Research On Fault Section Location Method In Non-Effectively Grounded Network

With the large-scale construction and transformation of China's distribution network during the "13th Five-Year Plan" period and the ever-accelerating process of urban cable distribution,the capacitor current is continuously increasing when a single-phase ground fault occurs in the distribution network.In order to be able to extinguish the arc safely and reliably during the single-phase-to-earth fault,neutral grounding of the distribution network should be grounded via arc suppression coil according to the rules.However,when a permanent earth fault occurs,due to the compensation effect of arc suppression coil on the fault current,the magnitude of the steady-state fault current in single-phase earthing is small and the fault features are hard to be extracted and discriminated,which poses a severe challenge to the fault zone positioning.However,in order to ensure the safety of distribution network and the reliability of power supply,the fault lines and fault sections must be quickly identified and effective protection measures should be adopted to isolate faults so that the distribution network can resume normal operation.Therefore,this article has important theoretical significance and practical value for the research on the section location method under the condition of single-phase ground fault in the distribution network through the arc suppression coil grounding system.The main work and innovations of the dissertation include:(1)For the arc suppression coil grounding system,a fault transient equivalent circuit including equivalent process and parameter calculation is established.Aiming at the shortcomings of the traditional transient equivalent circuit,which can only be qualitatively analyzed,the zero-sequence distribution parameter model of ground fault including the upstream and downstream networks at the fault point is established.Then,according to the simplified constraint principle,Fault lines are equivalent,respectively,to establish a centralized parameter zero sequence equivalent circuit,the equivalent process includes parameter calculation,is conducive to the accurate calculation of the faulty electrical quantities.(2)A fast segment locating method based on transient zero sequence capacitance current slope correlation and transient zero sequence inductor current decay aperiodic components is proposed.First,according to the distribution characteristics of zero sequence current of arc suppression coil grounding system fault,based on Hilbert-Huang transform the transient signal decomposition method,the fault transient zero sequence current is divided into transient zero sequence current and zero sequence inductor current,and then based on transient zero sequence capacitance current slope correlation and transient zero sequence inductor current attenuation The non-periodic components are located on both sides of the fault point to realize the zone positioning.At last,the proposed method is validated by ATP-EMTP simulation software,which verifies the effectiveness of the proposed method.(3)For the neutral point flexible ground control system,a fault zone positioning method based on the zero sequence change of admittance is proposed.After the single-phase ground fault occurred in the distribution network,before and after the neutral point parameters are adjusted adaptively by the active decoupling control,the change characteristics of admittance in the zero-sequence measurement of each line detection point are achieved to locate the fault section.At last,the proposed fault location method is simulated by ATP-EMTP simulation software,which verifies the effectiveness of the proposed method.