A new method for locating faults in two-terminal transmission lines is discussed. The procedure is based on the fundamental components of fault and prefault voltage at 50/60 Hz measured at the two ends of a transmission line. The methodology allows one to establish a direct calculation procedure that is independent of fault and prefault currents, fault type, fault resistance, synchronisation condition of register devices located on line ends, and prefault condition, either balanced or not. This is achieved by defining a new concept called ‘distance factor’. The technique developed was validated at two levels: first, from exact data obtained using a fault simulation software program, which allows the accuracy to be evaluated, and secondly, from erroneous voltage data taken at the ends of the line or from erroneous source impedances, which allows assessment of the sensitivity against incorrect data.

International Electrotechnical Commission (IEC) 62351-6 standard specifies the security mechanisms to protect real-time communications based on IEC 61850. Generic Object Oriented Substation Events (GOOSE) and Sampled Value (SV) messages must be generated, transmitted and processed in less than 3 ms, which challenges the introduction of IEC 62351-6. After evaluating the security threats to IEC 61850 communications and the state of the art in GOOSE and SV security, this work presents a novel architecture based on wire-speed processing able to provide message authentication and confidentiality. This architecture has been implemented and tested to evaluate its performance, resource usage, and the latency introduced. Other proposals in the scientific literature do not support real-time traffic, so they are not suitable for GOOSE and SV messages. Whereas the others exceed the target latency of 3 ms or do not comply with the standards, our design authenticates and encrypts real-time IEC 61850 data in less than 7 μs-predictable latency-, and complies with IEC 62351:2020.