US3159765A - Lightning arrester spark gap - Google Patents

Description

Dec. 1, 1964 Filed March 10, 1961 INVENTORS. flaw/m? 4. 5mm? fikza J Sam/.47;

2mm VFW United States Patent 3,159,765 LHGHTNENG ARRESTER SPARK GAP Fred .l. Schuitz, Nilwaukce, and Edward lb. Sankey, Oat: Creek, Wis assiguors to McGraw-Edison Company, Milwaukee, Wis, a corporation of Delaware Fiicd Mar. 10, 196i, Ser. No. 94,812 7 Claims. (Cl. 315-65) This invention relates to lightning arrestors generally and more particularly to the spark gap component of lightning arresters.

Valve type lightning arresters in general comprise a series gap which normally electrically isolates the device from the line but which sparks over when a suiiiciently high voltage is impressed across the gap, and a valve element in series with the gap. The most commonly utilized valve element is a negative resistance element which evinces a high apparent resistance at low voltages but a low apparent resistance upon relatively high current flow therethru. The function of the valve element is to provide a path to ground during surge voltages and to limit the flow of follow current, subsequent to the surge discharge, to a value that the series gap can interrupt.

in recent years great advances have been made in lowering the IR drop across the valve element. While this is a particularly advantageous situation during surge discharge it also serves to increase the magnitude of allowable follow currents. Consequently more and more dilficulty has been experienced in the design of Spark gaps which will interrupt the increased follow currents. It has been found that simple spark gaps will no longer perform the required current interruption.

Various means have been designed to supplement the interrupting ability of a simple gap. These means serve to constrict, elongate, and split the arc between the spark gap terminals. By and large the above effects on the are are initiated by magnetic means, i.e., the coil or permanent magnet utilized serves to force are motion in a predetermined manner.

In particular, when coils are utilized to obtain magnetic flux in order to force are motion, the coil itself is subjected to high overvoltages due to the surge current. Quite frequently these high overvoltages cause irreparable harm to the coil thereby rendering the arrester completely inoperable and/ or possibly causing permanent line lockout.

We have designed a spark gap structure which will not be subject to the damaging effects of high overvoltages.

It is therefore an object of this invention to provide an improved lightning arrester having means for protecting the arc motion initiating device from damaging overvoltages. I

Another object of this invention is to provide a simple and inexpensive means of protecting the arc motion initiating device which involves no moving parts.

Another object of this invention is to provide a spark gap structure which is compact in design.

A further object of this invention is to provide a spark gap structure with improved current interrupting ability and with improved self-protective characteristics.

Other objects and advantages of our invention will be apparent from the following description of the preferred embodiment of the invention taken in connection with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a portion of the invention;

FIG. 2 is an elevation view, partially in section, of a valve type lightning arrester embodying a spark gap arrangement in accordance with the invention;

P16. 3 is a cutaway plan view of the invention;

FIG. 4 is a view in elevation of the complete assembly of FIG. 3; and

same Patented Dec. 1, 1964 FIG. 5 is a partially cutaway view in elevation of a slightly modified device.

Referring now to the schematic diagram of FIG. 1, 1i) and 11 are spaced apart electrodes. The spaced apart electrodes 10 and 11 are so shaped that they first converge relative to one another and then diverge. The least distance between the two electrodes defines a spark gap 12. The electrode 10 is connected directly to the line (L) while the electrode 11 is connected to ground (G) thru a valve element 9 which may have a negative resistance characteristic.

An electrical coil 13 or similar are moving means is connected to the line electrode 10 as shown in FIG. 1. In series with the coil 13 is an auxiliary electrode 14 which has a portion 14 which extends between the electrodes 10 and 11. Since the end of the electrode portion 14 is not in contact with either of the electrodes 1%) and 11 two air gaps 15 and 16 exist, respectively, between the electrode portion 14 and the divergent surface of electrode 16 and between the electrode portion 14 and the divergent surface of electrode 11. It can therefore be seen that the coil 13, electrode i4, and gap 16 constitute a current path which is in parallel with the basic path between electrodes 19 and 11.

During a surge such as a lightning stroke the spark gap 12 sparks over and a path to ground is created. Subsequently 60 cycle follow current flows thru the electrode 10, gap 12, electrode 11 and to ground. Due to the divergent relation of the electrodes 16 and 11 and as a result of the magnetic interaction of the arc and current in the electrodes 16 and 11, the arc is moved outwardly between the electrodes 10 and 11 thereby elongating same. When the follow current are is moved a su'tiicient distance outwardly between the electrodes 10 and 11 it will transfer to the auxiliary electrode portion 14, i.e., arcs will exist between electrode lit and portion 14 and between portion 14 and electrode 11. Upon transfer of the arc to the electrode 14 (portion 14') follow current is transferred thru the coil 13 causing a great increase in the flux density and force on the arc. Since the coil 13 is now in the circuit a greatly increased magnetic flux density is created which can be used to constrict, split, elongate or otherwise manipulate the arc in order to expedite its interruption.

it is apparent from the above description that the coil 13 is protected from high overvoltages since it does not appear in the circuit until the surge has passed and 60 cycle follow current is flowing. This then is one aspect of the invention.

In FIGURE 3 an operative form of the invention is shown which is basically similar to FIGURE 1. The device of FIGURE 3 includes a relatively fiat insulating housing 17 having a plurality of inwardly extending finger projections 18. The inwardly extending fingers 18 may be a portion of the insulating housing 17 or they may be metallic or otherwise conducting portions. The different construction of the fingers It) involves somewhat difierent modes of operation which will be discussed subsequently. An inwardly extending line 1h is connected to the electrode 1i and a line to ground 2b is connected to the electrode 11'. The electrode 11 is generally V-shaped and first converges with respect to the electrode 10 and then diverges with respect thereto finally culminating in an area adjacent the periphery of the housing 17. The electrode 14 extends inwardly from the periphery of the housing 17 toward the center thereof and culminates in a portion 14 which is juxtaposed between portions of the electrodes iii and 11. As before a coil or similar means 13 is positioned in a circuit parallel with the gap 12 and in series with the auxiliary electrode 14.

The gaps l5 and 12 are so co-ordinated that in operation during a surge, only gap 12 sparks over between the electrodes Hi and 11. Subsequently, 60 cycle follow current flows and due to the configuration of the elec trodes and as a result of the magnetic interaction of the arc and the current in the electrodes the arc is moved outwardly between the electrodes it? and 13 until it con tacts the portion id of the auxiliary electrode 14, at which time the follow current are exists between electrode 1i) and portion 14 and portion 14 and electrode Ill. It will be noted that the original arc path across the gap 12 is generally normal to the direction of the current path in each of the electrodes lit) and 11. It is the inherent magnetic effect of the current flow itself which aids in moving the arc outwardly along the electrodes. When the electrode 14 becomes a part of the arcing circuit the arc volt-age drop in gap l5'is of such a magnitude as to cause current to transfer through the path including the coil 13. Therefore the coil 13 is inserted into the circuit, the are 15 becomes unstable and self-extinguished, and a current path exists through line 19, electrode 14, electrode f1 and through line 2-9 ultimately to ground.

Since the coil 13 is now operating on the are it (the arc) may be elongated and deformed to the extent that the termini thereof are moved along the surface of the electrodes 14 and if. toward the periphery of the housing 1.7. As the arc becomes elongated it conforms to the inner periphery of the housing 17 and is further elongated in that it extends up one side and down the other side of the inwardly extending insulating finger projections 18. in this manner extinction of the arc is greatly facilitated.

If the finger projections 13 are constructed of conducting material such as metal they may be properly termed finger electrodes. In this case the arc, instead of being elonagted by extending it around the finger projections, is broken up into a plurality of smaller arcs which exist between the adjacent metallic (conducting) fingers. In both cases (insulating or conducting fingers) the coil 13 serves to force the are into the vicinity of the finger projections so that are extinction is greatly facilitated.

We have found that the above described means of protecting the coil is exceedingly practical in that the coil may be switched into the power follow current circuit within 490-1200 microseconds depending upon the gap spacings and the particular configuration of the electrodes. Hence the coil is protected against surges and yet there is no appreciable time delay before the coil begins to act on the arc to aid in the extinction of same.

In FIG. 4 one means of providing the above described structure is illustrated. This involves a split housing 17 which is made up of portions 24 and 25 which are afixed together to encase the electrode and coil assemblies.

In FIG. 2 the spark gap structure is shown in conjunction with a lightning arrester having a skirted housing 21, a valve element 9' and an insulating cap 22. As can be seen, the spark gap structure 2131 is positioned atop the valve element 9' in series relation tl'ierewith and in series with the incoming line 1% though many other arrangements are equally possible. The basic spark gap unit described herein may be connected serially to similar units to form higher voltage assemblies but this or other modifications of the basic invention are not shown or discussed as the basic principle involved in the same for these modifications. The spark gap assembly of the invention may be utilized with a variety of lightning arrester housing structures and the particular structure shown and described herein is by way of example only of one such structure.

In FIG. 5 a partially cutaway portion of a slightly modified arrangement is shown. in this modification the faces of the mating portions 24', 25' (which serve to enclose the electrodes, coil etc.) of the insulated housing 17' are beveled toward one another so that as the arc is moved from portion A of the assembly to portion B it (the arc) comes more in contact with the mating insulating surfaces. This causes the arc to be cooled and constricted by the narrowing insulating surfaces thereby facilitating extinction of same. Finger projections similar to those previously discussed may or may not be utilized in this embodiment depending on the de sired operating characteristics of the assembly but these are not shown in order to shorten the disclosure and to facilitate the understanding thereof.

While only a few embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that various changes and modifications can be made therefrom without departing from the invention and, therefore it is intended for the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

We therefore claim:

1. A lightning arrester spark gap assembly comprising in combination, a pair of spaced apart divergent electrodes, said electrodes defining therebetween at their point of greatest confluence a spark gap, one of said pair of electrodes being connected to a source of higher potential than the other of said electrodes, are moving means connected to said source of higher potential, an auxiliary electrode in series with said are moving means and having a portion thereof spacedly juxtaposed between portions of said pair of electrodes, said one of said pair of electrodes and said auxiliary electrode and said other of said pair of electrodes and said auxiliary electrode defining respectively therebetween spark gaps; said are moving means, said auxiliary electrode, the spark gap between said auxiliary electrode and said other of said pair of electrodes and said other of said pair of electrodes conjointly defining a follow current path in parallel with said spark gap defined by said pair of electrodes, and means in the vicinity of said pair of electrodes for facilitating extinction of the follow current are, whereby said are moving means is inserted into the power follow current circuit subsequent to the surge to thereby protect said are moving means against the effects of the surge and to allow said are moving means to force the follow current are into contact with said are extinction facilitating means.

2. A lightning arrester spark gap construction comprising in combination, a first electrode, a second electrode spaced apart from said first electrode, said first electrode being connected to a source of higher potential than said second electrode, said electrodes being convergent and then divergent with respect to one another and defining therebetween in the vicinity of the point of their greatest confluence a main spark gap which is capable of breaking down on surges, coil means in electrical connection with said source of higher potential, auxiliary electrode means in series with said coil means, said auxiliary electrode means having a portion thereof disposed between said first and second electrodes, said auxiliary electrode and said second electrode defining therebetween a spark gap, said first electrode, said main spark gap and said second electrode constituting a surge current path; said coil, said auxiliary electrode, said gap between said auxiliary electrode and said second electrode, and said second electrode constituting a 60 cycle follow current path; and means associated with said electrodes for facilitating extinction of the follow current arc, whereby subsequent to a surge the arc existing between said first and second electrodes moves along the divergent portions of said first and second electrodes to said auxiliary electrode to insert said coil and said auxiliary electrode into the follow current circuit thereby providing a sufiicient value of flux to force the follow current are into contact with said are extinction facilitating means.

3. A lightning arrester spark gap assembly comprising a housing, a first electrode, a second electrode spaced a, art from said first electrode, said first and second electrodes defining therebetween a surge gap and further characterized by having portions thereof which are divergent to one another, coil means for moving the arc in said surge gap, auxiliary electrode means in series with said coil means, said auxiliary electrode means having a portion thereof situated between said first and second electrode means, said auxiliary electrode means and said second electrode defining therebetween a follow current gap, said first and second electrodes and the surge gap therebetween defining a surge path; said coil, said auxiliary electrode and said second electrode and the follow current gap therebetween defining a power follow current path, and are extinction means in proximity to said electrodes, whereby the arc instituted between said first and second electrodes during surges subsequently moves along said divergent electrode portions and transfers to said auxiliary and second electrodes whereupon said coil means is inserted into the circuit to force said are into contact with said arc extinction means.

4. A lightning arrester spark gap assembly comprising an insulating housing having a tortuous inner periphery, a first electrode, a second electrode spaced apart from said first electrode, said first and second electrodes defining therebetween a surge gap and further characterized by having portions thereof which are divergent to one another, coil means for moving the arc in said surge gap, auxiliary electrode means in series with said coil means, said auxiliary electrode means having a portion thereof situated between said first and second electrode means, said auxiliary electrode means and said second electrode defining therebetween a follow current gap, said first and second electrodes and the surge gap therebetween defining a surge path; said coil, said auxiliary electrode and said second electrode and the follow current gap therebetween defining a follow current path, whereby the arc instituted between said first and second electrodes during surges subsequently moves along said divergent portions of said electrodes and transfers to said auxiliary electrode whereupon said coil means is inserted into the circuit and by virtue of the increased magnetic fiux density the arc is forced around the tortuous inner periphery of said housing to elongate it and to facilitate extinction of same.

5. A lightning arrester spark gap assembly comprising an insulating housing, a first electrode, a second electrode spaced apart from said first electrode, said first and second electrodes defining therebetween a surge gap and further characterized by having portions thereof which are divergent to one another, coil means for moving the arc in said surge gap, auxiliary electrode means in series with said coil means, said auxiliary electrode means having a portion thereof situated between said first and second electrode means, said auxiliary electrode means and said second electrode defining therebetween a follow current gap, said first and second electrodes and the surge gap therebetween defining a surge path; said coil, said auxiliary electrode and said second electrode and the follow current gap therebetween defining a follow current path,

and a plurality of inwardly projecting finger electrodes arranged around the inner periphery of said housing, whereby the arc instituted between said first and second electrodes during surges subsequently moves along said divergent portions of said electrodes and transfers to said auxiliary electrode whereupon said coil means is inserted into the circuit and by virtue of the increased magnetic flux density the are is forced into contact with said finger electrodes to split it into a plurality of smaller arclets to thereby facilitate extinction of same.

a. A lightning arrester spark gap assembly comprising an insulating housing having convergent insulating surfaces, a first electrode, a second electrode spaced apart from said first electrode, said first and second electrodes defining therebetwecn a surge gap and further characterized by having portions thereof which are divergent to one another, coil means for moving the arc in said surge gap, auxiliary electrode means in series with said coil ieans, said auxiliary electrode means having a portion thereof situated between said first and second electrode means, said auxiliary electrode means and said second electrode defining therebetween a follow current gap, said first and second electrodes and the surge gap therebetween defining a surge path; said coil, said auxiliary electrode and said second electrode and the follow current gap therebetween defining a follow current path, whereby the arc instituted between said first and second electrodes during surges subsequently moves along said divergent portions of said electrodes and transfers to said auxiliary electrode whereupon said coil means is inserted into the circuit and by virtue of the increased magnetic flux density the arc is forced into contact with said insulating surfaces of said housing to constrict and to facilitate the extinction of said arc.

7. A lightning arrester spark gap construction comprising in combination, a pair of spaced apart electrodes defining therebetween a first spark gap surge path, are moving means, auxiliary electrode means in series with said are moving means and having a portion thereof in spaced proximity to at least one of said pair of electrodes so as to define a second spark gap therebetween, said are moving means, said auxiliary electrode, means said second spark gap and said one of said pair of electrodes defining a follow current path in shunt with said first spark gap, and means in the vicinity of said second spark gap for facilitating extinction of the follow current are, said follow current path being open and said second spark gap means not breaking down until subsequent to the surge in rder to protect said are moving means from the surge and said are moving means acting upon said follow current arc and moving it into the vicinity of said are extinction facilitating means.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A LIGHTNING ARRESTER SPARK GAP ASSEMBLY COMPRISING IN COMBINATION, A PAIR OF SPACED APART DIVERGENT ELECTRODES, SAID ELECTRODES DEFINING THEREBETWEEN AT THEIR POINT OF GREATEST CONFLUENCE A SPARK GAP, ONE OF SAID PAIR OF ELECTRODES BEING CONNECTED TO A SOURCE OF HIGHER POTENTIAL THAN THE OTHER OF SAID ELECTRODES, ARC MOVING MEANS CONNECTED TO SAID SOURCE OF HIGHER POTENTIAL, AN AUXILIARY ELECTRODE IN SERIES WITH SAID ARC MOVING MEANS AND HAVING A PORTION THEREOF SPACEDLY JUXTAPOSED BETWEEN PORTIONS OF SAID PAIR OF ELECTRODES, SAID ONE OF SAID PAIR OF ELECTRODES AND SAID AUXILIARY ELECTRODE AND SAID OTHER OF SAID PAIR OF ELECTRODES AND SAID AUXILIARY ELECTRODE DEFINING RESPECTIVELY THEREBETWEEN SPARK GAPS; SAID ARC MOVING MEANS, SAID AUXILIARY ELECTRODE, THE SPARK GAP BETWEEN SAID AUXILIARY ELECTRODE AND SAID OTHER OF SAID PAIR OF ELECTRODES AND SAID OTHER OF SAID PAIR OF ELECTRODES CONJOINTLY DEFINING A FOLLOW CURRENT PATH IN PARALLEL WITH SAID SPARK GAP DEFINED BY SAID PAIR OF ELECTRODES, AND MEANS IN THE VICINITY OF SAID PAIR OF ELECTRODES FOR FACILITATING EXTINCTION OF THE FOLLOW CURRENT ARC, WHEREBY SAID ARC MOVING MEANS IS INSERTED INTO THE POWER FOLLOW CURRENT CIRCUIT SUBSEQUENT TO THE SURGE TO THEREBY PROTECT SAID ARC MOVING MEANS AGAINST THE EFFECTS OF THE SURGE AND TO ALLOW SAID ARC MOVING MEANS TO FORCE THE FOLLOW CURRENT ARC INTO CONTACT WITH SAID ARC EXTINCTION FACILITATING MEANS.

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