Study On Medium Voltage Loop Network Relay Protection Mode Of Urban Rail Transit

In rail transit power supply system,AC medium voltage loop network is the aorta in urban rail transit power distribution,which is the key to guarantee the power supply system of power stable supply in normal or fault conditions.This thesis taking urban rail transit medium voltage loop network as the research object,conducts the deep research to the medium voltage loop network relay protection mood,and carries on the analysis of actual cases.The poor rapidity of traditional relay protection used by a certain city rail transit linel medium voltage loop network,which can't remove of the fault section,and also has a certain influence on the service life of equipment.It can't ensure selectivity under some operation mode.In case of failure,it may expand the scope of power failure,especially when a main substation to quit running,also needing to switch protection setting and exiting the spare power automatic switching on-site by the personnel on duty,seriously affected the rapid restoration of power supply and creates greater social impact.Aiming at the existing shortage of medium voltage loop network traditional relay protection,this thesis studies the protection mode of medium voltage loop network at home and abroad,and analyzing its improvement on the relay protection of medium voltage loop network,and also pointing out the existing shortage of not completely solving the traditional relay protection.On the basis of the study,this thesis proposes a rapid and accurate identification of the fault section and removal of relay protection mode namely optical fiber differential protection and current selection trip protection.This method can solve the shortage of traditional protection rapidity.In terms of rapidity,rapid removal of fault,and when the breaker failure,increased the failure protection function,not relying on failure removal by back-up protection;In terms of selectivity,no matter what mode of operation under a certain failure point,it can accurately and effectively identify;especially when a main substation to quit running,not needing to switch protection setting value,under any operation,a set of protection setting value has been adopted,and also exiting the remote spare power automatic switching,rapid recovery of power supply,reducing the effect of the operation service by power outage.The experimental verification meets the requirements of relay protection relevant characteristics,and which is superior to traditional protection,reached the design requirements.And running in line 2,its stability and reliability meet the requirements.Short-circuit fault appeared several times in the operation,it can accord to the design requirement for removal of the fault.The selectivity and reliability are verified by experiment,and a set of setting value can meet the requirements in various modes of operation.In view of the traditional protection of medium voltage loop network in the change of the operation mode,which has not the rapid restoration of power supply,this thesis makes two technical improvements to ensure the rapid restoration of power supply,which are proved in the actual operation.