Патент USA US2132044код для вставки
‘Oct. 4, 1938.‘ H. E_ OVERACKER _ 2,132,044 INTERFERENCE ATTENUATOR Filed April 13, 1935 SERVICE AREA 2 Sheets-Sheet l ggii a2 SERVICE AREA INVENTORY HORACE E. 0VERAC/(ER. ATTORNEYS. Oct. 4, 1938. H. E. OVERACKER 2,132,044 INTERFERENCE‘ ATTENUATOR Filed April 15, 1955 2 Sheets-Sheet 2 95m PEFRCTIVNS ()1 O I 500 I 700 I l I 900 l I I IOO l V I300 FREQUENCY IN KC. I INVENTORT HORACE E. OVERACKER. BY ,0 g a . ZIZIORNEYS. I500 2,132,044 Patented Oct. 4, 1938 UNITED STATES PATENT OFFICE 2,132,044 INTERFERENCE ATTENUATOR Horace E. Overacker, Palo Alto, Calif., assignor of one-half to Harry N. Kalb, San Francisco, Calif. Application April 13, 1935, Serial No. 16,180 8 Claims. (Cl. 178-44) My invention relates to the elimination of power line noise in radio broadcast receivers, and more particularly, to a means and method which can be applied to open wire lines to attenuate a de? 5 nite range of frequencies traveling thereon. Among the objects of my invention are: To isolate selected portions of open wire line service areas in order to prevent radio interference from reaching those portions; ‘to provide an attenua 10 tion system for open wire lines to prevent travel 'of radio interference thereon; to provide a means and method for increasing the attenuation of undesirable frequencies on open wire lines carry ing relatively low frequencies; and to provide a 15 means and method for reducing power line inter ference in radio reception. ‘ My invention possesses numerous other objects and features of advantage, some of which, to gether with the foregoing, will be set forth in the 20 following description of speci?c apparatus em bodying and utilizing my novel method. It is therefore to be understood that my method is applicable to other apparatus, and that I do not limit myself, in any way, to the apparatus of the 25 present application, as I may adopt various other apparatus embodiments, utilizing the method, within the scope of the appended claims. Referring to the drawings: Figure 1 is a diagrammatic view of a three 30 wire power line having a branch service area sup plied thereby, the branch line being provided with attenuation devices. Figure 2 is a similar diagram showing how a certain section of a power line may be isolated from the effect of traveling radio frequencies by the use of attenuation coils. Figure 3 is a view in elevation showing one means of attaching attenuation coils to a power conductor. Figure 4 is a perspective view of attenuation coils inserted in a three-wire transmission line. Figure 5 is‘ a diagram showing the per cent e?iciency of two attenuation stages on noise elimi nation within the broadcast band. Figure 6 is a sectional view showing how a 45 capacity member may be attached to the coil to increase distributed capacity and capacity to core. Noise heard in radio receivers comes from vari ous sources, the most important of which, is the 40 power line. Power line noise has been a source of receiving set interference since the beginning of radio broadcasting. In many cases, interfer ence originating in and being radiated from power lines is so strong that radio receivers cannot be 55 used at all and other power lines have su?icient local noise to prevent distant reception though local reception may be good due to the high power of nearby broadcasting stations. This interfer ence problem is one of the most troublesome the power companies have to contend with because 5 people living in localities with strong interference very justly believe they have a right to average radio reception. As yet, however, satisfactory ways of preventing such power noise have not been available. 10 The usual procedure is for power line inspectors to follow up individual complaints and then remedy a speci?c nearby noise source. As the remedy is individualistic, other complaints follow. The service thus becomes endless and expensive, and oftentimes the only solution offered is to recommend changes in the installation of the re ceiver. The‘only satisfactory solution of the problem is one which will apply towards the removal of all interference from the power lines so that the remedy can be applied directly to the power trans mission lines in such a manner that all of the receiving sets adjacent thereto will be protected from such interference. All power companies 2, now fully recognize the problem as above out lined and many do all they can to prevent radio noises on their lines. The technique, however, is largely empirical and not consistently reliable. Up to ten years ago, power transmission lines were built with no regard for possible radio noise or interference. As progress has been made in the understanding of the various causes of noise, many of the old lines have been altered with par tial success. Even the new lines, however, still 3 present several sources of radio interference which the power companies have been unable to elimi nate. In the meantime, however, much can be done to the transmission lines to prevent these noises, even though generated, from reaching groups of radio set users and it is with this phase of the problem that the present invention is con cerned. 0 Noises heard in radio receivers are caused by electrical disturbances and sparking originating 4, in insulators, transformers, and hardware asso ciated with power lines, and from corona on con ductors and around insulators. Both the corona and the spark discharges which take place in the various portions of the power system have the _, negative resistance characteristic of all electrical arcs and set up radio frequency oscillations which cause high frequency currents to flow along the power line. Fortunately, these currents do not @1156 radiation to any great distance, or power 55 2. ' 2,132,044 - . 1 ’ inserted in each conductor of the line on the same of interference than it is. pole. In Figure 1, service area I is supplied directly’ ‘ The radio frequency currents and voltages set up inductive and electrical ?elds which affect re from the line, whereas, in Figure 2, service area 2 ceiving antennas located within a few hundred feet of the power lines. ‘While the interferences ’ has the main transmission line 3 passing directly U! therethrough and having attenuated sections on thus extend .only a relatively short distance at right angles to the lines, the noise travels along thelines with little attenuation, a single source of noise sometimes causing interference for twen ty miles or more adjacent the conductor. either side. In either case, noise originating anywhere along line 3_is blocked off from the service area, by the attenuation sections. Furthermore, the modern distribution system introduces high voltage lines into the heart of thickly settled portions of metropolitan areas, 15 thus bringing the power noise originating at al most any point along the main line directly into inductive relationship with large numbers of re ceiving antennas. If, therefore, the’ problem of actually preventing the noise at all sources is de 20 ferred, at least, the noise can be prevented from Figure 3 shows one preferred embodiment of 10 an inductance ‘suspension adapted for high volt age transmission lines; and I prefer to utilize .what is ‘known in the art as a deadend pole 5 for the application of the attenuation coils A; and in this instance, I prefer to utilize two separate coils differing in their inherent capacity and tuned by their distributed capacity and by the capacity to the core to different frequencies. In Figure 3 only one conductor is shown and it is to. be un derstood that a similar coil assembly is, to be ap entering service areas. plied to the remaining conductors supported by Thus, insulators,’ transformers and other noise producing components ofv a power line may be the pole whether there be two, three or moreyas the invention is applicable to systems of any phase and. having any number of conductors, On the dead end pole 5 is fastened a cross arm 25 6‘ having attached thereto on opposite sides an insulator 9. The main line conductor H3 is dead treated within the service areas, but this will not 25 stop interference. unless the insulators oriother noisy components are treated along the'entire line. It is, therefore, very desirable from an economic standpoint to have ameans for prevent‘ ing noise on untreated parts of the line from 30 coming into the treated parts within ' de?nite service areas. ' ; '. ’ended on each side of the arm in the hook ll of the respective insulators 9-~9. I prefer to utilize separate’eye-bolts 'l—-'! for holding the insulators 30 to eliminate shunt capacity. Telephone,,telegraph,. and all other open. wire lines designed to carry relatively low frequency 'I'wo'tuned attenuation coils are usedyand each comprises an iron core l2 within the insulating currents have the same di?iculti‘es, and my in frame l3, the. ends of the core being within the coil winding, the insulated frame being supported 35 by an inverted U strap l4 and having a heavy 35 vention, while described as applied; to power lines, which are-the greatest offenders, is obviously ap plicable to any open wire, line or other line where on such interference exists. _ Broadly, the present invention comprisesiplac ing inductance coils in‘ series with allline wires at regular intervals. along a short section of the lines. If- these coils areplaced substantially less than about one-fourth wavelength apart, they have the eifectof reducing‘ the attenuationof the 45 line,.as in telephone practice. If; however, as in the present invention, the coils- are located at a distance onthe order of an odd number of one quarter wavelength of the lowest frequency to be attenuated, the. line attenuation for, that, and 50 higher frequencies, is greatly increased. By properly. spacing the coils a very great increase in attenuation is obtained over placing the same three coils or a single large coil, atone point in the 55 ' noise would be a much more widely spread source lines. - - . My invention also comprises the use‘ of two tuned coils in series with each wire of a line, all‘ coils being placed. at the‘ same. pole. In this ‘case’ the two coils in series are tuned‘ to different fre coil l5 preferably of the’same gauge wire as the line wound around the core and spaced there‘ from'.‘ The strap I4, is ?rmly attached to the main line conductor I 0 by clamps I‘! and one end of the coil i5 is attached to the strap by a con nection IS, the other end of the coil being con nected to the similar end of the opposite coil by a jumper 20 passing under the cross arm. In this case, the coil is left uncovered and exposed 45 to the elements. ' I‘prefer to tune the coilsto a different band in such a manner that thefrequency bands attenu ated overlap, thus broadening, by the use of two such’ coils the total band attenuated by the coils. 50 The tuning isv preferably accomplished by adjust ing the inherent capacity of the coil to where it . is resonant within the band. In order to accom pli'sh this,.wire l5 for example, may be insulated and bankwound, or crossed upon itself, but I ?nd 55 that a more convenient way to increase distrib uted capacity and capacity to core, is to place upon the core l2 an insulated metal piece 29' quencies within’ the‘ frequency band itisdesired passing through the coil and attach this piece to to attenuate, thus securing a. wider band of at tenuationv than can be‘secured by a slngle'tuned clamp I9, as shown in Figure 6. In this way, 60 standard coils may be used either tuned or un~ tuned, simply by virtue of whether or not the metal piece is connected to or disconnected from coil. - My invention also comprises the isolation of service areas as by blockingrthe main line wires 65 oneach‘ side of. the service areas’ with spaced in ductances. to attenuate frequencies coming in from either direction. By attenuating a short'section of open wire line with coils‘ spaced on the order of one-fourth 70 wavelength apart for the lowest frequency it is desired to stop, a high attenuation. of noise can be secured and Figures 1 and 2 show de?nite , service'areas l and 2 isolated from a main trans mission line 3 by attenuation coils 4 spaced more 75 than one-fourth wavelength‘ apart and preferably the line. a In certain other installations it may be desira 65 bleto utilize a single coil per conductor per loca tion either mounted as shown in Figure 3, or mounted on top of the cross arm as shown in another embodiment illustrated in Figurerll. Here, the coil’is wound on the core as before and 70 covered with a weatherproof cover 2|, the coil and core not being shown‘. The assembly, as before, is supported on. the U bar 22 which is mounted on a standard insulator and pin 24; for example, by an appropriate clamp 25; The U 75‘ 3 2,132,044 bar insulated from the core and connected at one end to line H), preferably through the outlet of the coil. The other end of the U bar has an insu lating leg 26 upon which is mounted a surge gap comprising gap arms 21 and 28, the lower'gap arm being connected'to the‘ U bar and the upper arm 21 being connected to the opposite emerging lead 29 of the inductance coil, which lead then drops to connect with the main conductor [0 on 10 the other side of- the pole. The gap between the arms 21 and 28 is adjusted so that surges which .-might cause trouble within the coil may pass around the coil without damage thereto. a r In both of the installations, as above outlined, 15 or in others which will be readily apparent to 20 the inductance per mile of two wires, for example, in the power line is about 4 m. h. Hence, one sec tion is equivalent to lengthening the power line only half a mile, a very small percentage of the length of most lines. . From the above data, it is evident that section al attenuation can be successfully used to stop in terference travel on high voltage power lines by using one, two or more sections of attenuation as required by the severity of the noise. However, 10 it should rarely be necessary to use more than two sections, i. e., coils at more than three con secutive positions. In this case, I prefer to make the middle coils substantially twice the induct those skilled in the art, the coils are preferably ance of either end coils. Isolating a section of 15 power line from radio noise produced on other placed on or close to the same cross arm. or pole parts of the system by this method is exception and inserted as connecting links in discontinu ities of the conductors carried by the cross arm ally inexpensive as the number of turns of wire is small per coil and no high voltage condensers or are involved. pole. I I ' The effect of attenuating the line has been computed, assuming the resistance of the coils to be negligible, which is the case for air core coils. It has been found that theattenuation of the line 25 with pure inductance does not continue to in crease as the frequency is raised above the value at which the coils become one-fourth wavelength apart. Rather, the attenuation increases to a maximum and then decreases at approximately 30 half a wavelength spacing to form a pass band. The attenuation thus alternately increases and 1. In combination with a power line. having a break therein, a loading coil comprising an iron core, an inductance wound on said core and in decreases and a series of pass bands occurs which pass bands are very undesirable from the stand sulated therefrom, a conductive hanger mechan ically attached to said core but electrically in sulated therefrom, and means for supporting point of stopping interference. said core and inductance in de?ned relation to In order to eliminate the pass bands for the purpose of stopping noise, the radio frequency resistance of the coils is made high. A high resistance to radio frequencies and a very low 60 cycle resistance is obtained in the same coil by 40 using an iron core. This result is obtained be cause the iron losses, principally eddy current losses, increase very rapidly as the frequency is increased. Experiments showed that a coil could be made with a 60 cycle resistance of .1 ohm, and yet have a resistance of over 1000 ohms at 1000 k. c. The term ‘.‘attenuation coil” as used here in means, therefore, a coil having a relatively low low frequency resistance and a relatively high said break and by said hanger, said inductance 35 being electrically bridged across said break. 2. In combination with a power line having a break therein, a loading coil comprising an iron core, an inductance wound on said core and in sulated therefrom, a conductive U-shaped hanger 40 the legs of which are mechanically connected to opposite ends of said core and insulated there from, and means for clamping said hanger to a conductor of said line at one side of said break, one end of said inductance being connected to said hanger and the other end crossing the break to close the break. 3. In combination with a power line having a high frequency resistance. break therein, a loading coil comprising an iron Figure 5 was computed from actual ?eld strength measurements made onpole No. 15 of a 3-wire, 60 cycle power line supplying an isolated area. Two stages of attenuation were used, the coils being applied to poles No. 6, 8 and 10, the noise originating at pole No. 1. The per cent ef?ciency of the attenuation coils over the broad core, an inductance wound on said core and in cast band was even greater than that shown by the curve, as there was a small amount of noise originating within the isolated area itself. The 00 coils were spaced two poles apart, in this case approximately approaching one-quarter wave length of. 600 meters, the lowest frequency it was desired to attenuate. It is possible in most cases to choose poles 65 closely approaching the proper spacing. How ever, it is to be understood that when pole spac ings are not such that proper attenuation can be had, the conductors may be opened between poles by a strain insulator, and a coil such as shown in 70 Figure 3, for example, mounted on the conductor in series therewith and bridging the discontinuity. The attenuation coils do not materially affect the transmission of 60 cycle power because the total inductance of one section is less than 2 m. h., 76 a section comprising two sets of spaced coils, and 20 The above described method of stopping noise along a power line by means of attenuating coils is superior to the actual application of band stop ?lters, for example, because of the fact that shunt condensers are exceptionally expensive and in themselves liable to create trouble in the line I claim: sulated therefrom, a metal piece disposed about 50 and insulated from said core within said induct ance, a conductive hanger mechanically attached to said core but electrically insulated there from, means for supporting said core and induct 55 ance in de?ned relation to said break from said power line by said hanger, said inductance being electrically bridged across said break, and means for electrically connecting said metal piece to said hanger. 4. In combination with a power line having a break therein and a loading coil comprising an iron core having an inductance insulated from 60 and Wound thereabout, said inductance being electrically bridged across said break, a conduc 65 tive hanger mechanically attached to but elec trically insulated from said core, said hanger be ing positioned to support said coil from said pow er line in de?ned relation to said break, a metal piece positioned between and insulated from said core and said coil, and means for connecting said metal piece electrically to said hanger. 5. In combination with a multi-conductor pow er line carrying commercial frequencies, means for attenuating radio frequencies on said line 75 7 2,132,044 xhigherdthan aipredetermined minimum compris '7.‘ Means for ' attenuating radio "frequencies on ing an attenuation coil in series-with each con ductor-at av'certain location?said coil-having are~ an open wire line,~comprising arplurality of iron core attenuation coils .spaced:along said clineat csistance in the order of 10.1 ohm‘and' an induct ance in the order of 0.24'vmil1ihenry at 1000 ‘a :distance of ‘the order of an -_odd number of cycles; and a-resistance in'the orderof 1000‘ohms and-van inductance in-the order'of>0.18 millihen ry at ‘1000 kilocycles, and a similar attenuation beattenuated, each of said coils havingavresist coil'in series with: each conductor separated from . said ?rst coil by a distance greater than-an odd :number- of quarter wavelengths of the lowest:fre vquency to be attenuated. ' ' '6. In combination with a multi-conductor pow er line carrying commercial frequencies, :means 'for attenuating radio frequencies on said line higher than a predetermined minimum ‘com o prising iron core attenuation'coils in-series with :each conductor atone; geographical location, and :additional iron-core ‘attenuation coils in series .20 with each conductor at another geographical‘lo cation spaced fromthe ?rst by a distance'of'the .orderof an odd number of quarter-wavelengths of the lowestfrequency to be attenuatedreaoh of said coils having a resistance'in the order'of 0.~1 .25 ohm andv an inductancein the order’ of 0.24 milli henry at 1000 cycles, and a resistance in the ' order of 1000 ohms and an inductance :in _.the order .of 0.18 millihenry vat-1000 kilocycles. quarter-Wavelengths of the'lowest'frequency'to 3 'ance in the order of 0.1 ohm and an inductance in the order of ‘30.24 millihenry at 1000cyc1es, andla resistanceyin the order of 1000-ohms and anin ductance in-the order of 0.18 v'millihenry‘at 1000 v10 kilocycles. ' V V 8. Means forattenuatingradioirekquencies on an open wire'line, comprising-a group of three iron core attenuation coils spaced along ‘Said, line at a distance of the order of an- oddnumber of quarter-wavelengths of the lowest :frequency to be attenuated, the central-coil of said group having-twice'theinduotance of either of-the end coilsin said'group, and each of said end coils having a resistance of the order of 0.1 ohm-landagor an inductance of the~order'of-0.24 millihenry at 1 kilocycle, and resistanceon ‘the order ‘of 1000 ohms andinductance onthe order of'0il'8 ‘milli ~henry at 1000Akilocycles. ‘ HORACE ‘E. OVERACKER.