A Study on Setting of Ground-Fault Distance Protection for the Overhead-Cable Hybrid Line
To address the uneven parameters of overhead lines and cables in the overhead and cable hybrid line,an optimal setting method for grounding distance protection of the hybrid line is proposed.First,the influence of the zero-sequence current compensation coefficient on the measured impedance is analyzed.The positive sequence impedance and zero-sequence impedance of 70%of the total length of the hybrid line from the bus are used to calculate the zero-sequence current compensation coefficient.Second,the waveform characteristics of the fault phase voltage collected by overhead line and cable side protection when the fault occurs in different positions are analyzed.It is found that the fault phase voltage collected by the cable side protection contains a large amplitude of non integral harmonics.Therefore,70%of the total length of the line from the bus is used as the setting impedance for the overhead line side protection,70%of the positive sequence impedance of the whole line is used as the setting impedance for the cable side protection.A simulation model for the hybrid line fault is built by PSCAD.The simulation results show that the method proposed in this paper can effectively improve the sensitivity and reliability of grounding distance protection of Section I.
overhead-cable hybrid linedistance protectionzero-sequence current compensation coefficientsetting impedancesensitivityreliability
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