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Engineering, 2013, 5, 101-103 doi:10.4236/eng.2013.51b018 Published Online January 2013 (http://www.SciRP.org/journal/eng) Copyright © 2013 SciRes. ENG A New Type of Damper and It s F iel d Tests on Ice-coating Transmission Lines Wan-li Zhong1, Wei Wang1, Hang-hang Chen2, Wei Luo2 , Yun-chao Song2 1Electric Power Research Institute of Guangdong Power Grid Company, Guangzhou, China 2Power and Mechanical Engineeri ng School, Wuhan Universit y, Wuhan, China Email: zhongwanli@163.com, wangwei@gddky.csg.cn, chenhang500@163.com, lw731588184@yeah.net, songyunchao2009@yahoo.cn Received 2013 Abstract The paper developed a type of damper with damping additive, of which the field tests were performed on 220kV trans- mission line to stud y its da mping ef fects on vibr ation of transmission lines. First, based on the common damping mea- surements, a scheme of filli ng the damping age nt in conventional damper is proposed to suppress the vibration ampli- tude of the phase/ground line, thus reduce the dynamic stress of the towers and lines and decrease the fatigue da mage of the system. Finally, the developed dampers were installed on a 220kV transmission line in Guangdong Province. The on-line monitoring data show that and the dampers are capable of suppressing the variation of pitch angle and yaw an- gle of the line, thus verify the effectiveness of the proposed damper. Keywords: Tra nsmission lines ; Damper ; Da mping fl uid ; Iced trans mission line ; Vibra tion 1. Introduction Transmission line is the key component of the power grid system, thus its structure strength and reliability is impo rtant fo r guarant ee the sa fety of p ower tra nsmis sion system. Common disasters of the transmission line sys- tem include ice coating, galloping and other types of win d-induce d vibration, et. a l. There are generally two type of icing disasters for the transmission line. One is due to the static stre ss o f tower and wires exceeding the allowable stress value, when t he ice weights up to several times of that of the wires. In this case, tower collapsing and lines broken may occur. For instance, in early 2008, when the rare snowing and freezing weather occurred in southern region of China, icing disasters leaded to a wide range of power supply interruption [1]. The second type of disaster is galloping of transmis- sion line, which is a type of large amplitude (typically from 0.1 to 1 times of the sag of the span) and low fre- quency (from 0.10Hz up to 3Hz) wind-induced vibration due to wind loads action on an ice-coated or wet snow accretion on the conductors. Comparing to other types of win d-induced vibration of overhead power transmission lines such as Aeolian vibration, turbulent wind-induced buffe ting, gall oping is the most noticeable and may cause such serious problems as phase-to-phase flashovers due to the short distances between phases, broken conductors, snapping of the line-to-line spacers, damage of insulator chains, and tower bolt failures or even the collapsing of whole tower [2]. Furthermore, there is one more type of harmful phe- nomenon, sustained small amplitude vibration of the tower-line syst em. Thi s will c aus e fa tig ue d ama ge o n the tower and l ine, which is caused b y dyna mi c stre ss. 2. Disaster Prevention Approaches There are types of measurements to prevent disaster of icing transmission line, such as thermal de-icing, me- chanical de-icing, et. al. (1) Thermal ice melting method: Using the principle of Joule effect. Improve the conduct temperature through increasing the load current and making short-circuit cur- rent, or de-icing with high-frequency high-voltage exci- tation. In 2001, Joshua D.McCurdy adopted an excitation at approximately 33kV, 100 KHz to melt ice [3]. The ice is a lossy dielectric at these frequencies which can be melted. (2) Mechanical de-icing method: Using mechanical force (manually or automatically). In the early time me- chanical de-icing was done by human being. This me- W. L. ZHONG ET AL. Copyright © 2013 SciRes. ENG 102 thod is simple but with low efficient and insecure. No- wada ys the hi gh-tech robot is being developed to replace human being by de-icing, in China, Hunan University develops a de-icing robot, which is an effective way of mechanical de-icing [ 4] . (3) Other new technology de-icing method: Many constructive ideas have been proposed, such as applying hydrophobic materials on transmission line, using laser to melt ice[5] , e t, al. 3. Damper Structure The new da mper structure prop osed in this paper co nsists of four parts. A fixed-length high-strength galvanized stranded wire is fixed with iron-casting hammer that has hollow cylindrical shape at both ends, and the hammer is filled with damping agent, while a clamp is used to fix the damper to the phase/ground wire. This structural can be transformed on the base of FR, FD-type da mper . The damping factor varies according to the composi- tion of the damping agent. We adopt different damping agent according the vibration-controlled objectives in different running situation. The vibration damper is fixed in the transmission line through the clamp. When the transmission line damper vibrates, the damper installed in the trans mission line ha s the upper and lower vibration. The steel strand wire con- nected to the hammerhea d bends up and down becaus e of inertia of the hammerhead. The continuous friction between steel strand wire and damping agent has been reducing the energy, as well as the continuous friction between damping agent and molecule inside the cylin- drical hammer. According to the law of conservation of energy, the vibration of the transmission line will be re- duced. The greater amplitude of the steel strand wire is, the greater t he energy will be damped. For the vibra tion of transmission l ine, the highest point of vibration amplitude is called the crest, while the point stays in the original position is named the node. The dis- tance between two adjacent nodes is called the half-wavelength of the vibration. The damper is usually installed in the crest points that make the biggest swing- ing amplit ude, thus co ns umes a s much e nergy as possible. Installation distance is determined by the maximum half-wavelengt h and minimum half-wavelength. max max min min / 22 22 λλ λλ λ =∗+ (1) where, λ is the damper installation distance(plywood centerline of the clamp centerline to the damper distance); λ max is the maximum half-wavelength of the vibration; λ min is minimum half-wavele ngth of the vibr atio n. 4. Field Application Tests and Data Analysis To test the effects of the damper, field tests have been performed on a 220kV high voltage transmission line system in Shao Guan of Power Grid Company of Guangdong Province. There dampers were fixed along one span of phase line. To comparative evaluate the damping effects, the dampers were only installed on phase C. Based on According to the monitoring and data col lec tion ter mi na l. Based on the on-line monitoring system of the test line, we collected three parameters, namely the wind yaw angle, pitch angle, and the tension of the line dur- ing an icing- deicing cycle from 1st to 10th January in 2012. Fig. 1, Fig. 2 and Fig. 3 indicate the time curve of the pitch angle, wind yaw angle, and tension. For the test span, the phase C is installed vibration dampers, while phase A is not. Compare and analyze the three parameters of phase A and phase C and make a statis- tical analysis of tension, pitch angle and wind yaw an- gle of them, we can draw a conclusion that, after in- stalling the vibration damper, the tension, pitch angle and wind yaw angle are reduced by 72.0%, 88.9%, and 2.0%, respect ively. TABLE 1. DATA COMPARISON ANALYSIS OF PHASE A AND PHASE C Phase A Phase C Relative inhibitory ratio of phase C rela- tive t o phase A(%) Max relative change of pitch angle(°) 4.3 2.5 72.0% Max relative change of wind yaw angle (°) 1.7 0.9 88.9% Max te nsion(N) 2.0% Figure 1. Time history of pitch angle of phase lin es A and Phase C W. L. ZHONG ET AL. Copyright © 2013 SciRes. ENG 103 Figure 2. Time history of wind yaw angle of phase lines A and Phase C Figure 3.Time history of tension force T of ph ase lines A and Phase C 5. Summary Through the field tests of the damper application and collected data analysis, we can conclude that the pro- posed damper with damp agent is capable of suppressing the vibration of transmission line effectively, thus re- duce the fati gue da mage , and p rolong the s ystem ser vice life. Moreover, this type of damp does not need power supply for it consumes vibration energy passively. REFERENCES [1] X.L Jiang, J. Ma, S.H. Wang, C.X. Sun, L.C. Shu. The Analysis o f Tran smission Line Ice Damage Acciden t and the R eas ons [J] .Electri c Power,Vol.11(2005). [2] Z.G. Lang, L. Liu, B.C Xu. Causes and Countermeasures to Ice Coating Galloping of Transmission Line in Tongliao Area[J]. Northeast Electric Power Tech- nolog y,Vol.1 1( 2 006).pp. 27 58-2761. [3] J.D. McCurdy, C.R. Sullivan, and V.F. Petrenko. Using Dielectric Losses to De-ice Power Transmission Lines with 100 kHz High-voltage Excitation, in Conf. IEEE Industry Applications Society Annual Meeting, Vol. 4, (2001), pp. 2515-2519. [4] H.X. Zhang, W. Sun, S.Y. Miao. Model Building and Motion Control of Deicing Robot on High Voltage Transmission Line[J].Computer Engineering and Ap- plications,Vol.46 No. 10 (2010) [5] S.Q. Gu, J.H. Chen, W. Cai, L.J.Qi, X. Zhu. Experimen- tal Analysis and Engineering Designing of Laser De-icing Technology for Transmission Lines. High Voltage Engineering, Vol. 9(2009). |