Research On Magnetic Field Measurement Based Method With Fault Line And Location For Single Phase To Ground Fault Occurred In Distribution Network

As economic development and urban construction,distribution network topology becomes more and more complicated.Although Rules order that it can run for 1 to 2 hours after the single phase to ground fault in small current grounding system,but it is liable to bring about single-phase ground to a multi-phase short circuit fault if it waste too long time to find fault location and remove it,the system will get more serious threat.at the same time it will cause overvoltage,lead to equipment damage and shorten the life of the machine,heat accumulation will even lead to an explosion in the ground.While petersen coil improve the power supply reliability,but because of the compensation of capacitive current by the compensation coil,the steady-state characteristic of the fault is not obvious,resulting in that fault detection relatively difficult in small current ground system.When Transmission line fault occurs,the magnetic field below the overhead line reflect the line fault information.Short-circuit current along the transmission line changes,corresponding to the different magnetic field below lines.It means that changes on magnetic field below the transmission lines can fully reflect the changes in current.By means of digging the distribution network fault steady-state and transient characteristics,this paper finds out the characteristic difference between fault line and normal line reflected by the change of magnetic field around overhead lines before and after the fault,reveal and establish the internal relations between the fault characteristic and fault location.The magnetoresistive sensors installed on the towers can non-contact measure the magnetic field,the fault line and point of failure are solved according to the magnetic field amplitude and phase.Since distribution network is complexity and the accuracy is low,a new non-contact magnetic field measurement based method is provided to detect faulty line and locate fault for single phase to ground fault occurred in distribution network on the basis of above theory.It is expected to take shape a program for fault line and location based on magnetic field detection.Magnetoresistive sensor measurement accuracy is high and it is low cost,the fault span can be determined between two towers.Use MATLAB to establish a line model,simulation result shows the feasibility of the theory.