The Ninth International Conference on Electronic Measurement & Instruments ICEMI’2009

Designation of an On-line Monitoring System of Transmission Line’s Galloping

Xinbo Huang1 Guanbo Huang1 Yun Zhang2

(1 Xi’an Polytechnic University, Xi’an 710048, China) (2 Xi’an Jiaotong University, Xi’an 710049, China )

E-mail: hxb1998@163.com

Abstract: Based on the analyses of the disadvantages and advantages of every on-line monitoring system of transmission line’s galloping, an on-line monitoring system of power transmission line’s galloping based on displacement sensors and acceleration sensors is developed in this paper, in which the wireless sensors network and the slave monitoring unit installed on towers are designed by wireless communication technique, by those monitoring units the galloping can be analyzed qualitatively and quantitatively. The operating principle, structure and function of the system are all analyzed at the same time. Moreover, the designation of the node of wireless sensors network based on ZigBee technique and the slave monitoring unit installed on towers are all shown in detailed in this paper. Based on the galloping mechanism as well as earlier data, the galloping is simulated in theory, and then some simulating results are shown in this paper at last. Key words: power transmission line; galloping; monitoring; displacement sensor; acceleration sensor; simulation

I. INTRODUCTIONS

The galloping of power transmission lines is a low frequency(about 0.1Hz 3Hz),large amplitude, wind self-induced vibration, and the amplitude can be as large as about 5 to 300 times of the power transmission line’s diameter which happens easily when the section of conductors is non-circle. For the galloping of power transmission line occurs frequently at a certain atmosphere, moreover, because of the characters of conductor galloping, such as large amplitude, oscillation, long-lasted time and so on, conductor galloping is easy to tend to evoke the nasty accident of inter-phase short-circuiting, conductor burned, hold down towers, and conductor broken, which bring about serious economy loss and do enormous damage to the safety of the running of transmission lines[1 2].Especially, China was hit by an exceptionally serious weather with long-lasting freezing rain and snow at January 2008, which affected the running of power system in 13 provinces (regions) and cause enormous economic losses. Then people put many attentions to the study on the galloping and icing of transmission line. Nowadays many countries all over the world do much research on the galloping of transmission liens, and all kinds of technologies on this study have developed. the study about galloping in wind tunnel and on test transmission lines focus on the basic theory of galloping, which can improve the mechanism as well as the mathematical

model of galloping. At the same time, the effect of anti-galloping devices, the parameters of air power and other testing can be test by the trial. For example aerodynamic testing was tested on transmission lines with crescent-shaped icing in Huazhong University of Science and technology, which can support the determination of parameters and loading of air power when the galloping occurs under icing condition with the first-hand information, but these technologies can’t be applied on the practical transmission lines. Combined with the forceful data processing capability of the computers, the galloping can be simulated by the computer simulation technology of galloping on transmission line which is limited to the theoretical study of galloping and can’t be applied in engineering practice in line with experimental data and relevant parameters monitored on the site, which is a low-cost, efficient research on galloping. Camera technology is adopted in the monitoring of galloping in practice, by which the qualitative results of galloping on the spot can be gained. Then the judgments and measurement can be made by staffs to prevent the galloping in the light of the photograph at the scene. This technology can’t gain the quantitative information of galloping, and then the accurate information is lack, which limits the technology to be spread in engineering practice. The on-line monitoring technology based on wireless network is a hot study on galloping in recent years comparatively, in which all kinds of data including pressure, vibration frequency, ambient information and others on the spot are monitored, by which the galloping can be calculated in the light of the three degrees of freedom mathematical model. Because of imperfect of galloping mechanism and mathematic model (especially, a more precise number of degrees of freedom mathematical model will present) as well as the affection of micro-meteorological conditions, there are some limitations in application and promotion of the technology. Based on these factors, combined with the actual situations of transmission lines on the spot (mainly the environment factors, styles and materials of transmission line and so on) and local weather information, the mathematical model should be modified reasonably to get more perfect results relatively. Based on these analyses, a new technology to monitor galloping of transmission lines which is based on acceleration sensors and displacement sensors is developed in the paper.

1-655

_____________________________978-1-4244-3864-8/09/$25.00 ©2009 IEEE

The Ninth International Conference on Electronic Measurement & Instruments ICEMI’2009

II. DESIGNED IDEA

The galloping of transmission lines is affected by all kinks of parameters, so the features of galloping are different, in which the half-waves plays a large role in waveforms of galloping. Specifically, the galloping with different half-waves are different apparently, the common observed numbers of half-waves are 1,2,3 and 4.Although the galloping with over 5 half-waves present, its amplitude is too small to cause accidents of transmission lines, then it often will not be considerated. Typical galloping waveforms under different half-waves are shown as figure 1[3].

Fig.1 Typical galloping waveforms under different half-waves

So, the transmission line between two adjacent towers can be chosen to be the monitored object, on which different numbers of displacement and acceleration sensors can be installed to gain some information of parameters which are sent to monitoring center on real-time or regularly (galloping frequency and environment information are all monitored by slave monitoring unit on towers) in line with the length of transmission lines. In monitoring center, the data can be fitted according to the least squares method or other algorithms by expert software, then the accurate galloping track can be get comparatively and some galloping features such as amplitude can also be gained. As long as the monitoring points on the spot and the send frequency are enough, much more enough data can be fitted, and then the accuracy is guaranteed. Moreover, according to the displacement and acceleration values as well as micro-meteorological information of this area, the galloping track at the following times can be calculated and forecasted, and then pre-alarm information and alarm information of galloping on transmission lines can be gained. The specific designed algorithm in this paper is shown as follows:

Provided a transmission line between tower A and tower B is shown as figure 2, displacements and accelerations at horizontal, vertical and reversing directions are considerated mainly according to the three freedom mathematical model of galloping. Totally, 21 displacements along the three axes directions and 7

accelerations can be installed at 7 monitoring points which are chosen on transmission line separately, which are shown in figure 2.In practice, the acceleration sensors can be installed in a region which are in the center of corresponding displacements, and the installation of sensors should be in line with the situation of transmission lines in engineering practice.

Fig.2 Schematic diagram of the installation of displacement

sensors and acceleration sensors

Shown as the figure2, with the galloping of transmission line, point 1 2 3 4 5 6 and 7 on between tower A and tower B with the fixed three coordinates x y z is moving, and the messages monitored by the displacement sensors in three axes can be sent to monitoring center real-time/regularly which can be fitted and approached by expert software, by which the galloping can be analyzed qualitatively, quantitatively, comprehensively .During the process, curve fitting is difficult, in which the least squares method is adopted widely, but in practice, the adoption of algorithms of curve fitting is depend on the situation.

On the other hand, the transmission line can be divided into 8 parts by point 1 2 3 4 5 6 and 7,the monitored displacement on one point is shown as the starting displacement 0S , and the monitored

acceleration on one point is shown as the starting acceleration, then the running track of transmission line S in the following time can be forecasted by integral operator:

0 0S a d t S vd t S� � � ��� � 1

In order to apply the forceful algorithm of computer to calculate and program, formula 1 must be dispersed into formula 2

20

1

12

n

iS a t S

�

� � �� 2

Although reversing along the axis present in galloping, the reversing can be neglected at this time, and only the displacements along the horizontal and vertical directions should be calculated:

20

1

12

n

x x xi

S a t S�

� � �� 3

20

1

12

n

y y yi

S a t S�

� � �� 4

1-656

The Ninth International Conference on Electronic Measurement & Instruments ICEMI’2009

where0XS 0 yS is the horizontal and vertical

displacement separately on one monitoring point [4] The galloping displacement curve on corresponding transmission line can be fitted by the xS yS and the displacement of each parts can be integrated to gain the galloping track of the transmission line between tower A and tower B at the following time T according to the boundary conditions. Curve 1'-2'-3'-4'-5'-6'-7' is the forecasting track of curve 1-2-3-4-5-6-7 at the following time T shown in figure 2.

Based on the idea, it is easy to understand the difficulty of this monitoring technology is the installation and the number of sensors as well as the selection of curve fitting algorithm. If the sensors are installed excessively, much more data can be got, the curves are fit perfectly and the precision can be higher, but the corresponding cost is higher, the calculating of software is much larger and the installation of excessive sensors can change the mathematical module of galloping. Otherwise, the cost can be reduced, but the galloping track can t be calculated and fitted because of limited sensors nodes. Weighing the pros and cons, we should considerate the problem combing the actual situation of transmission line in practice.

III. BRIEF INSTRUCTION OF THE SYSTEM

Based on the above designed idea, the whole block diagram of the system is shown as figure3. The whole system mostly is consist of acceleration/displacement sensor nodes, the slave monitoring unit on tower, monitoring center and other parts.

Fig.3 The whole block diagram of the system

Every acceleration/displacement sensors node with independent controller and power is installed on the feature point of transmission line. The sensor nodes are communicated with slave monitoring units by star master-slave topology network in which ZigBee network is applied in the paper[5].The massage about each sensors nodes are all centralized by the slave monitoring unit on towers. After analysis and data processing, the effective data can be sent to the monitoring center by long-distance wireless communication (GPRS/CDMA/GSM).According to the

galloping information of every transmission line in database, data should be processed correspondingly. During the processing, correspond data are fitted mainly to gain the displacement figure on one monitoring point in time interval and the mutative diagram of the displacement on the whole transmission line on-line. Moreover, the mutative displacement diagrams in the following time can be predicted by the previous relative information.

IV. DESIGNATION OF SLAVE MONITORING UNIT ON TOWER

A. The selection of monitoring parameters

The climatic in the easy-galloping areas is extremely complex. Galloping is strongly correlative with icing, ambient temperature, ambient humidity, wind speed and other factors, so these factors are all monitored on-line by monitoring system[6]. Moreover, wind angle which can be affected apparently by the galloping also should be monitored.

B. Function of slave monitoring unit on the tower

Wind edge angle, gravity changing of icing coating line, ambient temperature, humidity, the wind speed, the wind direction, rainfall and other signals should be transmitted to signal process unit by on-line slave monitoring unit regularly. After magnified and isolated, the magnified, filtered signals will be delivered to 16 bit A/D converter, and the gravity changing of conductor line, angles, wind speed, environment temperature and humidity and other environmental variable parameters will be computed by single chip processor. Moreover, the single chip processor also can receive the messages of acceleration/displacement nodes which are installed on the transmission lines or wire connectors in each local meteorological community to gain the running state of transmission lines by ZigBee network (2.4G Hz frequency). Then the messages of every sensors node as well as the preliminary processed data will be transmitted to the monitoring center by means of GSM SMS network, then the data about galloping will be governed centralized by expert software in monitoring center.

C. The hardware designation of slave monitoring unit

For the whole system works outside the door, it is required to be low-consumer and operated with no maintenance. The gravity changing of icing coating line, insulator helix angle, environmental messages (temperature, humidity, wind speed and wind direction) and messages of every acceleration/displacement node are mainly collected, storied and transmitted by slave monitoring unit on the towers. To store data effectively, flash-memory is chosen and even the power of slave monitoring unit is exhausted, the data still can be storied

1-657

The Ninth International Conference on Electronic Measurement & Instruments ICEMI’2009

over 10 years effectively. The principle block diagram is shown as figure 4.The slave monitoring unit is consisted of solar cell panel , charging circuit , high-property battery , flash-memory , low-consumer single chip processor , 16 bit A/D converter, pressure

sensor ,angular displacement sensor, temperature and humidity sensors , ZigBee communication module, GSM signal transmission module , software of slave monitoring unit and so on

.

D. Acceleration/displacement nodes

Acceleration/displacement nodes can gather much information about transmission line’s galloping, by the nodes, the acceleration and displacement components at three-axes of every monitoring site on the transmission lines can be collected in the process. The specific designation of sensor monitoring node ‘s hardware is shown as figure 5.In the system, batteries are adopted to supply system’s power, and ZigBee module is used to achieve short-distance wireless communication.

Fig.4 Block diagram of slave monitoring unit installed on towers

Fig.5 The hardware diagram of wireless sensor nodes

VI. SYSTEM SIMULATIONS

Based on the powerful features of Matlab software and some relevant preliminary information about the galloping of transmission lines, the data at every monitoring site are simulated. According to the designation of the system, the data monitored at every site and each moment are handled and fitted, then the changing of galloping on one monitoring site as well as on the whole transmission line are shown. The specific simulation results are shown as Figure 6.

(a) The fitting of data monitored on the same site but different times

(b) The observation of the fitting of data monitored at the same time

but on different sites from Z axis

(c) The fitting of data monitored at the same time but on different sites

(d) The observation of the fitting of data monitored at the same time but on different sites from Y axis

1-658

The Ninth International Conference on Electronic Measurement & Instruments ICEMI’2009

(e) The observation of the fitting of data monitored at the same time but on different sites from X axis

Fig.6 The simulation of the system

VII. CONCLUSIONS

An on-line monitoring system of power transmission line’s galloping based on displacement sensors and acceleration sensors developed in this paper can be improved in the practical applications in the future days. Moreover, the application of the on-line monitoring system can provide first-hand materials to the study on the mechanism of transmission line’s galloping and other studies.

REFERENCES

[1] YU Junqing,GUO Yinglong,XIAO Xiaohui. Computer simulation of power line galloping[J]. Journal of wuhan university of hydraulic and electric engineering, 2002,35 139-43

[2] LIANG Shaohong. Model Construction and Computer Simulation of High Voltage Overhead Transmission Line Galloping[D]. North China Electric Power University,2003

[3] LU Mingliang.The study on Monitoring Technique of transmission line’s galloping[J].Electric power,1994 6 24-27

[4] YANG Bin. Computerized Monitoring of Conductor Galloping Tracks on High Voltage Transmission Line[J]. Electric power,1996,29 1 43-45

[5] HAO Liguo,HU Shan,ZHU Yanfeng. Design of data acquisition platform for motion based on 3-axis accelerometer ADXL330[J]. journal of tianjin university of technology and education,, 2008,18 1 30-32

[6] HUANG Xinbo, SUN Qindong, DING Jianguo et al. Transmission line icing monitor ing system based on GSM SMS[J]. Electric Power Automation Equipment, 2008 28 572-76

[7] HUANG Xinbo, SUN Qindong, CHENG Ronggui et al. Mechanical Analysis on Transmission Line Conductor Icing and Application of On-line Monitoring System[J]. Automation of Electric Power System, 2007 31 14 98-101

1-659