US2548112A

US2548112A - Resistor type isolator for lightning arresters

Info

Publication number: US2548112A
Application number: US108878A
Authority: US
Inventors: Oscar H Kaminky
Original assignee: McGraw Electric Co
Current assignee: McGraw Electric Co
Priority date: 1949-08-06
Filing date: 1949-08-06
Publication date: 1951-04-10
Anticipated expiration: 1968-04-10

Description

April 10, 1951 o. H. KAMINKY .2,548,112

REsIsToR TYPE lsoLAToR FoR LIGHTNING ARREsTERs Filed Aug. 6, 1949 IN V EN TOR.

Z ornez/ Patented Apr. 10, 1951 RESISTOR TYPE ISOLATOR FORLIGHTNING ARRESTERS Oscar H. Kaminky, South; Milwaukee, Wis., assignor to McGrawA Electric Company,V a corporation of Delaware Application August 6, 1949,"Serial'N0. 108,878

(Cl. G-115) 5 Claims.

Thisinvention relates to a resistor type of isolator for lightning arresters.

Heretofore it has been the practice to provide an isolator for lightning arresters which is associated with a lightning arrester having spark Circuit-Interrupting Device owned by the as- 5 signee of the present invention.

Prior forms of isolators have been found to have radio interference which resulted from a charge accumulating on the upper electrode of the isolator and discharging to the lower electrode, thereby producing a corona effect, with resulting radio disturbance.

This invention is designed to overcome the above noted defects and objects of this invention are to provide a novel type of isolator which is so made that a resistor provides a path for the discharge from the upper electrode to the lower electrode of any slowly accumulating charge, the resistor being of high enough value so as to prevent the free connection of the electrodes of the isolator and also being of high enough value so as to insure the sparking over from the upper electrode to the cartridge having the explosive charge within the resistor or else the heating of the cartridge due to the heating of the resistor so as to cause the charge to explode and rupture the isolator, thereby disconnecting the lightning arrester from the ground.

"Further objects are to provide a very simple construction of resistor type isolator which is compact, which may be readily made, and which may be easily assembled with the usual type of lightning arrester without any alterations of the lightning arrester itself.

An embodiment of the invention is shown in the accompanying drawings, in which- Figure l is a side elevation with parts broken away showing the lightning arrester with the isolator in place.

Figure 2 is an enlarged view partly in section through the isolator showing it removed from the lightning arrester.

Referring to the drawings, it will be seen that the lightning arrester has been indicated generally by the reference character I and consists of a series of conducting members 2 forminga series of gaps 3 arranged for connection between the power line 4 and valve material 5, which latter has negative resistance characteristics. The lightning arrester may have a ceramic body part of cylindrical shapeyand anupper cap or cover l of linsulating material. It is provided with a lower terminal 3 into which is screwed theconnecting threaded portion 9 of an `,upper terminal of an isolating device indicated generally by the reference character l0. This isolating device has a second terminal or lower terminal II which is connected by means of a flexible ground conductor I2 to the groundas'indicated in Figure 1.

The isolating device is shown more in detail in Figure 2 and it will be seen that the upper ter minal consists of 'the disk-like member I3 which has the threaded stem 9 previously described, It also has a lower terminal consisting of a'disl:` like member I4 having the lower threaded por tion II.

The upper and lower terminals or rst and'V second terminals I3 and I4 of the isolating device are in abutting relation to the upper and lower faces of'an annular insulating spacing member or breakable shell I5. This shell is weakened by means of an annularY groove 'I6' intermediate its ends. Preferably, fastening means I6 in the form'of screws extend through the disks I3 and I4 and into the breakable shell I5. The breakable shell-surrounds an annular resistor il which is composed of negative resistance material such as siliconcarbide commonly known as Granulon. lThis-resistor may be of a compacted form so as to retain itsannular shape as shown in Figure 2,-or may be a Ypowder held in place by suitable means not shown.

The lower terminal I4 is provided with a hollow upwardly projecting stem I8 which carries an explosive charge such as the loaded cartridge i9. Preferably the upper terminal I is provided with a centrally located sparking tip 2t.

-The isolator operates in substantially the same manner as that of the isolator of the patent hereinabove mentioned. However, this isolator has an additional and different function from that of the prior isolator. As stated hereinabove, it has been found that there is an accumulation of charge on the upper electrode so that there is a diierence in voltage between the upper and lower electrodes. This causes a corona effect or slight sparking or slight discharge which produces radio interference. The provision of the resistor I1 of negative resistance material serves to effectively conduct away any accumu- 3f lated charge and to thus prevent radio interference. Itis preferable that the negative resistance material have relatively high resistance so that the upper and lower terminals of the isolator are substantially electrically separate. There is, however, a sun'icient amount of conduction to prevent the radio interference hereinabove noted.

When an excessive amount of current flows, the explosive charge is ignited either by sparking or by the heating of the resistor I1, the result being the same in both cases. The charge explodes, thus breaking the shell or casing I5 and allowing the bottom terminal of the isolator to drop away and electrically disconnect thelightning arrester from the ground.

It will be seen that a very simple type` isolator has been provided which is of the resistor type and adds to the heretofore known advantages of the isolator, such as shown in the prior patent, the additional features enumerated above thus eliminating radio interference.

Although this invention has been described in rconsiderable detail, it is to be understood that .such description is intended as illustrative rather than limiting, as'the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. The combination of a lightning arrester having one end arranged for connection to a power line and having a second end, an isolating device having a rst terminal connected to the .said second end of said lightning arrester and having a second terminal connected to the ground :and having an annular breakable shell normally holding said first and second terminals apart, an :explosive charge arranged to explode and break :said shell on excessive flow of current from said rst to said second terminals, and a resistor composed of negative resistance material bridging the said rst and second terminals of said isolatiing device.

2. The combination of a lightning arrester having one end arranged for connection to a power line and having -a second end, an isolating device having Va first terminal connected to the said .second end of said lightning arrester and having a second terminal connected to the ground and ,Thaving an annular breakable shell normally holding said rst and second terminals apart, an explosive charge arranged to explode and break :said shell on excessive flow of current from said irst to said second terminals, and a resistor composed of negative resistance material bridging the said rst and second terminals of said isolating device, said resistor being annular and surrounding said explosive charge.

3. The combination of a lightning arrester having one end arranged for connection to a power line and having a second end, an isolating device having a rst terminal connected to the said second end of said lightning arrester and having a second terminal connected to the ground and having an annular breakable shell normally holding said first and second terminals apart, an explosive charge arranged to explode and break said shell on excessive flow of current from said first to said second terminals, and a resistor composed of negative resistance material bridging the said iirst and second terminals of said isolating device, the explosive charge being in close proximity to said rst electrode and to said resistor and arranged to be ignited on excessive ow of current either by sparking between the lrst and second electrodes of said isolating device or by the heating of said resistor.

4. ,The combination of a lightning arrester having oneend arranged for connection to a power line and having a second end, an isolating device having a i'lrst terminal connected to the said second end of said lightning arrester and having a second terminal connected to the ground and having an annular breakable shell normally holding said rst and second terminals apart, an explosive charge arranged to explode and break said shell 'on excessive flow of current from said rst to said second terminals, an annular resistor surrounding said explosive charge and bridging the terminals of said isolating device, said i-lrst and second terminals abutting the ends of said shell, and fastening means extending through said first and second terminals and i'nto said shell.

5. The combination of a lightning arrester having one end arranged for connection to a power line and having a second end, an isolating device having a first terminal connected to the said second end of said lightning arrester and having a second terminal connected to the ground and having an annular breakable shell normally holding said first and second terminals apart, an explosive charge arranged to explode and break said shell on excessive flow of current from said first to said second terminals, an annular resistor surrounding said explosive charge and bridging the terminals of said isolating device, said first and second terminals abutting the ends of said shell, and fastening means extending through said first and second terminals and into said shell, said shell having an annular weakened portion intermediate its ends.

OSCAR. I-I. KAMINKY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,967,616 Hillebrand July 24, 1934 2,118,795 Littleton May 24, 1938 2,174,477 Pittman et al Sept. 26, 1939 2,283,685 McCreery et al. May 19, 1942 2,305,436 McMorris Dec. 15, 1942 2,315,320 Earle Mar. 30, 1943