US1947321A - Arcing horn for insulators - Google Patents

Description

Fb- 13, 1934- H. B, VINCENT Er AL 1,947,321

RCING HORN 4FOR INSULATORS Filed May 26, 1926 2 Sheets-Sheet 1 Feb. 13, 1934. H. B. VINCENT Er AL.

ARCING HORN FOR INSULATORS Filed May 26. 1926 2 Sheets-Sheet 2 Patented Feb. 13, 1934 UNITED STATES PATENT OFFICE ARCING HORN FOR INSULATORS Application May 26, 1926. Serial No. 111,821 401mm. (c1. 17a-31s) Our invention relates to insulator protection, and particularly to arcing horns of novel construction and operation, between which a ashv over arc plays. The object of our invention is to I provide 1) arcing horns with end surfaces which establish high speed sphere gap characteristics between them, (2) arcing horns of such shape that they may be more closely spaced than those hitherto used, (3) means for adjusting the span between the horns at one end of the insulator string, (4) means for varying the spacing between the horns at opposite ends of the string, (5) horns of such character that on flasheover the arc tends to travel away from the insulator string, (6) various features of detail which will be more particularly pointed out in the following specifi cation or shown in the accompanying drawings in Which- Fig. 1 is a side elevation of a vertically arranged suspension insulator string to which our invention is applied in one form;

Fig. 2 is a side elevation of a horizontally arranged insulator string to which our invention is applied in another form;

Fig. 3 is a detail elevation view of one of the horn terminals;

Fig. 4 is a section on the line 44, Fig. 3; and

Fig. 5 is a side elevation of a modified terminal construction.

It has heretofore been proposed to protect multi-unit insulators of the suspension, link or Hewlett type against the play of an arc on flashover, by providing arcing horns at opposite ends of the string. These horns as heretofore used have commonly comprised crescent shaped castings or bars of substantially cylindrical or rectangular cross-section, and generally tapering toward their free ends to more or less of a point. Horns of this type must be spaced fairly far apart 0 by reason of the corona formation at their tips, and the resulting ionization of the air in the neighborhood thereof which reduces the flashover value of a given spacing. This distant spacing of the horns increases the likelihood that on flash-over the arc will play, not upon the horns, but upon the insulator suspension elements, and that the arc will even cascade into the insulator intermediate its ends and play upon and rupture the links by which the insulator units are connected, thus in either case, endangering the suspension. Moreover, with arcing horns of this shape there is no tendency to cause the arc to move away from the insulator. Again, as these horns have been previously made, they are commonly of one piece and non-adjustable in their spacing.

Our invention provides a horn construction such that corona formation is reduced, if not entirely prevented; the spacing between the horns at opposite ends of the insulator may be substantially reduced without lowering the dash-over value ci the setting; the arc is automatically caused to move away from the insulator on flashover the horns at the liney end of the insulator may be spaced further from the insulator than those at the suspension end; the horn terminals are adjustable with respect to their supports to permit a variation in spacing; the horn terminals are independent of their supports and are thus replaceable in case of injury, without disturbance of the support or the discard of uninjured portions of the horn.

Referring to Fig. 1, we have illustrated a multiunit suspension insulator 15, the several insulator units of which are interconnected by means of metallic links 16. Terminal fittings 17 and 18 at the upper andlower ends, respectively, of the string are engaged by a suspension eye 19 and line clamp 20, respectively. The eye 19 may be engaged in any suitable Way with the cross arm (not shown) of a supporting structure, while the clamp 20 engages the table 21 in the usual fashion.

The arcing horn to which our invention particularly relates, comprises a supporting bar 22 pierced adjacent each end by a series of holes 23 to receive the Shanks of the bolts 24 by which the arcing terminals are secured to the bar. Each terminal comprises an arm 25 having at one end a foot piece 26 adapted to lie along the bar 22 and pierced to receive the shank of the bolt 24. At its opposite end the terminal arm 25 is provided with a terminal head or tip 27 which is convex on the face thereof remote from the bar 22. The terminal head 27 may conveniently he cupped for lightness, but this is not essential to our invention.

The supporting bar 22 may be secured in any suitable fashion to the terminal fittings 17 or 18 with the convex faces of the horn tips 27 faced toward each other at opposite ends of the insulator string. We prefer to form the bars 22 from fiat stock, the mid-portion being twisted to lie flat against the sides of the terminal fittings 17 and 18. Cross bolts 28 having square Shanks pass through squared apertures in the bars and fittings, thus holding the bars rigid with respect to both fittings. Under service conditions the bars are thus held in parallelism while the insulator as a whole is free to swing upon the eye 19 without altering the relation between the parts.

It will be noted that the spacing between the tips 27 of the horn at the suspension end of the insulator is less than the spacing between the tips 27 of the horns at the line end of the insulator. This has the eifect not only of protecting the cable 21 against the play of the arc, but also of causing the arc to form at an angle to the longitudinal axis of the insulator string. As a result the arc, after formation, tending as usual to rise, will be caused automtically to follow the inclination of the terminals 27 faced away from the insulator, and consequently will be automatically attenuated and extinguished by reason of the gradually increasing distance between the surfaces of the terminals on which the arc attempts to play. The arc is thus automatically drawn away from the insulator, attenuated and extinguished.

By reason of the fact that the areas of the arcing tips 27 are of considerable extent and spherical or spheroidal, the play of the aro is not concentrated upon a single point, but travels and spreads, thus reducing the likelihood of heat injury to the tips. Moreover, the volume of metal at the tips absorbs and dissipates the heat of the arc.

It is well known that the time lag in a gap formed between rounded or large flat surfaces is very small. Thus a gap between rounded or spheroidal surfaces, especially if of large extent, gives a high speed break down. It is also well known that corona is evidence of the ionization and the beginning of the breaking down of an air gap. Corona forms easily at points but not easily at rounded surfaces and very reluctantly around spheroidal surfaces. Now, it has been found that the time lag in a gap between the points is large as compared to that between rounded or spheroidal surfaces. Hence, spheroidal surfaces may be placed much closer together than pointed surfaces with no greater danger of the air breaking down and an arc forming. Thus by making the free ends of our arc horns of considerable extent and spheroidal in shape, a gap is established having the characteristics of a high speed break down and little or no corona formation.

In Fig. 2 the invention is applied to a horizontally arranged insulator 29. The supporting bars 30 of the horns extend in only one direction from the terminal fittings 17 and 18 and carry each but a single horn tip 31, the latter being secured to the bars 30 in like manner as in the construction above described, and of similar shape.

While the spacing between the arcing tips at opposite ends or the string may be effected by utilizing tip arms of diierent lengths, the arms may be made adjustable in length as illustrated in Fig. 5. Thus the tip arm is divided into a foot section 32 and a tip section 33. The foot section is adjustably secured by bolt 24 to the bar 22, and is itself pierced at its free end to afford adjustabln connection, by means of bolt 34 to the tip sections. The tips are thus not only adjustably spaced apart on the horn bar, but means are provided for adjusting the arcing span between the horns at opposite ends of the insulator.

With the understanding that the particular constructions shown are merely illustrative of the thoughts which underlie our invention, and that the latter may be embodied in many modified shapes, without departing from what we claim as our invention, we claiml. An arcing horn for a high tension insulator comprising a twisted flat bar, and an independent arcing terminal having a supporting arm adapted to be bolted to said bar, and provided at its free end with a concave-convex terminal area of materially greater width than its supporting arm, the concave surface of the terminal being faced toward said bar.

2. An arcing horn comprising a flat metal bar twisted at its ends and perforated for attachment to an insulator iitting, in combination with independent arcing terminals having supporting arms adapted to be clamped to the opposite ends of said twisted metal bar.

3. An arcing horn comprising a iiat metal bar twisted at its ends and perforated ior attachment to an insulator iitting, in combination with independent arcing terminals having supportng arms adapted to be adjustably clamped to the opposite ends of said twisted metal bar.

4. An arcing horn comprising a flat metal bar perforated for attachment to an insulator fitting and having end portions twisted with respect to the perforated portion, in combination with independent arcing terminals having supporting arms adapted to be clamped to the opposite end portions of said twisted metal bar.

HAROLD BLANCHARD VINCENT.

HAROLD P. SLEEMAN.

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