Distribution Transformer Monitoring System Based On Zigbee Communications Network Platform

With the upgrade of informationization,more and more information-based system have been applied in relevant units of power department. Monitoring of power distribution transformers, which is the main equipment of distribution network, becomes the most effective means of realizing the operation of distribution network.Through real time monitoring data index of current, voltage, three-phase imbalance degree, power factor etc.,the operation of power network and quality of electric energy can be estimated.Therefore, how to ensure the data of distribution transformer be sent to the relevant data base and greatly reduce the cost of manpower and material resources becomes the urgent problem for solution.This paper studies the real time on-line monitoring system for power distribution transformers,which are widely used in the power system.Firstly, the characteristic and application of ZigBee wireless access technology are analysed. Compared with other wireless access technology, ZigBee technology possesses advantages of simple protocol, low cost, small energy consumption and easy networking, the conclusion is reached that it is most suitable for building real time monitoring system for distribution transformer.Secondly, the paper specially analyses the routing protocol of ZigBee, elaborately introduces the basic idea and working process of it, deeply studies the performance of the routing protocol.In NS-2 simulation platform, based on IEEE802.15.4MAC layer and physical layer module, the development and test work of ZigBee network layer source code is completed, networking of ZigBee network layer, address assignment and routing protocol are realized. ZigBee routing protocol is elaborately and deeply analysed through simulation. The result of simulation shows ZigBee routing protocol possesses higher packet delivery ratio, lower control overhead for average terminal, that meet the requirement of ZigBee network. Aiming at technical characteristic of ZigBee, making use of determining RSSI (Received Signal Strength Indicator) between the two nodes, nodes from ZigBee single-hop communication range and inner fringe area have been selected as the nodes connection for sublayer nodes by parameters. Within the range of single-hop communication, other nodes serve as ordinary nodes (i.e.in the synchronization processing, those nodes do not have routing performance, only synchronize with upperlayer routing nodes.) Based on these, the paper raises an arithmetic for reducing numbers of routing nodes in the synchronization processing, the times should be more for information exchange in the routing nodes and ordinary nodes, therefore, times for information exchange in time synchronization are saved, that greatly lowers the communication costt in synchronization, prolongs the life of ZigBee nodes in synchronization.At last, the paper expounds the monitoring system of distribution transformer which is based on ZigBee communication, summarizes its application in Nanjing area, and explains the difficulties in further applications, points out the research direction.