HIGH VOLTAGE LIGHTNING ARRESTER HAVING A PLURALITY OF ARRESTER ELEMENTS

The present invention relates to lightning arresters, and more particularly to arresters adapted for servicing high voltage lines or equipment.

In the manufacture of high voltage lightning arresters, it is now common practice to provide a single series circuit of arrester elements through multiple (usually three and sometimes two, but other numbers are feasible) physical columns of the elements. In this manner, the required total arrester voltage rating can be achieved while physical height of the device is held sufficiently low to provide convenient use of the device.

The arrester elements must be physically supported in the columnar arrangement while intercolumnar connections are provided to establish a series arrester circuit through the elements. Sufficient insulation level (through gas and other insulative material) must exist between all physically proximate circuit points subject to any potential difference.

One basic structural approach is that in which a plurality of horizontally disposed insulative plates are interposed and spaced along the height of the arrester element columns. Physical support of the individual arrester elements is provided by the plates which in turn can be mechanically interconnected by means of insulative tie rods and thereby fixed in relation to the arrester housing. Intercolumnar connections between the arrester elements are made adjacent the vertically spaced insulative plates to provide a series arrester circuit which spirals along the arrester height.

It is desirable that the assembly of plates and arrester elements be characterized with mechanical strength and relatively minimum height as well as with manufacturing facility and economy including minimal usage of insulative materials consistent with required insulation levels. With respect to usage of insulative material, it is known that too much material in the wrong places can be detrimental to arrester operation since voltage gradients can be established across two materials of different dielectric constants that will cause ionization leading to insulation failure or radio interference. A primary determinant of these manufacturing and end product features is the structure of the insulative plates and the manner in which cooperation is provided among the plates and the arrester elements.

In accordance with the principles of the present invention, there is provided in an arrester device a multiple column assembly of arrester elements characterized with the foregoing as well as other structural and manufacturing features. The assembly comprises a plurality of suitable valve blocks and arrester gap units arranged in at least three physical columns and interconnected in a series circuit with insulative plates horizontally disposed at spaced levels along the assembly height to provide mechanical support and required insulation between

physically proximate but electrically diverse circuit points. Each physical column is divided by the plates into a plurality of sections, with each section having top and bottom vertical support provided by the bottom and 5 top sides of respective associated plates. In turn, top and bottom sides of each plate are provided with insulative wall means projecting in the vertical direction so as to provide a creepage barrier and, if desired, to provide side support for the arrester elements in adjacent 1Q sections of all but one of the columns. Each plate also has at least one opening preferably formed by a pair of arms in the plate solid plane to provide side support for arrester elements in a "transfer" section of the column. It is therefore an object of the invention to provide a 15 novel high voltage arrester in which a multiple column assembly of arrester elements is efficiently organized for achieving relatively minimal or comparatively reduced arrester height. Another object of the invention is to provide a novel 20 high voltage arrester in which a multiple column assembly of arrester elements is arranged for manufacturing facility and economy.

An additional object of the invention is to provide a novel high voltage arrester in which a multiple column 25 assembly of arrester elements is characterized with good mechanical strength.

It is a further object of the invention to provide a novel high voltage arrester in which a multiple column assembly of arrester elements is arranged with relatively mini30 mal use of insulative material.

It is an additional object of the invention to provide a novel high voltage arrester in which a multiple column assembly of arrester elements is provided with relatively optimal insulative separation between circuit points sub35 ject to relatively large potential drop during arrester operation.

These and other objects of the invention will become more apparent upon consideration of the following detailed description along with the attached drawings, in 40 which:

FIGURE 1 shows an exploded perspective view of an arrester constructed in accordance with the principles of the invention and having parts thereof broken away; FIG. 2 shows a schematic diagram of an arrester cir45 cuit formed within the device of FIG. 1;

FIG. 3 shows a top view of an insulative plate used in an arrester element assembly of the device of FIG. 1; and

FIG. 4 shows a cross-section of the insulative plate 50 taken along the reference line IV—IV of FIG. 3.

More specifically, there is shown in FIG. 1 a high voltage lightning arrester 10 constructed in accordance with the principles of the invention for connection, alone or in series with additional identical arresters or arrester 55 units, between a high voltage conductor and ground. The arrester 10 includes an insulative or porcelain housing 12 filled with an insulative atmosphere such as dry nitrogen and having end terminal plates 14 and 16 disposed at the top and bottom thereof and in sealed securance 60 therewith. Within the housing 12, an assembly 18 of arrester elements is supported between the terminal plates 14 and 16. Preferably, coil springs 20 hold the assembly 18 in compression to provide stable mechanical support for the assembly 18 during shipment and during use and Co to maintain reliable electrical connections throughout the arrester circuit provided by the assembly 18.

The arrester circuit comprises a suitable plurality of arrester elements or suitable gap units 22 and suitable valve blocks 24 connected in a single series electrical cir^° cuit physically disposed in three columns. The number and the voltage rating of the elements 22 and 24 are de3

terminative of the overall arrester voltage rating. It is apparent that the pluralistic columnar arrangement of elements 22 and 24 leads to height conservation for the arrester device 10.

Each gap unit 22 can for example comprise the mag- 5 netic blowout gap structure disclosed in a copending application Ser. No. 405,945, filed by J. Osterhout on Oct. 23, 1964 and assigned to the present assignee. To facilitate arrester discharge current flow while providing for gap interruption of power follow current, each block 10 24 is characterized with resistance which decreases with increasing voltage. To obtain this variant resistance property, each block 24 can be formed from granular silicon carbide with a suitable binder. As is well known, end surfaces of the blocks 24 can be suitably metallized (not 15 shown) to provide for circuit connections.

The assembly 18 includes top and bottom connector plates 26 and 28 between which the arrester elements 22 and 24 are supported in the columns by means of insulative (for example porcelain) plates 30 which are tied to- 20 gether to the connector plates 26 and 28 by means of insulative tie rods 32. The insulative plates 30 generally have an outer contour which encompasses that of the arrester element columns and further divide each column into vertical sections so that the arrester circuit can be 25 formed "spirally" through the sections from column to column along the assembly height.

Generally, each section of each column forms a series circuit segment and is supported at its top by means of a bottom side 34 of an adjacent plate 30 and at its bottom 30 by means of a top side 36 of an adjacent plate. Two exceptions are the topmost and bottommost sections which receive top and bottom support respectively by the end connector plates 26 and 28.

To provide such mechanical support throughout the 35 assembly 18 while providing for an intercolumnar series arrester circuit, each plate 30 is provided with an opening 38 (FIG. 3) preferably formed by a pair of arms 40 and 42 in the plane of the plate 30. The ends of the arms 40 and 42 are provided with accurate indents 44 and 46 be- 40 tween which there is horizontally supported in the opening 38 an element or block 24 of a "transfer" section of one of the columns. Preferably, an open space 48 is provided radially inwardly from the opening 38 for the purpose of providing the necessary single dielectric constant gaseous insulation and adequately long creepage 45 path between columns.

The term, "transfer" is used to denote a columnar section which provides a circuit path to a new higher or lower insulative plate level in the assembly 18. Accordingly, each transfer section is provided with midpoint sup- 50 port by the arms 40 and 42 of an intermediately located plate 30 as well as top and bottom support by top and bottom plates 30 located at the ends of the transfer section. In this instance, every alternate columnar section in the series circuit path is a transfer section. 55

In addition, each plate 30 is provided with vertically projecting wall means 50 on its top side 36 and preferably identical vertical projecting wall means 50 on its bottom side 34. The wall means 50 is in the form of a single vertically projecting wall 52 which circumscribes the end 60 arrester elements 22 or 24 of a pair of sections vertically supported therewithin. If desired, side support can thus be provided for the ends of each section, but primarily a barrier is provided against creepage between end elements aligned with each other in the same column and disposed 65 in spaced relation on opposite sides of the plate 30. Further, as can be observed in FIG. 1, the plates 30 are successively rotated from one another by 120° so that the spiraling intercolumnar circuit path can be formed as described. 70

To provide for assembly securance by means of the tie rods 32, each plate 30 is also provided with openings 54 and 56 in the plate arms 40 and 42 and an opening 58 extended through the solid plane of the plate radially outwardly of the creepage wall 52. When the insulative tie 75

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rods 32 are extended through the aligned plate openings 54, 56 and 58 of the various plates 30, side support is provided for the plates 30 against horizontal dislocation from the assembly 18. Vertical support is provided as previously described, namely by means of compressive force applied among the arrester elements 22 and 24 and the plates 30 by means of the coil springs 20.

The various arrester element columnar sections are cross connected in the overall arrester series circuit by suitable means, preferably by conductive metallic plates 60 respectively disposed within the plate walls 52 against the bottom side 34 or the top side 36 of each insulative plate 30. Preferably, the portion of the horizontal plate surface within the wall 52 on each plate side 34 or 36 is metallized or sprayed with conductive paint to establish fixed capacitance between the two plate sides 34 and 36. Such capacitance electrically parallels portions of the arrester circuit as more fully described in U.S. Patent No. 2,542,805, entitled, "Lightning Arrester," issued to A. J. Fink on Feb. 20, 1951, and assigned to the present assignee.

The purpose of the built-in capacitance is to produce substantially uniform voltage gradient across the arrester circuit. If the dielectric constant of the plate material is relatively high, it is not necessary to use auxiliary capacitors to supplement the indicated capacitance effect. For the lower frequency components of arrester voltage it is normally necessary to use suitably connected nonlinear resistors (not shown) for voltage grading purposes.

In FIG. 2, there is schematically illustrated a sample arrangement for the gaps 22 and the blocks 24 in the various sections of the columns. In this schematic, the reference characters 22 and 24 are used for the gaps and the blocks and the reference character 52 represents the insulation provided by the plate walls 52 against creepage. It is assumed in this example that an overall arrester rating of 48 kv. is specified and that the gaps are rated at 6 kv. and the blocks are rated at 4 kv. Further, to facilitate illustration, the columns of aligned elements in FIG. 2 do not correspond with the physical columns in FIG. 1.

A first columnar section 62 comprises a block 24 and a gap 22 supported at its top against top connector plate 26 and at its bottom within the top wall 52 of an insulative plate 30 indicated in this schematic by the reference character 64. The block 24 in the section 62 is operable at a potential of 48 kv.

Another section 66 is serially connected with the section 62 by means of a connector 60 and it also is supported within the top wall 52 of the insulative plate 64. The section 66 comprises a pair of blocks 24 which are operable at a potential of 42 kv. because of a 6 kv. voltage drop in the gap 22 of the section 62. A topmost insulative plate 68 is disposed on the section 66 with the topmost block 24 of the section 66 disposed within the bottom wall 52 of the plate 68. A connector 60 extends from the section 66 to the next columnar section which is a transfer section 70.

The section 70 cooperates with the section 66 in supporting the plate 68 and it includes a pair of gaps 22 separated by a block 24 (operable at 36 kv.) with the block 24 side supported by the arms 40 and 42 of the plate 64. The transfer section 70 is provided with bottom support by another insulative plate 72 within the top wall 52 thereof.

Another connector 60 within the top wall 52 of the plate 72 establishes connection between the transfer section 70 to another section 74 comprising a pair of blocks (operable at 30 kv.). The section 74 and another transfer section 76 support the plate 64, and the transfer section 76 in turn is supported by another plate 78. The arrester circuit is thus continued to the bottom connector plate 28 (operable at 0 kv.) at the bottom of the assembly 18. The gaps 22 and blocks 24 and plates 30 mutually support one another as indicated while a series intercolumnar arrester circuit is established with adequate but not excessive placement of insulation.