Combined earthing and protective device for a voltage and power converter of modular design

Abstract

The invention illustrates and claims a combined earthing and protective device for a voltage and power converter of modular design for converting a primary AC voltage with one or more phases to a secondary voltage. The combined earthing and protective device comprises input contacts and output contacts which are conductively connected to voltage inputs and voltage outputs of individual modules of the converter. The input and output contacts which are connected to the same individual module are connected to a varistor which becomes conducting when the voltage dropped across the varistor exceeds a first threshold value. A nonconductive switching strip with bridge contacts can be moved from an operating position to an earthing position. In the earthing position, the bridge contacts connect the input and output contacts of the individual modules to one another and to an earth connection. In the operating position, the same input and output contacts are not connected by the bridge contacts and not to the earth connection either.

Description

[0001] Combined earthing and protection device for a modular voltage and power converter

[0002] The present invention relates to a combined grounding and protection device for a modular voltage and power converter for converting a primary alternating voltage with one or more phases into a secondary voltage. The modular voltage and power converter comprises a plurality of individual modules connected in series for each phase of the primary alternating voltage. Each individual module has a voltage input and a voltage output for receiving a phase of the primary alternating voltage.

[0003] Modular voltage and power converters in the form of solid-state transformers (SSTs), also known as power electronic transformers, are designed to replace the function of conventional 50 Hz oil- or cast-resin transformers in special applications, for example, to convert a three-phase high voltage into a direct current. The power electronic transformers are constructed from a multitude of individual converters, with several individual converters connected in series for each high-voltage phase, and the series-connected individual converters in turn connected in parallel.

[0004] The individual converters, also known as cells, are at a high voltage potential during normal operation and are therefore inaccessible to personnel. If maintenance or other work on the SST nevertheless needs to be performed, various safety regulations must be observed. In particular, the system must be de-energized and a grounding assembly must be installed for each cell to ensure that each cell is grounded. Due to the large number of individual cells that make up an SST, the preparatory work before maintenance is very complex and time-consuming.

[0005] Furthermore, it can be problematic if an individual cell can no longer conduct current due to a fault in the cell, since in this case the line-to-line voltage of the high voltage, for example 20 kV, drops across the separation point, which can lead, for example, to the explosive destruction of the cell. The remnants of the explosively destroyed cell can also destroy other adjacent cells, so that the damage is not limited to a single cell. Against this background, the skilled person is faced with the task of providing a device with which at least some of the problems described above can be solved.

[0006] The present invention solves this problem by a combined earthing and protection device according to claim 1. Preferred embodiments of the combined earthing and protection device are the subject of the dependent claims.

[0007] According to a first aspect, a combined grounding and protection device is provided for a modular voltage and power converter for converting a primary alternating voltage with one or more phases into a secondary voltage. The voltage and power converter has a plurality of individual modules connected in series for each phase of the primary alternating voltage. Each individual module has a voltage input and a voltage output for receiving a phase of the primary voltage. The combined grounding and protection device comprises a plurality of input contacts and a plurality of output contacts, which are configured such that in each case an input contact can be conductively connected to a voltage input of an individual module of the voltage and power converter and in each case an output contact can be conductively connected to a voltage output of an individual module of the voltage and power converter.In addition, the input contact and the output contact, which can be connected to the voltage input and the voltage output of the same individual module, are each connected by means of a varistor. The varistor is configured to conductively connect the input contact to the output contact when the voltage drop across the varistor exceeds a first threshold. The combined grounding and protection device further comprises a non-conductive switching strip with a plurality of bridge contacts. The switching strip is configured to be moved from an operating position to a grounding position. When the switching strip is in the grounding position, one bridge contact of the plurality of bridge contacts conductively connects the input contact to the output contact, which can be connected to the voltage input and the voltage output of the same individual module.In addition, the input and output contacts, which are conductively connected by the bridge contacts, are connected to a ground terminal. When the safety edge is in the operating position, the input and output contacts that can be connected to the voltage input and voltage output of the same individual module are not conductively connected by the bridge contacts, and the input and output contacts are also not connected to the ground terminal.

[0008] This provides a device or apparatus which, due to its advantageous design, performs three functions at once: it connects the output and input contacts of individual cells or individual modules of the modular voltage and power converter which are connected directly one after the other in series, thus connecting the individual modules in series, protecting each of the individual modules from overvoltage using the varistors and, due to the conductive connection of the input and output contacts when the switching strip is in the earthing position, enabling all of the individual modules connected in series to be connected to a ground connection by moving the switching strip and thus to be earthed.

[0009] In other words, the present device comprises a plurality of input and output contacts, each of which is intended for contacting corresponding voltage inputs and voltage outputs of individual modules of the combined voltage and power converter. The number of input contacts and the number of output contacts of the grounding and protection device thus corresponds to the number of individual cells. Each pair consisting of an input contact and an output contact is assigned to an individual module and is intended to be connected to the voltage input or voltage output of the respective individual module.

[0010] In an exemplary embodiment, each combined grounding and protection device is provided to ground and protect all individual modules of a modular voltage and power converter intended for converting a phase of the primary AC voltage. Therefore, a separate combined grounding and protection device is provided for each of the phases of the primary AC voltage. For example, in a modular voltage and power converter intended to convert a three-phase high voltage into a DC voltage, three groups of individual modules are provided, one group of individual modules for each phase, and accordingly, three combined grounding and protection devices are also provided.

[0011] To protect the individual modules from overvoltage, the input and output contacts assigned to each individual module are each connected to a varistor. The varistors are designed to conductively connect the input and output contacts, thus bridging the individual modules when the voltage drop across the varistor exceeds a first threshold. Therefore, in the event of a defect in an individual module and the resulting voltage increase between the voltage input and voltage output of the cell or the assigned input and output contacts, the varistors act as voltage limiters.

[0012] In addition, the combined earthing and protective device comprises a plurality of conductive bridge contacts that are part of a non-conductive contact strip. The contact strip can be moved between two positions, one of which is referred to as the operating position and the other as the earthing position. For example, the movement of the contact strip between the operating position and the earthing position can be a translational movement in one direction, i.e., the contact strip is moved from the operating position to the earthing position or vice versa.

[0013] When the safety edge is in the grounding position, one of the bridge contacts connects an input contact to an output contact, whereby the interconnected contacts are assigned to the same individual module. In the grounding position, the bridge contacts thus establish a conductive connection between the input and output contacts and short-circuit them. The number of bridge contacts therefore corresponds to the number of individual modules for which the combined grounding and protective device is intended.

[0014] To ground the short-circuited individual modules, i.e., to connect them to ground, a ground connection is also provided. The ground connection can be connected to ground. The combined grounding and protection device is designed so that, in the grounding position, the input and output contacts short-circuited by the bridge contacts are also connected to the ground connection, thus connecting all individual modules of the combined grounding and protection device to ground.

[0015] However, if the safety edge is moved to the operating position, or when the safety edge is in the operating position, the bridge contacts are moved to a position where they do not conduct between the input and output contacts, meaning they are not short-circuited. There is also no longer any connection between the ground connection and the input and output contacts, meaning they are no longer grounded. This combined grounding and protection device thus advantageously provides a way for the individual modules to be protected against overvoltage and also grounded, for example, for maintenance purposes.

[0016] In a preferred embodiment of the grounding and protection device, for series connection of the individual modules of the voltage and power converter, the output contact, which can be connected to the voltage output of a preceding individual module to be connected in series, is conductively connected by means of a current band to the input contact, which can be connected to the voltage input of the subsequent individual module to be connected in series. In the preferred embodiment, the grounding and protection device thus advantageously also handles the series connection of all individual modules intended to accommodate the same phase in the modular voltage and power converter.

[0017] In other words, in the preferred embodiment, the grounding and protection device comprises a plurality of current strips, which can be formed, for example, by conductive metal rails. The number of current strips or current rails is one less than the number of individual modules to be protected and grounded by the grounding and protection device. Each of the current strips connects an output contact of the grounding and protection device to an input contact of the grounding and protection device. The output contact is conductively connected to the input contact, which are intended to be connected to the voltage output and voltage input of individual modules connected directly one after the other in series.

[0018] The bridge contacts used to ground the individual modules can, for example, when the safety edge is in the grounding position, conductively connect the two current strips that are connected to the input contact and the output contact, each of which is intended for connection to the same individual module. Thus, the conductive connection of the current strips short-circuits the input and output contacts when the modular voltage and power converter is to be grounded. In this case, the current strips would also be conductively connected to the ground connection and thus grounded. For this purpose, for example, an additional current strip can be provided that is adapted to be connected to the voltage output of the last individual module in the series connection. This is electrically connected to the ground connection when the safety edge is in the grounding position and is electrically separated from it in the operating position.In a preferred embodiment, a spark gap is formed between each input contact and the output contact, which can be connected to the voltage input and the voltage output of the same individual module, said spark gap being configured such that a voltage flashover occurs if the voltage drop across the spark gap exceeds a second threshold, wherein the second threshold is preferably greater than the first threshold. Should, in an extreme fault situation, for example if the high-voltage insulation of an individual module breaks down, the mains voltage drop across only a few remaining individual modules and should the varistors provided for protecting the individual modules fail, the individual modules are additionally protected via the spark gaps across which the voltage drops in this case.

[0019] Preferably, the spark gap is formed between a second end of the current strip, which is connected to the input contact, and a first end of the current strip, which is connected to the output contact. Therefore, no additional components need to be provided for the spark gaps. Rather, these are advantageously formed by suitable design and arrangement of the already provided current strips.

[0020] Spring-loaded contact pins are preferably provided to connect the current strips to the bridge contacts. These are preferably mounted in a common carrier made of a non-conductive material. The spring-loaded contact pins can, for example, be pre-tensioned toward the bridge contacts to ensure reliable contact when the bridge contacts are displaced.

[0021] It is further preferred if each current strip comprises two contact pins, which are each in contact with the same bridge contact in the operating position of the switch strip and which are each in contact with different bridge contacts in the earthing position of the switch strip. In the preferred embodiment it is thus provided that in normal operation the bridge contacts emanating from the same current strip rest with their contact surfaces on the same bridge contact or touch it. The contact pins assigned to the same current strip are thus conductively connected in the operating position of the switch strip both by the current strip and by a bridge contact. In the earthing position of the switch strip the contact pins assigned to the same current strip are only conductively connected by the current strip.However, they are connected to other current strips via the bridge contacts in order to short-circuit and thus ground the individual modules.

[0022] The grounding and protection device preferably comprises an electric drive that moves the safety edge from the operating position to the grounding position. The electric drive further moves the safety edge, preferably via a threaded spindle.

[0023] In a preferred embodiment, the ground connection is formed by a ground bar, and the switch strip is configured such that a contact blade conductively connected to the bridge contacts engages the ground bar when the switch strip is moved from the operating position to the grounding position. In other words, an electrical connection to ground is established through mechanical engagement between a contact blade that is conductively connected to the switch strip or is part of the switch strip and a ground bar. This allows a simple visual check of whether the contact blade is in contact with the ground bar to determine whether the individual modules of the modular voltage and power converter are grounded.

[0024] Preferably, the contact blade engages with the grounding bar when the switch strip is moved from the operating position to the grounding position. This prevents the connection between the contact blade and the grounding bar from becoming loose without external influence or actuation.

[0025] The grounding and protection device preferably comprises a lever with which the switch bar can be manually moved from the operating position to the grounding position. An operator of the grounding and protection device can preferably determine from the position of the lever whether the switch bar is in the operating position or the grounding position. Thus, an operator of the modular voltage and power converter can directly determine from the position of the lever whether the device is in operation or grounded.

[0026] According to a second aspect, a modular voltage and power converter for converting a primary alternating voltage with one or more phases into a secondary voltage with one or more combined grounding and protection devices according to one of the preceding embodiments is provided. The voltage and power converter comprises, for each phase of the primary alternating voltage, a plurality of series-connected individual modules, each individual module having a voltage input and a voltage output for receiving a phase of the primary voltage, each voltage input being conductively connected to an input contact of the grounding and protection device, and each voltage output being conductively connected to an output contact of the grounding and protection device.

[0027] The advantages of the voltage and power transformer correspond to the advantages of the combined earthing and protection device used in it.

[0028] Preferably, each individual module comprises a transformer for voltage and power conversion between an input side of the individual module and an output side of the individual module, as well as a spark gap. The voltage input and the voltage output of the individual module are arranged on the input side of the individual module, and the spark gap is arranged parallel to the transformer and configured such that a voltage flashover occurs if the voltage drop across the spark gap exceeds a third threshold. The spark gap within the individual modules can lead to controlled destruction of the individual modules in the event of a fault, particularly if the varistors and / or the spark gaps of the combined grounding and protection device are insufficient.

[0029] Each individual module preferably comprises a housing designed so that if an individual module is destroyed due to an overvoltage, the individual modules adjacent to the destroyed individual module are not damaged. This advantageously limits the damage caused by the destruction of individual modules, and the voltage and power converter remains fundamentally operational.

[0030] Preferably, the varistors are arranged so that if an individual module is destroyed due to an overvoltage, the varistor connecting the input contact to the output contact, which are respectively connected to the voltage input and the voltage output of the destroyed individual module, is not damaged. This can be ensured in particular by the varistor being able to take over the string current until it decays and, at the same time, contributing to the counter voltage of the string with its varistor voltage instead of the cell. This allows the voltage and power converter to continue operating, since the varistor bridges the destroyed individual module and is not itself damaged. We will now explain the present invention in more detail with reference to the drawing. It shows:

[0031] Figure i shows a schematic structure of an embodiment of a modular voltage and power converter,

[0032] Figure 2 is a schematic view of an embodiment of a voltage and power converter with a grounding and protection device in an operating position,

[0033] Figure 3 is a schematic view of the embodiment of Figure 2 in a grounding position,

[0034] Figure 4 is a perspective view of an embodiment of a voltage and

[0035] Power converter with an embodiment of a grounding and protection device in a grounding position,

[0036] Figure 5 is a second perspective view of the embodiment of Figure 4, in which the earthing and protective device is in an operating position,

[0037] Figure 6 is a sectional view through part of the embodiment of an earthing and protective device from Figures 4 and 5 in the operating position,

[0038] Figure 7 shows a further sectional view of part of the embodiment of an earthing and protective device from Figures 4-6 in the earthing position,

[0039] Figure 8 is a perspective view of part of the embodiment of an earthing and protective device from Figures 4-7 in the operating position,

[0040] Figure 9 is a further perspective view of a part of the embodiment of a

[0041] Earthing and protective device from Figures 4-8 in the earthing position,

[0042] Figure 10 is a perspective detailed view of another part of the embodiment of Figures 4-10,

[0043] Figure 11 is a sectional view of another part of the embodiment of Figures 4-10 and

[0044] Figure 12 is a schematic representation of the structure of a single module of a modular voltage and power converter.

[0045] Figure 1 shows an exemplary embodiment of a modular voltage and power converter 1, which converts a three-phase high voltage into a direct voltage. Figure 1 shows a solid-state transformer 2, also referred to as a power electronic transformer, as an example of a modular voltage and power converter 1. The high voltage can, for example, be a three-phase alternating voltage with a voltage of 20 kV, while the direct voltage is + / - 750 V.

[0046] The voltage and power converter 1 has a phase conductor R, S, T for each phase of the three-phase high voltage and two output conductors 3, 4 for the DC voltage. For example, the first output conductor 3 is at a voltage of -750 V, while the second output conductor 4 is at a voltage of +750 V.

[0047] The voltage and power converter 1 has six individual modules 5 connected in series for each phase of the primary alternating voltage. In total, the voltage and power converter shown in Figure 1 therefore has 18 individual modules. Since the individual modules 5, which can also be referred to as cells or individual cells, are connected in series, only a portion of the high voltage drops across each individual module. In Figure 1, only a few of the individual modules 5 are provided with reference symbols to ensure that the figure as a whole remains legible. Each individual module 5 comprises power electronics with which part of a phase of the high voltage is converted into a direct voltage. The structure of the (identical) individual modules 5 is explained in more detail elsewhere with reference to Figure 12.

[0048] Figures 2 and 3 disclose an embodiment of a combined grounding and protection device 6 for a modular voltage and power converter 1, as shown, for example, in Figure 1. Figure 2 shows the combined grounding and protection device 6 in an operating position, and Figure 3 shows the grounding and protection device 6 in a grounding position.

[0049] Figures 2 and 3 show four individual modules 5 of the modular voltage and power converter 1 as examples, which are used to convert one phase of the primary voltage. Each individual module 5 has a voltage input 7 and a voltage output 8. In order to connect the individual modules 5 in series, a voltage output 8 of each individual module 5 to be connected in series is conductively connected to a voltage input 7 of the subsequent individual module 5 to be connected in series. For this purpose, the combined grounding and protection device 6 comprises a plurality of current strips 9. Each current strip 9 connects the voltage output 8 of an individual module 5 to the voltage input 7 of the subsequent individual module 5. The current strips 9 thus represent, on the one hand, input contacts 11, with which the current strips 9 are each directly conductively connected to the voltage inputs 7 of the individual modules 5.On the other hand, the current strips 9 also form output contacts 12, at which the current strips 9 are directly conductively connected to the voltage outputs 8 of the individual modules 5. The input and output contacts 11, 12 can, for example, be in direct physical contact with the voltage inputs 7 and voltage outputs 8, respectively. To avoid overloading the illustration in Figures 2 and 3, only one input contact 11 and one output contact 12 are provided with a reference symbol.

[0050] The current band 9, which is directly conductively connected to the voltage input 7 of an individual module 5, and the current band 9, which is directly conductively connected to the voltage output 8 of the same individual module 5, are each connected via a varistor 10. The varistors 10 are configured to conductively connect the directly consecutive current bands 9 to one another when the voltage drop between the input contact 11 and the output contact 12, which are assigned to the same individual module 5 or which are directly connected to the voltage input 7 and the voltage output 8 of the same individual module 5, exceeds a first limit value or threshold.

[0051] If a defect occurs in an individual module 5, resulting in an interruption of the current flow within the individual module 5 or between the current strips 9 and the individual module 5, the line-to-line voltage of the high-voltage network, for example, 20 kV, would drop directly across the point of separation, resulting in corresponding damage. In particular, this could lead to the complete destruction of the individual module 5, which in turn would result in the destruction of other individual modules 5 and thus ultimately of the entire modular voltage and power converter 1. Varistors 10 are provided as a protective measure for this case; they limit the maximum voltage drop across the individual modules 5 to the first threshold.

[0052] A distance d between a second end 13 of a current strip 9, which is directly conductively connected to the voltage input 7 of an individual module 5, and a first end 14 of the current strip 9, which is directly conductively connected to the voltage output 8 of the same individual module 5, was selected such that a spark gap 15 is formed between the first end 14 and the second end 13 of the current strips. Due to the selection of the distance d, the voltage across the spark gap 15 flashes over when the voltage drop across the spark gap 15 exceeds a second threshold value. The second threshold value is greater than the first threshold value, upon exceeding which the varistors io connect the input and output contacts 11, 12 of two directly consecutive current strips 9.

[0053] The spark gap 15 thus serves as additional safety in the event of an extreme fault, such as a breakdown of the high-voltage insulation of an individual module 5, where the high voltage of, for example, 20 kV drops across only a few remaining individual modules 5 and one of the varistors 10 also fails. In this case, the short-circuit current is absorbed by the spark gap 15, which is formed between two current strips 9. This prevents further damage or limits the occurrence of damage. In Figures 2 and 3, only one of the spark gaps 15 is provided with a reference symbol to avoid overloading the drawing with reference symbols.

[0054] Finally, the combined earthing and protective device also comprises a non-conductive switching strip with a plurality of bridge contacts 16. The switching strip is not shown in Figures 2 and 3, but will be described in more detail below with reference to further embodiments.

[0055] The number of bridge contacts 16 corresponds to the number of individual modules 5 for which the combined earthing and protective device 6 in Figures 2 and 3 is provided, i.e., a bridge contact 16 is provided for each individual module 5 and is also assigned to it. The switch strip, not shown in Figures 2 and 3, can be moved back and forth between an operating position and an earthing position. The bridge contacts 16 are arranged on the switch strip in such a way that they move back and forth with it between the operating position and the earthing position.

[0056] The bridge contacts 16 are arranged on the switch strip in such a way that each bridge contact 16 conductively connects the input contact 11 to the output contact 12, which are assigned to the same individual module 5, when the switch strip is in the grounding position. In other words, when the switch strip is in the grounding position, the bridge contacts 16 short-circuit the input contacts 11 and the output contacts 12, which are intended for connection to the same individual module 5. When the switch strip is in the operating position, the input contacts 11 and the output contacts 12, which are assigned to the same individual module 5, are not connected by the bridge contacts 16. The input and output contacts 11, 12 are therefore not short-circuited.Finally, the combined grounding and protection device shown in Figures 2 and 3 also has a grounding element 17, via which the short-circuited input and output contacts 11, 12 can be connected to a ground terminal 18. In the embodiment shown in Figures 2 and 3, the grounding element 17, like the bridge contacts 16, is attached to the switch strip (not shown) and is moved back and forth together with the switch strip between an operating position and a grounding position.

[0057] Figure 3 shows the grounding and protective device 6 in a grounded state, in which the switching strip (not shown) is in the grounding position. In this position, the grounding element 17 connects the current strip 9, whose first end 14 is connected to the voltage output 8 of the last individual module 5 connected in series, to the ground connection 18. All current strips 9 are conductively connected or short-circuited to one another via the bridge contacts 16. Therefore, all current strips 9 and thus also the individual modules 5 are connected to the ground connection 18 and thus to ground 19. The individual modules 5 connected to the combined grounding and protective device 6 are therefore de-energized when the device is grounded.

[0058] The operating state of the grounding and protective device 6 is shown in Figure 2. In this state, the switch strip (not shown) is in the operating position, so that the individual current strips 9 are no longer connected by the bridge contacts 16, and no connection is established between the last current strip 9 and the ground connection 18 by the grounding element 17. The individual modules 5, which are to be protected by the grounding and protective device 6, are therefore ready for operation and can convert the applied phase of a high voltage into a direct voltage.

[0059] An exemplary embodiment of a modular voltage and power converter 1 with six exemplary embodiments of combined grounding and protective devices 6 is described below with reference to Figures 4 to 11. Figures 4 and 5 show perspective external views of the modular voltage and power converter 1, while Figures 6-11 show various details of the voltage and power converter 1 and the combined grounding and protective devices 6, respectively.

[0060] The voltage and power converter 1 shown in Figures 4 and 5 is again a solid-state transformer (SST) 2, which is designed to convert a three-phase 20 kV AC input voltage into a + / -750 V DC voltage. In Figure 4, the voltage and power converter 1 is grounded by means of the combined grounding and protection devices 6, while the converter i in Figure 5 is operational.

[0061] The converter 1 has 28 series-connected individual modules 5 for converting each phase of the input AC voltage or high voltage. Of the individual modules 5, only a few are identified by reference numerals in Figures 4 and 5 to avoid impairing readability. The individual modules 5 are arranged in stacks or columns 20 in the modular converter 1, with the individual modules 5 of each of two columns 20 being connected in series to convert one of the three phases of the input AC voltage into a direct current or a direct voltage.

[0062] Figure 5 also shows that each individual module 5 is arranged in its own housing 21. The housings 21 are made of metal, for example, and are designed such that, in the event of an explosive destruction of the components of an individual module 5 due to an overvoltage, the neighboring individual modules 5 are not damaged, or at least only slightly damaged.

[0063] For each column or stack 20 of individual modules 5, the modular voltage and power converter 1 has a separate combined earthing and protection device 6. Therefore, for each high-voltage phase, not just one combined earthing and protection device 6 is provided, but two combined earthing and protection devices 6. The details of the earthing and protection devices 6 are explained in more detail below with reference to Figures 6-11. However, it should already be noted at this point that each of the earthing and protection devices 6 has a lever 22, the position of which indicates whether the respective earthing and protection device 6 or the individual modules 5 connected to it are in operation (as in Figure 5) or earthed (as in Figure 4).

[0064] In order to switch between the operating position and the earthing position or the corresponding state, a user can manually move the lever 22 of the respective earthing and protective device 6, which is connected to a contact strip. Alternatively, switching can also take place automatically via electrical actuators 23 in the form of spindle drives 23, which also move the contact strip and thus also the levers 22. Only a few of the spindle drives 23 are provided with reference symbols in order not to overload the drawing. From the position of the levers 22, a user or operator of the device can advantageously see directly whether the converter i is de-energized, i.e., earthed, or not.

[0065] Figures 6 to 9 show a section of the exemplary embodiment of a combined earthing and protective device 6 from Figures 4 and 5. Figures 6 and 7 show sections through a section of the earthing and protective device 6, and Figures 8 and 9 show perspective views in which some elements of the device 6 are shown transparently. In Figures 6 and 8, the earthing and protective device 6 is shown in the operating position, and in Figures 7 and 9 the earthing and protective device 6 is shown in the earthing position. For the sake of completeness, it should be noted that Figures 6-9 show slightly different sections of the combined earthing and protective device 6.

[0066] The exemplary embodiment of a combined grounding and protective device 6 initially comprises a support rail 37 on which several varistors 10 are arranged. Only one varistor 10 is shown in each of Figures 6-9. Overall, the combined grounding and protective device 6 comprises 14 varistors, one for each individual module 5 to be protected by the device 6. A further varistor is arranged in the sections shown, as can be seen from the fastening means 24 shown in each case. However, these varistors have been omitted from the illustration in order not to obscure the underlying design of the grounding and protective device 6.

[0067] As already explained with reference to Figures 2 and 3, the varistors 10 are intended to be conductively connected to the voltage input 7 and the voltage output 8 of an individual module 5. The varistors 10 are configured to conductively connect the voltage input 7 to the voltage output 8 of the respective individual module 5 when the voltage drop across the varistor 10 exceeds a first threshold. Thus, the varistors 10 prevent the destruction of the individual modules 5 in the event of an overvoltage higher than the first threshold.

[0068] The grounding and protection device 6 further comprises a plurality of current strips 9, each of which is provided for conductively connecting the voltage output 8 of a preceding individual module 5 in the series connection of the individual modules 5 to the voltage input 7 of the subsequent individual module 5 in the series connection of the individual modules 5. The input and output contacts 11, 12 of the device 6, which establish contact between the current strips 9 and the voltage inputs and outputs 7, 8, are not shown in Figures 6-9.

[0069] In addition, the grounding and protective device 6 comprises a plurality of bridge contacts 16 arranged on a non-conductive contact strip 25. The bridge contacts 16 are arranged on the contact strip 25 such that they move with the contact strip 25 along an adjustment direction 26, in which the contact strip 25 is displaced between a grounding position (shown in Figures 7 and 9) and an operating position (shown in Figures 6 and 8).

[0070] When the switching strip 25 is in the operating position, each bridge contact 16 is connected to exactly one of the current strips 9 via two spring-loaded contact pins 27, 28. Thus, in the operating position, the bridge contacts 16 form a parallel current path to the current strips 9 and thus contribute to the series connection of the individual modules 5.

[0071] If, however, the switching strip 25 is arranged in the earthing position, as shown in Figures 7 and 9, each of the bridge contacts 16 connects a spring-loaded contact pin 27 of a current strip 9 preceding the series connection of the individual modules 5 with a spring-loaded contact pin 28 of a current strip 9 following the series connection of the individual modules 9. This short-circuits the current strips 9 and thus the individual modules, whose voltage inputs and outputs are each connected to two current strips 9 conductively connected by a bridge contact 16, and the individual modules 5 are de-energized while the bridge contacts 16 are simultaneously connected to ground.

[0072] Finally, a spark gap 15 is formed between the first and second ends 13, 14 of the current strips 9, which is configured such that the voltage flashes over from the second end 14 of a preceding current strip 9 in the series connection to the first end 13 of a subsequent current strip 9 in the series connection when the voltage between the ends 13, 14 exceeds a second threshold value that is greater than the first threshold value. The second threshold value can be set via the distance d between the first end 13 and the second end 14. The spark gaps 15 are thus arranged parallel to the varistors 10 and protect the individual modules 5 from damage caused by overvoltages should the varistors 10 fail. Figure 10 shows in more detail the structure of the lever arrangement 29, via which the switching strips 25 can be moved back and forth between the operating position and the grounding position.The switch strips 25 are typically moved by the actuator motors 23, which are powered by an external power source (not shown). The actuator motors 23 have a non-self-locking threaded spindle and are equipped with a brake. If the motors fail, the switch strips 25 can be moved manually using the levers 22.

[0073] The movement of the switching strips 25 also moves a contact blade 30, which connects the current strips 9 to a ground connection 18. The contact blade 30 engages with the ground connection 18, so that additional force is required to disengage the contact blade 30 from the ground connection 18.

[0074] Figure 11 shows a further detail of the structure of the lever arrangement 29. In particular, a bolt 31 is shown, which connects the contact blade 30, the (extended) current strip 9, the switching strip 25, and an adjusting element 32. The actuator motor 23 can change the position of the switching strip 25 via the adjusting element 32. The contact blade 30 and the extended current strip 9 are conductively connected to one another, while a disc spring 33 prevents conductive contact between the contact blade 30 and the adjusting element 32. The bolt 31 is also non-conductive.

[0075] Finally, Figure 12 shows an equivalent circuit diagram for an individual module 5. The individual module 5 comprises a voltage input 7 and a voltage output 8, via which the high voltage to be converted is input. The individual module 5 also has two DC voltage outputs 34. The central element of the individual module is a small-format transformer 35, which can advantageously be a medium-frequency transformer with a frequency of 10 kHz to 100 kHz, as this easily enables a small-format design. Should this transformer 35 fail due to an overvoltage, an additional spark gap 36 is provided. The spark gap 36 inside the individual modules 5 is designed such that a voltage flashover occurs when a third threshold is exceeded, wherein the third threshold is greater than the second threshold. The spark gap 36 prevents orLimits the destruction of individual modules 5 in extreme fault cases, which essentially result in a drop in the entire high voltage across individual module 5. List of reference symbols.

[0076] 1 modular voltage and power converter

[0077] 2 Solid state transformer, power electronic transformer

[0078] R, S, T phase conductors

[0079] 3, 4 output conductors DC

[0080] 5 single modules, single cell, cell

[0081] 6 combined earthing and protective device

[0082] 7 Voltage input

[0083] 8 Voltage output

[0084] 9 Current band

[0085] 10 varistors

[0086] 11 Input contact

[0087] 12 Output contact

[0088] 13 second end of a current band 9

[0089] 14 first end of a current band 9

[0090] 15 Spark gap d Distance between the second end of a current band 9 and the first end of a subsequent current band 9

[0091] 16 Bridge contact

[0092] 17 Earthing element

[0093] 18 Ground connection

[0094] 19 Mass

[0095] 20 columns or stacks of individual modules

[0096] 21 Housing of a single module

[0097] 22 levers

[0098] 23 Actuator, spindle motor

[0099] 24 fasteners

[0100] 25 safety edge

[0101] 26 Adjustment direction

[0102] 27 contact bolts

[0103] 28 contact bolts

[0104] 29 Lever arrangement

[0105] 30 contact blades

[0106] 31 bolts

[0107] 32 Control element

[0108] 33 Disc spring

[0109] 34 DC outputs

[0110] 35 Transformer

[0111] 36 spark gap

[0112] 37 support rail

Claims

Claims Combined earthing and protection device (6) for a modularly constructed voltage and power converter (1) for converting a primary alternating voltage with one or more phases into a secondary voltage, wherein the voltage and power converter (1) comprises, for each phase of the primary alternating voltage, a plurality of individual modules (5) to be connected in series, wherein each individual module (5) has a voltage input (7) and a voltage output (8) for receiving a phase of the primary voltage, wherein the combined earthing and protection device (6) comprises a plurality of input contacts (11) and a plurality of output contacts (12) which are configured in such a waythat in each case an input contact (11) can be conductively connected to a voltage input (7) of an individual module (5) of the voltage and power converter (1) and in each case an output contact (12) can be conductively connected to a voltage output (8) of an individual module (5) of the voltage and power converter (1), and in each case the input contact (11) and the output contact (12), which can be connected to the voltage input (7) and the voltage output (8) of the same individual module (5), are connected by means of a varistor (10), wherein the varistor (10) is configured to conductively connect the input contact (11) to the output contact (12) when the voltage drop across the varistor (10) exceeds a first threshold value, and wherein the combined grounding and protection device (6) further comprises a non-conductive switching strip (25) with a plurality of bridge contacts (16), wherein the switching strip (25) is configured toto be moved from an operating position into a grounding position, wherein when the switching strip (25) is in the grounding position, a respective bridge contact (16) of the plurality of bridge contacts (16) conductively connects the input contact (11) to the output contact (12), which can be connected to the voltage input (7) and the voltage output (8) of the same individual module (5), and the input contacts (11) and output contacts (12) conductively connected by the bridge contacts (16) are connected to a ground connection (18), and wherein when the switching strip (25) is in the operating position, the input contacts (11) and the output contacts (12) which are connected to the voltage input (7) and the voltage output (8) of the same individual module, (5) are connectable, are not conductively connected by the bridge contacts (16), and the input contacts (11) and output contacts (12) are also not connected to the ground connection (18). Grounding and protection device (6) according to claim 1, wherein, for series connection of the individual modules (5) of the voltage and power converter (1), the output contact (12), which is connectable to the voltage output (8) of an individual module (5) to be connected in series beforehand, is conductively connected to the input contact (11) by means of a current band (9), which is connectable to the voltage input (7) of the individual module (5) to be connected in series afterwards.Grounding and protection device (6) according to claim 1 or 2, wherein a spark gap (15) is formed between each input contact (11) and the output contact (12), which are connectable to the voltage input (7) and the voltage output (8) of the same individual module (5), said spark gap being configured such that a voltage flashover occurs when the voltage drop across the spark gap (15) exceeds a second threshold value, wherein the second threshold value is preferably greater than the first threshold value. Grounding and protection device (6) according to claim 2 and 3, wherein the spark gap (15) is formed between each second end (13) of the current strip (9), which is connected to the input contact (11), and a first end (14) of the current strip (9), which is connected to the output contact (12).Grounding and protection device (6) according to one of the preceding claims, wherein spring-loaded contact pins (27, 28) are provided for connecting the current strips (9) to the bridge contacts (16), which contact pins are preferably held in a common carrier made of a non-conductive material. Grounding and protection device (6) according to claim 5, wherein each current strip (9) comprises two contact pins (27, 28), which are each in contact with the same bridge contact (16) in the operating position of the switching strip (25) and which are each in contact with different bridge contacts (16) in the grounding position of the switching strip (25). - Grounding and protection device (6) according to one of the preceding claims, wherein the grounding and protection device (6) comprises an electric drive (23) that moves the switching strip (25) from the operating position to the grounding position, wherein the electric drive (23) preferably moves the switching strip (25) via a threaded spindle. . Grounding and protection device (6) according to one of the preceding claims, wherein the ground connection (18) is formed by a ground rail, and wherein the switching strip (25) is configured such that a contact blade (30) conductively connected to the bridge contacts (16) engages the ground rail (18) when the switching strip (25) is moved from the operating position to the grounding position. . Grounding and protection device (6) according to claim 8, wherein the contact blade (30) engages with the ground rail (18) when the switching strip (25) is moved from the operating position to the grounding position. 0.Grounding and protection device (6) according to claim 9, wherein the grounding and protection device (6) comprises a lever (22) with which the switching strip (25) can be manually moved from the operating position to the grounding position, wherein an operator of the grounding and protection device (6) can preferably determine from a position of the lever (22) whether the switching strip (25) is in the operating position or the grounding position.Modularly constructed voltage and power converter (1) for converting a primary alternating voltage with one or more phases into a secondary voltage with one or more combined earthing and protection devices (6) according to one of claims 1 to 10, wherein the voltage and power converter (1) comprises a plurality of series-connected individual modules (5) for each phase of the primary alternating voltage, wherein each individual module (5) has a voltage input (7) and a voltage output (8) for receiving a phase of the primary voltage, wherein in each case a voltage input (7) is conductively connected to an input contact (11) of the earthing and protection device (6) and each voltage output (8) is conductively connected to. an output contact (12) of the grounding and protection device (6). Voltage and power converter (1) according to claim 11, wherein each individual module (5) comprises a transformer (35) for voltage and power conversion between an input side of the individual module (5) and an output side of the individual module (5), as well as a spark gap (36), wherein the voltage input (7) and the voltage output (8) of the individual module (5) are arranged on the input side of the individual module (5), and wherein the spark gap (36) is arranged in parallel with the transformer (35) and is configured such that a voltage flashover occurs when the voltage drop across the spark gap (36) exceeds a third threshold value.The voltage and power converter (1) according to claim 11 or 12, wherein each individual module (5) comprises a housing (21) configured such that, if an individual module (5) is destroyed due to an overvoltage, individual modules (5) arranged adjacent to the destroyed individual module (5) are not damaged. The voltage and power converter (1) according to claim 11, 12 or 13, wherein the varistors (10) are configured such that, if an individual module (5) is destroyed due to an overvoltage, the varistor (10) connecting the input contact (11) to the output contact (12), which are respectively connected to the voltage input (7) and the voltage output (8) of the destroyed individual module (5), is not damaged.

Images