US1914394A - High potential transmission installation - Google Patents

Description

June 20, 1933. Q ug- 1,914,394

HIGH POTENTIAL TRANSMISSION INSTALLATION Filed Aug. 23, 1928 2 Sheets-Sheet l INVENTOR Arf/zz/r 0,4057%.

VETTORNEY June 20, 1933. A. o. AUSTIN 1,914,394 7 HIGH POTENTIAL TRANSMISSION INSTALLATION Filed Aug. 23, 1928 2 Sheet .s-Sheet 2 fig Fly 4 INVENTOR Arf/Yz/r 0. flw/m.

W 6t 1 (X A TTORNEY ratented June 20, 1933 Application filed August 23, 1928.

This invention relates to sion lines and has for one object the provision of'a transmission system that shall be of improved construction and operation. Another object is to provide a ground wire construction for transmission lines that will tend to increase the capacity of the line to ground andat the same time, pating the energy of charges induced by abnormal disturbances. Other objects will appear from the following descri tion.

The invention is exemplified y the combination and arrangement of parts shown in the accompanying drawings and described in the following specification and it is more particularly pointed out in the appended claims. This application is in part a continuation of application Serial Number 290,343, filed July In the drawings:

Fig. 1 is an elevation of a ground wire support comprised in the present invention.

Fig. 2 is a view at right angles to Fig. 1.

Fig. 3 is a diagrammatic view of a portion electric transmisof a transmission line having the present invention applied thereto.

Fig. 4 is a modified form of arcing gap. Fig. 5 is a section on line 5'5 of Fi 4.

Figs. 6, 7 and 8 are diagrammatic views respectively of modified circuit details.

.In the operation of transmission lines, the power conductors are frequently subjected to heavy potentials dueto the release of a bound charge following a stroke of lightning in the vicinity of the line. In many cases it has been customary to install ground or earth wires in order to keep down the resulting potential following the release of a bound charge. The principal function of the ground wire is to increase the electrostatic capacity of the line to earth, potential depends upon the charge released and the effective capacity to earth.

Where Q represents the charge and C the effective electrostatic capacity to ground, the resulting potential E will be c that the assist in dissias the resulting COMPANY, OF MANSFIELD, OHIO, CORPORATION OF NEW HIGH POTENTIAL TRANSMISSION INSTALLATION Serial N 0. 301,538.

function is that of an absorbing e ectrostatic tends to prevent a rise in While there is little question but wire is effective in reducmg th result expected.

In the ordinary functioning of the ground wire, it is evident that if the charge Q is not appreciably reduced, owing tothe presence of the ground wire, that the electrostatic charge on the conductor will be the same, although the potential Tests and theory go to show that the losses such as brush discharge increase very rapidly at the higher potentials so that an increase of 40 or per cent in the potential may produ'ce losses many times that at the lower po.- tential.

From this it follows that where a ground wire reduces the will be less.

harge present as where it is omitted, it naturally follows that the total effective energy available for setting up or maintaining an abnormal potential on the conductor may be much ground wire is used than where it is not present since the ground wire tends to delay the dissipation of the charge. ticularlytrue-where the induced potentials are high and the rise in potential is exceedingly rapid. Owing to the time lag in flashover, the potential may rise very rapidly, and owing to the dissipation of energy drop to normal potentialso quickly that the insulator may not flash over. If, however, a ground wire is used under the same conditions, the dissipation of energy will be less as explained above; hence, the potential, although of lower magnitude, will be sustained for a longer period of time so that in many cases an arc may take place over the insulator or from conductor to supporting structure, even though the maximum potential has been reduced.

greater where the This is par-v If the ground wire tends to lower the potential so that the surge energy will not be dissipated, allowing the same to be stored a greater length of time, it is possible that more fiashovers may take place where a. ground wire is used than with the higher potential having an exceedingly rapid rate of decay where the ground wire is omitted.

The induced surge on the line with the ground wire may have a considerably longer tail to the wave and, as the total energy is less, the magnitude of the surge at a distance may be higher than where no ground wire is used. This is particularly true where the conduc 5 tors are such that the losses will be very high ,conductor; hence, where at the high potentials. Owing to the effective increase in electrostatic capacity due to the use of a ground wire, the natural period of the system is reduced in accordance with the well known laws. Since the induced losses will be less as the natural period is decreased, it naturally follows that oscillations set up where the ground wire is in place are likely to have a slower period and dampen out less rapidly. A disturbance or wave traveling along the power conductor will induce currents in the ground wire. Where the resistance of the ground wire is low, the PR losses due to the induced current will be very small.

The energy supplying the losses in the ground wire must be supplied from the power conductor. It is evident that the greater the losses in the ground wire, the greater will be the amount of energy drawn from the power the PR losses in the ground wire are high due to currents induced by a surge in the power conductor, the dissipation of the surge potential or charge will be rapid and decidedly beneficial. In order to keep the induced potential at the point of disturbance low, it is necessary that the ground wire have an induced potential approximating ground potential. If the resistance or impedance of the ground wire is too high, its efiiciency will be lowered. On the other hand, if its resistance is low, its surge dissipating capacity will be reduced. This matter is covered to some extent in my prior Patent No. 1,581,154.

In many instances, it is necessary or desirable to use a low resistance ground, either to give life, mechanical reliability, or to keep the maximum induced voltage as low as possible. The low resistance in the ground wire, however, largely eliminates its surge dissipating function. In consequence, I have devised anew method of installing a ground wire so that it will be effective, not only in'reducing the maximum surge potential, but at the same time, will possess the surge dissipating capacity of the ground wire. In general, the scheme consists in insulating the ground wire at most of the structures, grounding the same only periodically or through a resistance. By using appropriate resistances, the ground conductor.

wire which is insulated from the structure through an insulator can be connected to ground at each structure.

The most suitable absorbing resistance will depend upon the effective electrostatic capacity and the wave front or magnitude of the sur e traveling upon the power conductor. This resistance may be varied in different parts of the system, depending upon the results desired. Where the ground wire is connected by a resistance to ground, its absorbing capacity in the vicinity of the disturbance will be greatly reduced as the IR drop over the resistance due to the sudden release of the bound charge will raise the potential of the ground wire similar to that on the power In order, therefore, that the maximum voltage on the power conductor be reduced, it is essential that the ground wire assume an ap roximate ground potential as quickly as poss le. This is accomplished by establishing a spark gap between the ground wire and earth. This spark gap may be in multiple with the resistance where the resistance is used in the same location. To give most beneficial results, the spark gaps should be used at every support, but the resistances need be used only occasionally. It is evident, however, that where the ground resistance is a few ohms only, the IR drop will be very appreciable, The absorbing resistances may be varied in accordance with the length of span so as to obtain the maximum 1 R loss for currents induced by a surge in the ground wire.

As comparatively little is known about the surges on the transmission line, it may be necessary to try several different resistances to obtain the best results. As a matter of fact, a variety of conditions can be taken care of by changing the resistances. Suppose that the resistance at one support is less than 10 ohms. The next support might have a resistance of several hundred ohms and the next one might have a resistance of several thousand ohms. Widely graded resistances of this type could then be used to produce an apgreciable loss over a wide range of conditions.

ince any I R loss will be beneficial and since the shunting gap need have a comparatively low break-down voltage, the efiiciency of the ground wire for keeping down the maximum voltage will be effective and, at the same time, the energy of the traveling wave will be dissipated by the resistances. \Vhere the ground wire has an appreciable resistance, it may be grounded only periodically and insulated at the intervening supports. These intervening supports, however, could be equipped with the discharge gaps.

Since it is desirable to dissipate as much energy aspossible so as to lower the voltage in the surge or traveling wave, it is necessary that the current induced in the ground wire flow over an absorbing or dissipating resistance. Where the ground wire is continuous and of low resistance, part of the current will tend to flow along the conductor as well as over the shunt resistance to ground. The

5 higher the shunt resistance, the more current will flow along the conductor, hence, the dissipation of energy may be greatly reduced as against the condition where this current is forced over a high resistance. 7

In many cases, particularly where the resistance of the ground wire 18 low, itis advisable to split the ground wire up'into sections by means of any suitable strain insulator. This sectionalizing insulator may be placed in the" middle of the span or at any suitable point. It is advisable, however, that each section of ground wire be connected to earth through an absorbing resistance. it is desired to provide electrical continuity along the ground wire, the sectionalizing insulator ma be shunted by a resistance.

It is evi ent that where the sectionalizin of the ground wire is frequentthat little atv tention need be paid to the wave length to the difference in voltage between diiierent portions of the power conductor ad'acent an section of ground wire will be rat or smal Where a high frequency'or oscillation ex- "ists on the ower conductors so that different portions of the power conductor adjacent a given section of ground,wire have potentials,

both above and below earth otential, it is evident that there will be a ow of current along the ground wire in the section. If, however, the section of the ground wire is small or equivalent only-toan alternatioman appreciable dissipation of energy will be induced in the adjacent section of ground wire and in the ground resistance.-

Where a ground wire is installedon wood pole structures embodying the above principles, it is not necessary to use the insulator at intervening points as the wood-will furnish sufficient insulation. Gaps, however, which will provide low resistance paths to ground when bridged may be used at each structure or only occasionally where the spans are rather short.

0 It is evident that where the ground wire has an a preciable voltage induced at low or normal requency, an appreciable energy loss will result in forcing-this charging current over the resistance connected to ground, parmethods may be used to reduce this loss to any desirable value.- In some cases, the location of the ground wire maybe such that it willhave little resulting potential induced by the voltage in the several conductors. This is shown in my prior Patent No. 1,581,154.

Another method of reducing the loss is to provide a very small gap in series with the resistance to ground,'as shown at in Fig. 6. This gap will be such that the voltage down of this obtain maximum dissipation of energy, for

ticularly if the resistance is high. Several induced normalfrequency will not brid e it but abnormal voltages will cause a brea gap and allow the resistance to function. I

Still another method is to place a reactance, shown at 31 in Fig. 7, in multiple with the resistance. 7 The current induced by the normal'frequency in the ower conductors would then flow through t is reactance. A high frequency, however, would be largely blocked by the reactance and forced over the absorbingresistance. Since the resistance of the reactance coil could be relatively low, the PR loss due to current induced at normal fr uency would be relatively small.

0 method applies to practically any type of transmission line and the ground wire may be supported by a suspension or other form of tension insulator, by a rigid insulator or on wood or other members which will supply the necessary resistance so that induced curg rents will be forced to flow either a considerable distance along the ground wire before going to ground or through the absorbing resistances.

In order that the ground wire may have high electrostatic absorbing capacity and assume a ground potential quickly, it is necessary to provide a discharge path which will shunt the insulator or supporting resistance. While it will ,be possible to support the ground wire with a resistance and shunt gap, 1n general it is difficult to obtain a resistance of the necessary mechanical properties and which will have a. resistance high enough to produce an appreciable PR absorption.

Fig. 1 showsone form in which the insulator 10 mounted on a support 11 insulates a ground wire 12. The ground wire is held to the insulator by a clamp 13 which forms part of a discharge gap 14. The other part of the gap 15 is connected to ground and may be made adjustable by means of the clamp.- ing bolt 16. An absorbing resistance 17 may be attached to the conductor 12. This absorbing resistance may be in any suitable form such as a resistance wire or a liquid placed in a tube. Where a liquid is used, this may be sealed to prevent evaporation or if allowed to evaporate should have a surplus. If a non-freezing liquid is used and provision is made for expansion, the whole may be sealed tightly so that it will require little or noattention in operation. By making the resistance large enough, the energy dissipated in the same will not raise the temperature seriously. Owing to the large number of these which would occur on the transmission line, the load would be relatively small. Unless the ground wire is placed in a neutral field, the normal line potential will induce currents in the ground wire causing a dissipation of energy. This is a disadvantage, but as-the current induced is low,compared to that due to the disturbance on the line, it is a comparatively easy matter to reduce these losses materially by periodically connecting the conductor to a lowresistance ground and depending upon the resistances at the intermediate points to absorb the abnormal potential.

The ground wire has a comparison in automotive practice. When a car is equipped with a very limber or flexible spring, the bounce is much greater, although the intial shock upon striking a bump is reduced. A ground wire has the same effect upon a power conductor. In automotive practice, it has become customary to install shock absorbers where limber springs are used. In the improved method of installing the ground wire, the absorbing resistances are the equivalent of the shock absorber. The absorbing resistance dampens out the disturbance rapidly similarly to the shock absorber through a dissipation of energy.

Fig. 3 shows diagrammatically a transmission line equipped with a ground wire ac cording to the present invention. The numeral 18 designates supporting structures having electrical transmission lines 19 carried thereon by cross arms 20 and insulators 21. The ground wire 12 is mounted on insulators 10 and is provided at each structure with a spark gap to ground. At greater intervals along the transmission line, the ground wire is connected to earth through resistance elements 17. sectionalizing insulators 32 may be interposed in the ground wire between the ground connections 17 as previously explained.

' In Fig. 4 there is shown a wood pole 22 which may be equipped with the usual form of cross arm, not shown, for supporting the power conductors. An insulator 23 is mounted on the pole 22 and carries the ground wire 12. An arcing member 24 is supported on the ground wire 12 at a distance from the pole 22 and is insulated from the ground wire by means of an insulator 25. A complementary arcing member 26 is electrically connected with the ground wire.

Insulating the conductor 12 from ground may have material advantages in some cases as this arrangement permits the use of the conductor for electrostatic coupling, for carrier current work, or will permit the use of the conductor for signal, pilot wire or other purposes without interfering with its use as a ground wire for reducing the magnitude'of surges and for their absorption.

Where a conductor is used for electrostatic coupling, a section of proper length is provided by inserting the sectionalizing insulators 32 shown in Fig. 3. The large discharge gap 1415 will be set so that discharge will not take place except under an abnormal charge. If an absorbing resistance 17 is used in this section of the line, it will be provided with a discharge gap 30 set large enough so that the discharge will not take place under the voltage induced on the section b the power line at normal frequency or un er the voltage induced on the section by the communication system.

Where the entire conductor 12 is used for signal purposes the gaps 30, while smaller than the gaps 14-15, will be set large enough so that discharge will not take place across these gaps under voltage induced in the conductor 12 by normal line voltage or by normal operation of a signal circuit.

Where it is desired to bleed the line occasionally to keep down high voltages induced at normal frequency, it is advisable to use some means in addition to the resistance 17 and the gap 30 to ground since, if the ground lead is open at the gap 30 no current will flow to ground at normal frequency and voltage and if the gap is closed, flow of current through the resistance 17 would absorb the energy of the signal circuit or dissipate energy taken from the power conductor. If the induced voltage is limited by the discharge of a gap, disturbances will be set up, interfering with communication and radio reception. A suitable reactance 31, however, placed in multiple with the resistance 17 and gap 30 will allow charging current to flow and keep the induced voltage down while preventing a serious loss of energy in the communication system.

Where the voltag induced in the conductor 12 by the normal voltage of the power conductors is considerable, transposition of the power conductors will reduce the resultant voltage on the ground and signal wire 12. In order for this transposition of the power conductors to be effective, however, adjacent sectionalizin insulators must include between them, a su cient number of transpositions to produce a balanced effect on the conductor 12 or else the sectionalizing insulators must be jumped by reactance 34 which will ermit sufficient current to flow at normal requency to kee the resultant potential down to the desire point.

Where it is desired to sectionalize the conductor 12 occasionally in order to force current induced by asurge over the resistance so as to dissipate the energy, it is evident that the conductor cannot be used for si al purposes. In order to eliminate this culty, the sectionalizing insulator 32 may be shunted by a resistance 33. These shunt resistances may be used for absorbing purposes, even though the conductor is not used for communication or other purposes. In some cases the absorbing resistance 33 may be used to take the place of absorbing resistance 17.

. I claim 1. The combination with an electrical transmission line, of a round wire extending adjacent said line and insulated therefrom to increase the ca acity of said transmission line to ground, sai ground wire being connected to earth only through appreciable resistance for dissipating energy induced in said round wire by abnormal surges in said cont uctor, and a spark gap between said ground wire and earth for limiting the potential of said ground wire above earth potential to maintain the capacity to earth of said transmission 2.-The combination with an electrical transmission line, of a support for said line, said line being insulated from said support, a ground wire mounted on said support and insulated therefrom and extending adjacent said transmission line, a resistance element electrically connected between said. ground wire and earth, and a spark gap in shunt with said resistance element between said ground wire and earth for limiting the potential of said ground wire above earth potential.

3. A transmission system, comprising a plurality of supports, an electrical transmission linemounted on said supports and insulated therefrom, a ground wire mounted on said supports and insulated therefrom, a resistance element electrically connected between said ground wire and earth, and spark gaps between said ground wire and earth located at spaced positions along said ground wire and forming discharge paths to earth from said ground wire, of which said resistance element is not a part.

4. A transmission system, comprising a plurality of supporting structures, an electrical transmission line mounted on said structures and insulated therefrom, a ground wire mounted on said structures and insulated from said transmission line and said structures, spark gaps interposed between said ground wire and earth and forming arcing paths from said ground wire to earth at spaced positions along said ground wire, and resistance elements electrically connected in shunt with said arcing gaps between said ground wire and earth said resistance elements being spaced from one another at greater distances than the distance at which said spark gaps are spaced from one another along said ground wire.

5. An electrical transmission system, comprising supporting structures, a transmission line carried by said structures and insulated therefrom, a ground wire carried by said structures and insulated from said structures and from said transmission line, a spark gap interposed between said ground wire and earth at each of said supporting structures,

and resistance elements electrically connected between said ground wire and earth, the resistance elements so connected being fewer in number than said supporting structures.

6. The combination with an electrical transmission line, of a support for said line, a ground wire extending adjacent said line and insulated from round and from said line, and resistance efements of difierent resistances electrically connected conductively between said ground wire and earth at different points along said ground wire, and arcing gaps forming discharge paths from said ground wire to earth separately and apart from the paths including said resistance elements.

7. The combination with an electrical transmission line, of spaced supports for said line, a ground wire carried by said supports and insulated from said transmission line and ground, limiting spark gaps between said ground wire and earth at each of said supports, and resistance elements of varying resistances electrically connected between said ground wire and earth at different itions along said ground wire different rom'the positions at which said spark gaps are located.

8. The combination with an electrical transmission line, of a ground wire extending adjacent said line and insulated from said line and earth, and an adjustable spark gap interposed between said ground wire and earth. a

9. The combination with an electrical transmission line, of a ground wire extending adjacent said line and insulated therefrom, sectionalizing insulators interposed in said ground wire and dividing said ground wire into sections insulated from one another, each section of said ground wire being electrically connected to earth only through appreciable resistance, and a discharge gap interposed between each section of said ground wire and earth for limiting the potential of said ground wire above earth potential.

10. A transmission system, comprising a plurality of supports, and electrical transmission line mounted on said supports and insulated therefrom, a ground wire mounted on said supports and insulated therefrom, sectionalizing insulators interposed in said ground Wire and dividing said ground wire into sections insulated from one another, a resistance element electrically connected between each of said ground wire sections and earth, the resistance of said resistance elements being different for different sections of said ground wire, and spark gaps connected between said ground wire and earth and located at spaced positions along said ground wire.

11. The combination with an electrical transmission line, of a support for said line, said line being insulated from said support, a ground wire mounted on said support and insulated therefrom and extending adjacent said transmission line, a conductor path having a resistance element therein electrically connected between said ground Wire and earth, a spark gap connected between said ground wire and earth, for limiting the potential of said ground wire above earth potential, and means in said conductor path for producin a greater dissipation of energy therein or high frequency otentials imposed on said path than for low requency potentials;

12. The combination with a transmission line, of a support on which said line is mounted and from which it is insulated, a supplemental conductor mounted on said support and insulated from said support and said transmission line, sectionalizing insulators interposed in said conductor, and resistance elements shunting said sectionaliz ing insulators.

13. The combination with a transmission line, of supports for said line on which said line is mounted and from which it is insulated, a supplemental conductor mounted on said supports and insulated therefrom and extending adjacent said transmission line, sectionalizing insulators interposed in said supplemental conductor, resistance elements shunting said insulators, ground leads connected with each section of said supplemental conductor and having resistance therein, and arcing gaps interposed between each section of said supplemental conductor and ground.

14. The combination with a transmission line, of supports for said line, a supplemental conductor extending adjacent said line, said line and supplemental conductor being insulated from each other and from said supports, sectionalizing insulators for said supplemental conductor dividing said supplemental conductor into sections, impedance jumpers for said sectionalizing insulators, and a ground connection for said supplemental conductor havinga discharge gap and resistance in series therein.

In testimony whereof I have signed my name to this specification this 20th day of August A. D. 1928.

ARTHUR O. AUSTIN.

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