Research On Automatic Monitoring Technology Of Remote Faults At Overhead Line

Line selection and location for small current grounding system fault has been the focus of distribution network research,especially the single-phase-to-ground fault.In the power grid of oilfield,due to the large number of grid lines connected to the agricultural power network,and the complex field environment of each oil extraction plant,the probability of single-phase-to-ground fault occurring is higher,which generally above 80%.In the case of small-current grounding faults,fault line selection and location are difficult due to small fault signals,difficulty in obtaining of fault signals,and intermittent arc grounding.The fault line selection and location methods used in many oilfield substations are so old that they can no longer meet automation requirements of distribution network in the oil grid.In addition,the impact of blackout caused by ground faults on crude oil production is very serious.Therefore,it is necessary to study a suitable automatic monitoring technology of oilfield overhead power line for remote single-phase ground fault.This paper analyzes the fault characteristics of line voltage and current in the case of single-phase-to-ground fault in low current grounding system in detail.Based on the obtained fault characteristics,some existing alignment and positioning algorithms are improved with the theory of elative entropy and fault measure function.In fault line selection,transient line current and zero sequence current data are used to propose a fault line selection method based on fault transient current comprehensive criteria.In fault location,a method of location based on the similarity of amplitude distribution of transient zero sequence current is proposed.This article designed the analog line selection device and data acquisition terminal with the control center of TMS320F28335 DSP(Digital Signal Processor).Combined with the computer small current grounding line selection device used in the oil field,the design of hardware circuit and software program were carried out in the aspects of power supply,signal sampling,data communication and so on.In order to meet the requirements of on-line monitoring overhead lines,the monitoring system computer-side software of VB(Visual Basic)is designed to facilitate staff to view.According to the data of oilfield network line,the simulation model of the oilfield power system is established by using MATLAB/ SIMULINK,and the fault line selection and fault location method are validated by setting a variety of fault conditions,especially include the simulation and verification of arcing ground fault.In addition,according to the existing laboratory conditions,a simple test simulation circuit of distribution network is constructed to test and verify the proposed fault line selection method and fault location method,and the overall hardware circuit structure and software program of the system.Through simulation and experiment,this technical scheme has high accuracy of fault line selection and fault location,and it is suitable for a less-automated power grid such as the oilfield power grid,it also has a small degree of modification and a low cost.This paper provides a feasible technical scheme for fault line selection and fault location for single-phase-to-ground fault in oilfield,which has broad application prospect and high practical value.