Research On Insulation Status Of High Voltage Cables Online Monitoring Based On Electrical Characteristics Analysis

At present,cable is applied more and more widely in the actual power grid.However,in the course of operation,due to the manufacturing process and operating environment,the cable may produce partial discharge,and develop into water branches,then trigger electrical branches and eventually lead to insulation breakdown of the cable,or even develop into a single-phase grounding fault.Nowadays,there is few effective and reliable practical methods for insulation state detection of distribution network.Preventive test method is widely used in engineering practice.However,this method needs to detect power failure and can only realize centralized defect detection of the whole cable power supply network.Also,it can not detect power failure of a certain cable.For cables without insulation deterioration,over-high frequency stop-and-recoil electrodes are prone to lead to "cumulative effect" and "rectification effect",resulting in insulation aging.Therefore,in order to timely and accurately understand the insulation status of distribution network cables,and then take effective measures to deal with it,reduce the blackout time of preventive tests and losses caused by blackouts,and improve the reliability of distribution network power supply,the following contents are studied in depth in this dissertation:Firstly,in order to study the insulation characteristics of cables with different insulation deterioration,MATLAB is used to establish the electrical characteristics of cables under the conditions of water tree aging,electrical tree aging,overall uniform deterioration,partial discharge and insulation breakdown,and the corresponding equivalent parameter circuit and simulation model are established to study the insulation of each line.Secondly,to study and determine the characteristic signals which reflect the different degree of cable insulation deterioration,using wavelet denoising and orthogonal decomposition methods to separate the capacitive and resistive components of grounding line current,combining with the relationship of grounding line rheological changes when insulation parameters change,using the characteristics of grounding line rheological changes and correlation coefficient calculation to judge the cable.Thirdly,the on-line monitoring technology of cable insulation in distribution network is studied,and the MATLAB distribution network simulation model is established to realize on-line monitoring of cable insulation in distribution network.Fourthly,online monitoring system of cable insulation in distribution network is established based on industrial computer and Labview software.In addition,hardware and software design of the system are completed,the design of software and hardware and anti-interference measures are also discussed.