U.S. patent application number 11/572473 was filed with the patent office on 2008-04-17 for overload and short-circuit protection device with improved breaker capacity.
Invention is credited to Guy Lafon.
Application Number | 20080087648 11/572473 |
Document ID | / |
Family ID | 34947463 |
Filed Date | 2008-04-17 |
United States Patent
Application |
20080087648 |
Kind Code |
A1 |
Lafon; Guy |
April 17, 2008 |
Overload And Short-Circuit Protection Device With Improved Breaker
Capacity
Abstract
A protective device for an electrical installation, having at
least two electrodes between which an elastic arc can electric arc
can form, and a device for interrupting (6) the arc, formed by an
assembly of divider plates (7) and extending between an upstream
end (6A) and a downstream end (6B), with an entry region (E) for
the arc at the upstream end (6A) thereof. The interrupter device
(6) has an insulation means (10), formed by caps (13) that form a
partial insulating barrier between the electrodes and the upstream
end (6A), the caps (13) are provided with teeth (16) housed between
two adjacent plates (7). The invention further relates to overload
and short-circuit protection devices.
Inventors: |
Lafon; Guy; (Bagneres de
Bigorre, FR) |
Correspondence
Address: |
POWELL GOLDSTEIN LLP
ONE ATLANTIC CENTER FOURTEENTH FLOOR, 1201 WEST PEACHTREE STREET NW
ATLANTA
GA
30309-3488
US
|
Family ID: |
34947463 |
Appl. No.: |
11/572473 |
Filed: |
July 21, 2005 |
PCT Filed: |
July 21, 2005 |
PCT NO: |
PCT/FR05/01888 |
371 Date: |
October 9, 2007 |
Current U.S.
Class: |
218/149 |
Current CPC
Class: |
H01H 9/36 20130101; H01T
4/04 20130101; H01T 1/02 20130101; H01H 2009/365 20130101 |
Class at
Publication: |
218/149 |
International
Class: |
H01H 9/30 20060101
H01H009/30 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 21, 2004 |
FR |
0408095 |
Claims
1. A device for protecting an electrical installation against
overvoltages, overloads or short circuits, comprising: at least two
main electrodes between which an electric arc is able to form; an
electric arc breaker device formed by an assembly of splitting
plates and extending, considering the direction of propagation of
the electric arc, between an upstream end and an downstream end,
and with an entry area for the arc at its upstream end, at which
the electric arc penetrates inside the breaker device, wherein the
breaker device includes at the upstream end, insulating means
against the return of the electric arc, structurally designed and
arranged to allow the electric arc to enter the breaker device
while forming an obstacle against the exit of the electric arc, to
prevent the electric arc from escaping from the inside of the
breaker device once the electric arc is inside the breaker device,
the insulating means consist of caps arranged to form a partial
insulating barrier between the electrodes and the upstream end, the
caps having teeth (16) positioned at a distance from each other and
adapted to fit in between two consecutive splitting plates.
2. The device of claim 1, wherein the caps are arranged to entirely
cover the upstream end of the breaker device located around the
entry area for the arc.
3. The device of claim 1, wherein the assembly of splitting plates
extends along the direction of propagation of the electric arc,
between a front end and a distal end, the splitting plates having a
notch to form, once they are assembled, a groove arranged in order
to attract the electric arc such that the entry area for the arc
substantially coincides with the groove.
4. The device of claim 3, wherein the caps are positioned on either
side of the groove and designed such a that, in their functional
position, the caps cover the front end of one or several splitting
plates.
5. The device of claim 4, wherein the caps are formed by a
substantially elongated strip, intended to cover the front end of
several splitting plates, and from which an edge extends, arranged
such that when the cap is in the functional position, the edge
naturally covers the upper edge of the groove.
6. The device of claim 5, wherein the edge of the cap is adapted to
penetrate inside the groove when the cap is in the functional
position.
7. The device of claim 3 wherein the caps have a substantially
U-shaped section.
8. The device of claim 1, further comprising: a casing in an
electrically insulating material, within which the main electrodes
and the breaker device are mounted, and in that the insulating
means are made of the same material as the casing.
9. The device of claim 8, wherein the insulating means and the
casing are made by moulding from an injected plastic, epoxy resin
or ceramic type material.
10. The device of claim 1, wherein the breaker device includes an
insulating screen at the downstream end positioned to at least
partially cover the downstream end of the breaker device to prevent
the electric arc from escaping from the breaker device after the
electric arc has passed through the breaker device.
11. The device of claim 2, wherein the assembly of splitting plates
extends along the direction of propagation of the electric arc,
between a front end and a distal end, the splitting plates having a
notch to form, once they are assembled, a groove arranged in order
to attract the electric arc such that the entry area for the arc
substantially coincides with the groove.
12. The device of claim 4, wherein the caps have a substantially
U-shaped section.
13. The device of claim 5, wherein the caps have a substantially
U-shaped section.
14. The device of claim 6, wherein the caps have a substantially
U-shaped section.
Description
PRIORITY CLAIM
[0001] This patent application is a U.S. National Phase of
International Application No. PCT/FR2005/001888, filed Jul. 21,
2005, which claims priority to French Patent Application No.
0408095, filed Jul. 21, 2004, the disclosures of which are
incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] This invention relates to devices for protecting electrical
equipment or installations against overvoltages, notably transient
overvoltages due to lightning, overloads or short circuits.
[0003] This invention more particularly relates to a device for
protecting an electrical installation against overvoltages,
overloads or short circuits, including at least two main electrodes
between which an electric arc may form, and a device for breaking
the electric arc formed from an assembly of splitting plates and
extending along the direction of propagation of the electric arc,
between an upstream end and a downstream end, and with an entry
area for the arc at its upstream end, at which the electric arc
penetrates inside the breaker device, the breaker device including
at its upstream end, insulating means against the return of the
electric arc, structurally designed and arranged so as to allow the
electric arc to enter the breaker device while forming an obstacle
against the exit of the electric arc, preventing the electric arc
from escaping from the inside of the breaker device once the
electric arc is inside the breaker device.
BACKGROUND OF THE INVENTION
[0004] There are different categories of devices that may interrupt
a current, particularly high intensity current at a conventional
frequency (50 Hz). A distinction is made between devices, such as
circuit breakers designed to protect an electrical installation
against overloads or short circuits, and devices used to protect an
electrical installation against overvoltages, such as lightning
arresters or surge suppressors.
[0005] Such protection devices are usually provided with a current
breaking device (or a breaking chamber). In the case of circuit
breakers, this breaker device is intended to provide breaking of
short circuit currents. In spark gap lightning arresters, the
breaker device is intended to provide breaking of follow
currents.
[0006] The breaker device is generally formed by a plurality of
metal splitting plates mounted in parallel so as to break the
electric arc down into small elementary arcs so as to increase the
arc voltage and to provide breaking of the current. Known breaker
devices intrinsically have a predetermined breaking capacity
corresponding to the maximum value of current that they are able to
extinguish.
[0007] Thus, it is found that when the current intensity values are
greater than the recommended values for a given breaker device, the
electric arc may escape from the breaker device after having
penetrated therein and then form again outside the breaker device,
for example following the shortest path between one of the main
electrodes and the end of the splitting plates.
[0008] Such a phenomenon is particularly detrimental to the
protection device insofar that its effect is to make the attempt to
cut off the current fail. Further, this phenomenon may occur
several times within a fairly short period. The electric arc may
thus enter the breaker device and then exit from the breaker device
and enter the breaker device once again, until the unit is
destroyed without having been able to cut off the follow or short
circuit current.
[0009] It is known that when higher breaking capacities are
required, these drawbacks may be overcome by increasing the number
of splitting plates, putting several protection devices in series
or in parallel, or using additional mechanisms for physically
breaking the electric arc. Nevertheless, all these solutions have a
number of drawbacks particularly related to their application,
which is often difficult, and due to the fact that they lead to a
significant increase in the size of the protection devices.
SUMMARY OF THE INVENTION
[0010] Consequently, the features provided by the present invention
provide a solution to the various drawbacks listed above and
propose a new device for protecting an electrical installation
against overvoltages, overloads or short circuits, with improved
current breaking capacity.
[0011] Another feature of the present invention proposes a new
device for protecting an electrical installation against
overvoltages, overloads or short circuits, with limited
bulkiness.
[0012] Another feature of the present invention proposes a new
device for protecting an electrical installation against
overvoltages, overloads or short circuits, with a structure
particularly well adapted to the case of strong intensity
currents.
[0013] Another feature of the present invention proposes a new
device for protecting an electrical installation against
overvoltages, overloads or short circuits that is particularly easy
to manufacture.
[0014] The features provided by the present invention are achieved
by a device for protecting an electrical installation against
overvoltages, overloads or short circuits including at least two
main electrodes between which an electric arc is able to form, and
an electric arc breaker device formed by an assembly of splitting
plates and extending, considering the direction of propagation of
the electric arc, between an upstream end and a downstream end, and
with an entry area for the arc at its upstream end, at which the
electric arc penetrates inside the breaker device, the breaker
device including at its upstream end, insulating means against the
return of the electric arc, structurally designed and arranged so
as to allow the electric arc to enter the breaker device while
forming an obstacle against the exit of the electric arc, so as to
prevent the electric arc from escaping from the inside of the
breaker device once the electric arc is inside the breaker device,
wherein the insulating means consist of caps arranged so as to form
a partial insulating barrier between the electrodes and the
upstream end, the caps having teeth positioned at a distance from
each other and adapted to fit between two consecutive splitting
plates.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Other features and advantages of the present invention will
become more apparent after reading the following description made
with reference to the figures, given as purely illustrative and
non-limiting, wherein:
[0016] FIG. 1 is a sectional view of one exemplary embodiment of an
overvoltage protection device according to the present
invention;
[0017] FIG. 2 is a side view of a first exemplary embodiment of a
breaker device according to the present invention;
[0018] FIG. 3 is a front view of the breaker device of FIG. 2;
[0019] FIG. 4 is a top view of the breaker device of FIG. 2;
[0020] FIG. 5 is a front view of another exemplary embodiment of a
breaker device for the protection device according to the present
invention;
[0021] FIG. 6 is a side view of another exemplary embodiment of a
breaker device for the protection device according to the present
invention; and
[0022] FIG. 7 is a side view of another exemplary embodiment of a
breaker device for the protection device according to the present
invention.
DESCRIPTION OF THE INVENTION
[0023] The device according to the present invention for protecting
an electrical installation against overvoltages, overloads or short
circuits, is designed to protect an electrical piece of equipment
or installation. The expression "electrical installation" refers to
any type of apparatus or network subject to voltage perturbations,
notably transient overvoltages due to lightning or even overloads,
notably overload or short circuit currents. Such devices may
consist of spark gap lightning arresters or surge suppressors
provided with a follow current breaking device or circuit breakers
fitted with a short circuit current breaking device.
[0024] In this description, we are more particularly interested in
a spark gap type lightning arrester type device for protection
against overvoltages, but the invention obviously applies to
circuit breakers.
[0025] FIG. 1 illustrates a protection device 1 according to the
present invention, advantageously formed by a spark gap lightning
arrester. The protection device 1 comprises at least a first and
second electrode 2, 3 that may form the two main electrodes of the
spark gap lightning arrester, within an insulating casing 20, as
illustrated in FIG. 1. These two electrodes 2, 3 are held at a
distance from each other and separated by a lamella 4 in a
dielectric material which may improve and better control striking
of an electric arc between the electrodes 2, 3. This so-called
upstream end part of the device is the area for striking the
electric arc 5.
[0026] In the case of a circuit breaker, the electrodes are formed
by two contacts, for example, a fixed contact and a mobile contact,
held in physical contact with each other so as to provide the
electrical connection. In this case, the electric arc is formed
between both contacts when the mobile contact separates from the
fixed contact to provide electrical disconnection.
[0027] According to the present invention and as illustrated in
FIG. 1, the protection device 1 includes a device 6 for breaking
the electric arc 5.
[0028] In a particularly advantageous way, the breaker device 6 is
formed by an assembly of splitting plates 7 made of electrically
conducting material, for example, in metal, positioned in parallel
and at a distance from each other. The splitting plates 7 are
advantageously kept at a distance from each other by supporting
strips 8 made of an electrically insulating material.
[0029] According to the present invention, the breaker device 6
extends, considering the direction of propagation F of the electric
arc 5, between an upstream end 6A and a downstream end 6B. As shown
in FIGS. 3-5, the breaker device 6 has at its upstream end 6A, an
entry area for the electric arc E at which the electric arc 5
penetrates inside the breaker device 6. Thus, before penetrating
into the breaker device 6, the electric arc 5 propagates along the
direction of propagation F within a divergent space 9 extending
between the striking area of the electric arc and the breaker
device 6. The divergent space 9 is advantageously delimited by
electrodes 2, 3, and preferably filled with air.
[0030] According to one essential feature of the present invention,
the breaker device 6 includes at its upstream end 6A, insulating
means 10 against the return of the electric arc 5.
[0031] These insulating means 10 are structurally designed and
arranged so as to allow the electric arc 5 to enter the breaker
device 6 while forming an obstacle against the exit of the electric
arc 5, in order to prevent the electric arc 5 from escaping from
the breaker device 6 once the electric arc is inside the breaker
device.
[0032] The insulating means 6 are adapted to prevent the electric
arc 5 from returning backwards along a direction opposite to its
normal direction of propagation F, in such a way that once the
electric arc 5 has been broken down into a plurality of elementary
arcs within the breaker device 6, the electric arc may no longer
form again outside the breaker device 6, notably in the divergent
space 9.
[0033] Therefore, the non-return insulating means 10 operate as a
ground and are built and positioned relative to the splitting
plates 7 on the one hand and to the electrodes 2, 3, on the other
hand, so as to significantly reduce the likelihood that the
electric arc 5 escapes from the breaker device 6. Therefore, the
design of the protection device 1 according to the present
invention may significantly improve its short circuit current
breaking capacity.
[0034] The insulating means 10 according to the present invention
must provide an answer to a new problem which is that of letting
the electric arc 5 penetrate into the inside of the protection
device 6 while limiting the likelihood that the electric arc
escapes and forms again outside the breaker device 6.
[0035] Advantageously, the insulating means 10 are arranged so as
to form a partial insulating barrier between the electrodes 2, 3
and the upstream end 6A of the breaker device 6. The expression
"partial insulating barrier" refers not only to physical barriers
made of electrically insulating material, but also to not
necessarily physical barriers which may be electrically insulating
barriers, capable of preventing the formation of an electric arc
between the electrodes 2, 3 and the upstream end 6A of the breaker
device 6.
[0036] Advantageously, the splitting plates 7 extend along the
direction of propagation F of the electric arc 5, between a front
end 7A and a distal end 7B. The front end 7A and the distal end 7B
are located at substantially the same level as the upstream end 6A
and the downstream end 6B of the breaker device 6. In a
particularly advantageous way, the splitting plates 7 are each
provided with a notch 11, at least partially separating each
splitting plate 7 into two separate branches 7C, 7D. Thus, when the
splitting plates 7 are assembled so as to form the breaker device
6, the notches 11 form a groove 12, the shape of which, for example
a V-shape, is specifically designed to attract the electric arc 5
towards the inside of the breaker device 6. In this way, the entry
area E for the electric arc 5 substantially coincides with the
groove 12.
[0037] According to a first exemplary embodiment of the present
invention, the insulating means 10 are arranged so as to at least
partially physically close off the upstream end 6A of the breaker
device 6, thus forming a physical insulating barrier between the
electrodes 2, 3 and the upstream end 6A of the breaker device
6.
[0038] Even more preferably, the insulating means 10 are arranged
so as to entirely cover the upstream end 6A of the breaker device
located around the entry area E for the electric arc 5, for
example, on either side of it. The insulating means 10 may be
positioned on either side of the groove 12, as illustrated in FIG.
3, so as to cover the front end 7A of the branches 7C, 7D of the
splitting plates 7.
[0039] According to a another exemplary embodiment of the present
invention, the insulating means 10 may be formed from one or
several rigid strips (not shown), for example, positioned on either
side of the groove 12 so as to cover the front end 7A of the
splitting plates 7. The rigid strips then preferably extend along a
plane approximately perpendicular to the direction of propagation F
of the electric arc 5, and coplanar with the plane formed by the
front ends 7A of the splitting plates 7.
[0040] The rigid strips may advantageously be perforated with a
plurality of orifices so as to provide air flow between the
divergent space 9 and the breaker device 6.
[0041] Preferably, the rigid strips, through one of their faces,
come into contact with the front ends 7A of the splitting plates 7,
and preferably bear on them in a sealed manner.
[0042] Even more preferably, the insulating means 10 are formed by
caps 13 arranged so as to form a partial insulating barrier between
the electrodes 2, 3 and the upstream end 6A positioned on either
side of the groove 12 and designed in such a way that, in their
functional position, they will also cover the front end 7A of one
or several splitting plates 7.
[0043] Advantageously, the caps 13 are arranged so as to entirely
cover the upstream end 6A of the breaker device 6 located around
the entry area E for the arc.
[0044] As illustrated in FIGS. 3 and 4, the caps 13 are preferably
formed by a substantially elongated strip 14, designed to cover the
front end 7A of several splitting plates 7, and from which a lip 15
is arranged and oriented such that when the cap 13 is in its
functional position, the lip 15 will naturally cover the upper edge
12A of the groove 12.
[0045] Preferably, the edge 15 of the cap 13 is adapted to
substantially penetrate inside the groove 12 when the cap 13 is in
its functional position (FIG. 3).
[0046] Even more preferably, and as illustrated in FIG. 3, the cap
13 has a substantially U-shaped section so as to cover the end of
the splitting plates 7, notably of branches 7C, 7D, approximately
conforming to the shape of the branches 7C, 7D.
[0047] According to one exemplary embodiment illustrated in FIG. 2,
the caps 15 include teeth 16 positioned at a distance from each
other, preferably at regular intervals, and adapted to fit in
between two consecutive splitting plates 7 when the cap 13 is in
its functional position. With the teeth 16, it is possible to
prevent the splitting plates 7 at their front ends 7A from
deforming and notably moving closer to each other, while improving
the insulation properties of the caps 13.
[0048] According to one exemplary embodiment of the present
invention (not shown in the figures), the insulating means 10 are
advantageously made from the same material as the casing 20 of the
protection device 1, the casing 20 including the main electrodes 2,
3 on the one hand and the breaker device 6 on the other hand.
[0049] In this case, the shape of the inner surface of the casing
20 is adapted, for example, at the time when the casing 20 is
moulded, to exhibit structures in relief capable of forming the
insulating means 10.
[0050] The insulating means 10 and/or the casing 20 may
advantageously be made from a rigid material able to withstand the
arc temperature, for example, injected plastic with good
temperature resistance, and even more preferably an epoxy resin or
ceramic.
[0051] According to another exemplary embodiment of the present
invention illustrated in FIG. 5, the insulating means 10 are
advantageously formed by one or several preferably flexible and
adhesive strips 17. As illustrated in FIG. 5, the strips 17
advantageously cover the front ends 7A of the branches 7C, 7D of
the splitting plates 7, thus forming caps, similar to the exemplary
embodiments described above.
[0052] Advantageously, the strips 17 are made in a
high-temperature-resistant insulating material, and notably
resistant to the temperature of the arc. Preferably, the strips 17
are made from fiberglass, coated on one of its faces with a
thermosetting type silicone adhesive so as to provide excellent
thermal and mechanical strength.
[0053] In a particularly advantageous way, the sticky portion of
the strips 17 will conform to the upstream end 6A of the breaker
device 6, so as to fix the ribbons 17 onto the latter end.
[0054] According to another exemplary embodiment of the present
invention illustrated in FIGS. 6 and 7, the insulating means 10 do
not form a physical barrier between the electrodes 2, 3 and the
upstream end 6A of the breaker device 6, but the insulating means
10 form an immaterial electrically insulating barrier instead.
[0055] According to a first exemplary embodiment illustrated in
FIG. 6, the insulating means 10 are advantageously formed by an
electrically insulating coating 18 deposited over substantially the
entire surface of the terminal portion 7E, located towards the
front end 7A of one or several splitting plates 7. The coating 18
is advantageously positioned so as to cover the terminal portion
7E. The coating 18 may notably increase the distance to be
travelled by the electric arc to form again outside the breaker
device 6. Therefore, the presence of the coating 18 may reduce the
likelihood that the electric arc may form again between both main
electrodes 2, 3 outside the breaker device 6.
[0056] According to another exemplary embodiment of the present
invention illustrated in FIG. 7, the insulating means 10 are formed
by insulating plates 19 positioned on either side of the groove 12
and inserted between two successive splitting plates 17 so as to
extend towards the outside of the breaker device 6, beyond the
front end 7A of the splitting plates 7. The insulating plates 19
may also prevent the electric arc from escaping outside the breaker
device 6 by increasing the distance that the electric arc needs to
travel to form again outside the breaker device 6, between the main
electrodes 2, 3.
[0057] According to another more preferred exemplary embodiment of
the present invention, the breaker device 6 includes, at its
downstream end 6B, an insulating screen 30 positioned so as to at
least partially cover the downstream end 6B of the breaker device 6
so as to prevent the electric arc 5 from escaping from the breaker
device 6 after the electric arc has passed through the breaker
device, for example once (FIG. 1).
[0058] In this preferred exemplary embodiment, the insulating means
10 have a crucial role in that, after passing through the breaker
device 6 along the direction of propagation F, the electric arc 5
"rebounds" on the insulating screen 30 and then continues in a
direction substantially opposite the direction of propagation F,
towards the upstream end 6A of the breaker device 6. In such a
configuration, the applicant has observed that the electric arc 5
preferably returns along the branches 7C, 7D of the splitting
plates 7 and much more rarely to the central portion 12B of the
groove 12.
[0059] Consequently, in this exemplary embodiment, the insulating
barrier formed by the insulating means 10 may notably reduce the
likelihood that the electric arc escapes at the upstream end 6A of
the breaker device 6, thereby preventing the electric arc 5 from
forming again between the main electrodes 2, 3.
[0060] Operation of the protection device 1 according to the
invention will now be described, with reference to FIGS. 1-7.
[0061] During operation, when an overvoltage exceeding a
predetermined threshold value occurs, notably as a result of a
lightning strike, an electric arc 5 is established between one of
the two main electrodes 2, 3 allowing the lightning current to flow
to ground. This electric arc 5 then moves up to the breaker device
6 into which the electric arc penetrates at the entry area E,
located in approximately the same plane as the groove 12. The
electric arc 5 is then broken down into a plurality of elementary
arcs so as to increase the arc voltage of the current above the
mains voltage and limit the intensity of the current drained by the
protection device. The elementary electric arcs move towards the
downstream end 6B of the breaker device 6 until they reach the
insulating screen 30. A "rebound" phenomenon then occurs and the
elementary electric arcs leave in the direction opposite to the
initial direction of propagation F of the electric arc 5, towards
the downstream end 6A of the breaker device 6. According to the
most likely operating mode, the elementary electric arcs move
towards the branches 7C, 7D and more specifically along these
branches as far as their front end 7A.
[0062] They are then trapped by the insulating means 10 which
prevent the electric arc 5 from forming again outside the breaker
device 6.
[0063] Therefore, the protection device 1 according to the present
invention has a better short circuit current or follow current
breaking capacity than the current breaking capacity for devices
according to the prior art, while limiting the likelihood that the
electric arc, once inside the breaker device and broken down into a
plurality of elementary arcs, escapes from the breaker device to
form again outside the breaker device between the main
electrodes.
[0064] By the presence of the insulating means 10, the protection
device according to the present invention has a current-breaking
power multiplied by at least two as compared with devices from the
prior art.
[0065] The invention finds one aspect of its industrial application
in the design, the manufacturing and the use of protection devices
against overvoltages, overloads, or short circuits.
* * * * *