Development of Snow-melting Magnetic Material Wire for Low Current Transmission Line H. Nakamura, D. Tagami, T. Kitamura, S. Katayama, Y. Asano and T. Saitoh effective element to increase calorific value. And more, we added Cr and Si to Fe-Ni alloy in order to lower Curie temperature. In this research, we manufactured snow-melting wires varying ~i and evaluated these magnetic characteristics and calorific value. Furthermore, we wound various SnOW-melting wires on conductor samples and evaluated snow-melting characteristics by artificial snowfall test in the wind tunnel. 11. CONVENTIONAL ALLOY COMPOSITION decided that the basic method would be to wind a magnetic idex ~~~bne, snow-me~tin& mawetic ~~~material covered with ~~AI iaround conductor in s~a spiral form. i~The diameter of spiral wire ranges between 2 and 2.6mm. The material FeNi alloy, eddy cnmnt core of magnetic material is clad with aluminum as shown Fig. 1. INTRODUCTION 1. NOW accumulation on transmission lines increases the conductor load. It may result in damage to transmission es due to abnormal load andlor conductor galloping Magnetic material oscillation. On another occasion, accumulated icy snow falling from transmission lines sometimes causes damage to the structures underneath the lines. As such, snow accumulation on Al clad transmission lines is one of the crucial problems. Therefore, various methods to prevent snow accumulation have been Fig. 1. me cross-sectional CDNlNCtion of snow-melting magnetic material using the heat generated by the wire. investigated, A alternating magnetic field of a magnetic material wire has been developed and put into practical use. The calorific value in a In order to satisfy above property, it is necessary to select magnetic material is due to the hysteresis loss and eddy current magnetic material with low Curie temperature. Main magnetic loss, and Fe-Ni alloy has been used as a magnetic material. materials, which are ferromagnetism element at ordinary However, the method using this conventional magnetic temperature, are Fe, Ni and Co. Co was excluded since it had material can not gain sufficient calorific value to melt snow at higher Curie temperature (1397K) than Fe (1043K) and Ni some transmission lines which only low current pass in winter (627K), and also it was expensive. For this reason, Fe-Ni alloy season. To solve these problems, we attempted to optimize was selected. Fe and Ni have high Curie temperature alloy composition of Fe-Ni alloy by increasing Ni which is respectively, however in Fe-Ni alloy, Curie temperature shows minimum value, approximately 573K, at around 40wt%Ni [l]. Of Fe-Ni-Cr-Si has been H. Nakamura, D. Tagami and T. Kitamura are with Tokyo Electric Power On the Other hand, quarter conventionally used in England and other countries as a Company, Incorporated, Tokyo, Japan. s. Katayama. Y. Asano and T. Sailoh are with Fujikura, Ud.. Tokyo, magnetic material with low Curie temperature [2]. Cr and Si lap.%\". have been known to effective element., which lower Curie Abstract- Snow accumulation on transmission lines increases the conductor load. It may result n damage to transdsion facilities due to abnormal load. As such, snow accumulation on transmission lines is one of the crncial problem. A method using the heat generated by the alternating magnetic field of a magnetic material wire has been developed and put into practical H~the method ~,,eng ~cnnventiompl ~~~material ,can not gain snmcient calorific value to melt snow at some transmission lines which only low current pass in winter season. To solve these problems, we attempted lo optimize alloy composition of Fe-Ni. In this research, we manufactured snow these magnetic wires varying ~i and characteristics and calorific value. In this result, magnetic characteristics and calorific value improved with increasing N content. A magnetic material optimized alloy Composition showed calorific value of approximately 1.4timesas much as C0nventio-l magnetic material. For a magnetic material used in transmission lines to melt snow, the desirable hysterisis loss and eddy current loss are large in a low magnetic field (low current) and small in a high magnetic field (large current). The magnetic substance must also be installed in transmission lines easily. Therefore, it was ~S Q 0-7803-7525-4/02/$17.00 0 2002 IEEE. 2150 temperature. Thus, Fe-Ni-Cr-Si alloy of which Ni content is approximately 40wt% has been used as magnetic material for snow-melting wire [3]. 111. OPT[M[ZINGALLOY COMPOSITION A. Basic Approach The alloy element, which satisfies both lower Curie temperature and higher calorific value, has not been found. In this research, main purpose is to gain high calorific value. Calorific value of the magnetic material could he represented sum of the hysteresis loss and eddy current loss. Eddy current 2 c 6000- loss is proportional to square of maximum magnetic flux density. Calorific value is expected to rise by increasing Ni B content, since the maximum magnetic flux density increase 2 4000- with Ni content. We manufactured 3 types of Fe-Ni-Cr-Si alloy varying Ni content. Cr and Si are also added lo prevent a '8 B -3- specimen B 2000- -& specimenC rise in Curie temperature. These 3 types of Fe-Ni-Cr-Si alloy E 4- conventional arc named specimen A, B and C respectively. 0 500 1000 1500 2000 2500 3000 magnetic field (Ah) B. Measurement of Magnetic Properries As a preliminary study, in order to confirm effects on Fig. 2. Maximum magnetic flux density at applied magnetic field adding nickel, we measured magnetic properties using DC magnetization. Fig. 2 shows a maximum magnetic flux density at applied magnetic field. The specimen A, B and C show higher maximum magnetic flux density than convenlional alloy composition. In this result, it is cleared that magnetic property is improved by adding nickel. These alloy composition added nickel is expected higher calorific value. C. Measurement of Calorific Value Since it is difficult to know calorific value of a magnetic substance placed in an alternating magnetic field from the magnetic characteristic only, we directly measure calorific value hy the calorimeter method. Fig. 3 shows results of measurement of calorific value. Specimen B shows highest calorific value in low magnetic field (low current). This is 1.4 times as much as conventional magnetic materid. In this result, alloy composition is determined as same as specimen B. The following 1 experiments are performed using only specimen B. 0t 0 ' 500 ' ' 1000 ' ' 1500 ' ' 2000 ' ' 2500 ' ' 3000 1 We also evaluated calorific value by measuring temperature of wound wire around LN-ACSR (Low Noise-Aluminum magnetic field (Ah) Conductor Steel Reinforced) 940mm2. Fig. 4(a) and @) show wound specimen around LN-ACSR 940mm'. Fig. 4(c) shows Fig. 3. Results of measurement of calorific value. LN-ACSR 940mm' without snow-melling wire. In this method, temperatures of conductors with wound wire were measured by using thermocouples, and calorific values were obtained by measured power loss. Fig. 5 shows a relationship between current of LN-ACSR and calorific value. It is confirmed that specimen B has higher calorific value than conventional alloy composition 2151 IV. ANTII.ICIAI suowt:AI.I.'rI.sl Furthermorc, we cvaluatcd snuw-melting characterides hy artificial snowfall test. This experiment was operatcd using snnw-mclting wires wound on sonduslor samples at National Kesuarch Institute fnr Earth Science 3nd Disasler Prevention. Fig. 6 shows the apparatus of the artificial snowfall leit. The test syhtcni consists essentially of equipmcnt of mowiall and wind tunnvl. Snov.fall intensity w35 also measured during tesl time. Fig. 7 shows a rclationship hctween snowkill intcnsity and accumulated snow Ihickness. Snow accumulatiun oi specimen B is smaller than which of convcntionsl alloy. 11 is confirmed that perinrmance of snow-melting of specimen I3 ih improved compared with uonvcntional alloy. Fig. 6. Apparatus of the artificial snowfall test. 61., . , I ,,.,., 0 0 conventional v E a .- Y) 4- 0 I: 0 0- 0 current (A) Fig. 5. Cunenl-calorificalion properly. 0 '=I 2 4 ,&a I 6 8 \" \" 'IO 12 14 I' 16 snowfall intensity (mdh) Fig. 1. Results of snowfall test. 2152 V. CONCINSION We optimized alloy composition of Fe-Ni-Cr-Si alloy by increasing Ni which is effective element to increase calorific value. We manufactured snow-melting wires varying Ni content and evaluated these magnetic characteristics and calorific value. In this result, magnetic characteristics and calorific value improved with increasing Ni content. A magnetic material optimized alloy composition showed calorific value of approximately 1.4 limes as much as convenlional magnetic material. Furthermore, it was confirmed that optimized magnetic material showed high snow-melting characteristics than conventional magnetic material by artificial snowfall test. As a result of this research and development, the high- performance snow-melting wire has been installed in several transmission lines. VI. ACKNOWLEflCMENT The authors would like to thank the engineers of the National Research Institute for Earth Science and Disaster Prevention for their help in operating an artificial snowfall test. VII. REFKRENCES [I) Thaddeus B. Massalski, BINARYALI.OY PHASE DIAGRAMS, 2nd cd., 2. ASM Intemational, 1990, p. 1737. . Toms, fl. A. Kidd, \"New mrlhad of prevenling ice formation on exposed power conductors,\" Proc. IEEE, vol. 112, p. 2125, 1965. 131 M. Yasui, K. Maekawa, Y. Naganuma, K. Suzuki, Y. Kojima and II. Ando, \"Removal of Icy Snow Accumulation on the Transmission Line by Applying IS-Spiral Rod,\" fbjikura Technical Review, No. 16, pp. 26-33, 1987. VIII. BIOGRAPHIES Himshi Naksmura received thc B.S.E.E. degree from Nihon Univcrsity in 1986, and joined Tokyo Eleclric Power Co., Inc. He has been engaged in the design and ComlruOion of overhead lransrnission lines. Daisuke Tagami received the B.S.E.E. and M.S.E.E. degree from Meiji University in 1987 and 1989, respectively. In 1989, he joined Tokyo Electric Power Co., Inc. He has been engaged in the design and construction of overhead Iransmission lines. Tashio Kitamura received the B.S.E.E. and M.S.E.E. degree from Yamagala Univenily in 1994 and 1996, respectively. In 1996, he joined Tokyo Electric Power Co., Inc. He has been engaged in Ihe design and construction of overhead trammission lines. Mr. Kitamura is a member of #he IEE of Japan. Shinji Katayama received the B.S. and M.S. degree from Tohoku University in 1996 and 1998, respectively. He joined the Ikjikura Ltd. in 1998. He has been engaged in Ihe research and development of metallic material. Yuji Asano received Ihe B.S. degree 1988. from Seikei University in1988, and joined Fujikura Ud. in He has been engaged in Ihc research and development of Iransmision line. Mr. Asano is a member of the lEE of Japan. Tslrashi Saitoh received the B.S. degree from Yokohama National Univerrily in 1973, and joined Fujikura Ltd. in 1973. He has been engaged in the research and development of metallic material. Mr. Sailoh is a member of the lEE of Japan. 2153