US2551858A - Resistor type of isolator for lightining arresters - Google Patents

Description

y 1951 H. o. STOELTING ET AL 2,551,858 RESISTOR TYPE OF ISOLATOR FOR LIGHTNING ARRESTERS Filed Au '22, 1949 2 Sheets-Sheet l y 1951 H. o. STOELTING ETAL 2,551,858

RESISTOR TYPE OF ISOLATOR FOR LIGHTNING ARRESTERS Filed Aug. 22, 1949 2 Sheets-Sheet 2 INVENTORS %7fl10/7 0 ace/2 12 fife v17 5% Qi ve/e Patented May 8, 1951 RESISTOR TYPE OF ISOLATOR FOR LIGHTNING ARRESTERS Herman 0. Stoelting, Milwaukee, Wis., and Joseph F. Kuzela, Oneida, N. Y., assignors to McGraw Electric Company, a corporation of Delaware Application August 22, 1949, Serial No. 111,726

Claims. 1

This invention relates to resistor types of isolators for lig tning arresters.

rleretofore it has the practice to provide an isolator for lightning arresters which is associated with a lightning arrest-er having spark gaps and negative valve material and which is so arranged that for ordinary discharges, the isolator will not function but for unusually heavy discharges which result from breaking down of the valve material, for instance, the isolator will function and permanently open the circuit to the ground of the lightning arrester. This type of structure is shown in the patent to R. H. E? 'le, No. 2,315,320 of March 30, 1943 for Automatic Circuitinterrupting Device, owned by the assignee of the present invention.

In. pior forms of isolators attached to the lower end of a lightning arrester and interposed between such lower ends and the ground, it has been found that radiointerference is produced. On investigation, it was discovered that t -i radio interference resulted from the building up of a potential difference between the upper and lower electrodes of the isolator which resulted in a slow leak to ground across the gap in the isolator, thus producing corona efect with subsequent radio interference.

Objects of this invention are to provide novel forms of isolator-s which are of the resistor type and are equipped with a high value resistor bric ng gaps of the isolator and furnishing a discharge path from the upper to the lower electrodes, thereby discharging any charge that may accumulate on the upper electrode and preventing the formation of corona with subsequent radio disturbance.

Furt ier objects are to provide novel forms of isolator-s having the characteristics hereinabove enumerated which are of very simple construction and which can be attached to the lower end of lightning arrest and to the ground wire with the utmost ease and which are relatively inexpensive to replace.

Embodiments of the invention are shown in the accoii panying drawings, in which- Figure 1 is an elevation of a lightning arrest-er with the isolator attached with parts broken away and parts in section.

Figure 2 is an enlarge isolator shown in Figure 1.

Figure 3 is a sectional view of a further form of isolator.

Figure 4 is an enlarged perspective view of a part of the structure shown in Figure 3.

sectional view of the Figures 5 and 6 are sectional views of still further forms of isolators.

Referring to the drawings, it will be seen that the lightning arrester comprises a ceramic or other insulating casing i within the upper part of which is housed the conductors 2 which are spaced apart to form a series of spark gaps 3. The upper part of the lightning arrester is connected to the line wire or power line by means of the conductor i and is capped by means of the insulating cap The lower part of the arrester is provided with a lower terminal 6 and negative resistance material 7 is inte"posed between the lower end of the spark gap structure and the lower terminal 5 in accordance with the disclosure in the patent to I-l. Earle, No. 2,315,320 of March 30, 1943 for Automatic Circuit-Interrupting Device, owned by the assignee of the present invention.

The isolator has the general characteristics of that ol the prior patent hereinabove men tioned, and is composed of an upper terminal indicated by the reference character 8 and a lower terminal indicated by the reference character 9. The lower terminal is provided with a shell-like portion In which carries an explosive charge in the form of a cartridge II. The shell it is spaced from a surrounding lip 92 of the upper terminal and is arranged to be heated when heavy sparking occurs and thereby ignite and cause explosion of the explosive during the flow of excessive current from the lightning arrester through the isolator. two terminals are held in spaced relation by means of a breakable shell 53 and. the ground wire i is electrically connected to the lower terminal, such ground wire being grounded as shown in Figure 1.

In order to carry away any accumulated charge, a high value resistor, such as carbon and other compacted materials indicated by the reference character 55, is electrically positioned between. the cartridge and the upper terminal 8. It is held downwardly in firm contact with the upper end of the cartridge H by means of a spring 56 and thus serves as a high resistance connector between the upper terminal 1'3 and the lower tern-anal 9 and thus carries away any accumulated charge prevents the formation of corona or any slight sparking that may cause radio interference such as hereinabove 1nentioned A simple way of constructing the upper terminal 8 is to provide a threaded stem ll which screws into the lower terminal (-3 of the lightning arr-ester, the lower terminal 9 being connected to the ground wire Us by means of a screw it, a suitable insulating shell l9 being provided for this connection.

In the form of invention shown in Figure 3 and 4 the same general idea is employed except in the manner in which the connecting resistor is used. In this form of the invention the upper terminal of the isolator is indicated by the reference character 29 and the lower terminal by the reference character 2!. The breakable shell or casing of insulating material is indicated by the reference character 22 and an annular compacted carbon resistor by the reference character 23. This annular, compacted carbon resistor is a high value resistor and is adapted to conductaway any charge that may accumulate on the upper electrode 2E3. It is electrically connected to the lower electrode because it rests on a flanged portion 24 thereof. It is electrically connected to the upper electrode 29 by means or a spring spider 25 shown more in detail in Figure 4. This spring spider may have a central aperture 2 see Figure t through which the shell 26 of the lower terminal 2! passes, such shell carrying the cartridge 2'! having, the explosive charge. The spring spider has upwardly extending, slightly outwardly sprung spring arms 28 which directly engage the conical lower surface of the upper terminal 20.

In the form of the invention shown in Figure 5, the upper terminal is indicated by the reference character 29 and the lower terminal by the reference character 36. The insulating shell is shown at 3i as provided with an internally located, high resistance conducting coating 32 of any suitable conducting material having the requisite value of resistance. This conducting coating extends from the lower electrode Bil to the upper electrode 29. The cartridge for the explosive charge is indicated at 33 and is carried in the shell-like portion 34 as hereinabove described.

In the form of the invention shown in Figure 6 the upper electrode is indicated at 35 and the lower electrode at 36. The lower electrode has the shell Bl, previously described, which carries the cartridge 38 having the explosive charge. The insulating shell or casing is indicated at 39. The upper and lower electrodes are connected by a high value resistor d6 whose upper and lower pigtails or terminals 45 and 42 are electrically connected to the upper and lower electrodes and serve as the support for the resistor 35.

It will be seen that in each form of the invention the high resistance carbon or other resistor serves to conduct away any accumulated charge and to thus prevent the formation of corona or sli ht sparking. However, it does not materially alter the flow of excessive current when such flow occurs, as in each instance the value of the resistor is very high. Therefore, the explosive charge is exploded in the ordinary way and rupture of the rupturable casing or breakable casing is obtained to thereby electrically separate the lightning arrester from the ground.

Although this invention has been described in considerable 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.

We claim:

1. The combination of a lightning arrester having one end arranged to be connected to a power line and having a second end, an isolating device having a first terminal connected to the second end of said lightning arrester and having a second terminal connected to the ground, a breakable shell holding said terminals apart, an explosive charge arranged to explode and break said shell on excessive flow of current through said device, and a high value resistor electrically joining said terminals for normally preventing the formation of a difference of potential between said terminals, said lightning arrester including a spark gap electrically interposed between the power line and said isolating device, whereby neither terminal of said isolating device is connected to said power line.

2. The combination of a lightning arrester having one end arranged to be connected to a power line and having a second. end, an isolating device having a first terminal connected to the second end of said lightning arrester and having a second terminal. connected to the ground, a breakable shell holding said terminals apart, an explosive charge arranged to explode and break said shell on excessive flow of current through said device, one of said terminals having a recessed part, a resistor located in said recessed part, and a spring located in said recessed part and holding said resistor in electrical connection with the other of said terminals, said lightning arrester including a spark gap electrically interposed between the power line and said isolating device, whereby neither terminal of said isolating device is connected to said power line.

3. The combination of a lightning arrester having one end arranged to be connected to a power line and having a second end, an isolating device having a first terminal connected to the second end of said lightning arrester and having a second terminal connected to the ground, a breakable shell holding said terminals apart, an explosive charge arranged to explode nd break said shell on excessive flow of current through said device, and a high resistance conducting coating formed on the inner side of said shell and electrically connecting said terminals for normally preventing the formation of a difference of potential between said terminals, said lightning arrester including a spark gap electrically inter posed between the power line and said isolating device, whereby neither terminal of said isolating device is connected to said power line.

4. The combination of a lightning arrester having one end arranged to be connected to a power line and having a second end, an isolating device having a first terminal connected to the second end of said lightning arrester and having a second terminal connected to the ground, a breakable shell holding said terminals apart, an explosive charge arranged to explode and break said shell on excessive flow of current through said device, an annular compacted high value resistor resting on one of said terminals, and a spring bearing on the other terminal and said resistor, whereby said resistor electrically joins said terminals for normally preventing the formation of a difierence of potential between said terminals, said lightning arrester including a spark gap electrically interposed between the power line and said isolating device, whereby neither terminal of said isolating device is connected to said power line.

5. The combination of a lightning arrester having one end arranged to be connected to a power line and having a second end, an isolating device having a first terminal connected to the second end of said lightning arrester and having a second terminal connected to the ground, a breakable shell holding said terminals apart, an

explosive charge arranged to explode and break REFERENCES CITED said shell on excessive flow of current through The following references are of record in the said device, and a high value resistor located me of this patent; externally of said shell and supported by and electrically joining said terminals for normally 5 UNITED STATES PATENTS preventing the formation of a difference of poten- N b r Na Dat tial between said terminals, said lightning ar- 1,967,616 I-Iillebrand July 24, 1934 rester including a spark gap electrically inter- 2,118,795 Littleton May 24, 1938 posed between the power line and said isolating 2,174,477 Pittman et al. Sept. 26, 1939 device, whereby neither terminal of said isolating 10 2,283,685 McCreery et a1 May 19, 1942 device is connected to said power line. 2,305,436 McMorris Dec. 15, 1942 HERMAN O. STOEL'I'ING. 2,315,320 Earle Mar. 30, 1943 JOSEPH F. KUZELA.

Images