Simple Robust Line Current Differential Protection Against Cyberattacks

Line current differential relays (LCDRs) depend on wide area communication networks (WANs) and global positioning systems (GPS), which is a major challenge since both WANs and GPS signals are vulnerable to cyberattacks. For instance, attackers may use false data injection (FDI) to tamper with the signals sent from one line terminal to the LCDR, causing the LCDR to make the incorrect decision. This wrong decision may disconnect a healthy line or fail to trip a faulty line, seriously harming the system. This paper proposes two techniques to (i) detect FDI attacks, (ii) distinguish between missed-tripping attacks and a healthy line, and (iv) ensure that the trip order is sent by the LCDR only when there is a real fault. In the first technique, after the LCDR is triggered, it evaluates the data received from the other terminal by using the local instantaneous voltage and current measurements. The second technique is based on sending a signal of an encrypted predefined value, which is only sent after the remote LCDR senses a fault. Manipulation of this signal is a sign of intrusion, which activates backup protection. Both techniques can be implemented in LCDRs to detect cyberattacks on LCDRs and ensure optimum dependability.