EP2402971B1 - Medium- or high-voltage electrical device including an insulating enclosure - Google Patents

Description

The invention relates to a medium or high voltage electrical device comprising an insulating envelope.

In a given configuration, a shielded arrester device for medium or high voltage comprises a polymer insulating jacket with inner and outer conductive layers, in which zinc oxide blocks are inserted. These blocks, made of a non-linear doped zinc oxide material, are insulating under normal operating conditions but become more conductive when the voltage increases, thereby suppressing transient overvoltages by discharging a certain amount of energy. by current conduction. When the overvoltage is gone, the arrester device is supposed to return to its insulating state.

However, under certain circumstances, it may happen that the current through the blocks remains too high, for example when the voltage is too high because of a ground fault somewhere upstream of the line or when the blocks become too conductive , for example at the end of life or because of an overload. This results in a rise in temperature of the blocks and the surrounding polymer material, which can lead eventually to an electrical fault of the product. When this occurs, the energy generated in the system can cause the arrester to explode, parts of which are projected several meters around, which is dangerous for equipment and people in the vicinity.

It is therefore envisaged, in such a case, to expel the series of blocks of zinc oxide material out of the envelope, which causes a less violent phenomenon and does not cause such damage. That being said, this solution poses another problem. When the blocks are evacuated, there is no longer in fact a surge arrester and the system is left unprotected and this condition can not be detected, except by direct visual inspection.

The US Patent 4,538,201 discloses a surge arrester device having a first and a second electrode, a heat sensitive means and a contact element, which is electrically connected with the first electrode and is mounted to contact the second electrode when the temperature of the temperature sensitive means reaches a predetermined value, following the heat transfer. This heat sensitive means is composed of a material whose shape is a function of temperature, for example a shape memory alloy, and also serves as a contact element.

In case of rise in temperature, this means therefore performs a short circuit of the surge arrester body carrying the two electrodes in question, eliminating its rise in temperature.

In principle, the short-circuit is reversible if the shape-memory alloy element is chosen with a reversible characteristic, that is to say that it resumes its initial shape and interrupts the short-circuit when the temperature has changed. down. This action is temporary and does not generate a fault in the electrical circuit.

This solution of the prior art is applicable only for low voltage systems, since the electrodes are in the air and the temperature sensitive element is arranged in parallel with the zinc oxide block system, with its contact tip at a short distance from the ground electrode.

The object of the invention is to provide an arrangement that solves this problem of temperature rise, for medium and high voltage applications that can be easily mounted on existing arrester bodies, without substantially changing their design.

More specifically described in the context of a surge arrester device, the invention finds application in any medium or high voltage electrical device comprising an insulating envelope.

The invention therefore relates to a medium or high voltage electrical device comprising, in an insulating envelope, a body and a fault generating arrangement, active when a predetermined value of the temperature inside said envelope is exceeded, connected to an electrode of said body and having a temperature-sensitive device, characterized in that said temperature-sensitive device ensures the piercing of said envelope, by said arrangement, in case of a temperature greater than said predetermined value, and its connection with an outer electrode (6) connected to the earth.

The integration of this heat-sensitive device ensures the piercing of the envelope, generally made of polymer, and the creation of a short-circuit between the inner electrode of the body and the electrode outside the envelope and grounding, in the event of a temperature exceeding said predetermined value. This short circuit will be detected by the electrical network protection systems that will operate instantly. Thus, on the one hand, the body is electrically disconnected before reaching the temperature that can cause it to explode, and on the other hand the hole made by drilling into the casing allows a reduction of the pressure inside the casing. envelope.

In addition, the short circuit created between the inner electrode of the body and the outer electrode allows the operator to detect the fault and intervene to repair immediately.

As the insulating envelope of the system has been pierced, this concept of operation is irreversible.

The arrangement according to the invention finds its application in various equipment, for example circuit breakers and medium and high voltage transformers.

According to a preferred embodiment, said temperature sensitive device is a shape memory alloy.

Said temperature sensitive device may be a direct actuator.

According to a first variant, said shape memory alloy device is J-shaped and is disposed near said housing, so as to take a straight form of drilling, in case of a temperature greater than said predetermined value.

According to a second variant, said shape memory alloy device is a push element of a piercing needle, in the event of a temperature greater than said predetermined value.

Said temperature sensitive device may also be an indirect actuator.

In this case, preferably, said shape memory alloy device is a release element of a piercing needle subjected to the force of a compression spring, in the event of a temperature greater than said predetermined value.

The energy source is then provided by a spring, but it is also possible to use a pressurized piston of gas or an explosive chemical element sensitive to pressure.

• La figure 1 est une vue en coupe verticale d'un dispositif de parafoudre blindé.
• Les figures 2 et 3 sont des vues en coupe verticale de variantes de réalisation d'un dispositif sensible à la température, partie d'un dispositif de parafoudre conforme à l'invention.
• Les figures 4 et 5 sont des vues en perspective d'une variante de réalisation d'un dispositif sensible à la température, partie d'un dispositif de parafoudre conforme à l'invention.
• La figure 6 est une vue en coupe verticale d'un dispositif de couplage blindé.

The invention is described below in more detail with the aid of figures representing only preferred embodiments of the invention.

• The figure 1 is a vertical sectional view of a shielded arrester device.
• The Figures 2 and 3 are vertical sectional views of alternative embodiments of a temperature sensitive device, part of a lightning arrester according to the invention.
• The Figures 4 and 5 are perspective views of a variant of embodiment of a temperature-sensitive device, part of a surge arrester device according to the invention.
• The figure 6 is a vertical sectional view of a shielded coupling device.

The figure 1 represents a shielded arrester device equipping an interface with a horizontal contact bar 1 contained in an envelope 4 for connection to equipment. This arrester device comprises a surge arrester body 2 consisting of a series of blocks of zinc oxide material and provided with an electrode 3 which comprises an upper flange 3A having an orifice in which is connected the end of the bar of contact. The arrester body 2 also has a lower electrode 5 connected to the earth.

The arrester body 2 is housed in the insulating casing 4, preferably in polymer coated on a portion of its inner face and on its outer face with a layer of conductive material.

The invention proposes to equip such a device with a defect detection arrangement, active when exceeding a predetermined value of the temperature, preferably of the order of 150 ° C., within the casing 4. This device is connected to the electrode 3 of the surge arrester body and comprises a temperature-sensitive device, preferably a shape-memory alloy, which pierces the envelope 4, by this arrangement, by case of temperature greater than the predetermined value, and its connection with an outer metal electrode 6 connected to the ground.

According to a first variant, represented on the figure 2 this arrangement consists of a direct actuator and the shape memory alloy device 5 is J-shaped and is disposed near the inner wall of the envelope 4, so as to take a straight form of drilling, dotted, in case of temperature greater than the predetermined value.

This device is more precisely a blade 5 folded at right angles and one branch is fixed to the electrode 3 by its free end and the other vertical branch here is disposed near the inner face of the envelope 4. This other branch has a sharp beveled free end and is free to move. In case of a temperature greater than the predetermined value, the blade 5 takes a straight shape as shown in dashed lines and pierces while making the casing 4 while being housed in the external electrode 6 connected to the ground and fixed on the external face of the casing 4. Advantageously, this external electrode 6 has a receiving cavity of the blade 5 which abuts against a lower bottom of this cavity.

According to a second variant, represented on the figure 3 this arrangement also consists of a direct actuator and the shape memory alloy device is a pushing element 7 of a piercing needle 8, in case of a temperature higher than the predetermined value.

This thrust element 7 is arranged as a spring in an extension of the piercing needle 8 and abuts against a fixed housing 9. Here represented with a longitudinal zigzag shape, at normal temperature, this thrust element 7 unfolds, in case of temperature higher than the predetermined value, and just push the needle 8 which pierces the envelope 4 and is housed in the external electrode 6 having a form of receiving the tip of the needle 8.

According to a third variant, represented on the Figures 4 and 5 this arrangement consists of an indirect actuator and the shape memory alloy device is a ring-shaped release member 10 of a piercing needle 8 subjected to the force of a compression spring 11 , if the temperature exceeds the predetermined value.

The compression spring 11 is housed in a cavity 7 arranged in the electrode 3, also visible on the figure 1 around an extension of the piercing needle 8 which is retained by the release device 10, itself also fixed to the electrode 3. In case of a temperature greater than the predetermined value, the release device 10 deforms and releases the needle 8 which, pushed by the spring 11, pierces the envelope 4 and is housed in the external electrode 6 having a form of receiving the tip of the needle 8.

Previously described in the context of a lightning arrester device, the invention finds application in any electrical device with an insulating jacket made of polymer or equivalent.

For example, is represented on the figure 6 , a coupling device for coupling or decoupling information signals in medium voltage power distribution networks comprising, in a polymer-type insulating envelope whose surface is provided with an electrically conductive coating which is potential of the earth, a coupling capacitor 12, which can be realized as a ceramic capacitor.

This coupling capacitor is formed of at least one ceramic disk, provided with both electrode sides and connections, one of the coupling capacitor connections being an electrode 3 which has an upper flange 3A having an orifice in which is connected the end of a high-voltage contact bar.

The other connection of the coupling capacitor 12 is connected to an electrical network, which is connected to the earth potential by means of a lower electrode 5 and which forms a voltage divider with the coupling capacitor, so that a interesting information signal can be taken at the signal output in the form of protective low voltage.

This electrical network is housed in a cartridge 13, replaceable, also housed in the insulating casing 4.

Just as in the variant illustrated on the figure 1 , the electrode 3 contains in a cavity 7 a device according to the invention as previously described.

Claims (8)

1. A medium- or high-voltage electrical device including, in an insulating enclosure (4), a body (2, 12, 13) and a fault generating arrangement, active when a predetermined value of the temperature inside said enclosure (4) is exceeded, connected on an electrode (3) of said body (2, 12, 13) and including a temperature-sensitive device, characterized in that said temperature-sensitive device pierces said enclosure (4), through said arrangement, in the event of a temperature above said predetermined value, and its connection with an outside electrode (6) connected to the ground.
2. The device according to claim 1, characterized in that said temperature-sensitive device is made from a shape memory alloy.
3. The device according to claim 1, characterized in that said temperature-sensitive device is a direct actuator.
4. The device according to claim 3, characterized in that said device made from a shape memory alloy (5) is in the shape of a J and is positioned near said casing (4), so as to assume a straight piercing shape, in the event of a temperature above said predetermined value.
5. The device according to claim 3, characterized in that said device made from a shape memory alloy is a thrust element (7) of a piercing needle (8), in case of a temperature exceeding said predetermined value.
6. The device according to claim 1, characterized in that said temperature-sensitive device is an indirect actuator.
7. The device according to claim 6, characterized in that said device made from a shape memory alloy is an element (10) for releasing a piercing needle (8) subjected to the force of a compression spring (11), in case of temperature exceeding said predetermined value.
8. A lightning protection device according to one of the preceding claims.

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