Patent Application
20210043400
The present invention relates to high voltage switches and, more particularly, to an electromechanical actuator transmitting a mechanical movement.
For connecting and disconnecting high voltages, a control signal generated in a lower voltage (LV) environment has to be translated into a mechanical movement that actuates a switching device in a high voltage (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. The diaphragm includes a bore therethrough for receiving the operating rod. 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. 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.
An electromechanical actuator includes an electrically insulating rod, an electrically insulating cover at least partly encompassing the electrically insulating rod, and an elastomeric diaphragm. The electrically insulating rod has a body, a first actuation portion connected to an electromechanical drive mechanism arranged in a first region, and a second actuation portion for actuating an electromechanical actuation mechanism arranged in a second region. The elastomeric diaphragm unit is arranged between the body and the cover. The elastomeric diaphragm unit has a flexible membrane electrically separating the first region from the second region. The elastomeric diaphragm unit is coated on at least one surface of the membrane with a semiconductive layer.
The invention will now be described by way of example with reference to the accompanying Figures, of which:
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 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.
The present invention may be 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.
A high-voltage switch 100 according to an embodiment is shown in
The actuator 106, as shown in
The actuator 106, as shown in
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 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. Thereby, the HV electrical field can be optimally managed and damaging of the insulating material of the flexible membrane 122 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, as shown in
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).
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 shown in
As shown in
As shown in
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.
The vacuum case 103 may be surrounded by an electrically insulating fluid, such as an oil or 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. In other embodiments, the electrical contacts 102, 104 may be enclosed in any electrically insulating enclosure that forms a compartment filled with an insulating fluid. The pressure limiter(s), such as the air reservoirs 151 within the compartment, may be fabricated at least partly from a semiconductive material, thereby improving the electrical field distribution.
Different from the previous embodiments, the diaphragm unit 218 comprises a first membrane 250 and a second membrane 252 distanced apart from one another along a longitudinal axis of the rod 208, as shown in
The first membrane 250 and the second membrane 252 enclose a compartment 254 between each other, as shown in
The first and second membranes 250, 252 may either be integrally formed with one common inner sleeve 234 and/or one common outer sleeve 260, 262. In the embodiment shown in
The embodiment shown in
The actuator 106 transmits a mechanical movement from the first region into the 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18305516.9 | Apr 2018 | EP | regional |
This application is a continuation of PCT International Application No. PCT/EP2019/060097, filed on Apr. 18, 2019, which claims priority under 35 U.S.C. § 119 to European Patent Application No. 18305516.9, filed on Apr. 25, 2018.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2019/060097 | Apr 2019 | US |
| Child | 17078449 | US |
