CA1105987A - Fail-safe/surge arrester systems - Google Patents
Fail-safe/surge arrester systemsInfo
- Publication number
- CA1105987A CA1105987A CA298,463A CA298463A CA1105987A CA 1105987 A CA1105987 A CA 1105987A CA 298463 A CA298463 A CA 298463A CA 1105987 A CA1105987 A CA 1105987A
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- Canada
- Prior art keywords
- fusible
- arrester
- electrodes
- electrode
- arrester system
- Prior art date
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Abstract
UNITED STATES PATENT APPLICATION
OF
JOHN NAPIORKOWSKI
FOR
FAIL-SAFE/SURGE ARRESTER SYSTEMS
Abstract An electrical surge arrester protects electrical power lines and telephones from excessive voltage as may occur in the presence of lighting. The arrester is formed of a gas filled, cylindrical, housing enclosing two cylind-rical electrodes which are spaced apart by a gap. In the presence of high voltage, the gas in the gap breaks down through ionization to provide an electrically conducting path between the electrodes. Spring type electrical contacts are spaced from the electrodes by a fusible insulating material.
Upon sustained arcing, heat of the arc melts the fusible material permitting contact between the electrodes and the spring contacts which provide an electrical short between the electrodes.
OF
JOHN NAPIORKOWSKI
FOR
FAIL-SAFE/SURGE ARRESTER SYSTEMS
Abstract An electrical surge arrester protects electrical power lines and telephones from excessive voltage as may occur in the presence of lighting. The arrester is formed of a gas filled, cylindrical, housing enclosing two cylind-rical electrodes which are spaced apart by a gap. In the presence of high voltage, the gas in the gap breaks down through ionization to provide an electrically conducting path between the electrodes. Spring type electrical contacts are spaced from the electrodes by a fusible insulating material.
Upon sustained arcing, heat of the arc melts the fusible material permitting contact between the electrodes and the spring contacts which provide an electrical short between the electrodes.
Description
S~87 Background Gas tube overvoltage protectors are widely used for the protection of equipment from overvoltage conditions which may be caused by lightning, high voltage line contact, and the like.
It is also a widely practiced technique to associate various fail-safe arrangements with such tubes and with other types of protectors, e.g., air gap arresters, to meet various contingencies. For example, the presence of a sustained overload, as where a power line has come in continued contact with a pro-tected telephone line, produces a concomitant sustained ioniz-ation of the gas tube and the resultant passaae of heavy currents through the tube. Such currents will in many cases destroy the overvoltage protector and may also constitute a fire hazard.
One common approach to this problem is to employ fusible elements which fuse in the presence of such overloads and provide either a permanent short circuitina of the arrester directly, or function to release another mechanism, e.g., a spring loaded shorting bar, which provides the short circuit connection (commonly, the arrester electrodes are both shorted and grounded). The presence of the permanent short and ground condition serves to flag attention to that condition thus signal-ling the need for its inspection or replacement. Examples of this type of fail-safe protection are found in U.S. Patents 3,254,179, 3,281,625, 3,340,431, 3,396,343 and 3,522,570.
Several of these patents also incorporate with the fail-safe feature, a backup air gap arrangement so that there is both fail-safe fusible (short) type protection as well as backup air aap protection. (U.S. Patent 4,062,054 issued December 6, 1977,) q _ _ ,~
~ r~ r~
: ; ~
S~7 entitled "Multi-Function Fail-Safe Arrangement For Overvoltage Gas Tubes", and owned by the assignee of the instant invention, also discloses several related arranaements.
A characteristic common in the foregoing arrangements is the employment of metallic materials for the fusible elements.
This is an established practice in the art directed by the object of forming from the fused material an electrically conductive shorting path to thereby short circuit the arrester electrodes.
The selection is also ordinarily dictated by the well known, widely exploited fusion properties of metals, and by thermal con-ductivity and related factors involved in fail-safe arrester designs.
The present invention is based on the discoveries that an effective fail-safe function can be achieved by employing a non-metallic fusible material and that important advantages are consequently realized. The fusible material is an electrical insulator which in the exemplary embodiments is interposed be-tween one or more of the electrodes and the shorting mechanism.
Surprisingly, the response of the non-metallic material to thermal conditions is precise and, moreover, does not leave an insulative film in the course of fusing which might otherwise interfere with the short circuit contact.
While the patent literature discloses the use of non-metallic fusible materials in certain fail-safe applications (see U.S. Patents 1,580,516 and 1,457,249) the arrangements suggested therein involve movement of the arrester electrodes and/or direct arc involvement, as well as other materials, tech-niques and environmental factors which compromise many of the ad-vantages that applicant has found can be realized from the jrc:~
5~
non-metallic fusion materials disclosed herein.
In accordance with the present invention-there is provided a fail-safe surge arrester system comprising: a gas filled housing including at least two electrodes defininq an ionizable gap; short circuiting means biased toward a short circuit connection with the electrodes; and non-metallic fusible means in thermal contact with the gap and interposed between at least one of the electrodes and the short circuiting means to prevent the short circuit connection except in the presence of a sustained overload causing the fusible means to fuse and yield to permit the establishment of the short circuit connection.
Objects Among the results achieved in the practice of the invention are:
(1) a marked improvement in the precision with which the fail-safe action occurs; in embodiments of the invention conditions which trigger the fail-safe action are more precisely predetermined and more predictable;
It is also a widely practiced technique to associate various fail-safe arrangements with such tubes and with other types of protectors, e.g., air gap arresters, to meet various contingencies. For example, the presence of a sustained overload, as where a power line has come in continued contact with a pro-tected telephone line, produces a concomitant sustained ioniz-ation of the gas tube and the resultant passaae of heavy currents through the tube. Such currents will in many cases destroy the overvoltage protector and may also constitute a fire hazard.
One common approach to this problem is to employ fusible elements which fuse in the presence of such overloads and provide either a permanent short circuitina of the arrester directly, or function to release another mechanism, e.g., a spring loaded shorting bar, which provides the short circuit connection (commonly, the arrester electrodes are both shorted and grounded). The presence of the permanent short and ground condition serves to flag attention to that condition thus signal-ling the need for its inspection or replacement. Examples of this type of fail-safe protection are found in U.S. Patents 3,254,179, 3,281,625, 3,340,431, 3,396,343 and 3,522,570.
Several of these patents also incorporate with the fail-safe feature, a backup air gap arrangement so that there is both fail-safe fusible (short) type protection as well as backup air aap protection. (U.S. Patent 4,062,054 issued December 6, 1977,) q _ _ ,~
~ r~ r~
: ; ~
S~7 entitled "Multi-Function Fail-Safe Arrangement For Overvoltage Gas Tubes", and owned by the assignee of the instant invention, also discloses several related arranaements.
A characteristic common in the foregoing arrangements is the employment of metallic materials for the fusible elements.
This is an established practice in the art directed by the object of forming from the fused material an electrically conductive shorting path to thereby short circuit the arrester electrodes.
The selection is also ordinarily dictated by the well known, widely exploited fusion properties of metals, and by thermal con-ductivity and related factors involved in fail-safe arrester designs.
The present invention is based on the discoveries that an effective fail-safe function can be achieved by employing a non-metallic fusible material and that important advantages are consequently realized. The fusible material is an electrical insulator which in the exemplary embodiments is interposed be-tween one or more of the electrodes and the shorting mechanism.
Surprisingly, the response of the non-metallic material to thermal conditions is precise and, moreover, does not leave an insulative film in the course of fusing which might otherwise interfere with the short circuit contact.
While the patent literature discloses the use of non-metallic fusible materials in certain fail-safe applications (see U.S. Patents 1,580,516 and 1,457,249) the arrangements suggested therein involve movement of the arrester electrodes and/or direct arc involvement, as well as other materials, tech-niques and environmental factors which compromise many of the ad-vantages that applicant has found can be realized from the jrc:~
5~
non-metallic fusion materials disclosed herein.
In accordance with the present invention-there is provided a fail-safe surge arrester system comprising: a gas filled housing including at least two electrodes defininq an ionizable gap; short circuiting means biased toward a short circuit connection with the electrodes; and non-metallic fusible means in thermal contact with the gap and interposed between at least one of the electrodes and the short circuiting means to prevent the short circuit connection except in the presence of a sustained overload causing the fusible means to fuse and yield to permit the establishment of the short circuit connection.
Objects Among the results achieved in the practice of the invention are:
(1) a marked improvement in the precision with which the fail-safe action occurs; in embodiments of the invention conditions which trigger the fail-safe action are more precisely predetermined and more predictable;
(2) .the fire hazard associated with conventional units because of the presence of molten metal, metal explosion and the like, during the fusion action is virtually eliminated;
(3) metal oxidation problems and metal splatter problems are avoided;
(4) packaging and encapsulation are greatly simplified;
(5) the foregoing improvements and new results are achieved with a structure which is more simple, compact and lighter than its predecessors and thus less costly, of greater ..
durability and reliability, and of greater flexibility for ,.
;~r- ~l ~' ~
~S~87 adaption to many protector environments including retrofits, OEM, applique, and station applications in the communication, power, data processing, traffic control, alarm and other fields where surge protection is desirable.
Other objects and advantages of the invention will be apparent from the following description and in the practice of the invention which may be summarized as comprising a surge arrester having two or more electrodes defining an ionizable (air or gas) gap; short circuiting means biased toward a short-circuit connection with said electrodes; non-metallic fusible means in thermal contact with said gap and interposed between at least one of said electrodes and said short circuiting means to prevent said short circuit connection except in the presence of overload causing said fusible means to fuse and yield to permit the establishment of said short circuit connection.
Drawings Illustrating exemplary embodiments of the invention are the drawings of which:
FIGURE 1 is an elevational view, partly in section and partly schematic, of a first embodiment;
FIGURE 2 is a cross-sectional view taken along the lines 2-2 of FIGURE l;
FIGURE 3 is a cross-sectional view taken along the lines 3-3 of FIGURE l;
FIGURE 4 is a cross-sectional view taken along lines 4-4 of FIGURE l;
FIGURE 5 is an elevational view, partly in section, of the modular component of another embodiment;
FIGURE 6 is a plan view of the embodiment of FIGURE 5 mounted in its housing; and .
.
5~7 FIGURE 7 is a plan view of the unit of FIGURE 6.
Detailed Description of the Invention In the embodiment illustrated in FIGURES 1-4 a gas tube 10 is provided, the tube including a center body lOA and electrode end caps lOB each separated from the center body lOA by a respec-tive insulated sleeve section lOC.
The arrester 10, which is of known construction and may comprise for example TII Model 31, has its end electrodes (not shown) extending inwardly from the end caps lOB toward the center of the tube interior to define a gap between the electrodes.
Spacing and dimensions are such that each electrode also forms a gap with the center body conductive casing section lOA.
The tube is filled with a gas and the electrode end caps lOB are each provided as by welding with a lead llB and terminal 12B, e.g., a spade lug, for connection to the circuit to be protected. Center body lOA is likewise provided with a lead llA welded thereto and the associated connection 12A for connection to ground.
In the presence of overvoltage conditions the gas in tube 10 ionizes thereby creating in known manner, conductive shunting paths between each line of the protected circuit and ground (via the respective terminal lead llB and ground lead llA) .
Coaxially fitted on center body lOA are a pair of annular members or sleeves 12 of fusible material, each located to one side of the center section of the center body where lead llA makes its connection.
Sleeves 12 are of non-metallic, electrically insulative composition. Suitable materials will have melt temperatures in the range corresponding to thermal conditions at arrester thermal X jrc~
.
5~1~7 overload and will have suitable dielectric strength, dielectric constant, dissipation factor and volume and surface resistivity to provide the requisite insulative function. The preferred material should also be free of embrittlement due to heat aaing, be non-flammable under the overload conditions, have good mechan-ical properties and be inert to corrosives and weather.
Exemplary of such a class of materials are certain of the fluoroplastics, such as a fluorinated ethylene propylene polymer (FEP), the polymer perfluoroalkoxy (PFA), the modified copolymer of ethylene and tetrafluoroethylene (ETFE) (marketed under the duPont company trademark Tefzel), and poly (ethylene-chlorotrifluoro-ethylene) (E-CTFE copolymer) marketed under the Allied Chemical Corporation mark Halfar. (The Fluoroplastic poly-tetrafluoroethylene (TFE), on the other hand, does not have suitable melt properties for the illustrated application.) In the example of Figures 1-4, sleeves 12 are formed of .38LG FEP
tubing, AWG 2.
As illustrated in the Figures, each sleeve 12 is resiliently engaged by pairs of fingers 14 of a short circuiting clip 15, an elevational view of which is shown in Figure 4.
Each clip 15, which is illustratively of grain oriented tin plated carbon steel, heat treated for stress relief from hydrogen embrittlement after plating, includes another set of spring fingers 16 which engage and electrically contact the respective end cap lOB, the spring fingers 14 and 16 being integrally connected by the bridge section 17 of each clip. As seen in greater detailin Figure 2, the fingers 14 of the short-circuit clips are spaced from contact with center body lOA by reason of the respective fusible sleeve 12. Specifically, each of the ~. , .
jrc~
:
~5~37 fingers 14 includes a contact portion 14A which is urged in the direction of contact with grounded center body lOA and which consequently presses resiliently on the sleeve section 12 interposed therebetween.
During normal operation of the arrester 10, transient surges produce ionization in the normal manner to protect the subject equipment. If, however, a sustained surge condition occurs as where a line is permanently contacted by a higher voltage line, the resultant ionization currents flowing through the arrester produce excessive heat; the sleeves 12, placed in the arrester region to respond to this heating, thereby fuse. As this occurs, spring fingers 14, and in particular the contact sections 14A thereof, move into contact with center body lOA as the fusible sleeve material beneath those contacts vields and flows. When electrical contact is made a short circuit is estab-lished between the respective end cap and the center body thus providing a fail-safe (short) action.
Non-metallic materials other than the foregoing may be used as the fusible members provided they have appropriate electrical insulation properites and undergo a predictable change of mechanical properties under the specified overload condition to permit the short circuiting action to occur.
In addition to facilitating the foregoing fail-safe features, the sleeves 12 may include a cutout portion as at 12D in Figure 2 to thus define an air gap between center body 10 and the respective clip 15 which is in electrical contact with one of the end electrodes.
With this additional provision a failure of the gas tube in the open mode, as for example by reason of a gas leak, does not result in a loss of protection; the air gap provides 1~ 8 ~5987 backup protection prior to arrester replacement.
To facilitate use in a wide variety of applications, the arrester assembly of Figures 1-4 is potted in a modular shell 18, the potting material 19 therein being an epoxy compound.
Prior to the potting the arrester assembly may be wrapped and voids filled with PTFE or equivalent material (not shown).
An application of the arrester to a station protector configuration is illustrated in Figures 5 through 7. Tube 10 per se together with fusible sleeves 12 and shorting clips 15 have already been described above. However, whereas the embodi-ment of Figures 1 through 4 employed welded flexible circuit coupling leads, the instant embodiment is encapsulated in a modular shell 20 installed in turn in a base assembly 30. Shell 20 also contains fixed line terminals 21 and ground strap 23. Each line electrode end cap lOB is electrically and mechanically con-nected to a respective line terminal 21 by way of a generally L-shaped connector 22 having one section in engagement with the respective end cap in the region between fingers 16 of the associated shorting clip. This section of connector 22 is of generally spade lug configuration with the end cap resiliently engaged by the fingers of the lug.
The opposite end of connector 22 is connected to the ribbed shank portion of threaded stud 21A of terminal 21, the stud being pressed fit into housing 20 as shown particularly in Figure 5. The threaded shaft portion includes nuts 21B and washers 21C to provide means for connection to the equipment lines.
Connection of center body lOA on tube 10 is provided by way of a generally L-shaped connector 25 having one section _ g _ of generally spade lug configuration which resiliently engages housing lOA, and another section which is secured to knurled shank 24A of a pin 24 which secures ground strap 23 to center body connector 25.
The distal end of the ground strap 23 is connected to a ground terminal assembly 26 having a threaded stud 27 secured to base 30 by means of nut 34. To facilitate this connection, strap 23 terminates in a lug which fits around shaft 27 and is secured by nut 37. As with the line terminals 21, ground terminal assembly 26 includes nuts 26A and associated washers 26B to facilitate connection to the around line.
The modular unit 20 with its tube and line terminals 21 and ground strap 23 are thus secured in the cavity in base 30 by way of the connection of ground strap 23 to the ground terminal assembly 26. Prior to assembly tube 10 is wrapped and potted in unit 20 as previously described relative to the first described embodiment.
The embodiment of Figures 5-7 functions in the manner previously described in connection with the systems of Figures '~
1-4. It furthermore illustrates the facility with which the arrester with its fail-safe features is packaged in various compact configurations.
From the foregoing description, application of the technique to both two-element and multi-element protectors will be apparent.
It should be noted that the fusible member configuration permits improved precision in the establishment of gap spacing in the backup airgap section.
Further, in the embodiment of figure 5 - 7 it should be -- 1.0 --jrc~
- - .
~59~7 noted that the absence of the module 20 from the sase assembly prevents the connections of the load circuit to the input lines thereby, precluding the making of unprotected connections.
,~, - 11 -jrc~
durability and reliability, and of greater flexibility for ,.
;~r- ~l ~' ~
~S~87 adaption to many protector environments including retrofits, OEM, applique, and station applications in the communication, power, data processing, traffic control, alarm and other fields where surge protection is desirable.
Other objects and advantages of the invention will be apparent from the following description and in the practice of the invention which may be summarized as comprising a surge arrester having two or more electrodes defining an ionizable (air or gas) gap; short circuiting means biased toward a short-circuit connection with said electrodes; non-metallic fusible means in thermal contact with said gap and interposed between at least one of said electrodes and said short circuiting means to prevent said short circuit connection except in the presence of overload causing said fusible means to fuse and yield to permit the establishment of said short circuit connection.
Drawings Illustrating exemplary embodiments of the invention are the drawings of which:
FIGURE 1 is an elevational view, partly in section and partly schematic, of a first embodiment;
FIGURE 2 is a cross-sectional view taken along the lines 2-2 of FIGURE l;
FIGURE 3 is a cross-sectional view taken along the lines 3-3 of FIGURE l;
FIGURE 4 is a cross-sectional view taken along lines 4-4 of FIGURE l;
FIGURE 5 is an elevational view, partly in section, of the modular component of another embodiment;
FIGURE 6 is a plan view of the embodiment of FIGURE 5 mounted in its housing; and .
.
5~7 FIGURE 7 is a plan view of the unit of FIGURE 6.
Detailed Description of the Invention In the embodiment illustrated in FIGURES 1-4 a gas tube 10 is provided, the tube including a center body lOA and electrode end caps lOB each separated from the center body lOA by a respec-tive insulated sleeve section lOC.
The arrester 10, which is of known construction and may comprise for example TII Model 31, has its end electrodes (not shown) extending inwardly from the end caps lOB toward the center of the tube interior to define a gap between the electrodes.
Spacing and dimensions are such that each electrode also forms a gap with the center body conductive casing section lOA.
The tube is filled with a gas and the electrode end caps lOB are each provided as by welding with a lead llB and terminal 12B, e.g., a spade lug, for connection to the circuit to be protected. Center body lOA is likewise provided with a lead llA welded thereto and the associated connection 12A for connection to ground.
In the presence of overvoltage conditions the gas in tube 10 ionizes thereby creating in known manner, conductive shunting paths between each line of the protected circuit and ground (via the respective terminal lead llB and ground lead llA) .
Coaxially fitted on center body lOA are a pair of annular members or sleeves 12 of fusible material, each located to one side of the center section of the center body where lead llA makes its connection.
Sleeves 12 are of non-metallic, electrically insulative composition. Suitable materials will have melt temperatures in the range corresponding to thermal conditions at arrester thermal X jrc~
.
5~1~7 overload and will have suitable dielectric strength, dielectric constant, dissipation factor and volume and surface resistivity to provide the requisite insulative function. The preferred material should also be free of embrittlement due to heat aaing, be non-flammable under the overload conditions, have good mechan-ical properties and be inert to corrosives and weather.
Exemplary of such a class of materials are certain of the fluoroplastics, such as a fluorinated ethylene propylene polymer (FEP), the polymer perfluoroalkoxy (PFA), the modified copolymer of ethylene and tetrafluoroethylene (ETFE) (marketed under the duPont company trademark Tefzel), and poly (ethylene-chlorotrifluoro-ethylene) (E-CTFE copolymer) marketed under the Allied Chemical Corporation mark Halfar. (The Fluoroplastic poly-tetrafluoroethylene (TFE), on the other hand, does not have suitable melt properties for the illustrated application.) In the example of Figures 1-4, sleeves 12 are formed of .38LG FEP
tubing, AWG 2.
As illustrated in the Figures, each sleeve 12 is resiliently engaged by pairs of fingers 14 of a short circuiting clip 15, an elevational view of which is shown in Figure 4.
Each clip 15, which is illustratively of grain oriented tin plated carbon steel, heat treated for stress relief from hydrogen embrittlement after plating, includes another set of spring fingers 16 which engage and electrically contact the respective end cap lOB, the spring fingers 14 and 16 being integrally connected by the bridge section 17 of each clip. As seen in greater detailin Figure 2, the fingers 14 of the short-circuit clips are spaced from contact with center body lOA by reason of the respective fusible sleeve 12. Specifically, each of the ~. , .
jrc~
:
~5~37 fingers 14 includes a contact portion 14A which is urged in the direction of contact with grounded center body lOA and which consequently presses resiliently on the sleeve section 12 interposed therebetween.
During normal operation of the arrester 10, transient surges produce ionization in the normal manner to protect the subject equipment. If, however, a sustained surge condition occurs as where a line is permanently contacted by a higher voltage line, the resultant ionization currents flowing through the arrester produce excessive heat; the sleeves 12, placed in the arrester region to respond to this heating, thereby fuse. As this occurs, spring fingers 14, and in particular the contact sections 14A thereof, move into contact with center body lOA as the fusible sleeve material beneath those contacts vields and flows. When electrical contact is made a short circuit is estab-lished between the respective end cap and the center body thus providing a fail-safe (short) action.
Non-metallic materials other than the foregoing may be used as the fusible members provided they have appropriate electrical insulation properites and undergo a predictable change of mechanical properties under the specified overload condition to permit the short circuiting action to occur.
In addition to facilitating the foregoing fail-safe features, the sleeves 12 may include a cutout portion as at 12D in Figure 2 to thus define an air gap between center body 10 and the respective clip 15 which is in electrical contact with one of the end electrodes.
With this additional provision a failure of the gas tube in the open mode, as for example by reason of a gas leak, does not result in a loss of protection; the air gap provides 1~ 8 ~5987 backup protection prior to arrester replacement.
To facilitate use in a wide variety of applications, the arrester assembly of Figures 1-4 is potted in a modular shell 18, the potting material 19 therein being an epoxy compound.
Prior to the potting the arrester assembly may be wrapped and voids filled with PTFE or equivalent material (not shown).
An application of the arrester to a station protector configuration is illustrated in Figures 5 through 7. Tube 10 per se together with fusible sleeves 12 and shorting clips 15 have already been described above. However, whereas the embodi-ment of Figures 1 through 4 employed welded flexible circuit coupling leads, the instant embodiment is encapsulated in a modular shell 20 installed in turn in a base assembly 30. Shell 20 also contains fixed line terminals 21 and ground strap 23. Each line electrode end cap lOB is electrically and mechanically con-nected to a respective line terminal 21 by way of a generally L-shaped connector 22 having one section in engagement with the respective end cap in the region between fingers 16 of the associated shorting clip. This section of connector 22 is of generally spade lug configuration with the end cap resiliently engaged by the fingers of the lug.
The opposite end of connector 22 is connected to the ribbed shank portion of threaded stud 21A of terminal 21, the stud being pressed fit into housing 20 as shown particularly in Figure 5. The threaded shaft portion includes nuts 21B and washers 21C to provide means for connection to the equipment lines.
Connection of center body lOA on tube 10 is provided by way of a generally L-shaped connector 25 having one section _ g _ of generally spade lug configuration which resiliently engages housing lOA, and another section which is secured to knurled shank 24A of a pin 24 which secures ground strap 23 to center body connector 25.
The distal end of the ground strap 23 is connected to a ground terminal assembly 26 having a threaded stud 27 secured to base 30 by means of nut 34. To facilitate this connection, strap 23 terminates in a lug which fits around shaft 27 and is secured by nut 37. As with the line terminals 21, ground terminal assembly 26 includes nuts 26A and associated washers 26B to facilitate connection to the around line.
The modular unit 20 with its tube and line terminals 21 and ground strap 23 are thus secured in the cavity in base 30 by way of the connection of ground strap 23 to the ground terminal assembly 26. Prior to assembly tube 10 is wrapped and potted in unit 20 as previously described relative to the first described embodiment.
The embodiment of Figures 5-7 functions in the manner previously described in connection with the systems of Figures '~
1-4. It furthermore illustrates the facility with which the arrester with its fail-safe features is packaged in various compact configurations.
From the foregoing description, application of the technique to both two-element and multi-element protectors will be apparent.
It should be noted that the fusible member configuration permits improved precision in the establishment of gap spacing in the backup airgap section.
Further, in the embodiment of figure 5 - 7 it should be -- 1.0 --jrc~
- - .
~59~7 noted that the absence of the module 20 from the sase assembly prevents the connections of the load circuit to the input lines thereby, precluding the making of unprotected connections.
,~, - 11 -jrc~
Claims (22)
PROPERTY OF PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A fail-safe surge arrester system comprising:
(1) a gas filled housing including at least two electrodes defining an ionizable gap:
(2) short circuiting means biased toward a short circuit connection with said electrodes; and (3) non-metallic fusible means in thermal contact with said gap and interposed between at least one of said electrodes and said short circuiting means to prevent said short circuit connection except in the presence of a sustained overload causing said fusible means to fuse and yield to permit the establishment of said short circuit connection.
(1) a gas filled housing including at least two electrodes defining an ionizable gap:
(2) short circuiting means biased toward a short circuit connection with said electrodes; and (3) non-metallic fusible means in thermal contact with said gap and interposed between at least one of said electrodes and said short circuiting means to prevent said short circuit connection except in the presence of a sustained overload causing said fusible means to fuse and yield to permit the establishment of said short circuit connection.
2. The arrester system as defined in Claim 1 in which said fusible means comprises a plastic material having mechanical properties which change substantially under pre-determined thermal conditions.
3. The arrester system as defined in Claim 1 in which said fusible means comprises a meltable fluoropolymer.
4. The arrester system as defined in Claim 1 in which said fusible means comprises heat shrinkable plastic material.
5. The arrester system as defined in Claim 1 in which said short-circuiting means includes a section defining an air gap electrode.
6. The arrester system as defined in Claim 1 in which at least one of said electrodes is of cylindrical configuration and said fusible means comprises a sleeve coaxially fitted thereon.
7. The arrester system as defined in Claim 6 in which said sleeve comprises heat shrinkable plastic material.
8. The arrester system as defined in Claim 7 in which said heat shrinkable plastic material comprises a meltable fluoropolymer.
9. The arrester system as defined in Claim 1 in which said short circuiting means comprises a conductive clip re-siliently engaging said housing.
10. The arrester system as defined in Claim 1 in which said short circuiting means includes one conductive section in electrical contact with one of said electrodes and another con-ductive section conductively connected to said one section and resiliently urged against said fusible means for contacting said other electrode in the event of fusion of said fusible means.
11. The arrester system as defined in Claim 10 in which said other electrode comprises a conductive part of said hous-ing and said fusible means comprises a thermoplastic cover-ing on at least a portion of said conductive part.
12. The arrester system as defined in Claim 11 in which said fusible means comprise a fusible fluoropolymer.
13. The arrester system as defined in Claim 1 in which said one electrode comprises a ground electrode.
14. The arrester system as defined in Claim 1 in which said housing includes two line electrodes and a ground electrode, and in which a pair of said short circuiting means and a pair of said fusible means are provided, one for each line electrode-ground electrode combination.
15. A fail-safe surge arrester comprising:
(1) at least two electrode structures defining an ionizable gap;
(2) electrically conductive short circuiting means biased toward a short circuit connection with said electrode structures and having resilient engaging means;
(3) non-metallic fusible means in thermal contact with said gap and interposed between at least one of said electrode structures and said resilient engaging means of said short circuit-ing means to prevent said short circuit connection except in the presence of a sustained overload causing said fusible means to fuse and yield to permit said resilient engaging means to pass through said fusible means and into short circuit connection with said one electrode structure.
(1) at least two electrode structures defining an ionizable gap;
(2) electrically conductive short circuiting means biased toward a short circuit connection with said electrode structures and having resilient engaging means;
(3) non-metallic fusible means in thermal contact with said gap and interposed between at least one of said electrode structures and said resilient engaging means of said short circuit-ing means to prevent said short circuit connection except in the presence of a sustained overload causing said fusible means to fuse and yield to permit said resilient engaging means to pass through said fusible means and into short circuit connection with said one electrode structure.
16. The arrester as defined in Claim 15 in which said fusible means comprises a thermoplastic material.
17. The arrester as defined in Claim 15 in which at least one of said electrode structures is of cylindrical con-figuration and said fusible means comprises a heat shrinkable plastic sleeve coaxially fitted thereon.
18. A fail-safe arrester system comprising a generally tubular shaped housing having at least two electrode structures defining an ionizable gap, said electrode stuctures each includ-ing an exterior section of said housing, said sections being axially displaced from each other, a fusible non-metallic electrically insulative element covering at least a portion of
18. A fail-safe arrester system comprising a generally tubular shaped housing having at least two electrode structures defining an ionizable gap, said electrode stuctures each includ-ing an exterior section of said housing, said sections being axially displaced from each other, a fusible non-metallic electrically insulative element covering at least a portion of
Claim 18 continued..
one of said sections and oriented to be responsive to thermal conditions of said arrester, short-circuiting means inter-connecting said fusible element and said other section and pressed against said fusible element such that it passes there-through into contact with said one section in the event of sus-tained ionization of said gap.
one of said sections and oriented to be responsive to thermal conditions of said arrester, short-circuiting means inter-connecting said fusible element and said other section and pressed against said fusible element such that it passes there-through into contact with said one section in the event of sus-tained ionization of said gap.
19. An arrester system as defined in Claim 18 including module means for retaining said housing, electrode structures, fusible element and short circuiting means, said module means also including terminal means for connecting said electrode structures to the circuit to be protected, said terminal means also being adapted to serve as the junction interconnecting said circuit and the network supplying same, whereby in the absence of said module means said interconnection cannot be made.
20. A fail-safe arrester system comprising:
(1) a gas filled housing including at least two electrodes defining an ionizable gap;
(2) a short circuiting structure adapted in one condition to provide a short circuit connection between said electrodes;
(3) non-metallic fusible means thermally responsive to thermal conditions of said ionizable gap and interconnected with said short circuiting structure to prevent said condition except in the presence of a sustained overload causing said fusible means to fuse and yield to permit the establishment of said short circuit connection.
(1) a gas filled housing including at least two electrodes defining an ionizable gap;
(2) a short circuiting structure adapted in one condition to provide a short circuit connection between said electrodes;
(3) non-metallic fusible means thermally responsive to thermal conditions of said ionizable gap and interconnected with said short circuiting structure to prevent said condition except in the presence of a sustained overload causing said fusible means to fuse and yield to permit the establishment of said short circuit connection.
21. An arrester as defined in claim 20 in which said fusible means comprises a meltable fluoropolymer.
22. An arrester as defined in Claim 20 in which said fusible means comprises heat shrinkable plastic material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA298,463A CA1105987A (en) | 1978-03-08 | 1978-03-08 | Fail-safe/surge arrester systems |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA298,463A CA1105987A (en) | 1978-03-08 | 1978-03-08 | Fail-safe/surge arrester systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1105987A true CA1105987A (en) | 1981-07-28 |
Family
ID=4110938
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA298,463A Expired CA1105987A (en) | 1978-03-08 | 1978-03-08 | Fail-safe/surge arrester systems |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1105987A (en) |
-
1978
- 1978-03-08 CA CA298,463A patent/CA1105987A/en not_active Expired
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| MKEX | Expiry |