Research On Sag Monitoring System Based On Dip Angle Measurement

Power supply plays very important role in both people’s daily life and social development, it has permeated into all aspects of daily life. In order to deliver the electric energy generated by power station to each load area, a complex power transmission system characterized by large-span, long distance has been set up. As an important part of the power transmission system, most of high voltage transmission lines are overhead transmission lines which are susceptible to internal and external environment influence. Therefore, increasingly importance has been attached to the monitoring on transmission line by the relevant department of power system, especially to the sag monitoring. On the other hand, facing the shortage of power transmission lines in our country, dynamic capacity-increasing technology can improve the transportation capacity under the original grid architecture. As to whether the running accords with safety and reliability, sag monitor data can be used to assess.This thesis elaborates on the current methods of sag monitoring from home and abroad. Comparing the characteristics of all kinds of monitoring methods, it is found that the sag change ultimately reflects on the dip angle, therefore the monitoring method of sag based on dip angle is determined. The main work includes the following several aspects:First of all, the relations of sag and dip angle can be concluded by establishing the wire catenaries model. In the process of using angle monitoring sag, due to the uneven distribution line load, as well as the influence of measurement error made by sensor itself, the computational accuracy of sag is low. Under such circumstance, the idea of applying the distributed sensor network and the least square method to the sag monitoring has been put forward together with the research of sensor’s installing position and successfully solved the problem that affects the accuracy of sag calculation.Secondly, the system structure keeps the ARM embedded system and sensor technology as the core, takes Zig Bee network and GPRS network as the way of wireless communication. This thesis designs the structure of both software and hardware of coordinator node and sensor node, selects LPC2368 of ARM7 series as the chip of main controller, applies MEMS acceleration dip angle sensor to collecting data. According to comprehensive comparison and analysis, a combination of solar panel and Li-ion battery series is confirmed to be treated as a way of power supply and establish large numbers of circuit including memory circuit, reset circuit, click circuit and other low-power circuits. In terms of software, based on the analysis of the workflow towards dip angle sensor and design of hardware, Z-Stack protocol stack is finally chosen to be used for achieving communication between the sensor nodes and the coordinator nodes and dealing with the problem of time synchronization among all the nodes by utilizing Hong Fan time synchronization protocol.Last but not the least, the accuracy of sag monitoring model is verified by using the data from 110 k V line in Zhoukou, Henan. In addition, the design rationalities of the charging management circuit and the charging-discharging management circuit are also to be proved. Using Z-Sensor Monitor software, the capacity of node network is verified.