US2103366A - Arcing gap - Google Patents

Description

DEGo 28, 1937. R g g 2,133365 ARCING GAP Filed July 27, 1935 2 Sheets-Sheet l l @a i Fig. 1

INVENTOR fia/ph Higgins i ATToRN l flea 28, 19370 5%. HKGGINS 2,103,365

ARCING GAP Filed July 27, 1935 2 Sheets-Sheet 2 INVENTOR fia/ph Higgins Patented Dec. 28, 1937 PATENT OFFICE ARCING GAP Ralph Higgins, Akron, Ohio, assignor to The Ohio Brass Company, Mansfield, Ohio, a corporation of New Jersey Application July 27,

6 Claims.

This invention relates to arcing gaps for protecting electrical apparatus from excessive voltage and is illustrated as applied to a gap similar to that disclosed in Patent No. 2,011,136, granted '5' August 13, 1935.

One object of the invention is to provide means for quickly interrupting the arc across the gap before the current flowing in the arc has time to trip the main circuit breakers.

A further object of the invention is to provide an arcing gap equipped with arc interrupting mechanism in which the action of the interrupting means does not interfere with the operation of the gap for recurrent surges.

' A further object of the invention is to provide an arcing gap having means connected therewith for automatically interrupting the are after each of a series of recurrent operations of the gap. A further object of the invention is to provide an arcing gap equipped with arc interrupting means adapted for repeated operation, the gap being operative to protect the connected apparatus even after the interrupting means has been exhausted by repeated operations.

A further object of the invention is to provide a device of the class named which shall be of improved construction and operation.

. Other objects and advantages will appear from the following description.

1 The invention is exemplified by the combination and arrangement of parts shown in the accompanying drawings and described in the following specification, and it is more particularly pointed out in the appended claims.

' In the drawings:

Fig. 1 is a diagrammatic view illustrating one embodiment of the invention.

Figs. 2 and 3 are views similar to Fig. 1 showing other forms of the invention.

Fig. 4 is an elevation of arcing gap apparatus showing one embodiment of the form of the invention illustrated diagrammatically in Fig. 3.

Fig. 5 is an end view looking from the right in Fig. 4.

Fig. 6 is a fragmentary top plan view of the arc extinguishing portion of the apparatus shown in Fig; 4.

The primary function of a control gap, such as that shown in the Austin patent referred to above,

150 is to relieve the high tension line to which it is connected of abnormal lightning and switching surges before such surges have done serious damage. Sometimes, in order to afford adequate protection against insulation breakdown or flash- 55 over of station equipment, it is necessary to set the 1935, Serial No. 33,533

gap quite low. Naturally a low setting of the gap will cause it to function quite frequently. With one terminal of the gap solidly grounded, each operation of the gap requires the power are, which follows flashover of the gap, to be interrupted by the operation of one or more of the main line circuit breakers. The operation of the line circuit breakers is sometimes very objectionable, especially when large blocks of power are involved and when interruption of power service entails great losses to the customers. Also, on some lines that are not equipped with suitable ground relays or high speed over-load relays, the main circuit breakers will often require some time before they will open. In such cases the long duration of the power are is apt to do considerable damage to the arcing tips and other parts of the gap.

To overcome these difficulties, the present invention provides a high voltage fuse or some other H quick acting circuit breaker in series with the control gap to clear the control gap before the main line circuit breakers have a chance to open and before the arc can do any damage to the gap parts. If such a fuse or quick operating circuit interrupter were used alone in series with the control gap, the gap would no longer be solidly grounded after operation of the interrupter and thus should another surge follow immediately, before the fuse can be renewed, which happens quite frequently, the control gap would be inoperative and the desired protection would not be afforded.

To overcome this diificulty, the present invention provides an arrangement which is shown diagrammatically in simple form in Fig, 1. In this figure a control gap 10 is provided with a fuse l I in series with the control gap and be tween the control gap and ground. A relief gap I2 is connected in parallel with the fuse H, the

gap I2 being set just high enough that normal voltage will not cause it to arc over after the fuse ll blows. A condenser I3 is connected in parallel with the fuse II and gap l2. If the gap I2 alone were used in parallel with the fuse il, it is apparent that after the fuse I l blows, there would be two gaps l0 and I2 in series between the line and ground. This arrangement, of course, would require a higher voltage to produce a flashover than is required with the fuse H intact. The purpose of the condenser I3 is to avoid this change in the arcing voltage of the gap due to the opening of the fuse II. It has been found in practice that a condenser [3 of proper capacity, in parallel with the gap l2, will supply sufficient charging current to the gap E to maintain the fiashover voltage of the gap l6 substantially constant, notwithstanding operation of the fuse II. It is not desirable to have the capacity of the condenser l3 too great as too high a capacity in this condenser tends to maintain a sputtering arc across the gap If? after the fuse H has interrupted the power arc. On most sizes of control gaps for various ratings, it has been found that a capacitance of .0003 microfarad is sufficient to maintain a substantially uniform operation of the gap lll'with any practical gap l2 in series with the gap l0 and with the fuse H in place or out. The arrangement shown in Fig. 1 insures .continuous protection of the apparatus connected with the gap i 0, notwithstanding operation of the fuse I i to interrupt the power are following flashover of the gap l0. It will be apparent; however, that after one operation of the fuse il there is nothing to interrupt a second power are in case fiashover occurs a second time before the fuse l l hasbeen'replaced. However, the arrangement shown in Fig. 1 would operate satisfactory in' all cases except those where a second surge follows closely after the first and before the fuse H can be replaced. Even in that case the device affords protection for the apparatus since the'second surge will flashover the gap l0 and the series gap 12-, at substantially'the same voltage as the original flashover, but in the case of the second surge, before replacement of the fuse H, reliance will have to be placed upon the main line circuit breaker to interrupt the power arc.

To further reduce the number of possible interruptions, the arrangement shown in Fig. 2 may be used. In this figure a setof any number 7 of fuses I4, i and 16 are arranged for successive connection in parallel with the gap 12. A number of different repeating fuse arrangements are available to the trade at present, most of which are operated by a mechanical throw-over switch which automatically operates, when one fuse blows, to connect in an unblown fuse. Such a switch is indicated diagrammatically at H. With this arrangement of multiple fuses, it is still desirable to provide the relief gap 12 and condenser 13 to insure protection of the apparatus after the last of the multiple fuses has been exhausted. It is also desirable to employ the gap l2 and condenser l3 .to insure protection during, the time required for the switch to connect in the nextfuse after one has blown. The operation of any'switch requires an appreciable time and it sometimes happensthat a second surge follows so quickly after the first that theintervening time does not permit the connection of the next fuse in the set. With the arrangement shown in Fig. 2, including the condenser 13 and the relief gap l2, the apparatus is afforded protection even though the second surge should follow so quickly that no time is provided for operation of the switch IV. In case of such operation if the switch gap is less than the gap l2, the arc-over will occur across the switch gap and through the next adjacent fuse so that the fuse will. operate to break the power arc even though the switch has not yet been closed. If a solid ground connection were provided in place of the last fuse Hi, the gap 12 would not be, necessary but the condenser i 3 would still be required to supply "charging current and maintain the calibration of the gap in case a surge that blows a fuse is followed immediately by another before the switch has connected in the next adjacent fuse, for during the time the s'wit ch'is open it forms a'second gap in series with '1, 2 and 3.

the main gap that would increase the fiashover' voltage except for the presence of the condenser l3.

Another repeating fuse arrangement is shown in Fig. 3. In this arrangement no reclosing switch mechanism is required but each fuse has a series gap somewhat shorter than the auxiliary gap i 2. With this-arrangement, it is'readily seen that irrespective of the time interval between repeat surges, the next fuse is always ready to function. The gap 2| in series with the fuse l8 can be made very short or may even be omitted or bridged since after the operation of the first fuse 18, the. fuse gap itself will be sufficient to prevent arcing across the fuse gap on the normal linevoltage imposed upon the fuse gaps by an arc across the gap I0. It is not absolutely essential to have the gaps 22 and 23 of unequal length. However, it is preferred to have them' somewhat different in length in order to insure that both will not operate at the same instant, which may be possible on some extreme, heavy lightning strokes. r I

Fig. 4 shows the'arrangement illustrated'diagrammatically in Fig. 3 applied to a practical form of arcing gap of the type shown in Austin patent referred to above. In this figure the numeral 24 designates the mounting for the ter minal of the gap connected by any suitable means 25 to the line to be protected. The terminals 26 and 27 of the gap are provided with control members 28 for adjusting the gap to various op erating conditions. The mounting 24 is supported by insulators 29 carried by a grounded base 30. The terminal 2! is carriedby a suitable head 3| mounted upon a condenser 32 which also serves to insulate the head 3| from ground. The, condenser 32 corresponds to the condenser 13 shown in Figs. 1, 2 and 3. The lower terminal of the condenser 13 is grounded through its supporting standard 33 which is provided with an arcing horn 34. V

The head 3! is provided with a plurality of arcing horns 35,36 and 31 which cooperate respectively with horns 38, 39 and 40 connected to the terminals of fuse members 4|, 42 and 43. The gaps between the horns 35, 36 and 3! and their respective fuse members are of varying lengths, the gap between the centralimembers 36 and 39 being the greatest. The horn 34 is in the same vertical plane with the horns 36 and 39 and forms'a gap between the horn 36- and ground which is in parallel with the various fuse members andrwhich corresponds to the gap l2 inFigs.

and the members 34 and '39 respectively have substantially the same electrostatic field conditions so as to insure arcing of the gap 36- -39 ahead of the longer gap 36-34 to ground. It will be seen that the fuse members 4|, 42 and 43 are mounted upon'a hinged head 44 which may be swung backwardly into the position shown in broken lines in Fig. 4 to facilitate renewal of the fuses without danger to the operator. A grounding arm 45 is preferably connected to the head 44 in position to engage one of the arcing horns when the head 44 is rotated into its inoperative position. This grounds the head 3| and its connected parts to insure protection to the operator during renewalof the fuses. been found desirable to have the-individual :fuse gaps made 'of rod or bar ends similar to that of theauxiliary relief gap in order to eliminate any polarity or over-voltage effects which would be The gaps between the member 36 It has "1 liable to cause. dissimilar gaps to operatein an improper sequence. The operating head 44 for the fuse gaps is mounted on a grounded shaft which may be rotated by any suitable mechanism without endangering the operator. Since the condenser 32 serves the double purpose of condenser and insulating support for the terminal 21, the cost of a gap provided with a condenser is very little greater than a similar gap with the usual insulation for the terminal 21.

The flashover voltage of the condenser 32 need be only slightly greater than the fiashover voltage of the auxiliary gap between the members 34 and 35.

I claim:

1. In a surge arrester the combination with an arcing gap, of a circuit interrupter adapted, when open, to provide an open break in the circuit in which it is connected, said interrupter being electrically connected between one terminal of said gap and ground, and a condenser in parallel with said circuit interrupter between said terminal and ground for supplying charging current to said arcing gap when said circuit interrupter is open, the capacitance of said condenser being insufficient to produce efl'ective reduction in the crest of a surge voltage causing discharge across said gap, but the resistance of the path through said circuit interrupter being low enough to divert the major portion of the surge current from said condenser and to provide a substantially direct ground for said current.

2. In a surge arrcster the combination with an arcing gap, of an overload circuit interrupter adapted, when open, to provide an open break in the circuit in which it is connected, said interrupter being electrically connected between one terminal of said gap and ground for interrupting the power are following operation of said gap, and means for enabling said gap to operate at approximately the same voltage irrespective of whether said circuit interrupter is open or closed, said means comprising a condenser in parallel with said circuit interrupter the capacitance of said condenser being not materially more than .0003 microfarad, while the impedance of the path through said circuit interrupter is comparatively, substantially negligible.

3. The combination with an arcing gap, of a circuit interrupter in series with said gap between one terminal of said gap and ground, a condenser in parallel with said circuit interrupter, and an auxiliary gap in parallel with said circuit interrupter and said condenser.

4. The combination with an arcing gap, of a circuit interrupter in series between one terminal of said gap and ground, a condenser in parallel with said circuit interrupter, and an auxiliary gap having a lower flashover value than said condenser in parallel with said condenser and circuit interrupter.

5. The combination with an arcing gap, of an overload circuit interrupter in series between one terminal of said gap and ground, a condenser of approximately .0003 microfarad in parallel with said circuit interrupter, and an auxiliary gap of a lower fiashover value than said condenser in parallel with said condenser and circuit interrupter.

6. Means for protecting electrical apparatus from over-voltage impulses comprising an arcing gap having one terminal connected with said apparatus, said gap being adapted to determine the over-voltage impulse at which discharge will occur, a second gap in series with said firstnamed gap, and a condenser in parallel with said second gap providing capacity between its terminals sufiiciently in excess of the capacity between the terminals of said first-named gap so that the predominate portion of an impulse voltage impressed on said gaps in series will be apportioned to said first-named gap to produce fiashover at approximately the same voltage as if said condenser were a grounded conductor.

RALPH HIGGINS.

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