US2256232A

US2256232A - Electric cutout with lightning protection

Info

Publication number: US2256232A
Application number: US250787A
Authority: US
Inventors: Ralph S Bennett
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1939-01-13
Filing date: 1939-01-13
Publication date: 1941-09-16
Anticipated expiration: 1958-09-16

Description

Sept. 16, 1941. R. s. BENNETT 2,256,232 ELECTRIC CUTOUT WITH LIGHTNI NG PROTECTION v Filed Jan. 13, 1959 Fig. 1.

Ifiventor: Falph 5. Bennett,-

HIS Attorneg.

Patented Sept. 16, 1941 ELECTRIC CUTOUT WITH LIGHTNING PROTECTION Ralph SrBennett, Pittsileld, Mass., assignor to General Electric Company, a corporation of New York Application January 13, 1939, Serial No. 250,787

' 9 Claims.

The present invention relates to electric cutouts and more particularly to improvements in protective equipment for fuse cutouts.

In some applications of fuse cutouts, troubles have been experienced from flashovers ,between the open circuited terminals or contacts of the cutout due to lightning surges. For example, in an installation where a fuse cutout is employed for transformer protection and is connected on the line side of the lightning arrester employed with the transformer, blowing of the fuse link leaves the cutout unprotected and tends to form at the line terminal of the cutout a reflecting point for lightning surges. As a result of this there may occur flashovers between the cutout terminals. with danger of damage-t0, or even complete destruction of, the cutout casing or other insulating suppo This danger exists I also in cases where fuse cutouts are employed for line sectionalizing p rposes and the circuit between the terminals is left open due to fuse operation. Itis a principal object of the present invention to provide, in a fuse cutout, simple and economical, yet reliable, protective means for preventing flashover and damage to the cutout due to lightning surges.

A more specific object .of the invention is the provision of a unitary protective assembly, ineluding a fuse and lightning protection means therefor, which may be substituted readily for an unprotected fuse assembly in an existing cutout installation without disturbance or alteration of the cutout support.

Other objects and the details of that which I consider to be novel and my invention will become apparent from the following description and the claims appended thereto, .taken in con- Junction with the accompanying drawing in which Fig. 1' shows an exemplary embodiment of the invention as applied to a fuse cutout of the enclosed type, and Figs. 2 and 3 are sectional views along the line 2-2 and 3-3 of Fig. 1. Although the invention is illustrated and will be. described herein as applied particularly to a cutout of the enclosed type, it is to be understood that the invention in its broader aspects is not limited to the details lar form of cutout disclosed and is applicable also to cutouts of the open type.

The cutout casing ll shown on the drawing is of a form well known in the art and heretofore commonly employed in cutout installations-incorporating only a single fuse holder or disconnect is constructed of porcelain or blade. This casing respectively of the particuother suitableinsulation and is formed with electric creepage and gas barriers l I and I2. Mounted in the casing are upper and lower terminal contacts it closed and claimed in my Patent 2,011,391, issued Augu t 13, 1935, and assigned to the assignee of the present invention. Each element It has two sets of prongs designated l8 and I9. Prongs l9 have lugs engaging recesses.

in the inner faces of the side walls of Casing It for supporting the contact assembly. Prongs l8 serve as backing strips for the contact fingers of element l6 and serve also as latching fingers in a manner which will become apparent hereinafter. The contact assembly includes also a base member 2| secured to elements II and I! by rivets l1 and provided with a clamping member 22 for securing to the contact assembly a line conductor or lead inserted through an opening 23 in the side wall of the casing. The open front of the casing is closed by means of a door 25, of suitable insulation material, which is pivotally mounted at its lower end on removable studs 28 carried by projections at the lower end of the casing. The door has an eyelet handle 21 for manipulation thereof to and from closed position and has also barriers 28 arranged for cooperation with the barriers H and I2 of the easing.

On the inner face of door is mounted a protective assembly including a fuse holder and ex-. pulsion gap interrupting device. The fuse holder is of a common form including an expulsion arcing tube 30, of insulation, having a contact sleeve 3| mounted on the upper end thereof. .Within the fuse holder is disposed a fuse link, generally designated 32, the button-head upper terminalof which is secured in place by a removable cap 38, and the lower cable extension 24 of which fuse link projects out of the lower end of tube Ill.

The expulsion gap interrupting device ha a double walled tube of insulation'upon the upper end of which is threaded a terminal can 36. Within this tube is disposed a rod electrode 31 having a buttonhead terminal 38 secured in placeby cap 38. A second electrode in the form of a metallic sleeve 39 is disposed within and adjacent the lower end of tube 35. The electrodes?!-v and 39 are arranged in spaced relationship as illustrated, so as to provide an arcing gap within and H respectively of the form dis-.

the tube 35, and the sleeve form of electrode 39 provides for discharge of gases from the tube.

The upper ends of the fuse holder and the expulsion gap interrupter are secured together and 3 over when the circuit isopen between its con- I tacts by reason of fuse operation.

With the arrangement described it is not essential to provide a gap in series with the expulsion gap interrupter since, under normal operation, the fuse link is in the circuit so that the voltage across the terminals of the gap is very low. Thus there is not the danger, present in some expulsion gap interrupter installations, of creepage between the gap electrodes with -rcsultant progressive carbonization of the tube two devices in parallel juxtaposition. This clamp is secured to tube 35 and electrically connected with sleeve electrode 39 by means of screws 3. The two tubes are maintained in properly spaced relationship by means of a notched sleeve 4| sup-- ported on a thumb-screw 45 extending between and supported by downwardly projecting spaced extensions 46 of clamp 42. One end of thumbscrew 45 is provided with a flange M for clamping fuse link extension 34 to clamp 42.

The protective assembly just described is removably secured to the inner face ofdoor 21 by quick detachable means in the form of resilient metallic clips 50 and Clip 50 is secured to the door adjacent the upper end thereof by means of molded-in inserts 52 and has an opening 53 for engagement with the terminal cap 33 on the fuse holder. Clip Slis U-shaped and is secured to the door adjacent the lower end thereof by a molded-in insert 55. The spaced resilient arms of clip 5| have knobs 55 engageable with sockets in clamp Q2, as will be seen best from Fig. 3, to latch the lower end of the protective assembly to the door. The protective assembly is readily attached to the door by first of the interrupter.

One of the important features of the arrangement in accordance with my present invention is that the tubes of the fuse and the expulsion gap interrupter are supported in alinement parallel to the rear face of the door. By reason of this, the protective assembly is adapted to fit into standard cutout casings originally designed for accommodation only of a single fuse assembly. Thusit is possible to replace an unprotected single fuse assembly with a new cover having attached thereto the protective assembly hereinbefore described. Increased protection may thereby be secured with little additional expense since dismounting or alteration of the cutout casing or other support is not required.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric cutout, the combination with an insulating support having a pair of spaced inserting cap 33 into opening 53 in upper clip' 50, soas to latch the upper end of the assembly, and then pressing the lower end of the assembly into latching engagement with lower clip 5i. Thus the clips 50 and 5t serve to hold the assembly securely in position as shown.

When the door is closed, contact fingers it of the upper stationary contact assembly engage the sides of contact sleeve 3!, as shown in Fig. 2, to effect electric connection with the upper end of the protective assembly, and inwardly bent portions of prongs i8 engage the spaces between sleeve 3| and cap 36 to latch the upper end of the protective assembly in operative position. At the same time the contact fingers of element I6 and the prongs B8 of the lower stationary contact assembly engage clamp 32 to effect electric connection with the lower end of the protective assembly. Thus the circuit between the stationary contacts is completed through fuse link 32.

In case the fuse link blows upon excess current, the resultant open circuit condition between the stationary contacts would render the cutout subject to fiashover between the stationary contacts due to lightning surges were it not for the provision of the expulsion gap interrupter. However, with the arrangement of the present invention, the expulsion gap interrupter provides an impulse current discharge path between the stationary contacts and the terminals of the protective assembly. The spacing between the electrodes Zil and 39 is so arranged that breakdown of the gap therebetween will occur before flashover between the stationary contacts or between external conductive parts of the protective assembly. Thus the cutout is at all times protected from damage due to flashline terminal contacts mounted thereon, and a fuse assembly carried by said support and including a fuse link electrically connected between said contacts; of an expulsion gap interrupter including an expulsion tube having spaced electrodes providing a discharge gap in the tube and having spaced terminals for said electrodes, means supporting said interrupter with its said terminals in electric association respectively with said contacts, and means including said terminals and electrodes operative to provide a lightning impulse discharge path interconnecting said contacts by way of said gap and tube when the circuit be-,

tween the contacts is open due to rupture of said fuse link.

2. In an electric cutout, the combination with an insulating support having a pair of spaced line terminal contacts mounted thereon, of an electric protective assembly detachably mounted on said support and comprising a pair of spaced terminals for connection respectively with said pair of contacts, a fuse electrically connected between said terminals, an expulsion gap interrupter including an expulsion tube having spaced electrodes providing a discharge gap in ,the tube, common supporting means for said fuse and interrupter, and means cooperative with said electrodes to provide a lightning impulse discharge path interconnecting said terminals by way of said gap and expulsion tube when the circuit between the terminals is open due to operation of said fuse.

3. In an electric cutout, the combination with an insulating support having a pair of spaced line terminal contacts mounted thereon, of an electric protective assembly comprising a tubular fuse holder having a fuse link therein, an expulsion gap interrupter including an expulsion tube having spaced electrodes providing a discharge gap in the tube, means common to said fuse holder and expulsion tube for detachably mounting the assembly on said insulating support, spaced terpulsion gap minals for said fuse link arranged for connection respectively with said contacts, and means connecting said electrodes respectively with said terminals.

4. In an electric cutout, the combinationwith an insulating casing having a pair of spaced line terminal contacts therein and a door for the casing, of an electric protective assembly supported on the inner side of said door and comprising spaced terminals for the assembly arranged for connection respectively with said contacts, a fuse electrically connected between said assembly terminals, an expulsion gap interrupter including an expulsion tube having spaced electrodes providing a discharge gap in the tube and having spaced terminals for said electrodes, which said electrode terminals are electrically associated respectively with said assembly terminals, and means including said electrode terminals and electrodes operative to provide a lightning impulse discharge path interconnecting said assembly terminals by way of said gap and expulsion tube when the circuit between the assembly terminals is open due to operation of said fuse.

5. An electric protective unit comprising in combination, a door adapted to close an open side of an electric cutout or like casing, a fuse, a pair of spaced terminals for said fuse arranged for connection respectively with a pair of spaced contacts in a cutout or like casing, an expulsion gap interrupter including an expulsion tube having spaced electrodes providing an arcing gap in the tube, means supporting said fuse and interrupter on the inner side of said door, and means cooperative with said electrodes to provide a lightning impulse discharge path interconnecting said terminals by way of said gap and expulsion tube.

6. An electric protective unit comprising in combination, a door adapted to close an open side of an electric cutout or like casing, a fuse, an exinterrupter including an expulsion tube having spaced electrodes providing an arcing gap in the tu means common to said fuse and interrupter detachably supporting the fuse and interrupter on the inner side of said door, a pair of spaced terminals for engagement respectively with a pair of spaced contacts in a cutout or like casing, means connecting said fuse between said terminals, and means connecting said electrodes respectively with said terminals.

7. An electric protective unit comprising in combination, a door adapted to close an open side of an electric cutout or like casing, a tubular fuse holder having a fuse link therein, an expulsion gap interrupter including an expulsion tube having spaced electrodes providing an arcing gap in the tube, means clamping said holder and tube in non-coaxial substantially parallel juxtaposition to form a unitary assembly, means detachably securing said assembly to the inner side of said door, a pair of spaced terminals for said assembly arranged respectively to engage a pair of spaced contacts in a cutout or like casing, means connecting said fuse link between said terminals, and means connecting said electrodes respectively with said terminals;

8. An electric protective unit comprising in combination, a door adapted to close the open front of an electric cutout or like casing, a tubular fuse holder having a fuse link therein, an expulsion gap interrupter including an expulsion tube having spaced electrodes providing an arcing gap in the tube, spaced terminals for engagement respectively with spaced contacts in a cutout or like casing, means connecting said fuse link between said terminals, mean connecting said electrodes respectively with said terminals, and means supporting said fuse holder and expulsion tube in non-coaxial substantially parallel extending juxtaposition on the inner side of said door with the axes of the holder and tube substantially in alignment in a plane perpendicular to the rear face of the door.

9. An electric protective unit comprising in combination, a first circuit interrupting device including a tubular insulating holder and conductive means therein operable to interrupt current flow in the holder, a second circuit interrupting device structurally separate and distinct from said first device and including an expulsion tube having spaced electrodes providing a surge gap in the tube, means common to said devices for supporting the same removably on an insulating support, and a pair of spaced terminals designed for engagement respectively with spaced contacts on such insulating support, which said terminals are electrically connected respectively with the opposite ends of said conductive means and also are electrically connected each with a respective one of said electrodes.

- RALPH S. BENNE'I'I'.