NZ233190A

NZ233190A - Heat-generative overhead electric line

Info

Publication number: NZ233190A
Application number: NZ233190A
Authority: NZ
Inventors: Sasaki Junichi; Higashida Shuichi; Kojima Tooru
Original assignee: Furukawa Electric Co Ltd
Priority date: 1989-04-05
Filing date: 1990-04-03
Publication date: 1992-01-29
Also published as: CA2013792A1; EP0391719A1; KR900017050A

Description

<div class="application article clearfix" id="description"> 23 3 1 Comp*-at^ c. Fl Iocs': r.z.SfOL C\*b%: {;.).H.Q.i.&Xy(o.>., h . o. ^r, Czx'n I no.se,/oO 2.9.M.^ ' ESV* gSAWP Patents Act 195.3 COMPLETE SPECIFICATION HEAT-GENERATIVE ELECTRIC WISE We, The Furukawa Electric- Co, Ltd.,, a Japanese company af No. 6-1, Murunouchi 2-ckome, Chiyo.da-kn,. Tokyo.,, Japan,, do hereby declare the invention,,, fox- which, we pray that a Patent may be granted to. us:,, and the: method by- which, it is to be: perfionned, to. be; particularly described; in. and by the^ following; statement: — —t— (Followed! by La) 23 3 190 - la - TITLE OF THB INVENTION HEAT-GENERATIVE ELECTRIC WIRE BACKGROUND OF THE INVENTION This invention relates to a heat-generative electric wire capable of preventing adherence of snow or ice to overhead electric wires. When snow or ice is attached to the overhead electric wire, the snow or ice grows while rotating along the stranded groove of the overhead electric wire, and finally develops into an extremely large cylindrical-form of snow or extremely large lump of ice. As a result, the load applied to the overhead electric wire increases, thereby causing wire accidents such as breakage of the overhead electric wire and fall of a pylon. In view of the above fact, a method is practically used in which a plurality of snow-adherence suppression rings are disposed at a regular interval in the longitudinal direction of the periphery of the overhead electric wire to prevent attached snow or ice from being rotated along the stranded groove and drop the attached snow or the like before it becomes large. However, according to this method, there occurs a problem that vinyl plastic hothouses, cars or the like lying directly below the overhead electric wire will be damaged by fall of snow or ice. Therefore, various methods have been proposed to solve the above problem. For example, there is proposed a method of melting snow or ice on the electric wire by winding magnetic substance on the overhead electric wire and causing the magnetic substance to generate heat by eddy current loss caused by an electric field of a 233 190 - 2 - current which flows in the overhead electric wire (Japanese Patent Disclosure No. 58-44609). Fe- and Ni-alloys such as Fe-Ni, Fe-Ni-Cr, Ni-Al, Ni-Si and Ni-Cr are used as preferable material for the above magnetic substance. The amount of heat generated by the above magnetic alloy significantly varies according to the amount of electric power transmitted by means of the overhead electric wire. Generally, the heat generation becomes small when the amount of transmission power is small, and it tends to increase as the amount of transmission power becomes larger. However, adherence of snow or ice to the overhead electric wire seldom occurs in the daytime during which the amount of transmission power is large and heat is generated by means of resistance of the overhead electric wire itself due to the large amount of transmission power, but it tends to occur in a period of time from the night to the morning during which the amount of transmission power is small and the temperature becomes low. Therefore, with the conventional magnetic alloy, the amount of generation heat is small when the amount of transmission power is small and a sufficiently large effect of melting snow or the like cannot be attained. Further, the conventional overhead electric wire using the above magnetic alloy is excessively heated in the daytime by heat generation due to the resistance of the overhead electric wire itself and heat generation in the magnetic alloy so that the temperature of the overhead electric wire may be excessively raised. As a result, there occurs a problem that the amount of transmission power in the overhead electric wire must be 3 233190 restricted. Further, electrolytic corrosion may occur and rust may occur in the overhead electric wire depending on the composition of the magnetic alloy wound on the overhead electric wire, thereby reducing the effective diameter. An object of this invention is to provide a heat-generative electric wire which can generate a sufficiently large amount of heat even in the case of small electric power transmission amount to melt snow or ice attached thereto so as to prevent formation of a cylindrical-form of snow or lump of ice, and which will not be excessively heated in a case where a large amount of electric power is transmitted. Another object of this invention is to provide a heat-generative electric wire in which influence by electrolytic corrosion of an overhead electric wire due to magnetic alloy is suppressed. A still further object of this invention is to provide a heat-generative electric wire on which magnetic alloy can be easily wound. The inventors of this invention devoted themselves to research in view of the above fact and found that Ni-Fe alloy is a suitable material as the magnetic alloy. They have made further experiments and researches to find that the Ni-Fe alloy may have different heat generation characteristics depending on the amount of Ni contained therein in cases where the power transmission amount is small and large, and thus completed this invention. That is, this invention is a heat-generative electric wire which has a feature that a Ni-Fe alloy wire member containing 45 to 80 % by weight of Ni and the remaining portion of Fe is wound on or strandeid with the outermost layer of the overhead electric wire. In the specification of this invention, the Ni-Fe alloy wire member includes a Ni-Fe alloy wire member *'9 SUMMARY OF THE INVENTION containing a small amount of Mn, Cr, A1 or the like in addition to Fe as the remaining portion. Preferably, the Ni-Fe alloy wire member has a metal coating formed on the surface thereof. The aforementioned and other objects, features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view showing a heat-generative electric wire of this invention; Fig. . 2 is a circuit diagram of an energization circuit used for energization test for the heat-generative electric wire having a Ni-Fe alloy wire member wound as shown in Fig. 1; Fig. 3 is a heat generation characteristic diagram in a case where the values of energizing current in Ni-Fe alloy wire members containing different amounts of Ni are changed; Fig. 4 is a side view of a heat-generative electric wire having a Ni-Fe alloy wire member wound in a direction different from that in the heat-generative electric wire shown in Fig. 1; Fig. 5 is a cross sectional view of a heat-generative electric wire having Ni-Fe alloy wire members stranded with strands on the outermost layer Hto-" 233 190 - 5 - constituting a overhead electric wire; Fig. 6 is a heat generation characteristic diagram of a Ni-Fe series alloy wire member in a heat-generative electric wire in a case where a Zn coating is formed on the Ni-Fe series alloy wire member wound on the overhead formed; i > § j electric wire and in a case where the Zn coating is not f Fig. 7 is a side view showing a heat-generative | 4 electric wire having a Ni-Fe series alloy wire member | t pre-formed in a spiral form and mounted thereon; J Fig. 8 is a heat generation characteristic curve diagram depending on the difference in the pitch of the Ni-Fe series alloy wire member mounted in the heat-generative electric wire of Fig. 7; Fig. 9 is a side view of a Ni-Fe series alloy wire member pre-formed of three wires integrally formed in a spiral configuration; Fig. 10 is a side cross sectional view showing the state in which a protection member is mounted on the end portion of a Ni-Fe series alloy member wound on the overhead electric wire; and f Fig. 11 is a cross sectional view taken along the I line XI-XI of Fig. 10. f I DETAILED DESCRIPTION In this invention, a Ni-Fe series alloy wire member j which i3 wound on or stranded with the outermost layer of j a overhead electric wire generates a significantly j increased amount of heat when the power transmission j amount is large in a case where the amount of Ni j contained therein is less than 45 % by weight (which is j V hereinafter simply expressed by %). It generates a less j -JW.- S'T* -1 233190 - 6 - r amount of heat when the power transmission amount is ! small in a case where the amount of Ni is more than 80 %. I thereby preventing a sufficiently effective snow or ice ( melting effect from being attained. The content of Ni is • more preferably 47 to 54 %, and most preferably, 50 to 52 j %. \ £ Since the Ni-Fe series alloy wire member has a large } relative magnetic permeability, it generates a sufficient | amount of heat for melting snow or ice even in a case | $ where the power transmission amount along the overhead a electric wire is small. Further, since the Ni-Fe series |, alloy wire member may reach a magnetic saturation in which the magnetic flux density B of the magnetic metal wire member is saturated, by weak magnetic field H, the heat generation amount thereof is small even if the power transmission amount becomes large. Thus making it unnecessary to limit the power transmission amount for suppressing temperature rise in the overhead electric wire. Therefore, the heat-generative electric wire of this invention may provide a sufficiently large snow or ice melting effect even in a period of time from the midnight to the early morning during which the power transmission amount becomes small and snow or ice adherence may easily occur. Further, in the daytime during which the power transmission amount is large, it does not accelerate temperature rise of the overhead electric wire. EMBODIMENT 1 As shown in Fig. 1, a heat-generative electric wire 1 of this invention has a Ni-Fe series alloy wire member 3 wound on the outermost layer of a overhead electric - 7 - 23 3 1 wire 2. The heat-generative electric wire 1 was formed by winding the Ni-Fe series alloy wire member 3 containing a variously changed amount of Ni on the overhead electric wire 2 formed of aluminum conductor steel reinforced (ACSR) having a cross sectional area of 610 mm2. The surface temperature of the alloy wire member 3 at the time of conducting current through the overhead electric wire 2 was measured. The amount of Ni contained in the alloy wire member 3 was set to 35, 40, 46, 51, 60, 70 and 80 %, seven kinds of cold-extended wire members with a diameter of 2.6 mm were prepared and were sequentially wound at a regular interval on the overhead electric wire 2. in a direction opposite to that of the stranding direction of the outermost layer thereof. Then, as shown in Pig. 2, the heat-generative electric wire 1 having seven kinds of alloy wire members 3 wound thereon was connected to a current supplying transformer 4. The surface temperatures of the alloy wire members 3 were measured when A.C. currents of 100 A and 800 A were supplied to the overhead electric wire 2 in a thermostatic laboratory kept at -4"C. In this case, the alloy wire members 3 were wound on the overhead electric wire 2 at a distance of more than 1 m from one another so as to prevent the mutual thermal influence. In measuring the surface temperature, a thermocouple was used and the surface temperatures measured by the thermocouple were recorded by use of a chopper bar type recorder. The result of the measurement is shown in Fig. 3. In Fig. 3, the abscissa indicates the content [%) of Ni and the ordinate indicates the surface temperature (°C) vs ■> •• *■ '1"; % 233 190 - 8 - of each alloy wire member 3. As is clearly understood from Fig. 3, in the heat-generative electric wire 1 of this invention having the Ni-Fe series alloy wire member with the Ni content of 45 to 80 % wound thereon, the surface temperature of each alloy wire member 3 was raised to such a temperature as to melt snow, that is, to 10 to 18 "C even when the amount of current supply was as small as 100 A. Further, when the power transmission amount was as large as 800 A, the surface temperature of each alloy wire member 3 was fell in a temperature range of 20 to 45 °C. In contrast, in the heat-generative electric wire having the Ni-Fe series alloy wire member with the Ni content of 35 or 40 % wound thereon, the temperature was excessively raised when the power transmission amount was large, and the surface temperature was extremely lowered when the power transmission amount was small. The surface temperatures of the alloy wire member 3 were respectively approx. 2 °C and 3 *C when the power transmission amount was 100 A, and respectively approx. 140 °C and 80 °C when the power transmission amount was 800 A. Further, as shown in Fig. 4, each of the alloy wire members 3 was wound on the overhead electric wire 2 in a stranding direction of the outermost layer. The surface temperature of each alloy wire member 3 was measured in the same manner as in the former embodiment. As the result, substantially the same result as in the former embodiment was obtained. There occurred no difference in the amount of generated heat even when the Ni-Fe series alloy wire member 3 was wound on the overhead electric wire in any direction with respect to the stranding 233190 - 9 - direction of the outermost layer thereof. In the above embodiment, the heat-generative electric wire 1 was explained with the Ni-Fe series alloy wire member 3 wound on the outermost layer of the overhead electric wire 2, but the same snow melting effect as in the case wherein the Ni-Fe series alloy wire member was wound could be obtained when the Ni-Fe series alloy wire members 3 were stranded with strands 2a constituting the outermost layer of the overhead electric wire 2 as shown in Fig. 5. In a case where the alloy wire members 3 are stranded with the strands 2a, it is preferable to equally distribute the Ni-Fe series alloy wire members 3 of the number corresponding to 1/4 to 1/2 of the number of the strands 2a constituting the outermost layer. Further, in the above embodiment, a circular-form wire having a circular section is used as the Ni-Fe series alloy wire member 3, but a wire of a desired form, such as a wire having a rectangular section or a tapelike wire, can be used. EMBODIMENT 2 Cold-drawing wire members containing Ni of 50.5 to 52 %, Mn of 0.20 to 0.35 %, Si of less than 0.20 % and Fe as the remaining portion and having a diameter of 2.6 mm were used as the alloy wire member 3, and Zn coatings are formed to a thickness of 0.035 mm on the alloy wire member 3 by plating. The alloy wire members 3 were wound on the overhead electric wire 2 constructed in the same manner as in the embodiment 1 in a direction opposite to that of the stranding direction of the outermost layer thereof. Then, the overhead electric wire 2 was :p^,., ■ - '* '."Vt/Vt/ ) 233 190 - 10 - connected to the current supplying transformer 4 shown in Fig. 2 under the same measurement condition as in the I embodiment 1, and A.C. currents of 50 A, 80 A, 100 A, 150 A and 200 A were supplied thereto. Then, a temperature ! \ rise AT which is a difference between the room ! rj temperature (-4 °C) and the surface temperature of the \ t alloy wire member 3 after the current supply was I J measured. I The result is shown in Fig. 6 together with the measurement result used as a comparison example and relating to the heat-generative electric wire having the alloy wire member 3 with no Zn coating and of the same composition wound thereon. In Fig. 6, the abscissa indicates a current value (A), the ordinate indicates the temperature rise AT (°C)i and the results of this invention and the comparison example are respectively indicated by A and O- As is clearly seen from Fig. 6, in the heat-generative electric wire, the heat generation amount increases by approx. 20 % at maximum when the Zn coatings are formed on the alloy wire members 3, and thus the snow or ice melting effect can be enhanced. Further, antirust tests in which salt water was sprayed onto the heat-generative electric wire 1 having the alloy wire members 3 with Zn coatings and the alloy wire members of the same composition without Zn coatings for 1500 hours while currents (100 A) were supplied to them were effected. As the result, in the case of the heat-generative electric wire 1 having the alloy wire members without Zn coatings, an electrolyte corrosion phenomenon occurred between the overhead electric wire 2 and the alloy wire member, and much rust occurred in the ! | overhead electric wire 2, thus reducing the effective % J J } I X 'i £ s i ■ 233 190 y - 11 - diameter. On the other hand, in the case of the heat-generative electric wire 1 having the alloy wire members 3 with Zn coatings, the water repellency was enhanced and occurrence of rust due to the electrolyte corrosion was not observed. EMBODIMENT 3 Fig. 7 shows an embodiment in which the alloy wire member 3 is pre-formed in a spiral form with a preset pitch, and this alloy wire member 3 is preferable since it can be rapidly mounted on an overhead electric wire 2 which has already been constructed, for example. Alloy wire members 3 having various pitches from 1.5 up to five times the diameter D of the overhead electric wire 2 and previously formed in a spiral form were prepared. They were mounted on the respective overhead electric wires 2 having a cross sectional area of 610 mm2 and formed in the same manner as in the embodiment 1 as shown in Fig. 7. A temperature rise AT caused when an A.C. current of 100 A was supplied was measured. A heat generation characteristic curve obtained as the result is shown in Fig. 8. In Fig. 8, the abscissa indicates a winding pitch P (mm) expressed by the multiple of the diameter D (mm) and the ordinate indicates the temperature rise AT (°C) . The winding pitch P was set to 1.3D, 1.5D, 2.ID, 2.6D, 3.0D, 3.3D, 4.2D and 4.9D. Assuming that the temperature rise AT due to current supply is 9 *0 in order to attain heat generation amount required for melting snow or ice attached to the electric wire, then, as seen from Fig. 8, the pitch P (mm) at which the alloy wire member 3 is wound on the - 12 - overhead electric wire 2 is preferably set in the range of 1.5 to 3 times the diameter D of the overhead electric wire 2 indicated by an arrow in Fig. 8. However, in a case where the winding pitch P is less than 1.5 times the diameter D, it becomes difficult to mount it on the overhead electric wire 2. On the other hand, in a case where the pitch P exceeds three times the diameter D, the heat generation amount is abruptly reduced, causing an undesirable result. Further, if Zn coatings are previously formed on the pre-formed alloy wire members 3, the water repellency and corrosion resistance thereof can be enhanced. Further, a plurality of alloy wire members 3, for example, as shown in Fig. 9, three alloy wire members 3 can be integrally pre-formed in a spiral form with a pitch of 1.5 to 3 times the diameter D of the overhead electric wire 2. In addition, the three alloy wire members 3 integrally pre-formed in a spiral form can be formed Zn coatings on the surface thereof. In each of the above embodiments, if protection members 5 shown in Figs. 10 and 11 are mounted on both ends of the alloy wire member 3 wound on the overhead electric wire 2, it is preferable in protection for the overhead electric wire 2. The protection member 5 is formed of semi-spherical half-divided bodies 6 and 7 coupled by use of a' hinge. The half-divided bodies 6 and 7 respectively have recesses 6a and 7a formed in the respective inner portions, and they are coupled by a bolt 8 and a nut 9 fixed in grooves 6b and 7b formed in the outer central portions thereof. The protection member 5 is disposed to shield the end of the alloy wire member 3 arranged as 233 1 - 13 - shown in Fig. 10 with the recesses 6a and 7a previously filled with filler 10 such as grease, silicone-series filler or the like. Occurrence of corona discharge between the overhead electric wire 2 and the alloy wire member 3 can be prevented by mounting the protection member 5. Further, the alloy wire member 3 wound on the overhead electric wire 2 can be prevented from becoming loose. </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 14 233 WHAT WE CLAIM IS:

1. A heat-generative electric wire comprising a Ni-Fe alloy wire member which contains 45 to 80 % by weight of Ni and the remaining portion being Fe and which is wound on or stranded with the outermost layer of an overhead electric wire.

2. A heat-generative electric wire according to claim 1, wherein said Ni-Fe alloy wire member contains 47 to 54 % by weight of Ni.

3. A heat-generative electric wire according to claim 1, wherein said Ni-Fe alloy wire member contains 50 to 52 % by weight of Ni.

4. A heat-generative electric wire according to claim 1, wherein said Ni-Fe alloy wire member has a metal coating formed on the surface thereof.

5. A heat-generative electric wire according to claim 4, wherein said metal coating is Zn.

6. A heat-generative electric wire according to claim l, wherein said Ni-Fe alloy wire member wound on the outermost layer of said overhead electric wire is pre-formed in a spiral form with a present pitch.

7. A heat-generative electric wire according to claim 6, wherein the winding pitch of said Ni-Fe alloy wire member wound on said overhead electric wire is 1.5 to 3 times the diameter of said overhead electric wire.

8. A heat-generative electric wire according to claim 6, wherein said Ni-Fe alloy wire member has a metal coating formed on the surface thereof.

9. A heat-generative electric wire according to claim 1, wherein said Ni-Fe alloy wire member wound on the outermost layer of said overhead electric wire has a plurality of wire members integrally formed and is preformed in a spiral form with a preset pitch.

10. A heat-generative electric wire according to claim 9, wherein the winding pitch of said Ni-Fe alloy wire members having a plurality of integrally pre-formed wire members and wound on said overhead electric wire fis 15 233 1.5 to 3 times the diameter of said overhead electric wire.

11. A heat-generative electric wire according to claim 9, wherein said Ni-Fe alloy wire members having a plurality of integrally pre-formed wire members has a metal coating formed on the surface thereof.

12. A heat-generative electric wire according to claim 1, wherein said Ni-Fe alloy wire member wound on the outermost layer of said overhead electric wire has a protection member mounted on the winding end of said heat-generative electric wire.

13. A heat-generative electric wire according to claim 6, wherein said Ni-Fe alloy wire member has a protection member mounted on the winding end of said heat-generative electric wire.

14. A heat-generative electric wire according to claim 9, wherein said Ni-Fe alloy wire member having a plurality of integrally pre-formed wire members has a protection member mounted on the winding end of said heat-generative electric wire.

15. A heat-generative electric wire substantially as herein described with reference to the accompanying drawings. THE FURUKAWA ELECTRIC CO., LTD. By its Attorney Don Hopkins & Associates Per: </div>