CA1137545A - Fail safe surge arrester systems - Google Patents
Fail safe surge arrester systemsInfo
- Publication number
- CA1137545A CA1137545A CA000313479A CA313479A CA1137545A CA 1137545 A CA1137545 A CA 1137545A CA 000313479 A CA000313479 A CA 000313479A CA 313479 A CA313479 A CA 313479A CA 1137545 A CA1137545 A CA 1137545A
- Authority
- CA
- Canada
- Prior art keywords
- layers
- layer
- short circuit
- air gap
- fusible
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
UNITED STATES PATENT APPLICATION
OF
CHARLES A. ROBERTS
AND
RAYMOND D. JONES
FOR
FAIL SAFE SURGE ARRESTER SYSTEMS
ABSTRACT
Laminar air gap devices include two overlapping con-ductive layers separated by a non-metallic insulating layer. The insulating layer is perforated to provide at least one air gap between the conductive layers. The devices are positioned between a line electrode and ground electrode of a gas filled surge arrester and resiliently retained thereon by conductive clips.
Non-metallic fusible elements, preferably plastic, are interposed between the clip legs and the associated electrode. The fusible element may also be the insulating layer between the conductive layers.
OF
CHARLES A. ROBERTS
AND
RAYMOND D. JONES
FOR
FAIL SAFE SURGE ARRESTER SYSTEMS
ABSTRACT
Laminar air gap devices include two overlapping con-ductive layers separated by a non-metallic insulating layer. The insulating layer is perforated to provide at least one air gap between the conductive layers. The devices are positioned between a line electrode and ground electrode of a gas filled surge arrester and resiliently retained thereon by conductive clips.
Non-metallic fusible elements, preferably plastic, are interposed between the clip legs and the associated electrode. The fusible element may also be the insulating layer between the conductive layers.
Description
~137S~
CROSS-REFERENCE TO RELATE~ APPLICATION
This application is related to commonly assigned Canadian Appli~ation Serial No. 298,463, filed March 8th, 197g .
BACRGROUND
Gas tube overvoltage protectors are widly 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 over-load, as where a power line has come in continued contact with a protected telephone line, produces a concomitant sustained ionization of the gas tube and the resultant passage 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 circuiting of the arrestor 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 presents of the permanent short and ground condition serves to flag attention to that condition thus signalling the need for ~,~
Pg/
1~7~
its inspection or replacement. Examples of this type of failsafe 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 bo~h fail-safe fusible (short) type protection as well as backup air gap protection.
Still another approach, disclosed in commonly assigned Canadian application serial No. 298,463, 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 between one or more t of the electrodes and the shorting mechanism. Surprisingly, the response of the non-metallic material to thermal con-ditions is precise and, moreover, does not leave an insul-ative fîlm in the course of fusing which might otherwise interfere with the short circuit contact.
The need exists, nonetheless, to develop ail-safe arrangements which provide both surge and failure protection ~or gas tube arresters.
SUMMAR~
The present invention is directed to fail-safe surge arrester assemblies in which both back-up surge and air gap back-up protection is provided with economically producible systems.
Accordingly, the present invention may be summarized as follows:
n~ f~ ~ r 3 _ 1~375g~i ~ .
A combination fail sa:Ee and air gap device for use with a gas filled surge arrester, comprising first and second metallic electrically conductive layers, the layers being in overlapping relationship, and an inter-mediate insulating layer of non-metallic fusible material interposed between and in contact with the first and second .
layers to prevent short circUitlng therebetween except in the presence of a sustained overload causing the fusible material to fuse and yield to permit establish~ent of a short circuit between the first and second layers, the intermediate layer having at least one predetermined aper-ture therein in the area of overlap between the first and second layers to define an air gap electrode therebetween.
sRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an elevation view, partly in schematic, of a gas filled arrester with a first embodiment of this invention;
Figures 2 and 3 are cross-sectional views taken along-lines 2-2 and 3-3, respectively, in Figure l;
Figure 4 is an enlarged plan vi.ew of the air gap device shown in Figure l;
Pg/~ d 4 -75~i Fi~ure 5 is a cross-sectional view taken along line 5-5 in Figure 4;
E'igure 6 is a plan view, partly in schematic and partly in cross-sect:ion, of a gas fil].ed arrester of the second embodiment;
.~ , sd/i~`6 -4A-.
1~75~5 ,, .
1 1I Figure 7 is a cross-sectional view tsken along line 7-7
CROSS-REFERENCE TO RELATE~ APPLICATION
This application is related to commonly assigned Canadian Appli~ation Serial No. 298,463, filed March 8th, 197g .
BACRGROUND
Gas tube overvoltage protectors are widly 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 over-load, as where a power line has come in continued contact with a protected telephone line, produces a concomitant sustained ionization of the gas tube and the resultant passage 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 circuiting of the arrestor 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 presents of the permanent short and ground condition serves to flag attention to that condition thus signalling the need for ~,~
Pg/
1~7~
its inspection or replacement. Examples of this type of failsafe 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 bo~h fail-safe fusible (short) type protection as well as backup air gap protection.
Still another approach, disclosed in commonly assigned Canadian application serial No. 298,463, 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 between one or more t of the electrodes and the shorting mechanism. Surprisingly, the response of the non-metallic material to thermal con-ditions is precise and, moreover, does not leave an insul-ative fîlm in the course of fusing which might otherwise interfere with the short circuit contact.
The need exists, nonetheless, to develop ail-safe arrangements which provide both surge and failure protection ~or gas tube arresters.
SUMMAR~
The present invention is directed to fail-safe surge arrester assemblies in which both back-up surge and air gap back-up protection is provided with economically producible systems.
Accordingly, the present invention may be summarized as follows:
n~ f~ ~ r 3 _ 1~375g~i ~ .
A combination fail sa:Ee and air gap device for use with a gas filled surge arrester, comprising first and second metallic electrically conductive layers, the layers being in overlapping relationship, and an inter-mediate insulating layer of non-metallic fusible material interposed between and in contact with the first and second .
layers to prevent short circUitlng therebetween except in the presence of a sustained overload causing the fusible material to fuse and yield to permit establish~ent of a short circuit between the first and second layers, the intermediate layer having at least one predetermined aper-ture therein in the area of overlap between the first and second layers to define an air gap electrode therebetween.
sRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an elevation view, partly in schematic, of a gas filled arrester with a first embodiment of this invention;
Figures 2 and 3 are cross-sectional views taken along-lines 2-2 and 3-3, respectively, in Figure l;
Figure 4 is an enlarged plan vi.ew of the air gap device shown in Figure l;
Pg/~ d 4 -75~i Fi~ure 5 is a cross-sectional view taken along line 5-5 in Figure 4;
E'igure 6 is a plan view, partly in schematic and partly in cross-sect:ion, of a gas fil].ed arrester of the second embodiment;
.~ , sd/i~`6 -4A-.
1~75~5 ,, .
1 1I Figure 7 is a cross-sectional view tsken along line 7-7
2 ¦1 in Figure 6 and illustrating sn air gap device and clip with
- 3 1l fusible material on the clip legs;
4 1¦ Figure 8 is a cross-sectional view taken along line 8-8 ! in Figure 6;
- 6 il Figure 9 is a cross-sect~onal view taken along line 9-9 7 ~¦ in Figure 6 and il~ustrating an air gap device and fusible member 8 ' in the form of a cylindrical sleeve about the gas tube;
9 Figure 10 is an enlarged plan view of an air gap device ¦
l used in Figure 6;
11 , Fig-~re 11 is a longitudinal cross-sectional view ~aken 12 along l~ne 11-11 in Figure 10;
13 , Figure 12 is a top plan view of another air gap device - 14 l similar to that illustrated in Figure 10;
'I Figure 13 is a longitudinal cross-~ectional view taken : 16 ll along line 13-13 in Figure 12;
17 ll Figure 14 is a bottom plan view of the embodiment in 18 Il Flgure 12; and 19 ll Figure 15 i6 a cross-sectional view taken along line 'i 15-15 in Figure 12 and enlarged for clarity of illustration.
22 DE~ILED DESCRIPTI~N
,-23 ¦ While this invention is susceptible of embodiment in ~any dlfferent ~orms, there is shown in the drswings and will 1 herelnafter be described in detail a preferred embodiment of the 26 ' invention, and modifications thereto, with the understand~ng that 27 ~I the preser.t disclosure is to be considered as an exemplification -_ 5 _ ,~ . . : .
1 vf the principles of the inventlon and is not intended ~o llmit 2 1I the invention to the e~h~diments illustrated.
3 ¦ In the embodi~en~ illustrated in Flgure!s 1-3 and 6-9, 4 1 a gas tube 20 i8 provided, the tube lncluding a c:enter body 20A
¦¦ and electrode end caps 20B each separated from the center body 6 1 20A by a respective insulated sleeve;section 20C.
7 I The arrester 20, which is of ~lown constructioa and may 8 l¦ comprise for e~ample TII Model 31, has its end electrodes ~not 9 ll shown) extending inwardly from the end caps 20B toward the center , of the tube ~nterior to define a gap between the electrodes.
11 Spacing and di~ensions are such that each electrode also forms 12 l a gap with the center body conductlve casing section 20A.
13 , The ~ube is filled with a &as and the electrode end 14 '1 c~ps 2QB are each provided as by welding with a lead 21B and ,, terminal 22B, e.g., a spade lug, for connection to the circuit 16 ll to be protected. Center body 20A is likewise provided with a 17 ll lead 21A welded thereto and the associated connection 22A
18 , for connection to groundO
19 1 In the prese~ce of overvoltage conditions the gas i~ ¦
~I tube 20 ioni~es thereby creating in known manner, conducti~e 21 l¦ shunting paths between each line of the protected circuit and 22 ¦I ground (via the respective ter~inal lead 21B and ground lead .;
~3 11 2LA)~
24 ¦ A short circuiting ~eans 25,illustrated as a clip, is Ij disposed between each line electrode 20B and the ground elec~rode 26 l 20A. Clip 25 is illustrative, since it will be understood by 27 Ij those skllled in the art that other clip arrang~ments are readily ~-~8 ,' adaptable to this function.
., ., l .
1~375~S
Il .
ll .
1 ', Each ~l~p 25, which is illustratively of grain oriented 2 tin plated carbon s~eel, heat treated for s~ress relief fsom 3 'I hydrogen embrittlement after plating, includes a first set of 4 spring fingers 26 resiliently engaging, respectivelyl end cap S I,' (line electrode) 20B and another set of spring fingers 27 dis-6 ll posed about cen~er body (ground electrode) 20A. The spring fin-7 I gers 26 and 27 are integrally connected by the bridge section 28 8 , of each clip. The spring fingers 26, as best illustrated in 9 Figures 3 and 8, are in direct contact with the end caps 20B to provide electrical contact therewith. Conversely, as shown in 11 greater detail in Figures 2, 7 and 9, the fingers 27 of the 12 short^circuit clips are spaced from contact with center body 20A l 13 by reason of fusible elements 30, 31 and 32 described in greater ¦
14 ' detail below. Specifically, each of the fingers 27 includes a ,, contact portion 27A which is urged in the direction of contact ¦
16 lI with grounded center body 20A and which consequently presses j resiliently on the fusible member interposed therebetween.
18 l Fusible elements 30, 31 and 32 are of non-metallic, 19 , electrically insulative composition. Suitable materials will ¦ have melt temperatures in the range corresponding to ther~al con-21 ditions at srrester thermal overload and will have suitable 22 dielectric strength, dielectric constant, dissipation factor and ; .
23 ! volume and surf8ce resistivity to provide the requisitive insula-24 I tive functioD. The preferred material should also be free of 1 embrittlement or plastic flow due to aging and high ambient tem-26 1 perature efects, be non-in1ammable under the overload conditionsl, 27 , have good mechanical properties and be inert to corrosives and ~-, 1 , .
28 i weather.
,~, , ,, . . . . : , , 75~a~
1 I Exemplary of such a cla6s of m~te~ als are certain of ¦ I
2 li the fluoroplast~cs, sueh as fluorinated ethylene propylene polyme~
3 , (FEP), the pol~mer perfluoroalkoxy (PFA), the modified copolymer 4 ¦, of ethylene and tetrafluoroethylene (ETFE) (m~rketed under the !; DuPont Company trademark ~efzel), and poly (ethylene-chlorotri-6 fluoro-ethylenej(E-CTFE copolymer) marketed under the Allied 7 I Che~ical Corporation mark Halfar. (The fluoroplastic poly-8 1I tetrafluoroethylene (TFE), on the other hand, does not have suit-9 l, able melt properties for the illustrated application.) In the examples, element 30 is formed of FEP film, and 31 and 32 are 11 I formed of approximately 38" long FEP tubing, sizes AWG 6 and 25 12 respectively.
13 With reference to the embodi~ent of Figures 1-5, fusible 14 ~~ element 30 is generally rectangular in shape and interposed be-tween a first layer 35 and a second layer 36 of conductive mate-~i . . '.
16 , risl, e.g., copper. Layers 35 and 36 are generally rectangular 17 in shape and in register but smaller in dimensions than layer 30 18 ~o that layer 30 extends beyond the periphery of the conductive 19 ,' layers. Insulative layer 30 includes two rectangular openings il 30A which together with the thickness of the layer 30 provide a 21 il, pair of air gaps between the first and second layers, Preferably, 22 1I the air gap is about 3 mils and provides a strike voltage in the 23 l' range of 500 to 1000 volts.
24 1I The entire assembly 40 including the first and second 1l layers 35 and 36 and insulative layer is a safety device which is 26 positioned circumferentially about the center body 20A as shown ~7 in Figures 1 and 2. Fingers 27 engage copper lsyer 35 and bias I ;
Z8 it against fusible layer 30, layer 36, and center body 20A, I
, .
~ ~37S~ l ,, . , .
During normal operation of the arrest~r 20, transient 2 surges produce ionization in the normal ~anner to protect the 3 ~ subject equipment. If, however, a sustained surge condition 4 occurs as where a line is permanently oontacted by a higher voltage line, the resultant ioniz8tion currents fl~wing through the ar-6 rester produce excessive heat; the ~usible layer 30, placed in 7 I the arrester region to respond to this heating, thereby fuses.
8 ' As this occurs, spring fingers 27, and in particular the contact 9 sections 27A thereof, move layer 35 lnto contact with layer 36 and center body 20A as the fusible layer 30 yields and flows.
11 When electric~l contact is made a short circuit is established 12 between the respective end cap and the center body thus providingi 13 a fail-safe (short~ action.
14 ' Additionally, the air gap 30A between layer 35 and layer 36 provides back-up protection in the event of gas tube 16 , failure. With this additional provision a failure of the gas 17 I tube in the open mode, as for example by reason of a gas leak, 18 does not re8ult in a lo~s of protection; the air gap provides 19 l, back-up protection prior to arre8ter replacement.
1ll Figures 6-15 illustrate still further modifications to 21 l~ the invention. In these embodiments the air gap devices 50 and 22 ,l 60, Figures 10 and 12 respectively, are arranged in longitudinal 23 ,¦ relation8hip on the gas tube 20 beneath the clips 25.
24 11 The fusible elements may take alternative forms. In ,I Figure 7, tubul~r sleeves 31 are arranged about the fingers 27 of 26 I clips 25 so that a layer of fusible material ls interposed between 27 contact sections 27A and center body 20A, In Figure 9, a tubular ,1 . I
g _ , . .
1~3~5~
.
,, . .
1 1! sleeve 32 is arr~nget circumferentially about center body 20A to 2 ~ m~inta~n contact section 27A of the clip in spaced relation~h~p 3 1l thereto. Additionally, sleeve 32 overlaps device 50 or 60 to re-4 ~I tain the device on snd in contact with center body 20A.
¦ Air gap device 50, Figures 10 and 11, includes a first 6 ¦I conductive layer 51 in the form of a rectangular iayer of metallic 7 ~ I! conductor material, e.g. copper. Layer 51 is t~kn~e in electrical 8 ¦ contact with end cap 20B by clip 25. A second layer 52 of conduc-9 1 tive material is in overlapping relationship with layer 51. Layer ¦ 52 is in direct contact with center body 20A. Interposed between 11 l' layers 51 and 52 is a non~-metallic layer 54 of insulating materiaL
12 '' Layer 54 may be of the type previously described or a high melting 13 point material, such as a polyimide, an exemplary example is the 14 polyimide sold under the designation Kapton and may be surface li coated with adhesive to secure layers 51 and 52. Layer 54 includesl 16 1l an aperture 54A therein to define an air gap between the ~ rlapping, 17 ll portion of layers 51 and 52. Since gas tube 20 has two line 18 ~ electrodes, a pair of conductive layers 51 and associated air 19 gaps 54A are provided. However, it will be understood that the i device wor~s egually well when the gas tube has one line electrode 21 and one ground electrode, I
22 , In the air gap device 50, the insulating layer 54 e~- ¦
23 , tendg béyond the periphery of both layers 51 and 5~. Layers 51 24 1,l snd 52 may be fabricated by known methods, preferably by printed ¦ circuit techniques.
26 !¦ Figures 12-15 illustrate sn air gap device similar to 27 ldevice 50 which has been modified to improve its contact and 28 I conforming characteristic with the gas tube 20 as well as faci-29 litating and improving its fabrication and operation.
More specifically, each first conductive layer 61, e.~.
-10- .
.
.3754 i . . .1 . 1 1 co~per, includes an end cap snd/or clip contact portion 6LA of 2 I geDerslly rectangular shape. Portions 61A are plsced in direct 3 contact with their associated end caps (electrodes) 20B. A neck 4 1 portion 61B connects portion 6LA t~ a generally ~ircular shape i' portion 61C overlying the air gap formed by aperture 64A describe~
6 1 below.
Correspondingly, second conductive layer 62 includes 8 ~ two circular shaped portions 62A concentric with sir gap 64A and ¦
g interconnected by rectang~llar shaped portion 62B.
Insulacing layer 64 is interposed between layers 61 and I -~
11 62 and formed with cut-out portions 64B. These cut-out portions 12 facilitate in the wrapping and conformance of the air gap device 13 ; about the gas tube.
14 Moreover, with particular reference to Figure 15, the !~ insulating layer 64 includes a layer 65 of plastic material of 16 i the types de~cribed above and is faced on each surface with an 17 ¦ adhesive layer 66 which bonds the layer 64 to the associated con- !
18 ' ductive layers 61 snd 62. Preferably, the edges 66~ of the adhe-l l~ !
19 , sive layer ad~acent the hole 64A in the plastic layer 65 is set 24 ~11 back a short distance. By wsy of illustration, with a hole dia- ¦
2~ meter of .OS inch in the plastic layer 65, a set back of .OOS
22 ¦1 inch provides sufficient clearance. The set back clearance ame-23 I liorates the possibility of the adhesive flowi..g into the air gap 24 ¦ during assembly. Moreover, the air gap dimension, e.g. 3 mils, ¦ must take into account the thickness of the adh~sive, for example 26 l, when the adhesive layers 66 are 1 mil thick, a plastic layer 65 27 , o 1 mil is used to achieve a 3 mil air gap. The set of the ad-, I
~8 ; hesive also functions to prevent bridging or short circuiting , ~ '7S~S
' . , 1 ll of the air g8p which might occur as a result of electrical dis-2 charges if the adhesive entered the alr g8p.
3 The operation of the arrester assembly of Figures 6-15 4 ,l ls similar to that prev~ously described. During normal operation of the arrester 20, transient surges produce ionization in the 6 ,I normal manner to protect the sub3ect equipment. If a sustained 7 I surge condition occurs, the resultant ionization currents flowlng ô through the arrester produce excessive heat; the sleeves 31 or 9 I 32, placed in the arrester region to respond to this heating, thereby fuse. As this occurs, spring fingers 27 move into con- j 11 tact with center body 20A as the fusible sleeve material beneath ~ those contacts yields and flows. When electrical contact is nade 13 a short circuit is established between the respective end cap and l 14 the center body th us providing a fail-safe (short circuiting~ action.
~ Non-mPtallic materials other than the foregoing may be 16 used as the fusible members provided they have appropriate elec-17 ' trical insulation properties and undsrgo a predictable change of 18 ~echanical properties under the specified overload condition to 19 'I permit the short circuiting action to occur.
ll Moreover, the air gaps 54A or 64A provide back-up pro-21 l¦ tection in the event of failure of the gas tube.
22 To facilitate use in a wide variety of applications, 23 ll the arrester assembly of Figures 1 & 6 may be potted in a modular 24 l¦ shell, the potting material therein being an epoxy compound.
ll Prior to the potting the arrester assembly may be wrapped and 26 l voids filled with PTFE or equivalent material (not shown).
27 iAlternatively, the arrester assembly may be used in d station .- .
.
.
11~37~L5 ~' , Il .. , 1 ¦ protector configuration well known in the art. Obviously, the 2 I present invention is useful with gas tube arrester having more or 3 11 less number of electrodes than the three electrode tube a,r~,es,ter 4 1 shown. The ability to provide an sir gap which i9 sealed from env~..ns
- 6 il Figure 9 is a cross-sect~onal view taken along line 9-9 7 ~¦ in Figure 6 and il~ustrating an air gap device and fusible member 8 ' in the form of a cylindrical sleeve about the gas tube;
9 Figure 10 is an enlarged plan view of an air gap device ¦
l used in Figure 6;
11 , Fig-~re 11 is a longitudinal cross-sectional view ~aken 12 along l~ne 11-11 in Figure 10;
13 , Figure 12 is a top plan view of another air gap device - 14 l similar to that illustrated in Figure 10;
'I Figure 13 is a longitudinal cross-~ectional view taken : 16 ll along line 13-13 in Figure 12;
17 ll Figure 14 is a bottom plan view of the embodiment in 18 Il Flgure 12; and 19 ll Figure 15 i6 a cross-sectional view taken along line 'i 15-15 in Figure 12 and enlarged for clarity of illustration.
22 DE~ILED DESCRIPTI~N
,-23 ¦ While this invention is susceptible of embodiment in ~any dlfferent ~orms, there is shown in the drswings and will 1 herelnafter be described in detail a preferred embodiment of the 26 ' invention, and modifications thereto, with the understand~ng that 27 ~I the preser.t disclosure is to be considered as an exemplification -_ 5 _ ,~ . . : .
1 vf the principles of the inventlon and is not intended ~o llmit 2 1I the invention to the e~h~diments illustrated.
3 ¦ In the embodi~en~ illustrated in Flgure!s 1-3 and 6-9, 4 1 a gas tube 20 i8 provided, the tube lncluding a c:enter body 20A
¦¦ and electrode end caps 20B each separated from the center body 6 1 20A by a respective insulated sleeve;section 20C.
7 I The arrester 20, which is of ~lown constructioa and may 8 l¦ comprise for e~ample TII Model 31, has its end electrodes ~not 9 ll shown) extending inwardly from the end caps 20B toward the center , of the tube ~nterior to define a gap between the electrodes.
11 Spacing and di~ensions are such that each electrode also forms 12 l a gap with the center body conductlve casing section 20A.
13 , The ~ube is filled with a &as and the electrode end 14 '1 c~ps 2QB are each provided as by welding with a lead 21B and ,, terminal 22B, e.g., a spade lug, for connection to the circuit 16 ll to be protected. Center body 20A is likewise provided with a 17 ll lead 21A welded thereto and the associated connection 22A
18 , for connection to groundO
19 1 In the prese~ce of overvoltage conditions the gas i~ ¦
~I tube 20 ioni~es thereby creating in known manner, conducti~e 21 l¦ shunting paths between each line of the protected circuit and 22 ¦I ground (via the respective ter~inal lead 21B and ground lead .;
~3 11 2LA)~
24 ¦ A short circuiting ~eans 25,illustrated as a clip, is Ij disposed between each line electrode 20B and the ground elec~rode 26 l 20A. Clip 25 is illustrative, since it will be understood by 27 Ij those skllled in the art that other clip arrang~ments are readily ~-~8 ,' adaptable to this function.
., ., l .
1~375~S
Il .
ll .
1 ', Each ~l~p 25, which is illustratively of grain oriented 2 tin plated carbon s~eel, heat treated for s~ress relief fsom 3 'I hydrogen embrittlement after plating, includes a first set of 4 spring fingers 26 resiliently engaging, respectivelyl end cap S I,' (line electrode) 20B and another set of spring fingers 27 dis-6 ll posed about cen~er body (ground electrode) 20A. The spring fin-7 I gers 26 and 27 are integrally connected by the bridge section 28 8 , of each clip. The spring fingers 26, as best illustrated in 9 Figures 3 and 8, are in direct contact with the end caps 20B to provide electrical contact therewith. Conversely, as shown in 11 greater detail in Figures 2, 7 and 9, the fingers 27 of the 12 short^circuit clips are spaced from contact with center body 20A l 13 by reason of fusible elements 30, 31 and 32 described in greater ¦
14 ' detail below. Specifically, each of the fingers 27 includes a ,, contact portion 27A which is urged in the direction of contact ¦
16 lI with grounded center body 20A and which consequently presses j resiliently on the fusible member interposed therebetween.
18 l Fusible elements 30, 31 and 32 are of non-metallic, 19 , electrically insulative composition. Suitable materials will ¦ have melt temperatures in the range corresponding to ther~al con-21 ditions at srrester thermal overload and will have suitable 22 dielectric strength, dielectric constant, dissipation factor and ; .
23 ! volume and surf8ce resistivity to provide the requisitive insula-24 I tive functioD. The preferred material should also be free of 1 embrittlement or plastic flow due to aging and high ambient tem-26 1 perature efects, be non-in1ammable under the overload conditionsl, 27 , have good mechanical properties and be inert to corrosives and ~-, 1 , .
28 i weather.
,~, , ,, . . . . : , , 75~a~
1 I Exemplary of such a cla6s of m~te~ als are certain of ¦ I
2 li the fluoroplast~cs, sueh as fluorinated ethylene propylene polyme~
3 , (FEP), the pol~mer perfluoroalkoxy (PFA), the modified copolymer 4 ¦, of ethylene and tetrafluoroethylene (ETFE) (m~rketed under the !; DuPont Company trademark ~efzel), and poly (ethylene-chlorotri-6 fluoro-ethylenej(E-CTFE copolymer) marketed under the Allied 7 I Che~ical Corporation mark Halfar. (The fluoroplastic poly-8 1I tetrafluoroethylene (TFE), on the other hand, does not have suit-9 l, able melt properties for the illustrated application.) In the examples, element 30 is formed of FEP film, and 31 and 32 are 11 I formed of approximately 38" long FEP tubing, sizes AWG 6 and 25 12 respectively.
13 With reference to the embodi~ent of Figures 1-5, fusible 14 ~~ element 30 is generally rectangular in shape and interposed be-tween a first layer 35 and a second layer 36 of conductive mate-~i . . '.
16 , risl, e.g., copper. Layers 35 and 36 are generally rectangular 17 in shape and in register but smaller in dimensions than layer 30 18 ~o that layer 30 extends beyond the periphery of the conductive 19 ,' layers. Insulative layer 30 includes two rectangular openings il 30A which together with the thickness of the layer 30 provide a 21 il, pair of air gaps between the first and second layers, Preferably, 22 1I the air gap is about 3 mils and provides a strike voltage in the 23 l' range of 500 to 1000 volts.
24 1I The entire assembly 40 including the first and second 1l layers 35 and 36 and insulative layer is a safety device which is 26 positioned circumferentially about the center body 20A as shown ~7 in Figures 1 and 2. Fingers 27 engage copper lsyer 35 and bias I ;
Z8 it against fusible layer 30, layer 36, and center body 20A, I
, .
~ ~37S~ l ,, . , .
During normal operation of the arrest~r 20, transient 2 surges produce ionization in the normal ~anner to protect the 3 ~ subject equipment. If, however, a sustained surge condition 4 occurs as where a line is permanently oontacted by a higher voltage line, the resultant ioniz8tion currents fl~wing through the ar-6 rester produce excessive heat; the ~usible layer 30, placed in 7 I the arrester region to respond to this heating, thereby fuses.
8 ' As this occurs, spring fingers 27, and in particular the contact 9 sections 27A thereof, move layer 35 lnto contact with layer 36 and center body 20A as the fusible layer 30 yields and flows.
11 When electric~l contact is made a short circuit is established 12 between the respective end cap and the center body thus providingi 13 a fail-safe (short~ action.
14 ' Additionally, the air gap 30A between layer 35 and layer 36 provides back-up protection in the event of gas tube 16 , failure. With this additional provision a failure of the gas 17 I tube in the open mode, as for example by reason of a gas leak, 18 does not re8ult in a lo~s of protection; the air gap provides 19 l, back-up protection prior to arre8ter replacement.
1ll Figures 6-15 illustrate still further modifications to 21 l~ the invention. In these embodiments the air gap devices 50 and 22 ,l 60, Figures 10 and 12 respectively, are arranged in longitudinal 23 ,¦ relation8hip on the gas tube 20 beneath the clips 25.
24 11 The fusible elements may take alternative forms. In ,I Figure 7, tubul~r sleeves 31 are arranged about the fingers 27 of 26 I clips 25 so that a layer of fusible material ls interposed between 27 contact sections 27A and center body 20A, In Figure 9, a tubular ,1 . I
g _ , . .
1~3~5~
.
,, . .
1 1! sleeve 32 is arr~nget circumferentially about center body 20A to 2 ~ m~inta~n contact section 27A of the clip in spaced relation~h~p 3 1l thereto. Additionally, sleeve 32 overlaps device 50 or 60 to re-4 ~I tain the device on snd in contact with center body 20A.
¦ Air gap device 50, Figures 10 and 11, includes a first 6 ¦I conductive layer 51 in the form of a rectangular iayer of metallic 7 ~ I! conductor material, e.g. copper. Layer 51 is t~kn~e in electrical 8 ¦ contact with end cap 20B by clip 25. A second layer 52 of conduc-9 1 tive material is in overlapping relationship with layer 51. Layer ¦ 52 is in direct contact with center body 20A. Interposed between 11 l' layers 51 and 52 is a non~-metallic layer 54 of insulating materiaL
12 '' Layer 54 may be of the type previously described or a high melting 13 point material, such as a polyimide, an exemplary example is the 14 polyimide sold under the designation Kapton and may be surface li coated with adhesive to secure layers 51 and 52. Layer 54 includesl 16 1l an aperture 54A therein to define an air gap between the ~ rlapping, 17 ll portion of layers 51 and 52. Since gas tube 20 has two line 18 ~ electrodes, a pair of conductive layers 51 and associated air 19 gaps 54A are provided. However, it will be understood that the i device wor~s egually well when the gas tube has one line electrode 21 and one ground electrode, I
22 , In the air gap device 50, the insulating layer 54 e~- ¦
23 , tendg béyond the periphery of both layers 51 and 5~. Layers 51 24 1,l snd 52 may be fabricated by known methods, preferably by printed ¦ circuit techniques.
26 !¦ Figures 12-15 illustrate sn air gap device similar to 27 ldevice 50 which has been modified to improve its contact and 28 I conforming characteristic with the gas tube 20 as well as faci-29 litating and improving its fabrication and operation.
More specifically, each first conductive layer 61, e.~.
-10- .
.
.3754 i . . .1 . 1 1 co~per, includes an end cap snd/or clip contact portion 6LA of 2 I geDerslly rectangular shape. Portions 61A are plsced in direct 3 contact with their associated end caps (electrodes) 20B. A neck 4 1 portion 61B connects portion 6LA t~ a generally ~ircular shape i' portion 61C overlying the air gap formed by aperture 64A describe~
6 1 below.
Correspondingly, second conductive layer 62 includes 8 ~ two circular shaped portions 62A concentric with sir gap 64A and ¦
g interconnected by rectang~llar shaped portion 62B.
Insulacing layer 64 is interposed between layers 61 and I -~
11 62 and formed with cut-out portions 64B. These cut-out portions 12 facilitate in the wrapping and conformance of the air gap device 13 ; about the gas tube.
14 Moreover, with particular reference to Figure 15, the !~ insulating layer 64 includes a layer 65 of plastic material of 16 i the types de~cribed above and is faced on each surface with an 17 ¦ adhesive layer 66 which bonds the layer 64 to the associated con- !
18 ' ductive layers 61 snd 62. Preferably, the edges 66~ of the adhe-l l~ !
19 , sive layer ad~acent the hole 64A in the plastic layer 65 is set 24 ~11 back a short distance. By wsy of illustration, with a hole dia- ¦
2~ meter of .OS inch in the plastic layer 65, a set back of .OOS
22 ¦1 inch provides sufficient clearance. The set back clearance ame-23 I liorates the possibility of the adhesive flowi..g into the air gap 24 ¦ during assembly. Moreover, the air gap dimension, e.g. 3 mils, ¦ must take into account the thickness of the adh~sive, for example 26 l, when the adhesive layers 66 are 1 mil thick, a plastic layer 65 27 , o 1 mil is used to achieve a 3 mil air gap. The set of the ad-, I
~8 ; hesive also functions to prevent bridging or short circuiting , ~ '7S~S
' . , 1 ll of the air g8p which might occur as a result of electrical dis-2 charges if the adhesive entered the alr g8p.
3 The operation of the arrester assembly of Figures 6-15 4 ,l ls similar to that prev~ously described. During normal operation of the arrester 20, transient surges produce ionization in the 6 ,I normal manner to protect the sub3ect equipment. If a sustained 7 I surge condition occurs, the resultant ionization currents flowlng ô through the arrester produce excessive heat; the sleeves 31 or 9 I 32, placed in the arrester region to respond to this heating, thereby fuse. As this occurs, spring fingers 27 move into con- j 11 tact with center body 20A as the fusible sleeve material beneath ~ those contacts yields and flows. When electrical contact is nade 13 a short circuit is established between the respective end cap and l 14 the center body th us providing a fail-safe (short circuiting~ action.
~ Non-mPtallic materials other than the foregoing may be 16 used as the fusible members provided they have appropriate elec-17 ' trical insulation properties and undsrgo a predictable change of 18 ~echanical properties under the specified overload condition to 19 'I permit the short circuiting action to occur.
ll Moreover, the air gaps 54A or 64A provide back-up pro-21 l¦ tection in the event of failure of the gas tube.
22 To facilitate use in a wide variety of applications, 23 ll the arrester assembly of Figures 1 & 6 may be potted in a modular 24 l¦ shell, the potting material therein being an epoxy compound.
ll Prior to the potting the arrester assembly may be wrapped and 26 l voids filled with PTFE or equivalent material (not shown).
27 iAlternatively, the arrester assembly may be used in d station .- .
.
.
11~37~L5 ~' , Il .. , 1 ¦ protector configuration well known in the art. Obviously, the 2 I present invention is useful with gas tube arrester having more or 3 11 less number of electrodes than the three electrode tube a,r~,es,ter 4 1 shown. The ability to provide an sir gap which i9 sealed from env~..ns
5 ~J the enn~k~t~ by the laminar construction deccribed provides a ¦ significant advance.
7 ~ These modifications and others may be made by those ¦
8 1i skilled in the art without departing from the scope and spirit 9 ¦, of the present invention as pointed out in the appended claims.
i~1 ' !
'11 ''' 12 ll 13 ii 14 ~ ;
18 1 l -I
221 ~ l . , I
23 ~ ' ,.' 224 ~ . .
,
7 ~ These modifications and others may be made by those ¦
8 1i skilled in the art without departing from the scope and spirit 9 ¦, of the present invention as pointed out in the appended claims.
i~1 ' !
'11 ''' 12 ll 13 ii 14 ~ ;
18 1 l -I
221 ~ l . , I
23 ~ ' ,.' 224 ~ . .
,
Claims (16)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A combination fail safe and air gap device for use with a gas filled surge arrester comprising first and second metallic electrically conductive layers, said layers being in overlapping relationship, and an intermediate insulating layer of non-metallic fusible material interposed between and in contact with said first and second layers to prevent short circuiting therebetween except in the presence of a sustained overload causing said fusible material to fuse and yield to permit establishment of a short circuit between said first and second layers, said intermediate layer having at least one predetermined aperture therein in the area of overlap between said first and second layers to define an air gap electrode therebetween.
2. A device of claim 1, wherein said first and second layers and insulating layer are rectangular in shape.
3. A device of claim 1, wherein said insulating layer extends beyond the periphery of said first and second layers.
4. A device of claim 1, wherein said first and second layers are coterminous in dimensions and arranged in register.
5. A device of claim 1, wherein said first and second layers are copper.
6. A device of claim 1, wherein said intermediate layer is a heat shrinkable plastic material.
7. A device of claim 6, wherein said intermediate layer is a meltable fluoropolymer.
8. In a surge arrester assembly having a gas filled surge arrester including at least two electrodes defining an ionization gap and short circuit clamp means biased towards a short circuit connection with said electrodes, the improvement comprising:
safety means interposed between at least one of said electrodes and said short circuit clamp means, said safety means including first and second layers of metallic, electrically conductive material in contact with said clamp means and electrode, respectively, said layers being in overlapping relationship, and an intermediate insulating layer of fusible material in-terposed between said first and second layers, said intermediate layer defining an aperture therein to provide an air gap and operative to prevent said short circuit connection except in the presence of a sustained overload causing said fusible layer to fuse and yield to permit said short circuit means to bias said first layer into short circuit connection with said second layer.
safety means interposed between at least one of said electrodes and said short circuit clamp means, said safety means including first and second layers of metallic, electrically conductive material in contact with said clamp means and electrode, respectively, said layers being in overlapping relationship, and an intermediate insulating layer of fusible material in-terposed between said first and second layers, said intermediate layer defining an aperture therein to provide an air gap and operative to prevent said short circuit connection except in the presence of a sustained overload causing said fusible layer to fuse and yield to permit said short circuit means to bias said first layer into short circuit connection with said second layer.
9. An assembly of claim 8, wherein said gas filled surge arrester is provided with two line electrodes and a ground electrode, said assembly including safety means for each line electrode located on said ground electrode.
10. An assembly of claim 8, wherein said intermediate layer is a meltable fluoropolymer.
11. In a total fail safe surge arrester assembly having a gas filled surge arrester including at least two electrodes defining an ionization gap, and short circuit clamp means biased towards a short circuit connection with said electrodes, the improvement comprising:
air gap means interposed between a portion of said short circuiting clamp means and each of said electrodes, said air gap means including a first layer of metallic electrically conductive material in electrical contact with said clamp means and a second layer of metallic electrically conductive material in electrical contact with one of said electrodes and in overlapping relationship with said first layer; and an intermediate layer of insulating non-metallic fusible material interposed between and in contact with the over-lapping portions of said metallic layers, to prevent short circuiting therebetween except in the presence of a sus-tained overload causing said fusible material to fuse and yield to permit establishment of a short circuit between said first and second layers, said intermediate layer having an aperture therein to provide an air gap; and non-metallic fusible means in thermal contact with said ionization gap and interposed between said clamp means and one of said electrodes to also prevent short circuit connection there-between except in the presence of sustained overload causing said fusible means to fuse and yield to permit establishment of said short circuit connection.
air gap means interposed between a portion of said short circuiting clamp means and each of said electrodes, said air gap means including a first layer of metallic electrically conductive material in electrical contact with said clamp means and a second layer of metallic electrically conductive material in electrical contact with one of said electrodes and in overlapping relationship with said first layer; and an intermediate layer of insulating non-metallic fusible material interposed between and in contact with the over-lapping portions of said metallic layers, to prevent short circuiting therebetween except in the presence of a sus-tained overload causing said fusible material to fuse and yield to permit establishment of a short circuit between said first and second layers, said intermediate layer having an aperture therein to provide an air gap; and non-metallic fusible means in thermal contact with said ionization gap and interposed between said clamp means and one of said electrodes to also prevent short circuit connection there-between except in the presence of sustained overload causing said fusible means to fuse and yield to permit establishment of said short circuit connection.
12. An assembly of claim 11, wherein said air gap means and said fusible means are located at the same electrode.
13. An assembly of claim 12, wherein said first layer is in direct contact with the other of said electrodes and said clamp means.
14. An assembly of claim 12, wherein said fusible means is a sleeve positioned on said same electrode.
15. An assembly of claim 12, wherein said fusible means comprises a meltable fluoropolymer.
16. An air gap electrode device of claim 12, wherein said intermediate layer is polyimide.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000403191A CA1152558A (en) | 1977-10-18 | 1982-05-18 | Fail safe surge arrester systems |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US84332077A | 1977-10-18 | 1977-10-18 | |
| US843,320 | 1977-10-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1137545A true CA1137545A (en) | 1982-12-14 |
Family
ID=25289629
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000313479A Expired CA1137545A (en) | 1977-10-18 | 1978-10-16 | Fail safe surge arrester systems |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1137545A (en) |
| MX (1) | MX146968A (en) |
-
1978
- 1978-10-16 CA CA000313479A patent/CA1137545A/en not_active Expired
- 1978-10-17 MX MX17525078A patent/MX146968A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| MX146968A (en) | 1982-09-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4212047A (en) | Fail-safe/surge arrester systems | |
| US6211770B1 (en) | Metal oxide varistor module | |
| US6710996B2 (en) | Surge arrestor | |
| US5113306A (en) | Non-fragmenting arrester with staged pressure relief mechanism | |
| CA1122268A (en) | Thermal switch short circuiting device for arrester systems | |
| US5311164A (en) | Surge absorber | |
| US11223200B2 (en) | Surge protective devices, circuits, modules and systems including same | |
| US4303959A (en) | Fail safe surge arrester systems | |
| US6477025B1 (en) | Surge protection device with thermal protection, current limiting, and failure indication | |
| US4150414A (en) | Air gap short circuiting device for gas tube arrester | |
| US4320435A (en) | Surge arrester assembly | |
| US5029302A (en) | Fail safe gas tube | |
| US4319300A (en) | Surge arrester assembly | |
| US6157286A (en) | High voltage current limiting device | |
| US4394704A (en) | Surge arrester assembly | |
| JP2718169B2 (en) | Surge absorber with security function | |
| CA1137545A (en) | Fail safe surge arrester systems | |
| CA1152558A (en) | Fail safe surge arrester systems | |
| CA1105987A (en) | Fail-safe/surge arrester systems | |
| CN107910488A (en) | One kind is connected in series part, battery and battery pack | |
| JPH04217813A (en) | Surge absorber provided with security function | |
| KR100952072B1 (en) | A Disconnector For Arrester | |
| WO1999010897A9 (en) | Improvements relating to high voltage electric installations | |
| WO2019220171A1 (en) | Voltage limiter with a short-circuiting device | |
| JPH0453101A (en) | Surge absorber with safety function |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |