In order to reduce grounded current and restrain arc-grounded over voltage during single-phase grounded faults in transmission line and realize fault-line selection, the neutral grounded mode with Peterson coil in parallel with big reactor is proposed in the paper. The simulation and comparative analysis of the performance of the 10 kV distribution grid systems in different neutral grounded modes have been done. The simulation results have shown that the neutral grounded mode via Peterson coil in parallel connection with big resistances can restrain the fault current effectively and it is the best mode.

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This paper proposes a pilot-assisted joint estimation algorithm of carrier frequency offset (CFO) and sampling frequency offset (SFO) in orthogonal frequency-division multiplexing (OFDM) systems based on a slow fading channel. The proposed algorithm firstly completes the coarse estimation of fractional carrier frequency offset (FCFO) by researching the phase relation of neighboring pilots in time-domain, and then reduces the interchannel interference (ICI) markedly by compensating the received signal in time-domain. At last, the fine estimation of FCFO and SFO is implemented by comparing the phase shifts of different sub-carriers in neighboring pilots. By using the average as the final estimating value, the Influence of noise is reduced and the estimation accuracy of the CFO and SFO is increased. Theoretical analysis and simulation results for multi-path channel show that the proposed algorithm has higher estimation accuracy and needs less pilot symbol than the existing similar methods.