibility may enable attackers to fool LCDRs into issuing unwarranted trip signals, and potentially to create an instability if several attacks are coordinated. Through case-studies, this paper shows how coordinated attacks against LCDRs in DC and AC networks can create a voltage collapse in the system. The case-studies are carried on the IEEE 14-bus AC network, as well as on a DC microgrid.