The present invention relates to high voltage switches and in particular to an electromechanical actuator for transmitting a mechanical movement from a first region into a second region, the first and the second region being galvanically separated from each other.

For connecting and disconnecting high voltages, there exists the problem that a control signal generated in a lower voltage environment has to be translated into a mechanical movement that actuates a switching device in the HV environment without endangering the low-voltage environment by the high voltages. In particular, a safe galvanic separation has to be ensured between both environments.

Conventional high voltage switches have contacts that are located within an insulating environmental enclosure, such as a ceramic bottle. One of the contacts may be actuated by a mechanical system outside of the enclosure connected by a shaft extending through an enclosure seal. The actuating mechanisms typically form a ground connection in the switch and, unless precautions are taken, current may arc from the switch assembly to the actuating mechanism, causing failure or damage. To address this, conventional high voltage switches, such as overhead re-closers, typically utilize a lengthy fiberglass pull rod to connect the actuating mechanism to the switch contact. The insulative fiberglass rod extends through an air filled cavity. However, this configuration takes a significant amount of physical space. Consequently, it is known from EP 2482301 A1 to provide an electrical switch comprising a tubular housing having a conductor receiving end and an operating end opposite the conductor receiving end, wherein the tubular housing includes an interface positioned intermediate the conductor receiving end and the operating end. An operating rod extends through the operating end toward the conductor receiving end, and a fixed contact electrically is coupled to the conductor receiving end.

A moveable contact is electrically coupled to the interface and the operating rod, wherein the moveable contact is moveable between a first position contacting the fixed contact and a second position separated from the fixed contact. A diaphragm is positioned in the tubular housing between the interface and the operating end to prevent voltage from the interface from arcing to the operating end, wherein the diaphragm includes a bore therethrough for receiving the operating rod, wherein the diaphragm includes a first tubular portion and a second tubular portion having an outside diameter smaller than an outside diameter of the first tubular portion, and a shoulder portion between the first tubular portion and the second tubular portion, wherein the first tubular portion is frictionally engaged with an inside of the tubular housing and the second tubular portion is frictionally engaged with the operating rod, and wherein movement of the operating rod from the first position to the second position causes the second tubular portion to move relative to the first tubular portion, the movement deforming the shoulder portion.

This known arrangement, however, still has the problem that under certain conditions the electric field is not sufficiently managed so that electric discharges may occur that may damage the insulation material. Furthermore, the single diaphragm might not present a sufficient electrical insulation between the HV and the LV environment.

There is still a need for an improved electromechanical actuator for transmitting a mechanical movement from a first region into a second region, the first and the second region being galvanically separated from each other, which ensures safe galvanic separation, is long term stable and robust, and can be fabricated in an economic manner.

This object is solved by the subject matter of the independent claims. Advantageous embodiments of the present invention are the subject matter of the dependent claims.

The present invention is based on the idea to provide an elastomeric diaphragm unit separating the HV and the LV (or ground) environment on at least one surface with a semiconducting layer having static dissipative or static shielding properties. For instance, a polymer containing carbon black may be used for such a semiconducting layer. Any other suitable material that exhibit the necessary highly resistive conductivity for reducing static charges may of course also be used.

In particular, the present invention provides an electromechanical actuator for transmitting a mechanical movement from a first region into a second region, the first and the second region being galvanically separated from each other and the actuator comprising an electrically insulating rod with a body, a first actuation portion for being connected to an electromechanical drive mechanism which is arranged in said first region, and a second actuation portion for actuating an electromechanical actuation mechanism which is arranged in said second region. An electrically insulating cover is provided that at least partly encompasses said electrically insulating rod. According to the present invention, an elastomeric diaphragm unit, which is arranged between said electrically insulating body and said cover and has at least one flexible membrane for electrically separating said first and second region, is coated on at least one surface of the membrane with a semiconductive layer.

This arrangement has the advantage that it safely separates the HV environment from the LV (or ground) environment, and avoids static charges being built up causing heating and damaging the insulation material. Moreover, the actuator has a small space requirement and can be fabricated economically by using well-established standard manufacturing techniques. According to an advantageous embodiment of the present invention, the cover comprises an electrically insulating tube which is formed as a part separate from said diaphragm unit. This allows the actuator being built into a plurality of different switch types by only modifying the tube so as to fit into the housing of the particular switch. Advantageously, the diaphragm unit comprises an inner sleeve, which is arranged at said body of the electrically insulating rod in a sealing manner. This inner sleeve therefore safely avoids any electrical currents exiting the HV environment along the rod.

In order to ensure that the inner sleeve does not move with respect to the rod when the rod is moving, so that only the membrane is deflected and no wear can be caused at the interface between the rod and the diaphragm unit, the body of the rod has an elongated essentially cylindrical shape with a longitudinal axis, wherein the body comprises at least one fixing protrusion for fixing said inner sleeve at the body.

In particular, the body may comprise two ring-shaped stopper protrusion distanced apart along said longitudinal axis corresponding to a longitudinal dimension of the inner sleeve, so that the inner sleeve is held between the stopper protrusions. This allows a particularly safe mechanical fixing and also enhances electrical creepage distances.

According to an advantageous embodiment of the present invention, the diaphragm unit comprises at least one outer sleeve, which is arranged at said cover in a sealing manner. This outer sleeve allows a secure mechanical fixing at the cover, which in tur can be firmly attached to a housing of the HV switch. Advantageously, the diaphragm unit is coated with a semiconductive material on two surfaces of the membrane. This allows an effective electrical field management on the HV as well as on the LV side of the diaphragm unit.

In order to further enhance the security of the electrical insulation, the diaphragm unit may comprise not only one membrane, but comprises a first and a second membrane which are distanced apart along the longitudinal axis of the rod. In order to further enhance the insulation performance, the first and second membranes may form a compartment between each other, said compartment being filled with an electrically insulating fluid. The electrically insulating fluid for instance comprises a dielectric oil. Of course any other suitable material, such as silicon gel or an insulating powder may also be employed. Advantageously, the diaphragm unit comprises at least one inlet for filling in said insulating fluid. This inlet may for instance comprise an oil filling screw with a lead through that is connected to the compartment between the first and second membranes.

In order to avoid a detrimental build-up of over-pressure inside the compartment between the first and second membranes, the diaphragm unit may comprise at least one venting element for allowing pressure compensation of the fluid.

According to the present invention, the first and second membranes may either be integrally formed with one common inner sleeve and/or one common outer sleeve. However, for facilitating the manufacturing of the diaphragm unit, at least one of the inner and outer sleeve may be separated into two sections. In particular, the diaphragm unit may comprise a first and a second outer sleeve, which are arranged at said cover in a sealing manner, the first outer sleeve being connected to the first membrane and the second outer sleeve being connected with the second membrane.

Although the present invention is explained in detail referring to one or two membranes, it is clear for a person skilled in the art that also more than two membranes can be provided resulting in a still higher quality of the electrical insulation. Using multiple membranes instead of only a single membrane has also the advantage that thinner membranes with a higher flexibility can be used.

The present invention can be advantageously used with high voltage switches, such as vacuum circuit breakers comprising an electromechanical actuator according to one of the preceding claims, wherein the first region is a low voltage (LV) environment or ground, and wherein the second region is a high voltage (HV) environment. In particular, the cover is attached to an enclosure enclosing said HV environment, so that the membrane effectively seals the HV environment.

Furthermore, according to an advantageous embodiment of the present invention, the high voltage switch comprises a first and a second HV electrical contact enclosed in an electrically insulating enclosure, wherein said enclosure is encompassed by a compartment filled with an insulating fluid, and wherein a pressure of said insulating fluid is controlled by at least one air reservoir provided in said compartment. The insulating fluid may be an oil, but more advantageously is an electrically insulating gel. By providing the at least one air reservoir, the pressure can be limited, which is important under high temperatures. Furthermore, such a pressure limiter is also advantageous under low temperature conditions because then, any oil, gel, or other insulating filling contracts and the air reservoir(s) can expand in order to compensate this volume reduction. Thereby, the formation of undefined air pockets can be avoided. Additionally, the pressure limiter(s) may be fabricated at least partly from a

semiconductive material, thereby improving the electrical field distribution.

The present invention advantageously is used with high-voltage switches such as e. g. vacuum breakers, in particular for 42 kV applications. The term "high-voltage" as used in the following is intended to relate to voltages above approximately 1 kV. In particular, the term high-voltage is intended to comprise the usual nominal voltage ranges of power transmission, namely medium voltage, MV, (about 3 kV to about 72 kV), high-voltage, HV, (about 72 kV to about 245 kV), and also extra high-voltage (up to presently about 500 kV). Of course also higher voltages may be considered in the future. These voltages may be direct current (DC) or alternating current (AC) voltages. In the following, the term "high-voltage cable" is intended to signify a cable that is suitable for carrying electric current of more than about 1 A at a voltage above approximately 1 kV. Accordingly, the term "high-voltage switch" is intended to signify a device that is suitable for connecting and disconnecting high-voltage facilities and/or high-voltage cables. The present invention provides means for safely transmitting a mechanical movement from the so-called "low-voltage", LV, environment that relates to voltages below 1 kV to the HV environment. Of course, instead of an LV environment, the first environment may also be ground potential.

The accompanying drawings are incorporated into the specification and form a part of the specification to illustrate several embodiments of the present invention. These drawings, together with the description serve to explain the principles of the invention. The drawings are merely for the purpose of illustrating the preferred and alternative examples of how the invention can be made and used, and are not to be construed as limiting the invention to only the illustrated and described embodiments.

Furthermore, several aspects of the embodiments may form— individually or in different

combinations— solutions according to the present invention. The following described embodiments thus can be considered either alone or in an arbitrary combination thereof. Further features and advantages will become apparent from the following more particular description of the various embodiments of the invention, as illustrated in the accompanying drawings, in which like references refer to like elements, and wherein:

FIG. 1 is a schematic representation of a high voltage switch according to a first embodiment;

FIG. 2 is a detail of Fig. 1;

FIG. 3 is a schematic representation of the high voltage switch shown in Fig. 1 without attached connectors; FIG. 4 is a schematic representation of a high voltage switch according to a further embodiment.

The present invention will now be explained in more detail with reference to the Figures and firstly referring to Fig. 1.

Fig. 1 shows an advantageous embodiment of a high-voltage switch 100 according to a first advantageous embodiment of the present invention. On the high voltage (HV) side, a first electrical contact 102 can be connected to a second electrical contact 104. In Fig. 1, these two contacts are shown in a disconnected state. For closing the electrical connection, the electrical contact 102 has to be moved in a direction indicated by arrow 120 towards the electrical contact 104. According to the present invention, this is done by means of an actuator 106. The first and second electrical contacts 102, 104 may be encased in a vacuum case 103, also called bottle.

The actuator 106 comprises an electrically insulating rod 108 with a body 110, a first actuation portion 112 for being connected to an electromechanical drive mechanism (not shown in the Figures), and a second actuation portion 114 for actuating an electromechanical actuation mechanism which is arranged in the HV region (not shown in the Figures). The first actuation portion 112 is arranged in a low-voltage (LV) environment or is connected to ground (also referred to as the "earth side". An electrically insulating cover 116 at least partly encompasses said electrically insulating rod 108.

The actuator 106 comprises an elastomeric diaphragm unit 118, which is arranged between said electrically insulating body 110 and said cover 116, and has a flexible membrane 122 for electrically separating said first and second region. According to the present invention, the diaphragm unit 118 is coated on at least one of the surfaces 124, 126 of the membrane 122 with a semiconductive layer. Thereby, the HV electrical field can be optimally managed and damaging of the insulating membrane material can be avoided.

The cover 116 is formed from a solid electrically insulating tube. On the outside, it is covered by a flexible insulating layer 128, which is for instance fabricated from silicone. This insulating layer 128 may be covered by a semi-conductive outer layer. In order to quickly discharge a flash-over in the region of the electrical contacts 102, 104, a grounding contact 105 is provided which is connected to ground.

The membrane 122 is flexible and therefore allows the rod 108 to move along the longitudinal direction 120 and back again, thereby deflecting the membrane 122. On the other hand, the electrically insulating flexible membrane 122 provides an effective electrical insulation between the HV side and the LV side (or ground). Fig. 2 illustrates the actuator 106 in more detail. As can be seen from this Figure, the rod 108 has a longitudinal axis 130 which runs along the movement direction 120. In order to safely anchor the diaphragm unit 118 at the inside of the tube shaped cover 116, the diaphragm unit 118 comprises an outer sleeve 132. Furthermore, for mechanically contacting the electrically insulating rod 108, the diaphragm unit 118 comprises an inner sleeve 134 which encompasses the body 110 of the electrically insulating rod 108.

In order to avoid that the inner sleeve 134 slides along the outer surface of the body 110, when the rod 108 is moved, two ring-shaped fixing elements 136, 138 are provided around the circumference of the rod 108. Thereby, the inner sleeve 134 is mechanically fixed in a longitudinal direction on both sides. It is clear for a person skilled in the art, that these ring-shaped protrusions 136, 138 may of course also be replaced by fixing elements that cover only a part of the circumference of the rod's body 110. Flowever, the ring-shaped solution is preferred because it enhances the creepage distance for any electrical currents.

As shown in Fig. 2, the silicone cover 128 may also be provided with a semiconductive layer 140 that provides an electrical field control and acts as a Faraday cage. A grounding contact 105 allows for a fast discharge of a flash-over in the region of the electrical contacts 102, 104.

For securing the actuator 106 according to the present invention at the remainder of the switch, two caps may be provided. In particular, an outer cap 142, which has an essentially tubular shape and a tapered region 144, can be inserted between the cover 116 and the silicone layer 128 in order to safely secure the cover 116 at the switch 100.

Further, in order to mechanically fix the outer sleeve 132 of the diaphragm unit 118 inside the cover 116, an inner tube shaped cap 146 is inserted between the cover 116 and the free space needed for the deflected membrane 122. A retention shoulder 148 interacts with the outer sleeve 132 for fixing the sleeve 132 in a longitudinal direction.

According to the present invention, the first surface 124 as well as the second surface 126 of the membrane 122 are covered with a semi-conductive layer for managing the HV electrical field.

Furthermore, the vacuum case 103 may be surrounded by an electrically insulating fluid, preferably a gel filling 149 for better electrical insulation. In order to control and limit the occurring pressure of the gel 149 (in particular under elevated temperatures), the HV switch 100 has pressure limiters with one or more air reservoirs 151. In contrast to the gel, the air is compressible and can therefore balance the pressure. Fig. 3 illustrates the HV switch 100 according to the present invention without the attached various connectors.

Fig. 4 illustrates a further advantageous embodiment of an actuator 206 according to the present invention. According to this embodiment, the rod 208 is essentially the same as the rod 108 of the previous figures. The rod 208 has a body 210 and a first actuation portion 212 and the second actuation portion 214. The actuator 206 further comprises a cover 216 which is fabricated as an essentially tubular electrically insulating part. The body 210 of the rod 208 has two essentially ring-shaped protrusions 236, 238 which engage with an inner sleeve 234 of a diaphragm unit 218.

Different from the previous embodiments, the diaphragm unit 218 comprises a first membrane 250 and a second membrane 252. Those membrane 250, 252 are thinner than the membrane 122 shown in Figures 1 to 3 and are therefore more flexible and can be deflected more easily.

Furthermore, the first membrane 250 and the second membrane 252 enclose a compartment 254 between each other. According to the present invention, this compartment may be filled with an electrically insulating fluid, for instance a dielectric oil. An inlet 256 is provided for filling in the oil and an outlet 258 may serve for venting the compartment 254 in order to avoid dangerous overpressure.

According to the present invention is shown in Fig. 4, each of the membranes 250, 252 has its separate outer sleeve 260, 262 which is attached to the cover 216.

Furthermore, at least one of the membranes 250, 252 is coated with a semiconductive layer on at least one of its surfaces in order to provide an optimal management of the HV electrical field. The embodiment shown in Fig. 4 has the advantage that the membranes 250 and 252 can be fabricated with much thinner walls compared to the membrane 122 of Fig. 1 to 3, so that they can be deflected more easily and the actuator 206 requires lower forces for moving the rod 208. The oil filling of the compartment 254 significantly enhances the electrical insulation quality.

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