US1642241A - Protective device - Google Patents

Description

sept. 13, 1927. 1,642,241

L.. R. GOLLADAY PROTECTIVEv DEVICE Filed April 24, 1925 INVENTOR I Lau/.rence a//ad'ay @i w BY SMTBM I ATT'ORNEY Patented Sept. 13, 1927.

UNITED STATES PATENT f OFFICE.

LAWRENCE RICE GOLLADAY, OF EAST PITTSBURGH, PENNSYLVANIA, ASSIGNOR yTO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

PROTECTIVE DEVICE.

My invention relates to protective devices and it has particular relation to means for producing a visual indication of the failure of lightning arresters employed in modern distribution systems and 'for disconnecting such arresters from the lines.

The copending application of Smith and Golladay, Serial No. 743,549, filed on October 14, 1924, and assigned to the lVestinghouse Electric & Mfg. Company, describes a lightning arrester wherein the porcelain housing inclosing the members constitutingv the protective discharge path is so designed that the lower portion thereof cracks off whenever the arrester has failed to interrupt the discharge of line current and the power input of the line current flowing therethrough has heated the portion of the arrester which is 'in direct thermal contact with the members constituting the discharge ath. P My present invention solves the .problem in a different manner and has as its principal object a lightning arrester having a fusible member constituting a portion of the casing inclosing the discharge members and so related theretothat an excessive heat evolution, caused by abnormal flow of line current throughv the arrester, will render the same inoperative and will produce a visual sign of the failure of the arrester.

A more specific object of my invention is to provide a lightning arrester wherein the Vterminal lead that contacts with the lower discharge member is supported by a plate of fusible material constituting an enclosure of the lower portion of the arrester casing, the fusible plate being melted and the lower terminal member and terminal lead being expelled from the arrester casing upon failure of the arrester. Y

With the foregoing and other objectsin view, my invention comprises the organiza# tions and details of construction described and claimed hereafter and shown in the accompanying drawing, wherein- F ig. 1 is a sectional view of a distribu-V tion-type lightning arrester` embodying my invention,

Figs. 2, 3 and 4 are views similar to Fig.V

1 illustrating modications of my inven-` tion.

I will describe my invention in connection with the type of arresters known as auto-valve arresters which combine properties very desirable for the protection of distribution lines, on account of their compact structure, their highprotective qualities and their abilityto prevent'the flow of line current after the termination of the eXcessfvoltage discharge.

In isolated cases, it may happen that the line which is protected'by such arresters will come into contact with a line of high voltage, resulting in a continuous flow of cur rent for an appreciable time, thus subjecting theV arrester to conditions for which no economical arrester can be designed. Undcr suchv circumstances it is desirable to quickly disconnect the arrester from the line and to provide some indication that the arrester has failed, in order to simplify the maintenancey of the line and the inspection and renewal of the damaged equipment.

The broad features of my invention are, however, not limited to use in connection with auto-valve arresters and will be found applicable to other types of arrest-ers and, in general, wherever similar problems arise. Referring to Fig. l, an auto-valve arrester is shown comprising a valvedischarge unit 1 and al series isolating -gap device 2, both inclosed in a porcelain casing 3 which is similar in shape to a line insulator. v unit comprises a plurality of circular plates 4 of a relatively high-resistance composition material, which are separated from each other by mica washers 5y of approximately 3 mils thickness, to provide-a series of minute gaps adapted to discharge always in the form of a-glow, whenever the voltage across the gaps rises above a definite criticall value or breakdown voltage. Such a discharge unit interrupts the discharge whenever the voltage thereacross drops'below the same critical value or breakdown voltage, which is usually The valve chosen to be higher than the voltage of the y ing 6 of the porcelain casing 3. In assem-v bling the unit, it is usual to invert the same and pour a layer 11 of pitch or wax of'low melting point over the outer side of the fusible p 'late 10, in order to insulateithe same and protect the interior of the casing from atmospheric influences. z The terminal plates, the valve unit and the series gap are held under pressure by means of a spring member 13 disposed between the upper surface of the series gap device 2 and a porcelain cap 14E inclosing the upper side of the casingt terminal lead 1), provides a connection to the upper end of the discharge path, the porcelain cap and the lead 15 being securedl in place means of insulating pitch 16 which is poured into the space between the cap and the porcelain casing. 1

Under abnormal conditions, when the arrester continues to discharge line current, the heat generated in the valve unit flows, from the bottom plate of the unit, to the terminal plate 7 and heats the fusible plate 10.

VUnder the pressure of the spring member 13, the fusible plate will yield", after being softened o r melted, giving an unobstructed passage for the terminal plate 7, which is expelled from the casing, interrupting the discharge through the arrester and also producing -a visual sign of its failure. The

damaged arrester is easily noticed by those passing near the bottom of the poles, since the terminal lead is entirely removed from the casing and hangs down.

In F ig. 2 is shown a modification of my invention wherein the terminal plate 21 has a turned-over edge which increases the height of the plate and also concentrates the flow of heat` to that portion of the fusible plate 22 which is located near the edge of the opening 6. Such construction accelerates the interruption of the flow of current through the damaged arr-ester, since the fusible plate is softened more quickly and the expelling action of the spring 13 is more positive.

' InFig. 3 is shown a modification of my invention wherein the fusible plate 23 also constitutes the terminal plate which makes contact with the bottom plate or electrode ofthe valve unit 1.4

In F ig. 4f isshown a modification of my inventionfwherein the connection between thel terminal plate 24k, which is in Contact with the valve unit, and the terminal lead 25 is utilized in order to secure the interruption of the discharge and the visual indication of the arrester failure. The terminal plate 24 may be of brass and has a conical extension 26 which projects downwardly through the central opening in the porcelain case 27. rEhe insulated terminal conductor 25 comp .is'es a conducting lead 28 which is clamped in a flanged ferrule 29, the latter being held in the conical extension 26 by means of solder or other conducting fusible substance 30. A helical spring 31 surrounds the conical extension 26 and is mounted between the plate 24 and the flanged ferrule 29 toV exercise a pressure tending to expel the lead 2S from the opening. i

,l/hen the terminal plate 24C is heated by excessive current vthrough the arrester, the solder 3() holding the lead 28 in the conical stension 26 is melted and the spring 30 removes the lead from the casing, interruptingrthe discharge and producing an indication of the damage to the arrester.

I claimv as my invention:

1. An Velectrical protective device comprising a plurality of members constituting a discharge path, an enclosing device surrounding said members, a terminal conductor leading into said enclosing device and disposed' in contact with a terminal of said discharge path, and means tending to expel said terminal conductor from said enclosing device, said enclosing device including a fusible wall portion releasing said terminal conductor from said enclosing device upon abnormal operation.

2. An electrical protective device comprisingl a plurality of members constituting a discharge path, a. casing enclosing said members, a terminal conductor for said discharge path leading to said casing, means tending .tol remove said terminal conductor from said casing and fusible means, melting upon abnormal operation of said device, to release said conductor.

3. A lightning arrester comprising a plurality of members constituting adischarge path, one of said members'being associated with the principal source of heat evolution during a discharge through said device an insulating casingenclosing said members, a terminal wirev leadingto said discharge path and connected toV said casing, means tending to remove said wire from said casing, and fusible means inthermal Contact with' said source of heat evolution holdingfsaid wire in normal operating position. i l

4. A lightning arrester comprising a porcelain casing having a fusible bottom portion,

v.a plurality of members lconstituting a dis* charge path, and resilient means for holding said members in operating position by pres-v sure against the bottom portion of 'said cas ing whereby said portion drops off said casing upon` abnormal heating.

. 5. A lightning arrester comprising a plurality of members constituting aV discharge Ulf) path, a casing surrounding said members, a terminal conductor for said discharge path leading into said casing and a base member of fusible material closing said casing and holding said terminal conductor under pressure in normal operating position, said terminal conductor falling off said casing upon abnormal heating of said base member.

6. A lightning arrester comprising a plurality of members constituting a discharge path, a casing surrounding said members, high-potential and low-potential terminal conductors for said discharge path leading into said casing and a base member of fusible material closing said casing and holding said low-potential terminal conductor under pressure in normal operating position, said lown potential terminal conductor falling off said casing upon abnormal heating of said base member.

7, A lightning arrester comprising a porcelain casing having a fusible bottom por-- tion, a'plurality of members constituting a discharge path, and resilient means for holding said members in operating position by pressure against the bottom portion of said casing whereby said portion drops off said casing upon abnormal heating, said casing including means for retaining substantially all the contents thereof after said bottom portion drops off.

8. A lightning arrester comprising a plurality of stacked resistance discs, a lowpotential terminal Conductor having a terminal plate of reduced diameter in contact with the bottom disc, a tubular porcelain casing surrounding said discs and having an opening in the base thereof, said opening being larger than said terminal plate but smaller than said discs, and a fusible member enclosing said opening and holding said terminal plate under pressure against said discs.

9. A lightning arrester comprising a plurality of stacked members constituting a discharge path, a terminal conductor having a terminal plate contacting with the bottom member of said stack, a porcelain casing en closing said stack, said casing having an opening at the bottom permitting the free passage of said terminal plate but obstructing the passage of said stack, means for resiliently pressing said stack towards said opening, and a fusible member enclosing said opening for normally holding said terminal plate underpressure toward said stack and in immediate thermal connection therewith.

l0. A lightning arrester `comprising al stack of members constituting a discharge path, a porcelain casing enclosing said stack,

said casing having a bottom opening smaller than required for the passage of said stack and fusible means pressing against the bottom of said stack and enclosing the bottomv and a metallic fusible base member closing said casing and holding said ymembers under pressure.

In `testimony whereof, I have hereunto subscribed my name this 8th day of April LAWRENCE R. GOLLADAY.

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