CA1131297A - Heat transfer system for voltage surge arresters - Google Patents
Heat transfer system for voltage surge arrestersInfo
- Publication number
- CA1131297A CA1131297A CA345,235A CA345235A CA1131297A CA 1131297 A CA1131297 A CA 1131297A CA 345235 A CA345235 A CA 345235A CA 1131297 A CA1131297 A CA 1131297A
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- Canada
- Prior art keywords
- housing
- varistor
- heat transfer
- radius
- varistors
- Prior art date
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Abstract
HEAT TRANSFER SYSTEM FOR VOLTAGE SURGE ARRESTERS
ABSTRACT OF THE DISCLOSURE
A heat transfer system for voltage surge arresters employs a dual radius arrester housing in combination with a plurality of sleeved zinc oxide varistors to efficiently cool the varistors during operation. The sleeved varistors are held in thermal contact with a large portion of the porcelain housing. The porcelain housing provides a heat sink facility to the arrester both during normal operating and voltage surge conditions.
ABSTRACT OF THE DISCLOSURE
A heat transfer system for voltage surge arresters employs a dual radius arrester housing in combination with a plurality of sleeved zinc oxide varistors to efficiently cool the varistors during operation. The sleeved varistors are held in thermal contact with a large portion of the porcelain housing. The porcelain housing provides a heat sink facility to the arrester both during normal operating and voltage surge conditions.
Description
~13~2g7 HEAT TRANSFER SYSTEM FOR
VOLTAGE SURGE ARRESTERS
Bac~ground of the Invention Zinc oxide varistors are employed in voltage surge arrester devices for shunting surge currents while maintaining the ability to operate under line voltage conditions. These varistors have a high exponent "n" in the voltage current relationship I=KVn for a varistor, where I is the current through the varistors, K is a constant and V is the voltage across the varistor. ~igh exponent zinc 10 oxide compound varistors can have sufficient resis-tance at normal line voltage to limit the current through the varistor to a low value, but resistance at high currents i5 such that th~ varistor voltage with surge current flowing is held to a level low enough to prevent damage to the insulation of the equipment being protected by the varistor.
Because the varist3rs are continuously connected from line-to-ground a continuous current 10ws through the varistor, and the current causes a small amount of power to be dissipated by the varlstors at normal system voltage and a normal operating temperature.
The ma~nitude of both the current and the resulting power increases as the varistor temperature increases.
Some means must therefore be provided to remove heat from tne varistor to prevent thermal runaway. ~The , ' ~, "~ :
~31;Z97 means must not only be capable of preventing thermal runaway under normal conditions, but it must also be capable of dissipating the heat resulting from high current surges. One effective means for removing heat from the varistor bodies employs an aluminum oxide filled silicone resin. Each individual varistor disc is cast within a thick quantity of the resin material prior to insertion within the surge arrester housing The thick silicone material acts as a heat sink and eventually the heat is carried to the walls of the surge arrester boady. The use of a silicone encapsulant for heat sinking zinc oxide varistors is described within U.S. Patents 4,092,694 and 4,100,588.
Another method for cooling zinc oxide varistor disc is described within Canadian patent application S.N.
336,635 dated Sept.28.1979, wherein zinc oxide varistor discs are fitted with a metal disc heat sink held in place by means of a flexible elastic sleeve.
The metal discvaristor combination is held in thermal contact within the surge arrester body by means of a resilient positioning member and a~ially applied spring force. The metal disc rapidly removes heat from the varistor body during surge conditions and transmits the heat to the heat radiating arrester housing through the flexible elastic sleeve surrounding both the varistor body and the metal disc. The thickness of metal disc required results in an arrester housing of significantly greater length~ Controlling the length of the housing is an important consideration in surge arrester design because wind loading and earthquake resistance stronly depend upon housing length. In addition surge arrester cost and weight increase with arrester length. The purpose of this invention is to provide an efficient heat transfer assembly with surge arrester housings of reasonable length having superior heat transfer properties.
~31Z9~
SUMMARY OF TEIE INVENTION
A dual radius surge arrester housing multi-func-tionally houses a plurality of zinc oxide varistors and heat sinks the varistors during normal operating, over voltage, and surge current conditions. A flexible el-astic sleeve surrounding each varistor provides effective thermal contact with a large area of the interior arrester housing wall.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a top perspective view of a zinc oxide varistor for use within the heat transfer system of the invention;
FIGURE 2 is a side view in partial section of a prior art voltage surge arrester assembly;
FIGURE 3 is a cross sectional view of the heat transfer arrangement of FIGURE 2;
FIGURE 4 is a side sectional ~iew of a sleeved zinc oxide varistor for use with the heat transfer assembly of the invention;
FIGURE 5 is a top perspective view of the sleeved varistor of FIGURE 4;
FIGURE 6 is a cross sectional view of one embodiment of the heat transfer arrangement according to the invention;
FIGURE 7 is a cross sectional view of a two column surge arrester housing according to the invention;
FIGURE 7A is a further embodiment of the housing of FIGURE 7 containing a coating of silicone resin;
FIGURE 8 is a cross sectional view of the arrester housing of FIGURE 7 containing a pair of varistors;
FIGURE 9 is a further embodiment of the arrester housing according to the invention;
FIGU~E 10 is. a cross sec~ional view of the embodi-ment of FIGURE 9 containing a sleeved varistor;
FIGURE 10A is a cross sectional view of an arrester housing having a modified geometry according to z9~
the invention; and FIGURE 11 is a graphic representation of the relationship between varistor temperature and time after a transient current surge for different included angles of contact with the varistor housing.
The invention relates, in general, to zinc oxide varistors such as varistor 10 shown in FIGURE 1 and consisting of a sintered disc of zinc oxide material 11 having an insulated ceramic collar 13 around the periphery of the disc and a pair of top and bottom electrodes 12 on opposing surfaces. When the varistors are used for surge voltage protection they are generally contained within an arrester 14 shown in FIGURE 2, which consists of a porcelain housing 15 having a pair of top and bottom terminals 16, 17 for providing electrical access to a plurality of varistors 10 within the housing.
This arrester is shown for comparison purposes with the heat transfer arrangement according to the invention.
The heat transfer mechanism of FIGURE :2, as described in the aforementioned Canadian Patent Application comprises an elastic sleeve 18 surxounding the varistor 10 and metal heat sink 20 and contacting a positioner 19 at one side, and the internal wall of porcelain housing 15 at the other side. The metal heat sink rapidly re-moves heat from the varistor and transfers the heat through silicone sleeve 18 to the housing where it becomes dissipated to the surrounding environment. The mechanism of heat transfer from the varistor and the - heat sink to the porcelain housing can be seen by re-ferring now to FIGURE 3. The positioner 19 forces the varistor and metal heat sink which, is attached to the bottom of the varistor, into thermal contact with the internal wall of housing 15. The heat then passes from thé varistor 10 and the heat sink through elastic 35 sleeve 18 to the housing 15. The space 21 between the .~
' _5_ SD5 6 33 varistor and the housing wall serves for the passage of gas generated by the internal assembly during varistor failure. Since the heat contained within the varistor and metal heat sink must ultimately transmit to the housing for dissipation purposes the limit in the heat transfer efficiency of the configuration depicted in FIGURE 3 is determined by the small contact area ~e~ween the varistor metal heat sink assembly and the housing interior. This inven~on improves the heat transfer efficiency between the varistors and the housing by changing the configuration of the interior housing in order to substantially increase the contact angle between the varistor and the interior of the housing.
FIGURE 4 shows a varistor 10 of the type similar to that depicted earlier in FIGURE 1, containing a top and bottom electrode 12 on a sintered disc of zinc oxide material ll and surrounded by a ceramic collar 13.
The varistor further includes a circumferentially arranged sleeve 18 made of an elastic material such as silicone rubber. The purpose of the sleeve is to pro-mote good the~mal contact between the varistor lO and the surrounding housing structureO Since the varistors 25 are arranged within the porcelain housing without any ~.
intervening metal heat sink the sleeve 18 must not extend along the entire thickness of the varistor so that the top and bottom electrodes of one varistor are - not prevented from contacting electrodes on neighboring varistors. This configuration is shown in FIGURE 5.
FIGURE 6 shows the heat transfer arrangement of the invention wherein a dual radius porcelain housing lS contains a varistor 10 surrounded by the elastic sleeve 18 and contacts a positioner l9. The positioner interposed between one side of the porcelain housing lS
and one side of the varistor 10 forces the varistor into tight thermal contact with another portion of the housing. It is to be noted that the sleeve 18 is made g7 from a flexible material that readily conforms to the inner housing when compressed, as~s~own in 18'.
The provision of the dual radius interior of porcelain housing 15 will be discussed in greater detail below.
~he contact angle a is shown to contact a much greater surface of the modified porcelain housing than with the prior art arrangement shown in FIGURE 3. This larger contact angle existing between the varistor and the modified porcelain housing allows varistors to operate without the provision of an additional metal heat sink and without the longer housing requirement called for with the prior art configuration.
FIGURE 7 shows one embodiment of a dual radius arrester housing 15 ~or use with the heat transfer system of the invention. A flrst radius depicted by radius rl matches the approximate radius of the sleeved varistor to promote good contact with the housing.
The first radius rl defines a first area Al within which the sleeved varistor is inserted. A second radius r2 defining a second area A2 provides for the passage of gas during varistor ~ailure. A dual radius housing 15 having a coating of sleeve material 9 coated on the inner surface for use with unsleeved varistors is shown in FIGURE 7A.
25 The provision of opposing surfaces of the housing having a radius approximating the radius of a sleeved varistor allows two varistors to be stacked in a para-llel array within the housing. This is shown in FIGURE 3 wherein a pair of sleeved varistors 10 are positioned within the housing 15 and contain a posi-tioner 19 to force the varistors against the housing.
Each vaxistor contains an individual sleeve 18 which promotes the thermal transer between the varistors and housing by filling the interstices existing between the outer perimeter of the varistor and the housing.
Space 21 is provided, as described earlier, for the 113129~7 passage of gas generated by both varistors in the event of varistor failure.
FIGURE 9 shows a single varistor modiried arrester housing 15 containing a first radius rl and a second radius r2. The heat transfer assembly for the housing of FIGURE 9 is shown in FIGURE 10 and includes a var-istor 10, elastic sleeve 18 and spacer 19. The space holds the varistor in good thermal contact with the por-tion of the varistor housing defined by radius rl. The configurations depicted within the porcelain housings of FIGURES 6-9 can have varying degrees of contact angle a depending upon the thermal requirements of the varis-tors. The greater the contact angle the more efficient the heat transfer between the varistors and the housing.
This is depicted in FIGURE ll wherein representative varistor cooling curves are generated by plotting the varistor temperature vs. time following ~ transient current surge. The temperature of a varistor within the arrester housing providing a contact angle of 10 between the varistor and the housing is shown at A.
It can be seen that the varistor temperature,after a surge that is within the thermal capability of the varistor~approaches a constant steady state temperature.
The line voltage across the varistor in combination with the varistor current determines the varistor watts loss under steady state conditions which in turn deter-mines the varistor temperature.
As described in the aforementioned Can^adian-Pat., Application, the critical operating sequence of a ZnO
surge arrester involves a transient current surge followed by the steady state system voltage. Since the arrester is su~jected to additional energy input from the surge, it must be able to withstand an elevated wattage and temperature upon returning to the system voltage. If no heat transfer means were employed, the varistor temperature and watts could continuously increase to such an extent that the varistor reaches a thermal run-away condition. Thereore the aster that heat is removed from the varistor the lower the possibility of the occur-ence of thermal runaway~ Varistors having a contact angle of 90 as shown at B, cool more rapidly than varistors having a 10 contact angle. Varistors having a contact angle of 180 as shown at C approach the steady state operating temperature at an even greater rate. FIGURE 11 shows therefore, that the greater the degree of contact angle between the sleeved varistor and the arrester housing the more effective the heat transfer from the sleeved var-istor to the arrester housing. As described earlier it is extremely important to cool the varistor rapidly because it is necessary to reduce the ti~e that the varistor is exposed to a temperature close to the condition of thermal runaway.
This is further important because o the possibility of repetitive transient surges occurring while the varistor is - still at an elevated temperature. An ideal situation would be for varistors having a contact angle of 360. This is not feasible however, due to the requirements of providing some volume for the release of gases generated in the event o varistor failure.
The dual radius modifications to the arrester housing were made on porcelain type arresters although other insulating materials may be used to form the arrester housing. The housing can be cast or extruded from silicone resin or from other electrically insulating resins such as epoxy. It is further within the scope of this invention to modify the interior geometry of a standard uniformly circular arrester housing by coating or inserting some means to provide for large contact angles between the sleeved varistors and the housing interior. A housing 15 having a quantity of silicone material 8 on the inner surace to modiy the interior geometry is shown in FIGURE lOA. Although the spacers depicted in FIGURES 6, 8 and 10 comprise a silicone _9_ 5D5~33 resin similar to that employed for the sleeves, other electrically insulating and flexible materials can also be employed. In some applications it may be more convenient to apply a coating of thermally conductive and electrically insulating material to the entire perimeter o the varistor in place of the elastic sleeve or to apply the material only in the vicinity of the varistor that is in contact with the arrester housing.
The heat transfer system of the invention is disclosed ~or surge voltage arrestPrs as one example.
However the heat transfer system of the invention can be used wherever surge voltage devices may be employed.
VOLTAGE SURGE ARRESTERS
Bac~ground of the Invention Zinc oxide varistors are employed in voltage surge arrester devices for shunting surge currents while maintaining the ability to operate under line voltage conditions. These varistors have a high exponent "n" in the voltage current relationship I=KVn for a varistor, where I is the current through the varistors, K is a constant and V is the voltage across the varistor. ~igh exponent zinc 10 oxide compound varistors can have sufficient resis-tance at normal line voltage to limit the current through the varistor to a low value, but resistance at high currents i5 such that th~ varistor voltage with surge current flowing is held to a level low enough to prevent damage to the insulation of the equipment being protected by the varistor.
Because the varist3rs are continuously connected from line-to-ground a continuous current 10ws through the varistor, and the current causes a small amount of power to be dissipated by the varlstors at normal system voltage and a normal operating temperature.
The ma~nitude of both the current and the resulting power increases as the varistor temperature increases.
Some means must therefore be provided to remove heat from tne varistor to prevent thermal runaway. ~The , ' ~, "~ :
~31;Z97 means must not only be capable of preventing thermal runaway under normal conditions, but it must also be capable of dissipating the heat resulting from high current surges. One effective means for removing heat from the varistor bodies employs an aluminum oxide filled silicone resin. Each individual varistor disc is cast within a thick quantity of the resin material prior to insertion within the surge arrester housing The thick silicone material acts as a heat sink and eventually the heat is carried to the walls of the surge arrester boady. The use of a silicone encapsulant for heat sinking zinc oxide varistors is described within U.S. Patents 4,092,694 and 4,100,588.
Another method for cooling zinc oxide varistor disc is described within Canadian patent application S.N.
336,635 dated Sept.28.1979, wherein zinc oxide varistor discs are fitted with a metal disc heat sink held in place by means of a flexible elastic sleeve.
The metal discvaristor combination is held in thermal contact within the surge arrester body by means of a resilient positioning member and a~ially applied spring force. The metal disc rapidly removes heat from the varistor body during surge conditions and transmits the heat to the heat radiating arrester housing through the flexible elastic sleeve surrounding both the varistor body and the metal disc. The thickness of metal disc required results in an arrester housing of significantly greater length~ Controlling the length of the housing is an important consideration in surge arrester design because wind loading and earthquake resistance stronly depend upon housing length. In addition surge arrester cost and weight increase with arrester length. The purpose of this invention is to provide an efficient heat transfer assembly with surge arrester housings of reasonable length having superior heat transfer properties.
~31Z9~
SUMMARY OF TEIE INVENTION
A dual radius surge arrester housing multi-func-tionally houses a plurality of zinc oxide varistors and heat sinks the varistors during normal operating, over voltage, and surge current conditions. A flexible el-astic sleeve surrounding each varistor provides effective thermal contact with a large area of the interior arrester housing wall.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a top perspective view of a zinc oxide varistor for use within the heat transfer system of the invention;
FIGURE 2 is a side view in partial section of a prior art voltage surge arrester assembly;
FIGURE 3 is a cross sectional view of the heat transfer arrangement of FIGURE 2;
FIGURE 4 is a side sectional ~iew of a sleeved zinc oxide varistor for use with the heat transfer assembly of the invention;
FIGURE 5 is a top perspective view of the sleeved varistor of FIGURE 4;
FIGURE 6 is a cross sectional view of one embodiment of the heat transfer arrangement according to the invention;
FIGURE 7 is a cross sectional view of a two column surge arrester housing according to the invention;
FIGURE 7A is a further embodiment of the housing of FIGURE 7 containing a coating of silicone resin;
FIGURE 8 is a cross sectional view of the arrester housing of FIGURE 7 containing a pair of varistors;
FIGURE 9 is a further embodiment of the arrester housing according to the invention;
FIGU~E 10 is. a cross sec~ional view of the embodi-ment of FIGURE 9 containing a sleeved varistor;
FIGURE 10A is a cross sectional view of an arrester housing having a modified geometry according to z9~
the invention; and FIGURE 11 is a graphic representation of the relationship between varistor temperature and time after a transient current surge for different included angles of contact with the varistor housing.
The invention relates, in general, to zinc oxide varistors such as varistor 10 shown in FIGURE 1 and consisting of a sintered disc of zinc oxide material 11 having an insulated ceramic collar 13 around the periphery of the disc and a pair of top and bottom electrodes 12 on opposing surfaces. When the varistors are used for surge voltage protection they are generally contained within an arrester 14 shown in FIGURE 2, which consists of a porcelain housing 15 having a pair of top and bottom terminals 16, 17 for providing electrical access to a plurality of varistors 10 within the housing.
This arrester is shown for comparison purposes with the heat transfer arrangement according to the invention.
The heat transfer mechanism of FIGURE :2, as described in the aforementioned Canadian Patent Application comprises an elastic sleeve 18 surxounding the varistor 10 and metal heat sink 20 and contacting a positioner 19 at one side, and the internal wall of porcelain housing 15 at the other side. The metal heat sink rapidly re-moves heat from the varistor and transfers the heat through silicone sleeve 18 to the housing where it becomes dissipated to the surrounding environment. The mechanism of heat transfer from the varistor and the - heat sink to the porcelain housing can be seen by re-ferring now to FIGURE 3. The positioner 19 forces the varistor and metal heat sink which, is attached to the bottom of the varistor, into thermal contact with the internal wall of housing 15. The heat then passes from thé varistor 10 and the heat sink through elastic 35 sleeve 18 to the housing 15. The space 21 between the .~
' _5_ SD5 6 33 varistor and the housing wall serves for the passage of gas generated by the internal assembly during varistor failure. Since the heat contained within the varistor and metal heat sink must ultimately transmit to the housing for dissipation purposes the limit in the heat transfer efficiency of the configuration depicted in FIGURE 3 is determined by the small contact area ~e~ween the varistor metal heat sink assembly and the housing interior. This inven~on improves the heat transfer efficiency between the varistors and the housing by changing the configuration of the interior housing in order to substantially increase the contact angle between the varistor and the interior of the housing.
FIGURE 4 shows a varistor 10 of the type similar to that depicted earlier in FIGURE 1, containing a top and bottom electrode 12 on a sintered disc of zinc oxide material ll and surrounded by a ceramic collar 13.
The varistor further includes a circumferentially arranged sleeve 18 made of an elastic material such as silicone rubber. The purpose of the sleeve is to pro-mote good the~mal contact between the varistor lO and the surrounding housing structureO Since the varistors 25 are arranged within the porcelain housing without any ~.
intervening metal heat sink the sleeve 18 must not extend along the entire thickness of the varistor so that the top and bottom electrodes of one varistor are - not prevented from contacting electrodes on neighboring varistors. This configuration is shown in FIGURE 5.
FIGURE 6 shows the heat transfer arrangement of the invention wherein a dual radius porcelain housing lS contains a varistor 10 surrounded by the elastic sleeve 18 and contacts a positioner l9. The positioner interposed between one side of the porcelain housing lS
and one side of the varistor 10 forces the varistor into tight thermal contact with another portion of the housing. It is to be noted that the sleeve 18 is made g7 from a flexible material that readily conforms to the inner housing when compressed, as~s~own in 18'.
The provision of the dual radius interior of porcelain housing 15 will be discussed in greater detail below.
~he contact angle a is shown to contact a much greater surface of the modified porcelain housing than with the prior art arrangement shown in FIGURE 3. This larger contact angle existing between the varistor and the modified porcelain housing allows varistors to operate without the provision of an additional metal heat sink and without the longer housing requirement called for with the prior art configuration.
FIGURE 7 shows one embodiment of a dual radius arrester housing 15 ~or use with the heat transfer system of the invention. A flrst radius depicted by radius rl matches the approximate radius of the sleeved varistor to promote good contact with the housing.
The first radius rl defines a first area Al within which the sleeved varistor is inserted. A second radius r2 defining a second area A2 provides for the passage of gas during varistor ~ailure. A dual radius housing 15 having a coating of sleeve material 9 coated on the inner surface for use with unsleeved varistors is shown in FIGURE 7A.
25 The provision of opposing surfaces of the housing having a radius approximating the radius of a sleeved varistor allows two varistors to be stacked in a para-llel array within the housing. This is shown in FIGURE 3 wherein a pair of sleeved varistors 10 are positioned within the housing 15 and contain a posi-tioner 19 to force the varistors against the housing.
Each vaxistor contains an individual sleeve 18 which promotes the thermal transer between the varistors and housing by filling the interstices existing between the outer perimeter of the varistor and the housing.
Space 21 is provided, as described earlier, for the 113129~7 passage of gas generated by both varistors in the event of varistor failure.
FIGURE 9 shows a single varistor modiried arrester housing 15 containing a first radius rl and a second radius r2. The heat transfer assembly for the housing of FIGURE 9 is shown in FIGURE 10 and includes a var-istor 10, elastic sleeve 18 and spacer 19. The space holds the varistor in good thermal contact with the por-tion of the varistor housing defined by radius rl. The configurations depicted within the porcelain housings of FIGURES 6-9 can have varying degrees of contact angle a depending upon the thermal requirements of the varis-tors. The greater the contact angle the more efficient the heat transfer between the varistors and the housing.
This is depicted in FIGURE ll wherein representative varistor cooling curves are generated by plotting the varistor temperature vs. time following ~ transient current surge. The temperature of a varistor within the arrester housing providing a contact angle of 10 between the varistor and the housing is shown at A.
It can be seen that the varistor temperature,after a surge that is within the thermal capability of the varistor~approaches a constant steady state temperature.
The line voltage across the varistor in combination with the varistor current determines the varistor watts loss under steady state conditions which in turn deter-mines the varistor temperature.
As described in the aforementioned Can^adian-Pat., Application, the critical operating sequence of a ZnO
surge arrester involves a transient current surge followed by the steady state system voltage. Since the arrester is su~jected to additional energy input from the surge, it must be able to withstand an elevated wattage and temperature upon returning to the system voltage. If no heat transfer means were employed, the varistor temperature and watts could continuously increase to such an extent that the varistor reaches a thermal run-away condition. Thereore the aster that heat is removed from the varistor the lower the possibility of the occur-ence of thermal runaway~ Varistors having a contact angle of 90 as shown at B, cool more rapidly than varistors having a 10 contact angle. Varistors having a contact angle of 180 as shown at C approach the steady state operating temperature at an even greater rate. FIGURE 11 shows therefore, that the greater the degree of contact angle between the sleeved varistor and the arrester housing the more effective the heat transfer from the sleeved var-istor to the arrester housing. As described earlier it is extremely important to cool the varistor rapidly because it is necessary to reduce the ti~e that the varistor is exposed to a temperature close to the condition of thermal runaway.
This is further important because o the possibility of repetitive transient surges occurring while the varistor is - still at an elevated temperature. An ideal situation would be for varistors having a contact angle of 360. This is not feasible however, due to the requirements of providing some volume for the release of gases generated in the event o varistor failure.
The dual radius modifications to the arrester housing were made on porcelain type arresters although other insulating materials may be used to form the arrester housing. The housing can be cast or extruded from silicone resin or from other electrically insulating resins such as epoxy. It is further within the scope of this invention to modify the interior geometry of a standard uniformly circular arrester housing by coating or inserting some means to provide for large contact angles between the sleeved varistors and the housing interior. A housing 15 having a quantity of silicone material 8 on the inner surace to modiy the interior geometry is shown in FIGURE lOA. Although the spacers depicted in FIGURES 6, 8 and 10 comprise a silicone _9_ 5D5~33 resin similar to that employed for the sleeves, other electrically insulating and flexible materials can also be employed. In some applications it may be more convenient to apply a coating of thermally conductive and electrically insulating material to the entire perimeter o the varistor in place of the elastic sleeve or to apply the material only in the vicinity of the varistor that is in contact with the arrester housing.
The heat transfer system of the invention is disclosed ~or surge voltage arrestPrs as one example.
However the heat transfer system of the invention can be used wherever surge voltage devices may be employed.
Claims (12)
1. A heat transfer arrangement for voltage surge arresters comprising:
an electrically insulated housing having a passageway extending there through and defined by a dual radius configuration, the first radius conforming to the radius of a zinc oxide varistor within the housing and the second radius providing a gas transfer space; and heat transfer means intermediate the varistor and a housing wall for conducting heat away from the varistor into the housing wall.
an electrically insulated housing having a passageway extending there through and defined by a dual radius configuration, the first radius conforming to the radius of a zinc oxide varistor within the housing and the second radius providing a gas transfer space; and heat transfer means intermediate the varistor and a housing wall for conducting heat away from the varistor into the housing wall.
2. The heat transfer arrangement of Claim 1 further including a positioning member for forcing the varistor and thermal transfer means into contact with the housing wall.
3. The heat transfer arrangement of Claim 1 wherein opposing surfaces on the interior of the housing are formed with the first radius.
4. The thermal transfer system of Claim 1 wherein the thermal transfer means comprises a flexible sleeve surrounding the varistor.
5. The heat transfer arrangement of Claim 4 wherein the flexible sleeve comprises a silicone resin.
6. The heat transfer arrangement of Claim 2 wherein the positioning member comprises a body of silicone resin.
7. The arrangement of Claim 3 wherein a pair of first and second varistors is positioned within the opposing surfaces on the interior of the housing defined by said first radius.
8. The arrangement of Claim 7 wherein the varistors contact the housing to define a contact angle ranging from 10° to 180°.
9. The heat transfer arrangement of claim 1 wherein the heat transfer means comprises a coating of thermally conducting electrically insulating material on a portion of the varistor.
10. The arrangement of claim 1 wherein the heat transfer means comprises a layer of thermally conductive and electrically insulating material applied to the interior of the arrester housing.
11. A housing for voltage surge arresters comprising:
a body of electrically insulating material having a passageway extending through the body, said passageway defined by a first and a second radius, said first radius corresponding to the diameter of a zinc oxide varistor and said second radius providing a passageway for the escape of gases.
a body of electrically insulating material having a passageway extending through the body, said passageway defined by a first and a second radius, said first radius corresponding to the diameter of a zinc oxide varistor and said second radius providing a passageway for the escape of gases.
12. The housing of claim 11 wherein the material is selected from the group consisting of porcelain, silicone and epoxy.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA345,235A CA1131297A (en) | 1980-02-07 | 1980-02-07 | Heat transfer system for voltage surge arresters |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA345,235A CA1131297A (en) | 1980-02-07 | 1980-02-07 | Heat transfer system for voltage surge arresters |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1131297A true CA1131297A (en) | 1982-09-07 |
Family
ID=4116193
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA345,235A Expired CA1131297A (en) | 1980-02-07 | 1980-02-07 | Heat transfer system for voltage surge arresters |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1131297A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2701163A1 (en) * | 2012-08-22 | 2014-02-26 | Siemens Aktiengesellschaft | Valve arrester and cooling body for same |
-
1980
- 1980-02-07 CA CA345,235A patent/CA1131297A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2701163A1 (en) * | 2012-08-22 | 2014-02-26 | Siemens Aktiengesellschaft | Valve arrester and cooling body for same |
| US9861009B2 (en) | 2012-08-22 | 2018-01-02 | Siemens Aktiengesellschaft | Valve diverter with heat sink |
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