This paper proposes a new scheme for locating the faults of three-terminal double-circuit transmission line without transposer in the phase domain that is not affected by type of fault. Synchronous voltage and current were measured by phasor measurement units (PMUs) installed at three busbars. Considering the coupling effect of parallel lines, the distribution line model was used to obtain more accurate results and third-order Taylor series expansion to decouple distributed line model. The phase and branch of all faults on the transmission lines were effectively identified, and various types of faults were accurately located including normal shunt fault, evolving fault and cross-country fault. The proposed algorithm was tested under different fault locations, resistances, initial angles and types (including cross-country faults and evolving faults). In addition, the effects of different sampling rates, measurement errors, earth resistivities and transmission line parameter errors were also considered. The simulation calculation was performed in MATLAB software and three-terminal transmission lines were simulated in PSCAD/EMTP software. The results indicate that maximum estimated error was less than 1.8631%.
The watch crystal oscillator can achieve very-lowpower time-keeping, even less than 1μW, which best overall accuracy with temperature-compensation has remained at about 1 ppm. For comparison, the timing system using Microprocessor Compensated (AT or SC-cut) Crystal Oscillator is capable of providing at least 10-to 100-times improvement in time-keeping accuracy, milliseconds-per-day, with the penalty of requiring considerably more power, about tens of milliwatts. In this paper a novel method for time-keeping based on MCXO is described, which is to simultaneously meet the needs of very-low-power and high-precision timing.I.
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