Accurate fault locating on transmission lines is of great value to power transmission asset owners and operators. Visual inspection methods evolved from road patrols to air patrols and, more recently, to trials with unmanned aerial vehicles. Most microprocessor-based relays implement fault location using different impedance-based methods. The SEL-411L-1 Advanced Line Differential Protection, Automation, and Control System and the SEL-T400L Time-Domain Line Protection are the only relays on the market that combine subcycle transmission line protection with traveling-wave fault location (TWFL).
Faults in power transmission lines cause transients that travel at a speed close to the speed of light and propagate along the line as traveling waves. Double-ended TWFL uses precise measurements of the traveling-wave arrival times at both ends of the transmission line to locate faults accurately. Single-ended TWFL sorts out multiple wave reflections to accurately calculate the distance to the fault using the TW line propagation time. Traveling-wave fault locators built into transmission line protective relays and using standard current transformers determine locations of faults to within a tower span while adding very little cost.
The SEL-411L includes the field-proven double-ended TWFL, which uses a TW87 communications channel to exchange wave arrival times. The SEL-T400L features both single-ended and double-ended TWFL. Single-ended TWFL does not require a communications channel.
The SEL-411L and SEL-T400L Relays can record traveling-wave data in order to provide a highly accurate fault location. synchroWAVe Event 2015 generates a Bewley lattice diagram from the traveling-wave data to enable visualization, analysis, and understanding of the traveling waves recorded for an event.
Bonneville Power Administration (BPA) owns and operates the Goshen and Drummond substations. The Goshen-Drummond 161 kV line (located in eastern Idaho close to the Wyoming border) is 117.11 kilometers long. The line shares a right of way with a 115 kV line for approximately 7.64 kilometers and also with a 161 kV line for the next 27.36 kilometers.
In 2012, there was a C-phase-to-ground fault on the Goshen-Drummond line. Using TWFL, SEL-411L-1 calculated a fault location of 109.74 kilometers from the Goshen terminal. When the line crew patrolled the line, they found a damaged insulator at 109.29 kilometers from the Goshen terminal. The line crew reported that the cause of the insulator damage was a flashover.
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