US2858476A - Lightning arrester - Google Patents

Description

Oct. 28, 1958 E.

Filed Feb. 29, 1956 WITNESSES F. w. BECK ETAL 2,858,476

Fig.|.

INVENTORS Edward F. W. Beck 8| Otro Ackermcnn ATTO EY Oct. 28, 1958 E, w, BECK ETAL 2,858,476

LIGHTNING ARRESTER Filed Feb. 29, 1956 3 Sheets-Sheet 3 Fig.3.

States Patent 2,858,476 LIGHTNING ARRESTER 7' Application February 29, 1956, Serial No. 568,557

' 3 Claims. (01. 315-36) i The present invention relates to lightning arresters and, more particularly, to a high-voltage lightning arrester unit of greatly reduced height, as compared to the height of lightning arrester units of conventional construction and equivalent voltage rating. The'lightning arrester unit of the present invention is especially adapted for use in high-voltage, station type lightning arresters of unit construction, although it is a complete lightning arrester in itself and may be used as such. .High-voltage, station type lightning arresters areusually of unit construction, and are made up of a suitable number of lightning arrester units, of standard voltage ratings, each of the units consisting of a number of'spark gap devices and valve elements assembled in series relation in a single stack and enclosed in a porcelain housing with metal end fittings. The individual arrester units are placed end-to-end in a vertical column, and the end fittings of adjacent units are bolted together for electrical and mechanical connection, so that all the units are connected in series. This type of construction results in a vertical column of great height as compared to its diameter, and in the higher voltage ratings the column isso high that it is not self-supporting but must be supported from some external support, such as part of .a

station structure, either by bracing or by suspension mounting. .In very high voltage arresters, the arrester column is so high that the required supporting structure and bracing become quite large and elaborate and are relatively expensive. The necessity of external bracing or support of high-voltage arresters is highly undesirable, but cannot be avoided with the conventional construction, because of the necessarily great height of the arrester column.

I Another problem in the design of high-voltage lightning arresters of conventional construction is that of obtaining sufficiently uniform voltage distribution across the tall column of arrester units. The arrester is connected between a transmission line conductor, or other protected device, and ground so that it is subjected to the line-to-ground voltage, but because of the height of conventional arresters, the voltage does not divide uniformly between theindividual arrester units. Satisfactory operation, however, requires a reasonably uniform distribution of the voltage. This is usually obtained by means of grading rings which control the electrostatic field surrounding the arrester to make the voltage distribution sufficiently uniform for satisfactory operation. In highvoltage lightning arresters of considerable height, however, it is quite difficult to obtain satisfactory voltage distribution in this way, and it is frequently necessary to employ relatively elaborate grading ring structures which are of large diameter and thus undesirably increase both the cost and the space required for the arrester to provide the necessary clearance distances to other nearby apparatus.

' The principal object of the present invention is to provide a lightning arrester unit for use in high-voltage, station type lightning arresters which is of greatly reduced and '& ICC

2 height, as compared to conventional lightning arrester units of the same voltage rating, so that a column of the new arrester units'is self-supporting and requires no external support and is short enough so that the voltage distribution is reasonably uniform. I

Another object of the invention is to provide a lightning arrester unit in which the arrester elements themselves are arranged in a plurality of columns disposed sideby-side in a'housing and connected in series to provide a compact construction of greatly reduced height. A further object of the invention is to provide a lightning arrester unit in which the arrester elements are disposed in series-connected columns placed side-by-side in a housing, and supported in the housing and insulated from each other in such a manner that a mechanically stable construction is provided and thatxthe. arrester columns are separated by insulating barriers which prevent any possibility of internal flashover between points of different potential in the various columns, but without undesirably increasing the diameter of the housing.

A still further object of the invention is to provide a lightning arrester unit in which the arrester elements are arranged in series-connected columns disposed side-byside ina housing, and in which means are provided for obtaining substantially uniform voltage distribution across the arrester elements within the housing in a simple and effective manner.

Other objects and advantages of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawing, in which:

Figure 1 is a vertical sectional view of a lightning arrester unit embodying the invention;

, Fig. 2 is a developed view, partly in section, of the lightning arrester assembly of Fig. 1 without the housing;

Fig. 3 is a plan view of an end member utilized for supporting the arrester elements. I As previously indicated, the lightning arrester unit of the present invention is particularly suitable for use as an arrester unit in high-voltage,- station type lightning arresters, although it will be apparent that the device is a complete arrester in itself and may be used as such. In the preferred embodiment of the invention shown in the drawing, for the purpose of illustration, the arrester unit is'contained in a generally cylindrical housing 1, which is preferably made of porcelain although any suitable weather-resistant insulating material might be used. The housing 1 is provided at each end with metal end fittings 2 of any suitable design which are secured to the housing 1 by cement, as indicated at 3, or in any other desired manner. The ends of the housing 1 are closed by metal diaphragms 4 which are secured to the end fittings 2 in any desired manner, as by bolts (not shown), a gasket 5 being interposed between each of the diaphragms 4 and the housing to seal the interior of the housing. It will be understood that any suitable construction may be used for the end fittings and closure means of the housing, the end fittings providing for electrical and mechanical connection of the unit in a column of similar units in the usual manner.

The arrester assembly itself, which is contained in the housing 1, consists essentially of three columns 6, 7 and 8 of lightning arrester elements disposed side-by-side in the housing. The arrester elements comprise spark gap devices and valve blocks, or non-linear resistor elements, which may be of any usual or desired type. Each of the columns may consist of any necessary number of spark gaps or valve elements or both. Thus, as shown in Fig. 2, the columns 6 and 8 are similar and each comprises a spark gap assembly 9 and a plurality of valve blocks 10 disposed in series relation, while the column 7 comprises only valve blocks 10. The columns may consist, however, of any combination of spark gaps and valve blocks arranged in any desired manner.

The spark gap assembly 9 is shown as comprising a plurality of gap devices 11 arranged in a column in a porcelain tube 12. The gap devices 11 may be of any suitable type and are shown as being of the type disclosed and claimed in a copending application of A. M. Opsahl and T. L. Dyer, Serial No. 560,146, filed January 14, 1956, and assigned to the assignee of the present invention. As more fully disclosed in that application, each of the gap devices 11 consists of a fiat electrode plate 13 and a formed electrode 14 having an annular ridge which cooperates with the electrode 13 to form an annular gap space, the electrodes 13 and 14 being spaced apart by an annular spacer 15 of high resistance material. An annular permanent magnet 16 is disposed in the space formed by the ridges of adjacent electrodes 14 to provide a magnetic field in the gap space to efiect movement of the arc to facilitate its extinction. 7

Any necessary number of spark gap devices 11 may be provided, depending on the desired voltage rating, and they are disposed in the tube 12 in a vertical column, conducting spacers 17 being provided if necessary. at the top and bottom of the column. The ends of the porcelain tube 12 are closed by metal end caps 18, which are sealed to the porcelain in any suitable manner, as by soldering, to a metallic glaze on the porcelain as indicated at 19. The gap devices are held firmly in contact with each other and with the end caps 18 by means of a spring plate 20, so that the gaps 11 are electrically in series between the end plates 18 which serve as contact means for the gap assembly.

The valve blocks 10 may be any suitable type of valve element or non-linear resistor, and are preferably made of granular silicon carbide molded to the desired size and shape with a binder of sodium silicate and baked to provide valve elements of a usual type.

In the particular construction shown in Fig. 2, the arrester columns 6 and 8 are shown as being identical, although inverted with respect to each other. Each column consists of a spark gap assembly 9 and two valve blocks 10 disposed in a series column in a tube 21 of any suitable rigid insulating material. One end of the tube 21 is closed by an insulating cap member 22 which is retained in position in the tube by pins 23 extending through the wall of the tube into recesses in the cap 22. The cap 22 has a central recess 24 in which a helical spring 25 -is received. A contact pin 26 extends through the cap 22 from the recess 24 and the spring 25 engages the pin 26 to urge it outwardly from on the cap 22, engaging the helical spring 25, and the col umn of gap devices and valve elements bears against the spring plate 27. It will be seen that the column of arrester elements is thus supported in an insulating tube and that the spring devices 25 and 27 hold the arrester elements in firm contact when the device is assembled in the complete arrester assembly, as described hereinafter, the contact pin 26 and the outer end cap 18 of the gap assembly providing contact means for the column of arrester elements.

The column 7 is shown as consisting of four valve elements 10 which are disposed in an insulating tube 21 between end caps 22, as previously described, placed at both top and bottom of the tube, a conducting spacer 28 being interposed in the column of valve elements to make the column of the desired height. Spring elements 25 and 27 and contact pins 26, as previously described, are provided at both top and bottom of the column to hold the valve elements 10 firmly in place and to provide for electrical contact to the column of valve elements. It will be understood that any suitable arrangement of valve elements and spark gap devices may be utilized, depending on the desired voltage rating, and that each of the three columns may include either spark gap devices or valve elements, or both, in any desired arrangement.

the cap 22. A spring plate 27 is placed The three columns 6, 7 and 8 of arrester elements are disposed side-by-side in the housing 1 in a triangular arrangement, as shown in Figs. 1 and 3, and are supported in insulating end members 29 and 38. The end members 29 and 30 may be molded of any suitable insulating material and, as shown in Figs. 1 and 3, each of the end members i generally circular with a flange portion 31 and a thick central portion 32 provided with strengthening ribs 33. The central portion 32 of each end member has three relatively deep recesses 34 of circular outline equidistantly spaced from each other as shown in Fig. 3, to receive the columns of arrester elements. Three openings 35 are provided in the flange portions 31 of each of the end caps for receiving tie rods 36 of insulating material, which are shown a being square "in cross section although any suitable shape could be used, and the openings 35 are made of corresponding shape to receive the tie rods.

Contact means are provided in the end members 29 and 30 for making electrical connection to the columns of are rester elements and for connecting them in series. In the illustrated embodiment, the end member 30 shown in Fig. 3 has a copper strap connector 37 embedded in the bottom of two of the recesses 34, the connector extending through a slot 38 between the recesses and having its ends disposed in position to engage the contact means of the arrester columns received in the recesses so as to connect these two columns together. The third recess 34 has a copper contact member 39 in the bottom of the recess in position to engage the contact means of the arrester column placed in that recess, and the contact member 39 has a strap portion 40 extending out of the end member through a slot 41. j

The upper end member 29 may be identical to the lower end member, and when assembled, the upper end member is inverted in position with respect to the lower end member, as clearly indicated in Fig. 1, so that the three arrester columns received in the corresponding re cesses 34 of the upper and lower end members are elec trically connected in series. Thus, for example, in the arrangement shown, the circuit extends from the strap portion 40 and contact member 39 of the lower end member 30 through the arrester column 6 to the connector 37 of the upper end member 29 and through this connector to the adjacent arrester column 7 and to the conductor 37 of the lower end member 30, which connects the arrester column 7 to the arrester column 8. The upper end of the column 8 is in contact with the contact member 39 of the upper end member 29 to complete the series circuit.

In assembling the arrester, the arrester columns 6, 7 and 8 are placed in the proper recesses in the two end members 29 and 30, and the tie rods 36 are inserted through the openings 35 in the end members to secure the assembly together. In the preferred embodiment shown in the drawing, steel shield plates 42 are also provided at the top and bottom of the assembly. The shield plates 42 are substantially coextensive with the end members 29 and 30, to extend Over the entire assembly, and are placed on the tie rods 36 on the outside of the end members, as shown, the shield plates 42 being spaced from the end members by insulating spacers 43 placed on the tie rods 36. The strap conductors 43 extending from the end members are connected to the shield plates 42 in any suitable manner, as by bolting them on studs 44 welded or otherwise attached to the shield plates.

The complete arrester assembly is preferably supported in the housing 1 by spring means to protect the assembly from mechanical shocks to which the arrester may be subjected during shipment and handling. For this purpose, the metal diaphragms 4 which close the ends of the housing 1 have a plurality of integral projections 45 extending inwardly and provided with reduced end portions 46. An annular steel spring plate 47 is supported on each of the diaphragrns 4, the spring plates 47 having openings which fit over the reduced portions 46 of the projections 45. Conducting bushings 48 are threaded on the ends of the tie rods 36 against the shield plates 42 to clamp the arrester assembly itself together in a unitary assembly, any necessary number of conducting spacers 49 being provided at one end of the assembly to adjust the total height to that of the housing 1. The ends of the tie rods are received in openings in the spring plate 47, positioned between the openings which receive the projections 46, so that the arrester assembly is supported on the spring plates and because of the resilience of the spring plates, the conducting bushings 48 are held in tight engagement with the spring plates to efiect electrical connection, thus completing the internal circuit from the shield plates 42 to the diaphragms 4 and end fittings 2.

A very compact high-voltage lightning arrester unit is thus provided, since the columns of arrester elements are disposed side-by-side in the housing, and the height of the arrester unit is thus greatly reduced as compared to that of arresters of conventional construction. The arrester columns themselves are contained in insulating tubes and are supported in deep recesses in the insulating end members. Thus, effective insulating barriers are provided between all points in adjacent columns which may be at diflerent potentials during a discharge and long creepage distances are provided between such points because of the depth of the recesses. There is therefore no danger of internal flashover between adjacent columns during a discharge, even though there may be a very considerable potential diflerence between corresponding points of adjacent columns. The construction shown thus provides adequate insulation and also provides a very stable mechanical structure since the arrester columns are securely held in the insulating tubes 21 and these, in turn, are well supported in the deep recesses on the end members.

The shield plates 42 serve to improve the voltage distribution between the gap assemblies 9, since they constitute equipotential surfacesat opposite ends of the assembly and tend to make the electric field uniform and symmetrical, so that substantially equal division of voltage between the gap assemblies is obtained. The shield plates thus improve the performance of the unit but they might be omitted, if desired, since even without the shield plates, the construction shown has a reasonably uniform voltage distribution. The spring support for the assembly in the housing is also a desirable feature of the invention, since the arrester assembly is well protected against mechanical shocks which might otherwise cause damage.

It should now be apparent that a high-voltage lightning arrester unit has been provided which has many advantages. The new arrester unit is of very compact construction and greatly reduced height, and a high-voltage column of these arrester units is not excessively high so that it is self-supporting and no external bracing or support is required, and so that reasonably uniform voltage distribution across the entire arrester can easily be obtained. A particular embodiment of the invention has been shown and described for the purpose of illustration, but it will be apparent that various other embodiments are possible within the scope of the invention. Thus, for example, for higher voltage units two, or possibly more, of the arrester assemblies described could be placed in series within a single housing, the tie rods 36 being extended through the two assemblies to provide a unitary structure. Similarly, numerous other modifications and embodiments will be apparent to those skilled in the art and all such modifications and embodiments are within the scope of the invention.

We claim as our invention:

1. A lightning arrester comprising upper and lower end members of insulating material, a plurality of columns of spark gap devices and valve elements disposed side by 6. side between said end members, each of said columns being series connected from end to end and extending continuously from said upper end member to said lower end member, each of said columns being enclosed in an insulating tube and having contact means at the ends thereof, the end members having relatively deep recesses therein and having conducting means in the recess in position to engage the contact means of the columns and connect the columns in series, insulating tie rods extending between the end members to clamp the end members and columns together in a unitary assembly, a metal shield plate supported on the tie rods outside of each end member, said shield plates being substantially coextensive with the end members, means for electrically connecting each shield plate to the adjacent end of the series-connected plurality of columns, an insulating housing, said housing closed at its ends by diaphragms, inwardly extending projections on said diaphragm, a resilient annular plate supported on said projections, said annular plate having openings intermediate said projections, the ends of said tie rods received in said openings.

2. A lighting arrester comprising upper and lower end members of insulating material, a plurality of columns of spark gap devices and valve elements disposed side by side between said end members, each of said columns being series connected from end to end and extending continuously from said upper end member to said lower end member, each of said columns being enclosed in an insulating tube and having contact means at the ends thereof, the end members having relatively deep recesses therein and having conducting means in the recesses in position to engage the contact means of the columns and connect the columns in series, insulating tie rods extending between the end members to clamp the end members and columns together in a unitary assembly, a metal shield plate supported on the tie rods outside of each end member, said shield plates being substantially coextensive with the end members, means for electrically connecting each shield plate to the adjacent end of the series-connected plurality of columns, and an insulating housing enclosing said assembly.

3. A lightning arrester comprising upper and lower end members of insulating material, a plurality of columns of spark gap devices and valve elements disposed side by side between said end members, each of said columns being series connected from end to end and extending continuously from said upper end member to said lower end member, each of said columns being enclosed in an insulating tube and having contact means at the ends thereof, the end members having relatively deep recesses therein and having conducting means in the recesses in position to engage the contact means of the columns and connect the columns in series, insulating tie rods extending between the end members to clamp the end members and columns together in a unitary assembly, a metal shield plate suported on the tie rods outside of each end member, said shield plates being substantially coextensive with the end members, means for electrically connecting each shield plate to the adacent end of the series-connected plurality of columns, an insulating housing, and resilient means in the housing engaging the tie rods for supporting said assembly in the housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,651,360 Atherton Dec. 6, 1927 2,611,107 Rydbeck Sept. 16, 1952 FOREIGN PATENTS 239,832 Switzerland Mar. 16, 1946 931,539 Germany Aug. 11, 1955

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