WO2024074270A1 - Combined earthing and protective device for a voltage and power converter of modular design - Google Patents

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

Combined earthing and protection device for a modular voltage and power converter

The present invention relates to a combined earthing 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 that can be 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.

Modular voltage and power converters in the form of solid state transformers (SST), also known as power electronic transformers, are intended 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 voltage. The power electronic transformers are made up of a large number of individual converters, with several individual converters connected in series for each phase of the high voltage and the individual converters connected in series being connected in parallel.

The individual power converters, also known as cells, are at a high voltage potential during normal operation and are therefore not accessible to people. If maintenance or other work must be carried out on the SST, various safety rules must be observed. In particular, the absence of voltage must be determined and an earthing set must be placed for each of the cells so that each cell is earthed. Due to the large number of individual cells that an SST comprises, the preparatory work before maintenance is very complex and time-consuming.

It can also be problematic if a single cell can no longer conduct electricity due to a fault in the cell, as in this case the line-to-line voltage of the high voltage, for example 20 kV, drops across the separation point, which can lead to the cell being destroyed explosively, for example. The remains of the explosively destroyed cell can also destroy other cells that are located next to it, so 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.

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

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 that can be connected in series for each phase of the primary alternating voltage. Each individual module has a voltage input and a voltage output to accommodate a phase of the primary voltage. The combined grounding and protection device comprises a plurality of input contacts and a plurality of output contacts that are configured such that an input contact can be conductively connected to a voltage input of an individual module of the voltage and power converter and 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 that can be connected to the voltage input and the voltage output of the same individual module are 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 value. 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 contacts and output contacts conductively connected by the bridge contacts are connected to a ground connection. When the switching strip is in the operating position, the input contacts and the output contacts, which can be connected to the voltage input and the voltage output of the same individual module are not conductively connected by the bridge contacts and the input contacts and output contacts are also not connected to the ground connection.

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, i.e. it connects the individual modules in series, protects 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, enables all individual modules connected in series to be connected to a ground connection by moving the switching strip and thus to be earthed.

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 correspond to the number of individual cells. A 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 the voltage output of the respective individual module.

In an exemplary embodiment, each combined grounding and protection device is intended to ground and protect all individual modules of a modular voltage and power converter that are intended to convert one phase of the primary alternating voltage. Therefore, a separate combined grounding and protection device is provided for each of the phases of the primary alternating voltage. For example, in a modular voltage and power converter with which a three-phase high voltage is to be converted into a direct 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.

In order to protect the individual modules from overvoltage, the input and output contacts assigned to an individual module in pairs are connected to a varistor. The varistors are designed to connect the input and output contacts to each other in a conductive manner, i.e. to bridge the individual modules when the voltage drop across the varistor Voltage exceeds a first threshold value. The varistors therefore act as voltage limiters in the event of a defect in an individual module and the associated voltage increase between the voltage input and voltage output of the cell or the associated input and output contacts.

In addition, the combined earthing and protective device comprises a plurality of conductive bridge contacts which are part of a non-conductive switch strip. The switch 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 switch strip between the operating position and the earthing position can be a translational movement in one direction, i.e. the switch strip is moved from the operating position to the earthing position or vice versa.

When the switch strip is in the earthing position, one of the bridge contacts connects an input contact with an output contact, whereby the interconnected contacts are assigned to the same individual module. In the earthing 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 earthing and protective device is intended.

In order 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 in such a way that in the grounding position the input and output contacts short-circuited by the bridge contacts are also connected to the ground connection and thus all individual modules of the combined grounding and protection device are connected to ground.

However, if the switch strip is moved to the operating position, or if the switch strip is in the operating position, the bridge contacts are moved to a position in which they do not connect the input and output contacts to one another in a conductive manner, i.e. they are not short-circuited. There is also no longer any connection between the ground connection and the input and output contacts, so that they are no longer connected to ground, i.e. no longer earthed. This combined earthing and protection device thus advantageously provides a way of Individual modules can be protected against overvoltage and also earthed, for example for maintenance purposes.

In a preferred embodiment of the grounding and protection device, for the series connection of the individual modules of the voltage and power converter, the output contact, which can be connected to the voltage output of an individual module to be connected in series beforehand, is conductively connected by means of a current band to the input contact, which can be connected to the voltage input of the individual module to be connected in series afterwards. In the preferred embodiment, the grounding and protection device thus advantageously also takes over the series connection of all of the individual modules that are intended to accommodate the same phase in the modular voltage and power converter.

In other words, the grounding and protection device in the preferred embodiment comprises a plurality of current bands, which can be formed, for example, by conductive metal rails. The number of current bands or current rails is one less than the number of individual modules that are to be protected and grounded with the grounding and protection device. Each of the current bands 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 the voltage input of individual modules that are to be connected in series directly one after the other.

The bridge contacts used to ground the individual modules can, for example, in the grounding position of the switching strip, conductively connect the two current bands 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 bands short-circuits the input and output contacts when the modular voltage and power converter is to be grounded. In this case, the current bands would also be conductively connected to the ground connection and thus grounded. For this purpose, for example, an additional current band can be provided that is adapted to be connected to the voltage output of the last individual module in the series connection and that is electrically connected to the ground connection in the grounding position of the switching strip and is electrically separated from it in the operating position. In a preferred embodiment, a spark gap is formed between the input contact and the output contact, which can be connected to the voltage input or the voltage output of the same individual module, which is configured in such a way that a voltage flashover occurs when the voltage drop across the spark gap exceeds a second threshold value, wherein the second threshold value is preferably greater than the first threshold value. If, in the event of an extreme fault, for example if the high-voltage insulation of an individual module breaks down, the mains voltage drops across only a few remaining individual modules and the varistors provided to protect the individual modules fail, the individual modules are additionally protected via the spark gaps across which the voltage drops in this case.

Preferably, the spark gap is formed between a second end of the current band, which is connected to the input contact, and a first end of the current band, 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 current bands already provided.

Spring-loaded contact bolts are preferably provided to connect the current strips to the bridge contacts. These are preferably held in a common carrier made of a non-conductive material. The spring-loaded contact bolts can, for example, be pre-tensioned towards the bridge contacts in order to enable reliable contacting of the bridge contacts when they are moved.

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 that originate from the same current strip rest with their contact surfaces on the same bridge contact or touch it. The contact pins that are 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 that are assigned to the same current strip are only conductively connected by the current strip. Via the Bridge contacts, on the other hand, are used to connect them to other current strips in order to short-circuit the individual modules and thus ground them.

The earthing and protection device preferably comprises an electric drive that moves the switching strip from the operating position to the earthing position. The electric drive preferably moves the switching strip further via a threaded spindle.

In a preferred embodiment, the ground connection is formed by a ground rail, and the switching strip is configured such that a contact blade that is conductively connected to the bridge contacts engages the ground rail when the switching strip is moved from the operating position to the grounding position. In other words, an electrical connection to ground is established by a mechanical engagement between a contact blade that is conductively connected to the switching strip or is part of the switching strip and a ground rail. This makes it possible to determine whether the individual modules of the modular voltage and power converter are grounded by simply visually checking whether the contact blade is in contact with the ground rail.

Preferably, the contact blade engages with the ground 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 ground bar from coming loose without external influence or actuation.

The earthing and protection device preferably comprises a lever with which the switching strip can be moved manually from the operating position to the earthing position, wherein an operator of the earthing and protection device can preferably recognize from a position of the lever whether the switching strip is in the operating position or the earthing position. An operator of the modular voltage and power converter can thus immediately recognize from the position of the lever whether the device is in operation or is earthed.

According to a second aspect, a modular voltage and power converter is provided 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. The voltage and power converter comprises a plurality of individual modules connected in series for each phase of the primary alternating voltage, each individual module being designed to accommodate one phase of the Primary voltage has a voltage input and a voltage output, wherein each voltage input is conductively connected to an input contact of the earthing and protective device and each voltage output is conductively connected to an output contact of the earthing and protective device.

The advantages of the voltage and power converter correspond to the advantages of the combined earthing and protection device used in it.

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 and a spark gap, wherein the voltage input and the voltage output of the individual module are arranged on the input side of the individual module and wherein the spark gap is arranged parallel to the transformer and configured such that a voltage flashover occurs when the voltage drop across the spark gap exceeds a third threshold value. The spark gap within the individual modules can lead to a controlled destruction of the individual modules in the event of a fault, in particular if the varistors and/or the spark gaps of the combined earthing and protection device are insufficient.

Each individual module preferably comprises a housing which is designed in such a way that if an individual module is destroyed due to an overvoltage, individual modules arranged adjacent to the destroyed individual module are not damaged. In this way, the damage caused by the destruction of individual modules is advantageously limited and the voltage and power converter remains fundamentally operational.

The varistors are preferably arranged in such a way that if an individual module is destroyed due to an overvoltage, the varistor that connects the input contact to the output contact, which are each 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. The voltage and power converter can thus continue to operate because the varistor bridges the destroyed individual module and is not damaged itself. In the following we will explain the present invention in more detail with reference to the drawing.

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

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,

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

Figure 4 is a perspective view of an embodiment of a voltage and

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

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

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,

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

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,

Figure 9 is a further perspective view of a part of the embodiment of a

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

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

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

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

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

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 direct voltage. The first output conductor 3 is, for example, at a voltage of -750 V, while the second output conductor 4 is correspondingly at a voltage of +750 V.

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 single 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 so 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.

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 or operating position, and Figure 3 shows the grounding and protection device 6 in a grounding position.

Four individual modules 5 of the modular voltage and power converter 1 are shown in Figures 2 and 3 as examples, which are used to convert a 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 an 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 bands 9. Each current band 9 connects the voltage output 8 of an individual module 5 to the voltage input 7 of the subsequent individual module 5. The current bands 9 thus represent, on the one hand, input contacts 11, with which the current bands 9 are each directly conductively connected to the voltage inputs 7 of the individual modules 5. On the other hand, the current bands 9 also form output contacts 12, at which the current bands 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 or voltage outputs 8. In order not to overload the illustration in Figures 2 and 3, only one input contact 11 and one output contact 12 are provided with a reference symbol.

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 such that they 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 value.

If a defect occurs in an individual module 5, as a result of which the current flow within the individual module 5 or between the current bands 9 and the individual module 5 is interrupted, the line-line voltage of the high-voltage network, for example 20 kV, would drop directly across the separation point, resulting in corresponding destruction. In particular, the individual module 5 may be completely destroyed, which in turn results 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 in this case, which limit the maximum voltage drop across the individual modules 5 to the first threshold value.

A distance d between a second end 13 of a current band 9, which is directly conductively connected to the voltage input 7 of an individual module 5, and a first end 14 of the current band 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 bands. 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, when exceeded, the varistors io connect the input and output contacts 11, 12 of two directly consecutive current bands 9.

The spark gap 15 thus serves as additional safety if, in the event of an extreme fault, for example a breakdown of the high-voltage insulation of an individual module 5, 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 taken over by the spark gap 15, which is formed between two current bands 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 in order not to overload the drawing with reference symbols.

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.

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.

The bridge contacts 16 are arranged on the switch strip in particular such 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, in the grounding position of the switch strip, 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. If 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 earthing and protection device shown in Figures 2 and 3 also has an earthing element 17, via which the short-circuited input and output contacts 11, 12 can be connected to a ground connection 18. In the embodiment in Figures 2 and 3, the earthing element 17 as well as the bridge contacts 16 are attached to the switch strip (not shown) and are moved back and forth together with the switch strip between an operating position and an earthing position.

In Figure 3, the earthing and protective device 6 is shown in a grounded state in which the switch strip (not shown) is in the grounding position. In this position, the grounding element 17 connects the current band 9, the first end 14 of which is connected to the voltage output 8 of the last individual module 5 connected in series, to the ground connection 18. All current bands 9 are conductively connected or short-circuited to one another via the bridge contacts 16. Therefore, all current bands 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 earthing and protective device 6 are therefore de-energized when the latter is in the grounded state.

The operating state of the earthing and protective device 6 is shown in Figure 2. In this, 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 earthing element 17. The individual modules 5, which are to be protected by the earthing and protective device 6, are therefore ready for operation and can convert the applied phase of a high voltage into a direct voltage.

An embodiment of a modular voltage and power converter 1 with six embodiments of combined earthing 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 earthing and protective devices 6.

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 input AC voltage into a +/-750 V DC voltage. In Figure 4, the voltage and power converter 1 is earthed by means of the combined earthing and protection devices 6, while the converter i in Figure 5 is ready for operation.

The converter 1 has 28 individual modules 5 connected in series to convert each phase of the input alternating voltage or high voltage. Of the individual modules 5, only a few are identified by reference numerals in Figures 4 and 5 in order not to impair readability. The individual modules 5 are arranged in stacks or columns 20 in the modular converter 1, with the individual modules 5 of two columns 20 connected in series in order to convert one of the three phases of the input alternating voltage into a direct current or a direct voltage.

In Figure 5 it can also be seen that each individual module 5 is arranged in its own housing 21. The housings 21 are made of metal, for example, and are designed in such a way that if the components of an individual module 5 are destroyed explosively due to an overvoltage, the neighboring individual modules 5 are not damaged or at least only slightly damaged.

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. For each phase of the high voltage, there is therefore not just one combined earthing and protection device 6, 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 pointed out 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 are earthed (as in Figure 4).

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 devices 6 back and forth, which is connected to a switch bar. Alternatively, switching can also be carried out automatically via electrical actuators 23 in the form of spindle drives 23, which also move the switch bar and thus also the levers 22. Only some of the spindle drives 23 are provided with reference symbols in order not to overload the drawing. A user or operator can use the position of the levers 22 the device can advantageously see directly whether the converter i is de-energized, ie, earthed, or not.

Figures 6 to 9 show a section of the 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 devices 6 are 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.

The embodiment of a combined grounding and protective device 6 initially comprises a support rail 37 on which several varistors 10 are arranged. In Figures 6-9, only one varistor 10 is shown in each case. In total, the combined grounding and protective device 6 comprises 14 varistors, one for each individual module 5 that is 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 not been shown in order not to obscure the underlying design of the grounding and protective device 6.

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 value. The varistors 10 thus prevent the individual modules 5 from being destroyed in the event of an overvoltage that is higher than the first threshold value.

The earthing and protection device 6 further comprises a plurality of current bands 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 contact between the current bands 9 and the voltage inputs and outputs 7, 8 The input and output contacts 11, 12 of the device 6 are not shown in Figures 6-9.

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

If 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 bolts 27, 28. In the operating position, the bridge contacts 16 thus form a parallel current path to the current strips 9 and thus contribute to the series connection of the individual modules 5.

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 bolt 27 of a current band 9 preceding the series connection of the individual modules 5 with a spring-loaded contact bolt 28 of a current band 9 following the series connection of the individual modules 9. This short-circuits the current bands 9 and thus the individual modules, whose voltage inputs and outputs are each connected to two current bands 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.

Finally, a spark gap 15 is formed between the first and second ends 13, 14 of the current bands 9, which is configured such that the voltage from the second end 14 of a current band 9 preceding in the series connection flashes over to the first end 13 of a current band 9 following 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 if the varistors 10 fail. Figure 10 shows in more detail the structure of the lever arrangement 29, by means of which the switch strips 25 can be moved back and forth between the operating position and the earthing position. The switch strips 25 are normally moved by the servomotors 23, which are supplied via an external power source (not shown). The servomotors 23 have a non-self-locking threaded spindle and are provided with a brake. If the motors fail, the switch strips 25 can be moved manually by means of the levers 22.

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 bring the contact blade 30 out of engagement with the ground connection 18.

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, (extended) current band 9, switching strip 25 and an adjusting element 32. The adjusting motor 23 can change the position of the switching strip 25 via the adjusting element 32. The contact blade 30 and the extended current band 9 are conductively connected to one another, while a plate spring 33 prevents conductive contact between the contact blade 30 and the adjusting element 32. The bolt 31 is also designed to be non-conductive.

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 received. The individual module 5 also has two direct 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 enables a small-format design in a simple manner. 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 in such a way that a voltage flashover occurs when a third threshold value is exceeded, the third threshold value being greater than the second threshold value. The spark gap 36 prevents or limits the destruction of the individual modules 5 in extreme fault cases, in which the entire high voltage across the individual module 5 essentially drops. List of reference symbols

1 modular voltage and power converter

2 Solid state transformer, power electronic transformer

R, S, T phase conductor

3, 4 output conductors DC

5 single modules, single cell, cell

6 combined earthing and protective device

7 Voltage input

8 Voltage output

9 Current band

10 Varistor

11 Input contact

12 Output contact

13 second end of a current band 9

14 first end of a current band 9

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

16 Bridge contact

17 Earthing element

18 Ground connection

19 Mass

20 columns or stacks of individual modules

21 Housing of a single module

22 levers

23 Actuator, spindle motor

24 Fasteners

25 Switch strip

26 Adjustment direction

27 contact bolts

28 contact bolts

29 Lever arrangement

30 contact blades

31 bolts

32 Actuator

33 Disc spring

34 DC outputs

35 Transformer

36 Spark gap

37 Support rail

Claims

Claims Combined grounding 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 a plurality of individual modules (5) to be connected in series 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 the combined grounding and protection device (6) comprises a plurality of input contacts (11) and a plurality of output contacts (12) which are configured such that 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 dropping 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 to be moved from an operating position to a grounding position, wherein when the switching strip (25) is in the grounding position, one 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 single module (5) 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). Earthing and protection device (6) according to claim 1, wherein for the 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 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), which is 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 a second end (13) of the current band (9), which is connected to the input contact (11), and a first end (14) of the current band (9), which is connected to the output contact (12). Earthing and protection device (6) according to one of the preceding claims, wherein spring-loaded contact bolts (27, 28) are provided for connecting the current strips (9) to the bridge contacts (16), which are preferably held in a common carrier made of a non-conductive material. Earthing and protection device (6) according to claim 5, wherein each current strip (9) comprises two contact bolts (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 earthing 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 electrical drive (23) which moves the switching strip (25) from the operating position to the grounding position, wherein the electrical 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. Earthing and protection device (6) according to claim 9, wherein the earthing and protection device (6) comprises a lever (22) with which the switching strip (25) can be moved manually from the operating position to the earthing position, wherein an operator of the earthing and protection device (6) can preferably recognize from a position of the lever (22) whether the switching strip (25) is in the operating position or earthing position. 1. Modular 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 individual modules (5) connected in series 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 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 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) and 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 parallel to the transformer (35) and configured such that a voltage flashover occurs when the voltage drop across the spark gap (36) exceeds a third threshold value. Voltage and power converter (1) according to claim 11 or 12, wherein each individual module (5) comprises a housing (21) which is designed 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. Voltage and power converter (1) according to claim 11, 12 or 13, wherein the varistors (10) are arranged such that if an individual module (5) is destroyed due to an overvoltage, the varistor (10) which connects the input contact (11) to the output contact (12), which are each connected to the voltage input (7) and the voltage output (8) of the destroyed individual module (5), is not damaged.