SDG&E built on this experience to develop transmission FCP (TFCP) systems. One scheme is based on real-time processing of the PMU data streams already being collected from ubiquitous transmission substation PMUs serving the WASA system. Figure 10 displays a typical TFCP system configuration for a two-terminal transmission line. TFCP schemes are being deployed for trial on 69-kV transmission circuits in 2022. Figure 2 included a timeline for a falling distribution conductor from 30 ft (9 m). A broken overhead transmission conductor 60 ft (18 m) in the air takes even longer-almost 2 s-to reach the ground. With PMU measurements and detection algorithms, substation controllers and relays can trip line terminal breakers and clear a line by the time a failed conductor has fallen only a few feet. It lands on the ground or underbuilt infrastructure, de-energized, and the fire ignition risk is avoided. The TFCP measurement system and algorithms are fundamentally different from those developed for distribution protection and depend more heavily on line current measurements. One TFCP method uses synchronized current comparisons from the line terminal PMU data streams to figure 9. A typical WASA display for a system operator. Transmission Line Voltage and Current Measurements Line Fault Protection Relay With PMU Measurement Function Trip Real-Time Automation Controller With TFCP Algorithms figure 10. The components of a TFCP system. january/february 2022 ieee power & energy magazine 75 Ethernet Wide-Area PMU Data Streams High-Speed Communications Network PMU Data Streams Trip Trip Voltage and Current Measurements Line Fault Protection Relay With PMU Measurement Function Trip Real-Time Automation Controller With TFCP Algorithms Precision Time Synchronization Precision Time Synchronization