US2619610A

US2619610A - Expulsion gap lightning arrester

Info

Publication number: US2619610A
Application number: US52318A
Authority: US
Inventors: Jr Tausias Irven Eldridge; Walter H Young
Original assignee: ELECTRIC SERVICE Manufacturing Co
Current assignee: ELECTRIC SERVICE Manufacturing Co
Priority date: 1948-10-01
Filing date: 1948-10-01
Publication date: 1952-11-25
Anticipated expiration: 1969-11-25

Description

Patented Nov. 25, 1952 nxroLsfon GAP LIGHTNING ARRESTER 'ra'usias Irven Eldridge, Jr., Brooklin'e, and WaljtcrH'. Yung, (}lenside, Pa., assignors to Electric y s'ervice Manufacturing Company, Philadelphia, Pa.,a corporation of Pennsylvania A pii'mt'ibii caster 1, 1948, Serial No. 52,318

4 Claims. (01. 313 -231) Our invention is an electrical protective device or lightning arrester providing a substantially unimpeded path from an electric circuit or equipment to ground for lightning orother transient, high potential, electric disturbances, and which quickly suppresses arcs maintained by follow current aeross gaps ionized by a high potential discharge in passing to ground.

In its preferred form, our invention comprises a series of telescoped, cylindrical walls of gas forming material having. spaces between them forming multiple, parallel, cylindrical arc slots of narrow cross-section but extensive area. Each slot is bounded laterally by concentrically curved spaced walls, and hence has, in transverse crosssection the shape of a narrow rectangular slot bent around and spaced from an axis. These parallel slots are intersected by are electrodes which are connected, mediately or immediately, with line and ground. Preferably, the walls form ing the constricted arc slots, and the electrodes intersecting such slots, are enclosed. in a nonconducting housing, which also encloses electrodes forming an isolating gap between line and a proximate electrode intersecting the arc slots. The isolating gap prevents application of line voltage to thearc-suppress'ing elements of the arrester except during acutal discharge to ground, and any surface leakage 'orcreep-age is over the housing and not through the 'arrester -elements. The enclosure of the isolating gap within the housing prevents any fouling of the gap which, if it occurred, would allow the application of line current to and deterioration of the walls of the arc slots. b

The walls forming th arc slots are; preferably reinforced by an encircling steel sleeve having its end nearest the isolating gap beveled or flared outward and preferably coated, wholly or partly, with insulation to prevent fiash over to the sleeve from the proximate isolating gap elec- 'rode'd uring a discharge to ground; I

The concentric cylindrical arc slots are preferably of unequal lengths, the slot of smaller cross-sectional area being the shorter. This tends to divert impulses of steep wave fronts to the outer and longer arc slot and to divert heavy currents of slower rising steepness to the inner, shorter arc slot, and the'multiple slots permit the use of walls therefor having gas generating areas magnitudes of very high order because of the multiple paths principle. v I

The gas generating surfaces of the arc slots are preferably composed of hard fibreor horn fibre, but may be composed of or contain other suitable gas generating substances, such as boric acid, activated by an arc to produce de-ionizing gases tending to suppress an arc.

The principles of our invention, and the best mode in which we have contemplated applying such principles will further appear from the following description and the accompanying drawings illustrating 'a preferred embodiment of my invention. v

In the drawings, Fig, 1 isja longitudinal sectional view of a lightning arrester or protective device embodying ourinvention; Fig. 2 is a transverse sectional view taken on the line 22 of Fig. 1 Fig.3 is a transverse sectional view taken on the line 3-3 of Fig. 1; Fig. i is an enlarged broken perspectiveview of the ground electrode at the bottom of the arc slots; Fig. 5 is an exploded, longitudinal sectional View of the electrode shown in Fig. 4 and of the core and tube to be seated therein; Fig. 6 is a transverse sectional view taken on the line G6 of Fig. 5; and Fig. 7 is a fragmentary part sectional view illustrating a modification of the flaring and coating ofthe top of the reenforcing sleeve. 7

The embodiment of our invention illustrated'in the drawings comprises an external housing composed of a cylindrical, wet-process porcelain body I having one end closed by a porcelain plug 2 glazed into the body. The opposite end of the housing is countersunk to form a seat 3 for the flangededge ll of a conducting cup 5 which may be provided with a hollow depending terminal boss 6 for the atachment of a ground I. The cup 5 is secured against the seat 3 by a plastic seal 8 and non-plasticcement 9.

A cylindrical hard fibre shell 13 has its end threaded into the threaded cup 5 and is encircled by .a steel, seamless, reinforcing sleeve or shield ll which may be staked to the cup 5 and is therethrough connected to the ground. The sleeve H projects along the shell Ill beyond the portion thereof containing the arc quenching slots and upper arc electrode hereinafter described. H v

As illustrated in Fig. 1, the upper end of the sleeve ii is flared outward by belling the rim 52 thereof to form a channel which maybe filled with a ring of non-conducting sealing material l3, such as'resin. In the'modifica'tion illustrated in Fig. 7, the upper end of the sleeve H is flared by beveling the edge 12' which may be surrounded by a non-conducting ring I3. The fiaring of the upper end of the sleeve H away from the tube It greatly decreases the liability to flashover.

A cylindrical electrode H2- is seated in the cup 5 within the shell l and has a peripherial wall 55 containing the countersink It at one end thereof and diametral slots I? which communicate, through an aperture 19 in the bottom of the electrode, with a discharge passage 20 through the terminal boss 3.

A core 2| is seated on a non-elastic metallic washer 22 in the countersink IE; the core preferably consisting of a filler rod 23 and a fibre tube 24.

A fibre tube 25 is telescoped over the core 2! and spaced slightly therefrom and from the inner wall of the shell [0 to form multiple, concentric, cylindrical arc slots each having walls of gas-forming material concentric with but spaced from one another.

The are slots are intersected, at the upper ends thereof, by an electrode 26 making a close fit with the inner wall of the shell l0 intermediate the ends thereof. The electrode 23 has a peripherial flange 2? closely encircling and centering the reduced upper end of the tube 25. An elastic gasket 28 and a felt gasket 29 are interposed between the end of the tube 25 and the electrode 26 and lie in a channel between the flange 21 and boss 30 of the electrode. The boss 30 extends into the end of the tube 25 and presses against the top of the core 2! to press it tightly against the washer 22. The electrode 26 may be secured to the core 2| by a screw 3|.

The head of the screw 3| is housed within a conducting tube 32 which is telescoped over the boss 33 on the top of the electrode 26.

A conducting plug 35 is threaded into the upper end of the shell II), with its periphery well inward from the periphery of the tube [0, and has a boss 35 extending into the tube 32. By tightening up the plug as in the shell ID, a desired degree of pressure may be applied to the electrode 23, tube 25, core 2! and electrode 14 to prevent axial or rotary movement of these parts and secure their concentricity to one another.

An electrode 36, seated in the plug 34, and an electrode 37, carried by the end closure 2, form an isolating gap 33 normally isolating the are quenching elements of the arrester from line but providing a path to ground for impulse surges due to lightning or the like.

The electrode 31 has a shank 39 which passes through an aperture 42 in the closure 2 and the joint between the shank and closure is sealed by the

fibre gasket

40 and 4| which are squeezed by the electrode 31 and gasket cup 43 when the nut 34 is drawn up on the shank 39. The nut 44 may be provided with a serrated surface complementary to the wire clamp 45 for gripping the line conductor 46 when the nut 41 is tightened up. A hollow cap 48 is detachably connected with the shank 39 to provide a weather shield for the line connection assembly.

The interior of the housing I is ventilated through ventilating apertures 49 through the fiange 4 and the cement 9.

The arrester may be mounted in any suitable position adjacent to a circuit to be protected by a metal bracket 50 encircling the housing I intermediate the ends of the reinforced sleeve II; the bracket 50 being spaced from the line terminal of the arrester by the corrugated area of the surface of the housing I.

When a lightning surge or other transient high potential electric disturbance reaches the section of the line with which the line terminal 39 is connected through the conductor 46, it is discharged across the isolating gap 38, through the electrode 36, plug 34, conductor 32, electrode 26, through one or both of the arc slots, electrode l4, terminal boss 6 and conductor 1 to ground. The are through the arc slots quickly generates large volumes of de-ionizing gas which extinguishes the arc maintained by follow current at or before the next zero point of the cycle of the alternating dynamic current. The generated gas is expelled from the arc slots through the electrode slots l1 and

passages

19 and 20, away from the ground conductor 1.

An arrester constructed in accordance with our invention has a low impulse spark-over voltage, a high discharge current capacity and a high dynamic failure voltage and are suppressive characteristics. Under standard test conditions, our arrester will cut ofi flow of 60 cycle dynamic follow current to ground within approximately an eighth of a cycle after the inception of a breakdown due to surge current, and will discharge without appreciable damage to itself test current of very high magnitudes, e. g. of the order of 180,000 amperes, and restore itself to its original operating condition. 7

The area of gas generating material is large proportionately to the length or volume of the arc slots and the arc is so distributed between the parallel slots that impairment of the walls of the slots is minimized. The impulse breakdown is inherently low and is further lowered by the conductive connection of the steel shield H to ground and consequent balancing which is accomplished by the capacitances between line and ground terminals.

Having described my invention, I claim:

1. An electrical protective device comprising a non-conducting external housing, a conducting cup seated in one end of said housing, a tubular shell seated in said cup, a reinforcing metallic sleeve encircling said shell and having one end secured to said cup and its other end flared, an electrode seated in said cup within said shell and having an apertured rim and a central socket, a core seated in said socket, a tube supported by the rim of said electrode and encircling said core, said core, tube and shell forming multiple concentric cylindrical arc slots having walls of material that generates gas in the presence of an arc and are concentric with but spaced from one another, an electrode intersecting said arc slots and having a boss engaging said core and a head engaging said tube, a conductor connected with said last named electrode, a plug threaded in said shell against said conductor and pressing said core, tube and electrodes axially, said plug having a member forming an electrode, a closure for the other end of said non-conducting housing, and an electrode carried by said closure and forming an isolating gap with said electrode last named.

2. An electrical protective device comprising a non-conducting external housing, a tubular shell within said housing and having an electrode intermediate the ends thereof and an electrode at each end thereof, a conducting member connecting the intermediate electrode with one of the end electrodes, a core and a tube interposed between the intermediate electrode and the other end electrode and forming with said shell parallel concentric cylindrical arc slots each having walls of material that generates gas in the presonce of an arc and are concentric with but spaced from one another, and an electrode at one end of the housing and complementary to the first named electrode at an end of said shell and forming therewith an isolating gap.

3. An electrical protective device comprisin a conducting cup, a tubular shell seated in said cup, an electrode at each end of said shell and an electrode intermediate the ends of said shell, a reinforcing metallic sleeve encircling said shell and conductively connected with said cup and having its end remote from said cup flared outwardly, a core and a tube within said shell between said intermediate electrode and one end electrode, said core, tube and shell formin parallel cylindrical arc slots each having Walls of materialthat generates gas in the presence of an arc and spaced from one another, and a conductor within said shell and mechanically spacing and electrically connecting said intermediate electrode and the other of said end electrodes.

4. An electrical protective device comprisin a hollow tubular shell of insulating material, an electrode seated in one end of said shell and having a peripherial wall countersunk at one end and diametral slots communicating with an axial gas venting passage through the other end. of said electrode, a core seated in the countersunk end of said electrode, a tube seated on the slotted end of the peripherial wall of the electrode, said core and tube forming an arc slot having walls of gas forming material spaced from one another, and an electrode intersecting said are slot at the end of said core and tube remote from said first electrode to support said core and tube in concentric relation, said slots and axial passage providing an escape path for gases resulting from an arc between said electrodes in said are slot.

T. IRVEN ELDRIDGE, JR,

WALTER H. YOUNG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,923,748 Roman Aug. 22, 1933 2,050,397 Torok Aug. 11, 1936 2,170,337 Pittman et a1 Aug. 22, 1939 2,285,198 Fitger June 2, 1942 2,330,918 Pittman Oct. 5, 1943 2,332,399 Pittman Oct. 19, 1943 2,338,479 Ackermann Jan. 4, 1944 2,414,308 Kalb Jan. 14, 1947 FOREIGN PATENTS Number Country Date 528,895 Great Britain Nov. 8, 1940