Patent Application
20090213518
The invention relates to a voltage surge protection device comprising a disconnection device with electric contacts. Said disconnection device comprises a first connecting electrode electrically connected with a first connecting strip, a second connecting electrode electrically connected with a second connecting strip, a third movable arc switching electrode electrically connected to the second connecting strip, and a surge arrestor connected in series between the third movable arc switching electrode and the second connecting strip. An actuating mechanism is designed to move the third movable arc switching electrode to cause permanent opening of the electric contacts.
Voltage surge protection devices are known comprising a surge arrestor with non-linear elements variable with the voltage and a disconnection device with contacts actuated by an actuating mechanism. The surge arrestor and disconnection device are connected in series.
As described in the document EP0441722B1, the disconnection device with contacts can take a break position and a make position respectively corresponding to the open state and closed state of the contacts. An actuating mechanism causes movement of the contacts of the disconnection device to the open state in particular in case of destruction of the surge arrestor when said non-linear elements are at the end of life.
The disconnection device with contacts is calibrated:
The contacts can generally open (repel) and reclose under a lightning surge without the actuating mechanism unlatching. This repulsion (opening) of the contacts during operation of the protection device is followed by automatic reclosing of said contacts.
What is meant by “permanent opening” of the contacts is opening caused by the actuating mechanism. This actuation can be brought about manually or be due to an electrical fault. In the case of manual opening, reclosing of the contacts then only being possible by deliberate external action by a user. In the case of opening due to an electrical fault, opening is then definitive.
Calibration of known protection devices is performed in such a way that the disconnection device actuating mechanism remains latched in the presence of electric surge currents of 10/350 or 8/20 type. It is generally not desirable for the disconnection device actuating mechanism to unlatch and cause permanent opening of the contacts each time an electric surge current flows through the latter.
The tripping energy threshold is directly dependent on electric surge currents of 10/350 or 8/20 type for which opening of the disconnection device contacts is not desirable. In other words, said tripping energy threshold corresponds to the threshold above which electric surge currents of 10/350 or 8/20 type would bring about permanent opening of the electric contacts.
Furthermore, AC or DC short-circuit currents having an electric energy greater than the tripping energy threshold cause opening of the disconnection device contacts.
For electric surge currents of 10/350 or 8/20 type having an electric energy lower than the tripping energy threshold, the protection device is efficacious and enables said electric surge currents to be discharged without their energy being responsible for material damage. Moreover, electric surge currents of 10/350 or 8/20 type having an electric energy lower than the tripping energy threshold do not unlatch the disconnection device actuating mechanism to bring about opening of the contacts.
However, under certain particular circumstances, known protection devices do not present a sufficient protection level.
Indeed, when the AC or DC short-circuit energy drops below that of the tripping threshold energy, the actuating mechanism is no longer actuated and does not cause permanent movement of the disconnection device contacts from closed state to open state. The risk of deterioration of components is then not negligible
This situation can in particular occur when:
In the two situations described above, the short-circuit current having a lower energy than that of the tripping energy threshold can cause material damage.
The object of the invention is therefore to remedy the shortcomings of the state of the art so as to propose a voltage surge protection device comprising efficient disconnection means for protection against short-circuits.
The voltage surge protection device according to the invention comprises at least a first thermal disconnector against AC or DC short-circuit currents connected in series with the surge arrestor between the third movable arc switching electrode and the second connecting strip. Said thermal disconnector comprises at least one fuse element extending through a passage gap between a first and second conducting radial wall inside an insulating side wall extending from an arc extinguishing chamber, said arc extinguishing chamber comprising at least one conducting separator secured inside the side wall to define two pressure relief volumes. Said thermal disconnector is out of circuit when an electric arc is switched between the first connecting electrode and the second connecting electrode. Disconnection of said disconnector is performed when AC or DC short-circuit electric currents having a lower energy than a tripping energy threshold is flowing through the latter, said tripping energy threshold corresponding to the threshold above which electric surge currents of 10/350 or 8/20 type bring about permanent opening of the electric contacts.
The fuse element preferably comprises a cross-section of substantially identical shape to the cross-section of the passage gap.
The cross-section of said at least one fuse element in a plane perpendicular to a longitudinal centre line is preferably of elongate shape so that the length of said cross-section is at least three times larger than the width thereof.
Advantageously, the thermal disconnector comprises two arc extinguishing chambers respectively having a fuse element passing there-through.
Advantageously, said at least one conducting fuse element is composed of a conducting metal foil.
Advantageously, the metal foil is secured by securing means on an insulating support constituting an element of the insulating side wall.
Preferably, said at least one conducting fuse element is placed on the edges of said at least one separator.
Advantageously, the side wall comprises holes for removing the gases contained in the pressure relief volumes.
Advantageously, the protection device comprises a case having at least two flange-plates made of insulating material, said flange-plates forming part of the side wall of the thermal disconnector.
Advantageously, the insulating side wall is composed of a gas-generating material.
According to a first particular embodiment of the invention, the surge arrestor is electrically connected in series with the disconnection device by at least one fuse link, drive means exert a movement force moving the surge arrestor in case said at least one fuse link melts, movement of said arrestor acting directly on the actuating mechanism to move the third movable arc switching electrode and cause permanent opening of the contacts.
Preferably, the surge arrestor is electrically connected to the second connecting strip by a first fuse link that melts in the event of overheating of said surge arrestor.
Preferably, the surge arrestor is electrically connected to the second connecting strip by a second fuse link acting as thermal disconnector.
According to a second particular embodiment of the invention, a second electromagnetic disconnector against AC or DC short-circuit currents is connected in series with the thermal disconnector and the surge arrestor between the third movable arc switching electrode and the second connecting strip.
Preferably, the electromagnetic disconnector comprises electromagnetic tripping means designed to act on the actuating mechanism to cause permanent opening of the electric contacts.
According to a mode of development, a high-energy disconnector is connected in series between the first connecting electrode and the first connecting strip, the high-energy disconnector being calibrated to disconnect when electric currents having a greater energy than the tripping energy threshold flow through the latter.
Advantageously, the high-energy disconnector comprises an arc extinguishing chamber being delineated by an insulating side wall extending between a first and second conducting radial wall, the arc extinguishing chamber comprising at least one conducting separator secured inside said chamber to define two pressure relief volumes and at least one conducting fuse element electrically connected between a first and second electrode, said at least one fuse element extending from the first to the second radial wall via a gap and being rigidly secured in the arc extinguishing chamber by securing means, the cross-section of said at least one fuse element being of elongate shape so that the length of said cross-section is at least three times larger than its width.
According to a mode of development, a closing stop is designed to directly or indirectly keep the third movable arc switching electrode at a separation distance from the first connecting electrode when the electric contacts are closed.
Preferably, the closing stop comprises two parts: a first part made of insulating material placed in contact with the stationary contact and a second part made of conducting material placed adjacently to the first part and in contact with the movable contact when the two contacts are closed.
Advantageously, the thickness of the insulating first part is equal to the separation distance.
Other advantages and features will become more clearly apparent from the following description of particular embodiments of the invention, given as non-restrictive examples only and represented in the accompanying drawings in which:
As represented in
Surge arrestor 2 preferably comprises a voltage-dependent resistor 21. In certain non-represented embodiments of the invention, a spark gap can also be fitted in series with voltage-dependent resistor 21.
Disconnection device 3 comprises a first connecting electrode 40 electrically connected with a first connecting strip 41 and a second connecting electrode 50 electrically connected with a second connecting strip 51.
If protection device 1 is connected between phase and earth, connecting strips 41, 51, are designed to be respectively connected to a phase and to earth or vice-versa.
Disconnection device 3 comprises a third movable arc switching electrode 60 electrically connected to second connecting strip 51.
A first electric contact 30 is placed on first connecting electrode 40 and a second electric contact 31 is positioned on third movable arc switching electrode 60.
As represented in
Third movable arc switching electrode 60 is in contact with first connecting electrode 40 when electric contacts 30, 31 are closed.
Disconnection device 3 further comprises an actuating mechanism 7. Said mechanism is designed to be actuated to move third movable arc switching electrode 60 and mechanically bring about permanent opening of electric contacts 30, 31.
Disconnection device 3 with contacts 30, 31 is calibrated on the one hand to discharge electric surge currents of 10/350 or 8/20 type without actuating mechanism 7 being actuated, and on the other hand to actuate actuating mechanism 7 and cause permanent opening of contacts 30, 31 for AC or DC short-circuit currents.
Calibration of protection devices 1 is performed such that actuating mechanism 7 of disconnection device 3 remains latched in the presence of electric surge currents of 10/350 or 8/20 type. Actuating mechanism 7 does not in fact cause permanent opening of the contacts each time an electric surge current flows through the latter.
The tripping energy threshold is directly dependent on electric surge currents of 10/350 or 8/20 type for which opening of contacts 30, 31 of disconnection device 3 is not performed. In other words, said tripping energy threshold corresponds to the threshold above which electric surge currents of 10/350 or 8/20 type would cause permanent opening of electric contacts 30, 31.
When electric currents having a higher energy than a tripping energy threshold flow in the protection device, actuating mechanism 7 is actuated and moves third movable arc switching electrode 60 and mechanically causes permanent opening of electric contacts 30, 31. The electric currents responsible for actuation of actuating mechanism 7 are generally AC or DC short-circuit currents.
When electric surge currents of 10/350 or 8/20 type having a lower energy than the tripping energy threshold flow in the protection device, the protection device is efficacious and enables electric surge currents to be discharged without their energy being responsible for material damage. Furthermore, said electric surge currents do not unlatch disconnection device actuating mechanism 7 to cause opening of contacts 30, 31.
The surge voltage protection device comprises at least a first disconnector against AC or DC short-circuit currents 9, 10. Said at least first disconnector is a thermal disconnector 9.
As represented in
When electric surge currents of 10/350 or 8/20 type flow in the protection device, an arc electric 100 is very quickly switched between first connecting electrode 40 and second connecting electrode 50. Surge arrestor 2 and thermal disconnector 9 are then simultaneously switched out of circuit and the voltage surge flows very little in the latter. Said arrestor and said thermal disconnector are thereby protected and are not damaged by surges. The protection device comprises an extinguishing chamber 101 of the electric arc 100. First connecting electrode 40 and second connecting electrode 50 are arranged facing arc extinguishing chamber 101 and delineate the mouth of said arc extinguishing chamber 101. Said arc extinguishing chamber 101 comprises deionizing fins 102 designed for cooling an electric arc 100 and for extinguishing the latter.
As represented in
The cross-section of said at least one fuse element 91 in a plane perpendicular to the longitudinal centre line Z is of elongate shape. Moreover, said cross-section is substantially identical to that of the passage gap. The length of said cross-section is preferably at least three times larger than the width thereof.
Fuse element 91 extends from first to second radial wall 90 through passage gap and is rigidly secured in arc extinguishing chamber 99 by securing means. Said securing means guarantee rigid securing of said at least one fuse element 91 in case of a lightning strike. They enable the electrodynamic forces due to lightning strikes to be withstood.
Advantageously, as represented in
Conducting fuse element 91 is preferably composed of a metal conducting foil. The conducting foil is preferably secured by securing means onto an insulating support able to form an element of insulating side wall 92.
When fuse element 91 melts, an electric arc arises at the level of the passage gap. Due to the elongate shape of said passage gap, said electric arc, which naturally has a cross-section of substantially circular shape, is forced to deform and leave said gap zone. Development of the arc in pressure relief volumes 97 is thereby fostered enabling a sufficient arcing voltage to be reached for satisfactory limiting of short-circuit currents. Furthermore, said arc tends to be laminated inside said passage gap. This lamination of the electric arc in the passage gap tends to raise its voltage rapidly for satisfactory limiting of the short-circuit currents.
As illustrated in
As represented in
Said at least one side wall 92 is preferably composed of four side plates extending in a longitudinal centre line Z. The four side plates are joined to one another. Arc extinguishing chamber 99 has the shape of a parallelepiped and separators 95 have a square or rectangular shape. Surge protection device 1 comprises a case made of molded plastic material formed by two parallel side flange-plates made of insulating material placed on each side of a longitudinal centre line. Said flange-plates can form a part of two plates of side wall 92. A part of the side flange-plates then constitutes a part of side wall 92 of arc extinguishing chamber 99 of thermal disconnector 9. Separators 95 are secured by two of the side flange-plates.
According to an alternative embodiment, side wall 92 is preferably made from gas-generating plastic material. As represented in
Furthermore, in certain non-represented applications, the insulating side wall can be made from glass or ceramic.
According to an alternative embodiment, said at least one side wall 92 comprises holes for removal of the gases contained in pressure relief volumes 97.
According to another alternative embodiment, filters are placed at the level of the gas removal holes, preferably outside the arc extinguishing chambers. These filters enable external manifestations of the protection device to be greatly limited. Indeed, the hot breaking gases present in the arc extinguishing chamber are greatly cooled at the moment the latter pass through the filters. The inside of the surge protection device is thereby less polluted.
According to a first particular mode of development of the preferred embodiment, surge arrestor 2 is electrically connected in series with disconnection device 3 by at least one fuse link 8, 91. As represented in
Drive means 22 preferably comprise a spring. According to the particular embodiment as represented in
Surge arrestor 2 can be electrically connected to second connecting strip 51 by two fuse links 8, 91. For example, a first fuse link 8 is subject to melting in the event of overheating of said surge arrestor. A second fuse link 91 acts as thermal disconnector 9. When at least one of fuse links 8, 91 melts, voltage-dependent resistor 21 moves due to the action of displacement force Fd to act directly on actuating mechanism 7. As represented in
The conducting metal foil constitutes fuse element 91 of thermal disconnector 9. The conducting metal foil thus secures the voltage-dependent resistor in a first position. The conducting metal foil connecting voltage-dependent resistor 21 to second connecting strip 51 then comprises a cross-section that is calibrated to melt when electric short-circuit currents whose energy is lower than the tripping threshold flow through said foil for a given time. Furthermore, the conducting metal foil connecting voltage-dependent resistor 21 to second connecting strip 51 is welded to the second terminal of the voltage-dependent resistor by a low-temperature weld forming first fuse link 8.
Operation remains unchanged if voltage-dependent resistor 21 is placed in a carriage or in a movable case forming a single block with voltage-dependent resistor 21. The displacement force Fd could then be applied on the carriage or on the movable case instead of being applied directly on the voltage-dependent resistor. The carriage or movable case could furthermore act directly on trip bar 71 of actuating mechanism 7.
According to an alternative embodiment as represented in
Moreover, fitting two arc extinguishing chambers 99 connected in series enables the arcing voltage to be doubled and short-circuit currents to thereby be better limited. Fuse elements 91 respectively passing through the two arc extinguishing chambers 99 are not calibrated in identical manner. First fuse element 91 which is directly connected to voltage-dependent resistor 21 via metal foil is in fact calibrated to melt before the second fuse element. This configuration ensures that in the presence of short-circuit current, melting of the first fuse element will systematically release said voltage-dependent resistor. The voltage-dependent resistor will move due to the effect of displacement force Fd to actuate actuating mechanism 7 and bring about permanent and definitive opening of electric contacts 30, 31.
As represented in
Operation of surge protection device 1 comprising at least a first thermal disconnector 9 is as follows:
When electric surge currents of 10/350 or 8/20 type flow in the protection device, an arc electric 100 is very quickly switched between first connecting electrode 40 and second connecting electrode 50. Thermal disconnector 9 is disconnected from the circuit and the lightning shock wave no longer flows through the latter. Thermal disconnector 9 is then protected and is not damaged by lightning strikes.
Due to the fact that said disconnector is very seldom subjected to lightning strikes, calibration thereof is essentially dependent on the energy of the short-circuit currents for which it is designed to disconnect.
When AC or DC short-circuit currents having a lower energy than the tripping energy threshold flow through surge protection device 1, said currents flow through first connecting electrode 40, third connecting electrode 60 and thermal disconnector protecting against AC or DC short-circuit currents 9, 10. Repulsion of movable contact 31 is then limited. The arcing voltage between contacts 30, 31 remains weak and switching of arc 100 is not possible or takes place very late. What is meant by weak arcing voltage is a voltage lower than the power system voltage, for example less than 100 Volts.
Thermal disconnector 9 is nevertheless calibrated to disconnect when AC or DC short-circuit electric currents whose energy is greater than a disconnection threshold flow through the latter. For example, the electric currents responsible for disconnection of said disconnector have an intensity of more than 100 A.
Fuse element 91 of thermal disconnector 9 is calibrated to then switch from a closed electric state to an open electric state due to the effect of the thermal stress generated by flow of the short-circuit currents. The voltage generated by arc extinguishing chamber 99 of thermal disconnector 9 is great due to fractioning in the separators 95 and/or lamination of the arc. For these short-circuit current values, limitation will therefore essentially be performed by thermal disconnector 9. Furthermore, melting of fuse element 91 leads to displacement of surge arrestor 2 and actuation of actuating mechanism 7 to bring about permanent and definitive opening of electric contacts 30, 31.
When strong AC or DC short-circuit currents having a greater intensity than that of those described above, in particular having an intensity of more than 6000 A, flow through voltage surge protection device 1, repulsion of third movable arc switching electrode 60 is considerable. Arcing voltage 100 increases rapidly and switching of the latter onto second connecting electrode 50 takes place quickly. This speed of switching depends on the level of the short-circuit current. After switching, increase of the arcing voltage is ensured by arc extinguishing chamber 101. In spite of this high-speed opening of electric contacts 30, 31, a residual current can flow in third movable arc switching electrode 60 and eventually lead to melting of fuse element 91 of thermal disconnector 9 or actuation of electro-magnetic disconnector 10. Said melting or said actuation then results in movement of surge arrestor 2 and actuation of actuating mechanism 7 to cause permanent and definitive opening of electric contacts 30, 31.
According to first alternative embodiments, a high-energy disconnector 11 is connected in series between first connecting electrode 40 and first connecting strip 41. Said high-energy disconnector 11 is calibrated to disconnect when electric currents having a greater energy than the tripping energy threshold flow through the latter. Said high-energy disconnector is preferably designed to act on actuating mechanism 7 to move third movable arc switching electrode 60 and cause permanent opening of electric contacts 30, 31. High-energy disconnector 11 is then calibrated to unlatch actuating mechanism 7 when electric currents having a greater energy than the tripping energy threshold flow through same. Said high-energy disconnector then comprises means for acting on actuating mechanism 7 to bring about permanent opening of electric contacts 30, 31. As an example embodiment, high-energy disconnector 11 is an electromagnetic disconnector comprising electromagnetic trip means. As represented in
According to a second alternative embodiment of the preferred embodiments of the invention, the device comprises a closing stop 80 designed to secure third movable arc switching electrode 60 directly or indirectly at a distance D from first connecting electrode 40 when electric contacts 30, 31 are closed. This separation distance D of the electric contacts in the closed position acts as a spark-gap 22 electrically fitted in series with voltage-dependent resistor 21 of surge arrestor 2. As described in Patent application filed by the applicant under the number WO 04/042762 as an embodiment example, closing stop 80 comprises a conducting fixed pad presenting a surface forming a fixed electrode facing first connecting electrode 40 and an opposite surface forming a contact electrode on which third movable arc switching electrode 60 rests. According to another embodiment example as represented in
According to another alternative embodiment, the disconnection device comprises resetting means 72. Resetting means 72 enable said third electrode to move from the position called switching position to the position called service position. In other words, closing of contacts 30, 31 can be brought about mechanically by means of resetting means 72 after permanent opening of said contacts. Resetting means 72 further enable action on actuating mechanism 7 to bring about permanent opening of electric contacts 30, 31. Resetting means 72 are no longer operational as soon as an AC or DC short-circuit current disconnector 9, 10 has caused definitive opening of electric contacts 30, 31 following a short-circuit fault.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0801072 | Feb 2008 | FR | national |
