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This paper presents a simple and effective method to extract the identification quantity of transient pulse waveform produced by the overhead transmission line short-circuit fault. This method employs the second-order time harmonic equation of the power frequency component to convert the fault full-wave data. After the conversion, only the identification quantity remains. This method can amplify high-frequency spectral content by the times of the square of the angular frequency, and hence improve the sensitivity of identifying fault transient. Using the identification quantity, one can clearly observe the arrival time and relative intensity of fault transient. A three-phase half wavelength transmission line of 50Hz/3000km is simulated with PSCAD to illuminate the effectiveness of this method. The effects of fault type, soil resistivity, fault resistance, power frequency fluctuation, sampling rate, transposition length,fault inception angle and white noise are analyzed. Calculated results show that this method can distinguish different fault type and can work effectively at low sampling rate down to 10kHz. This method is helpful for improving the performance of the traveling-wave based fault location method.

In order to solve the problem that suspension insulator in substation cannot effectively implement zero value detection, a terminal tool for suspension insulator resistance detection robot based on wireless remote control is designed and researched, which realizes the autonomous walking of the tool on insulator string in substation and the measurement of insulator resistance. The mechanical design, electrical system design, and experimental studies of the terminal tool for insulator resistance detection robots are presented emphatically. The test results show that the designed terminal insulator detection tool meets the requirements for suspension insulator detection in substations.

As it is scant for the linear power amplifier and the two-level switching power amplifier, the principle is analyzed for the three-level power amplifier. It is proposed for the power amplifier for magnetic bearings based on the three-level PWM modulation technique. The circuit is designed for the implementation of the function. The two triangular carriers are formed by the triangular wave superimposing the positive and negative voltage bias, and then, the two drives are formed by comparing the current error signal and the two triangular carriers based on the voltage comparator. The experiment results show that the method can achieve the three-level work, reduce the output current ripple, and have good characteristics. The conclusions have some guiding significance to the design of the three-level power amplifier for magnetic bearings.

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