Application Research On Line Selection And Protection Of Distribution Network

With the continuous development of yidu HEC,the power load is increasing year by year.The problems in the company’s internal 10 k V distribution system are increasingly prominent.The applied research on the line selection and protection of distribution network can effectively improve the internal power supply safety and reliability of HEC and ensure the company’s safe production,which has great political and economic significance.This paper analyzes the internal 10 k V power supply and distribution system of HEC finds out the existing problems,and focuses on the analysis and research of the 10 k V power supply and distribution system of power plant and pharmaceutical factory,which is mainly used to solve the 10 kv power distribution system of single-phase grounding fault line selection difficult problems above,trip,coal-fired power plants to the pharmaceutical industry developed rapidly into a single-phase earth fault occurred 10 kv line and grounding,three-phase short-circuit fault and other issues.First of all,this paper introduces the basic situation of HEC introduces the basic situation of thel power plant,the calculation of capacitive current,the fixed value of line protection and the brief situation of development.In the end,some problems that need to be solved in 10 k V power distribution system.Secondly,the fault loop of the ungrounded 10 k V neutral point system is found with low accuracy by the manual switch line selection method.It is easy to misselect by using small current earthing selecting device.And get an electric shock arc suppression method arc suppression coil compensation method and can’t choose fault circuit is put forward a kind of pulse current line selection integrated arc suppression method,this method is borrowed from small current line selection with the advantages of electric shock to compensation arc suppression coil,when single-phase earth fault happened,can find the fault circuit quickly through theoretical analysis,modeling and simulation to verify the proposed method is feasible,for 10 kv single-phase grounding fault circuit troubleshooting grounding distribution system provides new ideas.Thirdly,over-step tripping accidents frequently occur in the 10 k V line from the thermal power plant to the pharmaceutical factory.The reason is that the three-phase short-circuit currents at the beginning and end of the line have little difference,and the protection adopts three-stage current protection,while the over-current one-stage protection has poor selectivity,and it is easy to misoperate,and the accident of oversteptrip occurs.In order to improve the safety and reliability of 10 k V power supply line,in case of interphase short circuit,interphase ground short circuit and three-phase ground fault,the line protection device shall be required to reliably cut off the fault,and no overstep trip accident shall occur.Considering the 10 k V line protection between the thermal power plant and the pharmaceutical factory,the fiber differential protection is the main protection,and the overcurrent second and third section protection is the backup protection.By theoretical analysis,the fault line can be cut off immediately when the three-phase short circuit fault occurs in the line from the thermal power plant to the pharmaceutical factory.When the three-phase short circuit fault is found in the load line of the pharmaceutical factory,the over-step trip accident will not occur,which provides a reference for the protection setting of the 10 k V distribution system in HEC.The total capacitive current of the 10 k V distribution network is calculated as 121.07 A.Considering that the lines from 10 k V thermal power plant to pharmaceutical factory are mainly arranged in the cable trench and the cable bridge,single-phase ground fault is likely to cause other line faults.In case of an expansion accident,the fault circuit should be cut out immediately in case of single-phase ground fault.Then,the security and reliability of power supply are improved by further research and improvement on the selection and protection of power distribution network.The switches on both sides of the 10 k V line from thermal power plant to pharmaceutical factory are mainly protected by optical fiber longitudinal difference protection,and the second and third sections of overcurrent protection are backup protection.In case of phase-to-phase,phase-to-phase grounding and three-phase short circuit fault,the protective action shall be cut off;The impulse current integrated arc extinction device increases the zero-sequence current differential protection,which can accurately cut out the fault circuit in the case of single-phase ground fault.In the pharmaceutical plant 10 k V busbar contact switch equipment add device to ensure the reliability of power supply.The load side switch of the pharmaceutical factory is equipped with over-current protection of one,two and three sections,and a single-phase earthing line selection unit(signal)is added at the same time.In case of phase-to-phase and three-phase short circuit fault,the protective action shall remove the fault,and the single-phase earthing fault shall occur.After starting the standby equipment,the fault circuit shall be shut down to ensure safe production.Finally,according to the development plan of yidu HEC and the instructions of the company leaders to ensure the high reliability of power supply for the internal distributionnetwork,the next step of the research on the internal 10 k V distribution network of HEC is put forward.