ELECTRICAL SWITCHING DEVICE

Description

[0001] The invention relates to an electrical switching device comprising at least one switching point and at least one switching resistor, which is electrically connected in parallel to the switching point and comprises a stack of resistance elements.

[0002] An electrical switching device is known, for example, from German patent application DE 10 2006 004 811 A1. For potential control, a switching resistor is electrically connected in parallel to a switching point. Electrical switching devices are preferably manufactured in a modular design, so that assemblies can be used multiple times in different series. Furthermore, modular assemblies make it easier to adapt electrical switching devices to changing requirements.

[0003] CH 669 863 A5 discloses a high-voltage switch in a T- or Y-configuration, which has at least one switching point and at least one switching resistor, wherein the at least one switching resistor is electrically connected in parallel to the switching point. The switching resistor comprises a stack of resistive elements.

[0004] The SE 357 094 contains an electrical resistor that can be switched.

[0005] US 5,629,666 A discloses an electrical switching device according to the preamble of claim 1, comprising a power resistor having a large heat capacity per unit volume and a suitable and stable electrical resistance. This power resistor comprises a sintered body containing aluminum oxide and carbon, and a pair of electrodes formed on opposing surfaces of the sintered body.

[0006] The object of the invention is to further develop a switching device in such a way that it can be variably equipped, thereby enabling favorable heat dissipation in a simple and cost-effective manner.

[0007] According to the invention, the problem in an electrical switching device of the type mentioned above is solved by the fact that the number of resistance elements forming the stack is in a ratio to the electrical resistance of the stack of resistance elements in ohms within the limits of 0.5 to 2, in particular 0.5 to 1.5, and the length of the switching resistor in mm to the electrical resistance of the switching resistor in ohms has a ratio of less than or equal to 8, in particular less than or equal to 6.

[0008] An electrical switching device is a device used to interrupt or establish a current path. By interrupting or establishing a current path, the electrical switching device can either interrupt or switch on an electric current. Depending on its design, the magnitude of the electric current to be controlled can vary. For example, an electrical switching device can be designed as a load switching device, meaning it controls currents up to its rated value. However, it can also be designed as a so-called isolating switching device, meaning it is configured to control no electric current except for negligible charging and discharging currents.An electrical switching device can also be designed as a so-called power switching device, meaning it is also capable of handling currents exceeding its rated current. For example, a power switching device can handle short-currents that are many times the rated current. Depending on their design, electrical switching devices can be used at various points in electrical power transmission networks. These devices can be used in low, medium, high, and extra-high voltage ranges. It is advantageous if one of the switching points of the device is a mechanical switching point. At a mechanical switching point, the impedance of the switching point is changed by switching contacts that can be moved relative to each other.Alternatively, a switching point can be based on semiconductors, for example, whereby the impedance of the switching point can vary due to an external circuit.

[0009] Regardless of the switching point's design, a switching resistor may be arranged in parallel. A switching resistor supports the switching point's function. For example, if a phase conductor is interrupted, potentially interrupting an electrical current, feedback effects can occur at the switching point. In electrical power transmission networks, for instance, oscillations or fluctuations in energy flows can occur, leading to a voltage spike across the switching point. A switching resistor can limit these so-called return voltages, thus facilitating the safe and rapid establishment of a high-impedance state at the switching point.For example, oscillations can occur in AC networks, leading to voltage spikes across a switching point that exceed the rated voltage for which the electrical switching point is designed. However, it is also possible for the electrical switching device to be used in a DC system, where, to interrupt a phase conductor, a DC oscillation can be forced, for example, by a current zero crossing through an external circuit, in order to simplify the interruption of a phase conductor and thus, if necessary, interrupt the DC current.

[0010] For the design of the switching resistor, it can be advantageously provided that it is composed of several resistive elements, such that the desired resistance value of the switching resistor is achieved by combining the resistive elements. The resistive elements can, for example, be assembled in a stack. The resistive elements can, for example, each have a cylindrical shape, in particular with a circular cylindrical or hollow cylindrical cross-section. The end faces of several resistive elements can be arranged adjacent to one another and form a stack. To improve electrical contact, an arrangement of contact elements can also be provided between the resistive elements. The stack of resistive elements can be assembled to form a rigidly connected assembly.To create a rigid, angle-resistant structure and prevent a stack of resistance elements from falling apart, the resistance elements can be pressed together by applying an external force. Alternatively or additionally, the stack of resistance elements can also be surrounded by a casing, which serves to guide the stack axially.

[0011] The casing should be electrically insulating. For example, the stack of resistors can be positioned inside a tube made of electrically insulating material, with the tube serving to apply clamping forces to the resistor stack. Thus, it is possible, for instance, for the electrically insulating tube to hold the stack of resistors and for it to have contact points at its ends for connecting the switching resistor in parallel to a switching point. These contact points can also serve to hold and position the switching resistor.

[0012] According to the invention, the number of resistance elements forming a stack is in a ratio to the electrical resistance of the stack of resistance elements in ohms within the limits of 0.5 to 2, in particular from 0.5 to 1.5.

[0013] In an inventive ratio of the number of resistive elements in the stack to the electrical resistance of less than or equal to 2, and in particular less than or equal to 1.5, efficient heat dissipation from the stack of resistive elements is achieved. Furthermore, the length of the stack of resistive elements is limited such that parallel electrical connection at the switching point is simplified. By defining the ratio of resistive elements to the electrical resistance of the stack, the design of each individual resistive element is defined with respect to the partial resistance that the resistive element contributes to the total resistance of the stack. The mass of the stack of resistive elements is also limited. It has proven particularly advantageous if the ratio of the number of resistive elements to the electrical resistance of the stack, in ohms, is within the range of approximately 0.5 to 0.7 up to approximately 1.0 to 2.The dimensioning regulations allow the resistance elements to be manufactured cost-effectively, for example using sintering processes, especially of ceramics or similar materials.

[0014] Furthermore, according to the invention, the length of the switching resistor in mm to the electrical resistance of the switching resistor in ohms has a ratio of less than or equal to 8, in particular less than or equal to 6.

[0015] With this ratio of the length of a switching resistor to its electrical resistance in ohms, it is possible to construct the switching resistor from one or more stacks of resistive elements. The current-carrying capacity of the switching resistors can be improved by connecting several stacks in parallel. However, it is also possible for the switching resistor to consist of only a single stack of resistive elements, in which case the ratio of length to resistance in ohms of the on-resistance, particularly of the stack of resistive elements, must still comply with the dimensioning requirements. It has proven advantageous to define the ratio of the switching resistor's length to its resistance in ohms within a range of 3 to 4 to 6 to 8.

[0016] Advantageously, the electrical switching device may further provide for a multi-interrupting switching section with a first switching point and a second switching point which are electrically contacted with each other, wherein there is a distance in mm between the connection points of the multi-interrupting switching section which is at most 30 times, in particular at most 25 times, the magnitude of the switching resistance in ohms.

[0017] As described above, an electrical switching device serves to switch a current path or an electric current. If several switching points are used together to switch a current path / electric current, an electrical switching device with a multi-interrupted switching path is formed. The switching points are preferably connected electrically in series, so that the switching path has connection points at the endpoints of the interconnected switching points, between which a phase conductor (current path) or an electric current is switched. A contact element, for example, can be used to connect the first and second switching points, spacing them apart.This contact element is preferably designed to be electrically conductive, so that an electrically conductive connection between the first and second switching points is established via the contact element. For example, gear elements, such as a gear head, can serve as the contact element, coupling a movement to the first and second switching points, respectively. The switching points can extend from the contacting element. In particular, the switching points can be arranged on opposite sides of the contacting element. Advantageously, the switching points can extend from the contacting element in opposite directions to each other, essentially aligned. The connection points of the multi-interrupted switching path can be located at the ends of the two switching points facing away from the contacting element.Thus, it is possible, for example, to design an open-air switching device in live tank construction, which may, for example, have several encapsulation housings in T-shape extending from an electrically insulating support device.

[0018] A first switching resistor can be connected in parallel to the first switching point. A second switching resistor can be connected in parallel to the second switching point. It is possible for both the first and second switching points to have a switching resistor connected in parallel. However, it is also possible for only the first or only the second switching point to have a switching resistor connected in parallel. By connecting switching resistors in parallel, the switching point to which the resistor is connected is bypassed by the switching resistor. In other words, in addition to the impedance-varying switching point, a parallel current path is established via the switching resistor.However, the switching resistance is so high that, in the high-impedance state of the switching point, only a negligible leakage current can flow through it. If necessary, to prevent leakage current, the parallel current path established via the respective switching resistance must be temporarily disconnected. Such disconnection of the parallel current path can preferably occur after a phase conductor has been interrupted and the switching point has successfully solidified. Solidification of the switching point is particularly necessary in the case of a mechanical switching point, for example, to remove foreign substances such as arcing products or other contaminants from the switching point.The use of multiple switching points offers the further advantage of distributing an electrical voltage to be separated across the switching path across several switching points, so that each of the switching points only needs to handle a portion of the voltage to be controlled between the contact points of the switching path.

[0019] To form an encapsulation housing, essentially electrically insulating tubular structures can be used, which are fitted with fittings at their end openings. These fittings can be electrically conductive and can also serve to electrically connect the first and second switching points located inside the respective encapsulation housing. Furthermore, the switching resistors can be electrically connected in parallel to the first and second switching points via the fittings. In addition, the fittings can also serve as retaining elements for supporting or carrying the switching resistors. This can be particularly advantageous if the switching resistors are located outside the encapsulation housing. A switching resistor can also be located inside an encapsulation housing.

[0020] The above statements regarding the possibility of arranging or designing an encapsulation housing and the resulting construction for an electrical switching device are applicable in an analogous manner to the following described design variants, regardless of the number of switching points, regardless of the location and position of the switching points, and regardless of the design or location of the switching resistors.

[0021] Another advantageous embodiment may provide that the first or the second switching point is surrounded by an encapsulation housing, wherein a switching resistor is arranged outside the encapsulation housing.

[0022] Enclosing a switching point within a housing offers the advantage of protecting it from external influences. A housing can, for example, be in the form of an electrically insulating tube with a recess containing the switching point. The tube can be fitted with fittings at its ends to allow electrical contact with the switching point inside the housing. If a switching resistor is located outside such a housing, the housing's cross-section can be designed to match the dimensions of the respective switching point. A switching resistor can then be positioned outside the housing as needed.This further supports a modular design of an electrical switching device, in which the switching resistor is only placed outside the encapsulation housing when required, whereby the encapsulation housing itself can be optimized in its dimensions to the switching point.

[0023] Another advantageous embodiment can provide that the first and second switching points are each surrounded by an encapsulation housing, with a switching resistor being arranged outside of an encapsulation housing.

[0024] If both the first and second switching points are equipped with an encapsulated housing, each switching point can be installed in a protected space, and a switching resistor can be assigned to either both switching points or just one. Positioning the switching resistor outside the encapsulated housing allows for an essentially parallel alignment of the housing and the switching resistor. For example, the switching resistor can be electrically connected in parallel via electrically conductive components (fittings) located at its ends on the encapsulated housing, which contact the first and second switching points, respectively. In this configuration, the switching resistor can be supported by the respective encapsulated housing.

[0025] Another advantageous embodiment may provide that the first or the second switching point is surrounded by an encapsulation housing, wherein a switching resistor is arranged inside an encapsulation housing.

[0026] An arrangement within the encapsulation housing surrounding the first or second switching point offers the advantage that the switching resistor can benefit from the mechanical protection provided by the encapsulation housing and does not require a separate enclosure itself. This simplifies the electrical connection of the switching resistor to the respective switching point.

[0027] Another advantageous embodiment can provide that the first and second switching points are each surrounded by an encapsulation housing, wherein a switching resistor is arranged inside an encapsulation housing.

[0028] Equipping both the first and second switching points with their own encapsulated housings allows for the integration of a switching resistor into either the first or second switching point, or both switching points. The switching resistor is then housed within its respective encapsulated housing. This also provides protection for the switching resistor within the encapsulated housing.

[0029] An advantageous embodiment may provide that an encapsulation housing is a pressure vessel.

[0030] It may be advantageous to provide an encapsulation housing filled with an electrically insulating fluid.

[0031] Designing an encapsulation housing as a pressure vessel allows the interior of the housing to be filled with an electrically insulating fluid and pressurized, so that the pressure inside the housing differs from that of the surrounding environment. The pressure vessel is designed to withstand this differential pressure. This enables the enclosure of a suitable fluid within the housing. For example, the housing can be filled with an electrically insulating oil or gas. Gases or liquids containing fluorine components have proven particularly advantageous, as they exhibit both high electrical insulating properties and good arc-quenching characteristics. Sulfur hexafluoride, fluoroketones, and fluoronitriles, for instance, can be used.However, other electrically insulating fluids such as nitrogen, oxygen, etc. can also be used.

[0032] An embodiment of the invention is shown schematically in a drawing below and described in more detail thereafter. The drawing shows... Figure a side view of an electrical switching device.

[0033] The electrical switching device shown in the figure is designed as an open-air circuit breaker in a live tank design for high-voltage applications, particularly for voltages above 800,000 volts. The electrical switching device has a support frame 1, which is generally made of electrically conductive material and is at earth potential. A drive unit 2 is positioned on the support frame 1. The drive unit 2 is also generally at earth potential. The drive unit 2 enables the electrical switching device to be actuated, i.e., to open or close a current path. The drive unit 2 provides the necessary energy for this, in this case, the required kinetic energy. An electrically insulating section of a support column 3 is arranged on the support frame 1.The support column 3 is composed of a first and a second electrically insulating section, the electrically insulating sections being essentially tubular and closed at their ends with fittings. The opposing sides of the electrically insulating sections of the support column 3 are bolted together, forming an extended tubular support column 3. The support column 3 is positioned at one end against the support frame 1. The electrically insulating sections of the support column 3 are hollow and have ribbing on their outer surface. This ribbing improves air resistance by extending creepage paths on the surface of the support column 3 and forming drip edges. A gear head 4 is arranged at the end of the support column 3 facing away from the support frame 1.The gearbox head 4 closes off the support column 3 and is rigidly connected to it. A first switching point 5 and a second switching point 6 are mounted on the gearbox head 4 in the transverse direction to the axial direction of the support column 3. The first and second switching points are enclosed by a first encapsulation housing 7 and a second encapsulation housing 8, respectively. The two encapsulation housings 7 and 8 are designed to resemble an electrically insulating section of the support column 3. That is, the two encapsulation housings 7 and 8 are essentially hollow cylindrical, electrically insulating, and tubular, with a fitting for closing each encapsulation housing 7 and 8 located at its end. The two encapsulation housings 7 and 8 are arranged on opposite sides of the gearbox head 4 and project from it in opposite directions.The ends of the two encapsulation housings 7, 8 facing the gearbox head 4 are mechanically connected to the gearbox head 4 via the fittings located therein, so that the encapsulation housings 7, 8 are supported on the support column 3 via the gearbox head 4. The gearbox head 4 housing is made of a conductive material, and electrical contact is provided via the gearbox head 4 for the fittings connected to it.

[0034] Inside the encapsulation housings 7, 8, the first and second switching points 5, 6 are arranged. Each of the first and second switching points 5, 6 has switching contacts that are movable relative to each other. These movable switching contacts are designed to be able to make contact with each other or to be separated from each other. To effect a change in the state of the first or second switching point 5, 6, a kinematic chain, for example in the form of an axially displaceable switching rod, is arranged inside the support column 3, preferably acting as an electrical insulator. This makes it possible to transmit a movement originating from the drive unit 2 on the support frame 1 within the support column 3 to the gearbox head 4. In the gearbox head 4, the movement can be distributed into the two encapsulation housings 7, 8, so that a relative movement of the switching contacts of the first and second switching points 5, 6 can occur.The second switching point 5, 6 can be operated. The switching points 5, 6 are arranged such that they are electrically contacted with the fittings of the respective encapsulation housings 7, 8, which are attached to the gear head 4. Thus, the switching points are electrically connected in series via the fittings connected to the gear head 4, forming a multi-interrupting switching path. The two switching points 5, 6 are electrically connected at their opposite ends to a fitting that closes off the free end of each encapsulation housing 7, 8. The fittings positioned there form connection points 9, 10 for the multi-interrupting (double) switching path of the electrical switching device.Between the connection points 9, 10 there extends a distance D which includes the length of the electrically insulating sections of the encapsulation housings 7, 8 and the electrically conductive contacting element which serves to contact the two switching points 5, 6.

[0035] Each of the first switching point 5 and the second switching point 6 is assigned a switching resistor 11a, 11b. The two switching resistors 11a, 11b are electrically connected in parallel to the first switching point 5 and the second switching point 6, respectively. For this purpose, the switching resistors 11a, 11b are each electrically connected to the fittings that define the end faces of the encapsulation housing 7, 8 of the respective switching point 5, 6. In addition to the electrical contact of the switching resistors 11a, 11b via the fittings of the encapsulation housing 7, 8, the switching resistors 11a, 11b are also mechanically held or supported by the fittings and thus by the encapsulation housing 7, 8. The switching resistors 11a, 11b are of identical construction. Each switching resistor 11a, 11b comprises a stack of n-resistance elements.The resistance elements are each arranged in a tubular, electrically insulating cylinder, which provides mechanical protection for the respective stack of resistance elements. The cylinder also serves to apply force to the resistance elements located inside the switching resistor. The number of switching resistors can vary depending on the dimensions of the respective encapsulation housings 7, 8 or the gear head 4. Thus, a stack of resistance elements comprises n resistance elements.

[0036] The encapsulation housings 7, 8, the support column 3, and the gear head 4 are each designed as pressure vessels, allowing the interior of the encapsulation housings 7, 8, the support column 3, and the gear head 4 to be filled with an encapsulated electrically insulating fluid. Electrically insulating fluids are particularly advantageous for this purpose, as they enhance the insulation strength within the support column 3 and / or the encapsulation housings 7, 8. Preferably, the electrically insulating fluid inside the encapsulation housings 7, 8 can be pressurized, creating a differential pressure on the encapsulation housings 7, 8, the support column 3, and / or the gear head 4. In this case, the encapsulation housings 7, 8 must be designed as pressure vessels.

Claims

1. Electrical switching device comprising at least one switching point (5, 6) and at least one switching resistor (11a, 11b) which is electrically connected in parallel with the switching point and comprises a stack of resistance elements (n), wherein a ratio of the length of the switching resistor (11a, 11b) in mm to the electrical resistance of the switching resistor (11a, 11b) in ohms is less than or equal to 8, in particular less than or equal to 6, characterized in that a ratio of the number of resistance elements (n) forming a stack to the electrical resistance of the stack of resistance elements (n) in ohms is between the limits of from 0.5 to 2, in particular from 0.5 to 1.5.

2. Electrical switching device according to Claim 1, characterized in that the electrical switching device comprises a multiply interrupting switching gap having a first switching point (5) and having a second switching point (6), which are electrically contacted with one another, wherein between connection points (9, 10) of the multiply interrupting switching gap there is a distance (D) in mm which is a maximum of 30 times, in particular a maximum of 25 times, the absolute value of the switching resistor (11a, 11b) in ohms.

3. Electrical switching device according to Claim 2, characterized in that a first switching resistor (11a) is electrically connected in parallel with the first switching point (5) and / or in that a second switching resistor (11b) is electrically connected in parallel with the second switching point (6).

4. Electrical switching device according to Claim 2 or 3, characterized in that the first or the second switching point (5, 6) is surrounded by an encapsulation housing, wherein a switching resistor is arranged outside the encapsulation housing.

5. Electrical switching device according to Claim 2 or 3, characterized in that the first and second switching points (5, 6) are respectively surrounded by an encapsulation housing (7, 8), wherein a switching resistor (11a, 11b) is arranged outside an encapsulation housing.

6. Electrical switching device according to Claim 2 or 3, characterized in that the first or the second switching point (5, 6) is surrounded by an encapsulation housing (7, 8), wherein a switching resistor (11a, 11b) is arranged within the encapsulation housing (7, 8).

7. Electrical switching device according to Claim 2 or 3, characterized in that the first and second switching points (5, 6) are respectively surrounded by an encapsulation housing (7, 8), wherein a switching resistor (11a, 11b) is arranged within an encapsulation housing (7, 8).

8. Electrical switching device according to any of Claims 4 to 7, characterized in that an encapsulation housing (7, 8) is a pressure vessel.

9. Electrical switching device according to any of Claims 4 to 8, characterized in that an encapsulation housing (7, 8) is filled with an electrically insulating fluid.