Research And Development On On-line Monitoring System For XLPE Power Cable Insulation Fault

This paper first focuses on power cable with XLPE insulation on operation. It analyzes the importance of cable on-line monitoring, introduces the advantages and disadvantages for supplying power using power cable, sorts of power cable and typical fault, and discusses its technique level all over the world and its developing trend of on-line monitoring system for XLPE power cable insulation fault. Based on this, an on-line monitoring system for cable insulation according to local situation is required urgently.Secondly this article presents the growth process of water tree from point of view of microcosmic, introduces several on-line monitoring methods of XLPE cable that is in practice now. Due to different grounding methods of Voltage Transformer's neutral point grounded system in different voltage level cable, and comparing the advantages and disadvantages of every kind of methods, the different frequency method used in our systemic project of on-line monitoring is presented. Considering resistance characteristic in disturbance, the different frequency method is feasible and practical. The micro-process of on-line monitoring based on the different frequency method is analyzed in theory, and water tree model of cable is simulated, the result obtained well proves that the model is reasonable and the different frequency method is feasible.Thirdly, on-line monitoring equipment of XLPE cable based on the different method is in principle developed, and structure and component of the systemic equipment is introduced. It includes several parts as below:1. Studying the technique request, composition and work principle of producing equipment of double business frequency signal loading cable;2. Developing the composition and characteristic of small current measure equipment of detecting different frequency signal;3. Collecting and transmitting different frequency signal data to industry control computer;4. Determining loading location and quantity of double frequency signal in the monitoring system;5. Culturing the water tree of cable and selecting contrastive sample;6. Introducing test procedures in detail and attention items.Throughout the research on on-line monitoring system of power cable insulation, the working principle, systemic structure and procedure of data of on-line monitoringbased on the different frequency method is presented, and favorable principle foundation and practice experience are provided for on-line monitoring technology for cable insulation which can well apply into practice and safe, convenient and rapid obviating cable fault in power system.