李鵬飛

Abstract：A multi-parameter real-time monitoring scheme for power transmission line is proposed and experimentally demonstrated. The Fiber Bragg Grating （FBG） sensors are used to sensing the information of temperature and strain in the power transmission lines system， and a monitoring center based on client–server model is established to process and display the sensing information. Several FBG-based power transmission line temperature sensors interrogated based on the developed multi-parameter real-time monitoring scheme is experimentally investigated. The result shows that the system is very useful.

Keywords：Power transmission lines；real-time monitoring；FBG sensor；client/server model

I INTRODUCTION

With the development of society， the power transmission system shows a trend of high-capacity and automation， the safety of the power grid is essential. But there are some serious problems to safety of the power grid， such as line disconnection and tower tumble by icing of overhead power transmission lines caused by snow and ice storms in January 2008 in southern China， leading to severe damage to the power grid[1].

Due to this situation， the research on the real time monitoring of the power transmission lines is an important direction of the power grid technologies. A system monitored not only electrical characteristics but also physical parameters of power transmission lines， such as strain， sag and coated ice， should be monitored. A well designed monitoring system is indispensable to realize this mission.

At present， people usually use electro-sensors to detect the power transmission lines， and transmit the information by traditional copper wire or wireless[2]， but this solution is too complex and expensive to be widely used. On the other hand， optical fiber composite overhead ground wire （OPGW） is widely applied in the power grid to compose the optical fiber communication network， so the fiber sensors can easily send the detected information by OPGW.

In addition， development in the computer technology has enabled us to use a low cost and easy maintenance microcomputer to be the server of monitoring system.

To sum up， the overall structure of the monitoring system is shown in Fig.1.

II FBG SENSOR AND INSTALLATION

FBG sensor is a kind of optical sensor， it is a wavelength modulated optical fiber sensors.FBG sensor has so many excellent advantages such as electrically passive， simple structure， small size， resistance to electromagnetic interference， light weight， electrical insulation properties[3]. Because of these characteristics， FBG sensor can be splice with OPGW fiber.

III CALCULATION OF MONITORING PARAMETER

This newly Multi-parameter monitoring system can monitor not only temperature and strain， but the icing thickness and sag of power transmission lines. The data of temperature and strain is directly from the detected information of FBG sensors. Then， the calculation of icing thickness and sag of power transmission lines is based on a mechanical model.

IV THE CLIENT-SERVER MODEL OF COMPUTING

It has been mentioned that the monitoring system is based on client/server architecture software. The client–server model of computing is well suited with the real-time monitoring system for power transmission lines because the system is long-time running and real-time monitoring， the server is obliged to process and storage a lot of data. Furthermore， clients can be designed to ensure security， friendliness of the user interface， and ease of use.

The server collects detected information by optical sensing interrogator， calculates the monitoring parameters by the model mentioned before， saves computing results in cache and database， communicates with the clients by socket interface.

The client computer can access server computer though internet to obtain the monitoring information， therefore it can be located in anywhere. Power grid manager can use client software to access the server though internet around the world to monitor the current condition of power transmission lines. Real-time warning triggering is a basic function of the client， when the client get a warning record from the server. The client software also has window to display the real-time curve of monitoring information， the historical monitoring data is allowed to be saved.

V PRACTICAL APPLICATION AND CONCLUSION

After a long period testing of this newly developed multi-parameter real-time monitoring system for power transmission lines， the software of system can keep long-time running， and it is very useful for Power grid manager.

[REFERENCE]

[1]Hu，Y.“Analysis and counter measures discussion for large area icing accident on power grid，”.High Voltage Engineering.2008，vol.32，No.2，pp.215-219.

[2]Xinbo Huang，Qindong Sun，Ronggui Cheng，Guanjun，and Jiabin Liu.“Mechanical analysis on transmission line conductor and application of on-line monitoring system，”.Automation of Electric Power System.2007，Vol.31，No.14，pp.98-101.

[3]Alan D.Kersey，Michael A.Davis，Heather J.Patrick， Michel LeBlanc，and K.P.Koo.“Fiber grating sensors，”.JOURNAL OF LIGHTWAVE TECHNOLOGY.1997，vol.15，pp.1442-1463.