HIGH VOLTAGE INSTALLATION AND WAVEGUIDE FOR USE IN A HIGH VOLTAGE INSTALLATION

The present disclosure relates to a high voltage installation comprising at least two devices at di f ferent electrical potentials and a waveguide for exchanging signals between the at least two devices . The present disclosure further relates to waveguides for use in such high voltage installations .

Due to operational and safety considerations , di f ferent parts of high voltage installations are often connected using optical networks . It is an obj ect of the present disclosure to describe alternative communication arrangements and their components for use in high voltage installations .

Document EP 1 239 600 Bl discloses a wireless communication system using a waveguide . A communication device for transmitting signals between a substation control unit and control units of bay elements comprise transceiving devices connected to the substation and the bay element control units , and a waveguide enclosing and connecting antennas of said transceiving devices . The transceiving devices produce electromagnetic radio frequency waves to communicate information between the control units . The waveguide protects the waves against interference .

According to a first aspect of the present disclosure , a high voltage (HV) installation is provided . The HV installation comprises at least one first device at a first electrical potential , at least one second device at a second electrical potential , and at least one waveguide for exchanging signals between the at least one first device and the at least one second device . Each waveguide comprises a first conductive segment for carrying and shielding a high frequency electromagnetic wave , a second conductive segment for carrying and shielding the high frequency electromagnetic wave , and an insulation segment arranged between the first segment and the second segment for electrically separating the first electrical potential from the second electrical potential .

Such an arrangement is particularly useful for transmitting and shielding high frequency communication signals in distributed HV applications , such as di f ferent cells of a substation operating at di f ferent voltage potentials . Among others , the inventors have discovered that by the provision of at least one insulation segment between two neighboring conductive waveguide segments configured for carrying and shielding high frequency electromagnetic waves , various forms of wireless communication systems can also be applied in HV installations , wherein di f ferent devices operate at di f ferent electrical potentials and therefore need to be insulated from one another .

Compared to free-space , unshielded wireless communication techniques , the used communication channel can be protected from outside disturbances , such as network j ammers , to protect critical parts of an electrical network . At the same time , the relatively high installation ef fort required for installing dedicated optical links between cells of a HV installation can be avoided .

According to a second aspect of the present disclosure , a waveguide for use in an HV installation is provided . The waveguide comprises a first hollow conductor having a first termination area, a second hollow conductor having a second termination area, and an insulation element . The first termination area comprises at least one first field shaping element electrically connected to the first hollow conductor . The second termination area comprises at least one second field shaping element . The second hollow conductor is electrically insulated form the first hollow conductor by one or more insulating gaps . The insulation element at least partially encloses and aligns the first termination area and the second termination area, so as to enable an electromagnetic wave travelling within the first hollow conductor to travel through the second hollow conductor and vice versa .

The waveguide according to the second aspect provides an ef ficient structure for exchanging high- frequency signals across di f ferent electrical domains . Among others , it improves high- frequency signal exchange across an insulating gaps in a hollow, conductive channel , increases a creepage distance across the gap, controls and limits a width of the gap, protects and at least partially insulates the termination areas of the two hollow conductors from one another, and assists in field shaping along dielectric materials providing the insulation, in particular air filling the gap and/or the hollow conductors and an epoxy material of the insulation element . It is therefore useful for implementing a HV installation, for example the HV installation according to the first aspect .

The use of field shaping elements helps to reduce electrical field strength in the termination areas of the hollow conductors , thus avoiding critical field strength caused by potentially high di f ferences in their electrical potential . It may also improve the coupling and, at the same time , reduce unwanted reflections at the termination areas of two electrically insulated, hollow conductors facing each other .

According to a third aspect of the present disclosure , another waveguide for use in an HV installation is provided . The waveguide comprises an insulating core , a first conductive layer formed on a first surface area of the insulating core , and a second conductive layer formed on a second surface area of the insulating core . The first conductive layer is electrically insulated from the second conductive layer by one or more gaps filled with an insulating material .

The waveguide according to the third aspect provides another ef ficient structure for exchanging high- frequency signals across di f ferent electrical domains . Among others , it allows for good integration and easy manufacturing of waveguides having one or more insulating gaps , such as the waveguide according to the second aspect , and is useful for implementing a HV installation, for example the HV installation according to the first aspect .

The use of an insulating core enables simple aligning of two separate conductive layers with respect to each other and therefore provides a waveguide function and, at the same time , electrical insulation between devices connected to the respective or conductive layers .

While the present disclosure relates to several aspects of a HV installation and components thereof , every feature described with respect to one of these aspects is also disclosed herein with respect to the other aspects , even i f the respective feature is not explicitly mentioned in the context of the speci fic aspect .

The accompanying figures are included to provide a further understanding . In the figures , elements of the same structure and/or functionality may be referenced by the same reference signs . It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessary drawn to scale .

Figure 1 shows a schematic view of a first HV installation .

Figure 2 shows a schematic view of a second HV installation having a segmented bus structure .

Figure 3 shows a schematic view of a third HV installation having a continuous bus structure .

Figure 4 shows a schematic view of a fourth HV installation having a daisy chain structure .

Figure 5 shows a schematic view of a fi fth HV installation having a mesh structure .

Figure 6 shows a perspective , sectional view of a first waveguide with field shaping elements .

Figure 7 shows a simulation of the electrical field within the first waveguide of Figure 6 .

Figure 8 shows a cross section through an upper wall of the first waveguide according to Figure 6 . Figures 9 to 11 show di f ferent configurations of the upper wall of the first waveguide according to Figure 6 .

Figures 12 to 14 show di f ferent configurations for the field shaping elements of the first waveguide of Figure 6 .

Figures 15 and 16 show the reflection and transmission of the waveguide of Figure 6 .

Figure 17 shows a schematic, cross-sectional view of a second waveguide with an insulating core .

Figure 18 shows a schematic, cross-sectional view through a third waveguide with multiple insulating gaps .

Figure 19 shows a schematic, cross-sectional view through a fourth waveguide with two insulating gaps embedded in a single insulating part .

Figure 20 shows a schematic, cross-sectional view through a fi fth waveguide with grading electrodes embedded in an insulating part .

Figure 21 shows a schematic, cross-sectional view through a sixth waveguide with integrated coaxial-to-waveguide transition structure .

Figure 22 shows a flow diagram of a method for manufacturing a waveguide with an insulating core .

While the disclosure is amenable to various modi fications and alternative forms , speci fics thereof are shown by way of examples in the figures and will be described in detail below . It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described . On the contrary, the intention is to cover all modi fications , equivalents , and alternatives falling within the scope of the disclosure defined by the appended claims .

High voltage direct current (HVDC ) and flexible alternating current transmission systems ( FACTS ) converter stations exhibit several power semiconductor switching cells . These switching cells are arranged within valve structures in case of HVDC systems or power electronic building blocks ( PEBB ) in case of FACTS . In each case , each cell is connected to a control unit via a high speed, real-time communication network . The communication between the control unit and the individual cells and the electronic devices comprised therein includes gate firing signals , operating status signals and cell monitoring signals , for example .

As part of the operating environments and the power electronic building blocks used for switching di f ferent electrical pathways , di f ferences in the electrical potential between individual cells commonly occur, which need to be bridged by control signals . To comply with corresponding insulation requirements , control signals so far have been communicated via optical fiber links . However, implementing an optical fiber link network, in particular in relatively complicated network topologies , is very labor and cost intensive and needs to be configured and manually connected to each devices of each cell .

At the same time , conventional , e . g . radio-link, wireless communication systems , such as WiFi networks according to the IEEE 802 . 11 series of standards , are not suitable for the speci fic application area of HV installations . This is in part because radio signals can be distorted and attenuated by the metallic structures of HV equipment , or disturbed by neighboring communication, such as neighboring WiFi networks . Moreover, the use of a conventional wireless communication system may present a weakness in a corresponding part of the infrastructure . In particular, the use of a wide spectrum j ammer could be used to ef fectively block firing signal , thus deactivating the corresponding converter station .

Figure 1 shows a schematic view of a first HV installation 100 comprising two electrical devices 112 and 122 located in a first cell 110 and a second cell 120 , respectively . The first device 112 may operate at a first electrical potential Vi, and the second device 122 may operate at a di f ferent , second electrical potential V2 . The term high voltage (HV) may refer to any voltage in excess of 1 kV used in energy distribution networks . For example , it may refer to medium voltage , high voltage , extra high voltage or ultra-high voltage energy distribution networks having a rated operating voltage in excess of 1 kV, 60 kV, 220 kV, or 800 kV for example . It is useful in substations or converter stations operating, for example , at 10 kV, 15 kV, 18 kV, 20 kV or 30 kV or similar voltages in the range of 6 kV to 150 kV or even above this voltage level .

Each one of the devices 112 and 122 comprises a transceiver (not shown) for wirelessly communicating with one another . In particular, the transceivers of the devices 112 and 122 are configured to exchange high frequency electromagnetic waves , e . g . radio frequency (RE) signals , to exchange control signals . To ensure that the high frequency electromagnetic waves emitted by the transceiver of the first device 112 reaches the second device 122 and vice versa, a waveguide 130 connects , directly or indirectly, the first cell 110 and the second cell 120 , and preferably the transceivers of the electrical devices 112 and 122 contained therein . The waveguide 130 ef fectively forms a communication channel between the devices 112 and 122 . For example , the waveguide 130 may extend all the way to the connected devices 112 and 122 , extend to a wall or flange of a high frequency enclosure forming the cells 110 and 120 , or may end outside the cells 110 and 120 and be connected indirectly to the devices 112 and 122 by means of coaxial cables attached to the waveguide 130 as detailed later .

The waveguide 130 comprises a first conductive segment 132a, a second conductive segment 132b and an insulation segment 134 . The first conductive segment 132a is connected to the first device 112 in the first cell 110 and may surround an antenna of a corresponding first transceiver . The second conductive segment 132b is connected to the second device 122 , such as switching units or sensors , in the second cell 120 and may surround an antenna of a corresponding second transceiver . The conductive segments 132a and 132b may be implemented, for example , as a coaxial cable or waveguide , for example a hollow conductors having a rectangular, circular or elliptical cross section, as shown in Figure 1 .

To avoid any short circuit between the di f ferent electrical potentials Vi and V2 of the devices 112 and 122 , the insulation segment 134 of the waveguide 130 blocks any DC and low frequency, e . g . at or below 50 or 60 Hz , AC current between the two cells 110 and 120 . However, high frequency electromagnetic waves can pass the insulation segment 134 . For example , the insulation segment 134 may be configured to pass signals in a frequency range of 100 MHz to 100 GHz .

The above concept can be applied in HV installations having di f ferent communication network topologies . In Figures 2 to 4 , di f ferent communication network topologies for use in HV installations are shown for the case of one first device in the form of a central control hub 212 with integrated transceiver of a control unit and second devices in the form of a HV switching devices 222 or other switching unit with integrated transceiver arranged in corresponding switching cells at potentially di f ferent electrical potentials . Although not shown in the figures , other arrangements are also possible . For example , multiple control hubs 212 may be provided for large converter stations or as backup component to improve reliability . Moreover, several HV switching devices 222 may be arranged in a single cell .

Figure 2 shows a HV installation 200 comprising a segmented bus structure 230 . In the segmented bus structure 230 , each HV switching devices 222 is connected to a corresponding conductive segment 132 . Moreover, the central control hub 212 is connected to a further conductive segment 132 . Together, the segments 132 form the segmented bus structure 230 . That is to say, all devices 212 and 222 can access a common medium for exchanging signals . However, to avoid any unwanted DC currents between individual cells , each of the conductive segments 132 is separated from neighboring conductive segments 132 by a corresponding insulation segment 134 . Figure 3 shows an alternative HV installation 300 having a continuous bus structure 330 . Unlike the segmented bus structure 230 , a single conductive bus segment 332 extends over the entire length of the bus structure 330 . In the described example , the single conductive bus segment 332 is electrically connected to the central control hub 212 . To insulate the HV switching devices 222 of individual cells , each HV switching device 222 is connected by means of a conductive branch segment 334 and a corresponding insulation segment 134 to a corresponding t-connection of the single conductive bus segment 332 . Because only a single insulation segment 134 is included between any of the devices 212 and 222 , a single loss can be reduced in larger installations , resulting in an improved signal quality of the HV installation 300 .

Figure 4 shows a further HV installation 400 comprising a daisy chain structure 430 . Each of the HV switching devices 222 comprises an uplink port and a downlink port for communicating with one dedicated uplink device or downlink device , respectively . These ports are connected to respective conductive uplink segment 432 and conductive downlink segment 434 , respectively . Attention is drawn to the fact that the first HV switching device 222 is only connected to an uplink segment 432 and that the central control hub 212 is only connected to a conductive downlink segment 434 . Between each conductive uplink segment 432 and corresponding conductive downlink segment 434 , corresponding insulation segments 134 are employed for DC separation .

The configuration described with reference to Figure 4 has the advantage that each signal exchanged between a corresponding uplink and downlink port only needs to pass through a single insulating section 134 , this improving signal quality . While , the need to retransmit signals by intermediate transceivers of the daisy chain structure 430 may increase the signal propagation time , the sequential nature of the described daisy chain structure 430 also has the additional advantage that each of the insulation segments 134 only has to withstand the potential di f ferences between two neighboring cells . Thus , particularly in HV applications where cells are arranged in the order of increasing voltage potentials , relatively large potential di f ferences between HV switching devices 222 and the central control hub 122 can be bridged using insulation segments 134 that are only rated to withstand a corresponding fraction of the total voltage drop .

Figure 5 shows a further HV installation 500 having a more complex mesh structure 530 . In the described embodiment , the HV installation 500 comprises two control units 512 arranged in a control hub cell 510 and a total of eight HV switching unit 522 arranged in four di f ferent switching cells 520a to 520d . Various connections between the individual cells 510 and 520 exist . However, not every cell is directly connected to each neighboring cell . For example , while the control hub cell 510 may communicate directly to the upper right switching cell 520a, it cannot communicate directly with the upper left switching cell 520b . Firing and other control signals exchanged between the control hub cell 510 and the switching cell 520b are therefore exchanged indirectly via one of the switching cells 520a or 520c . Each of the cells 510 and 520 may have one or more conductive cell segments 532 . Corresponding segments 532 of neighboring cells are insulated from one another using insulation segments 134 . The mesh structure 530 described with respect to Figure 5 enables multiple pathways for high- frequency communication between the plurality of units 512 and 522 . At the same time , the number of waveguides 130 and corresponding insulation segments 134 is limited in the shown topology .

Although not shown in detail , further connection topologies , such as star structures and ring structures can also be reali zed using waveguides 130 having at least one insulation segment 134 between neighboring cells .

The key benefits of the disclosed HV installations 100 to 500 include the following :

- The disclosed networks of devices are simpler and cheaper to install compared to conventionally used fiber optic networks in HV voltage environments .

- The disclosed networks of devices can operate in challenging electromagnetic environments as the communication signals are well shielded from the surrounding electromagnetic environment .

- Components used for the conductive segments , such as coaxial cables and waveguides , are very robust and well suited for harsh environments , including outdoor environments subj ect to high humidity, rainy or icy conditions .

- A large number of reliable signaling schemes and communication protocols may be used for communicating along waveguides .

- Multiple communication channels may be multiplexed on the same waveguides , e . g . using time division, frequency division, code division, power division or other multiple-access methods . In the following, speci fic waveguides suitable for a HV installations like those described above are described in detail . While the following part of the description focuses on waveguides having an integrated insulation segment , attention is drawn to the fact that the various HV installations described above can also be implemented using separate , i . e . non-integrated, components to implement the conductive segments 132 and the insulation segment 134 as described above .

Figure 6 shows an embodiment of a waveguide 600 suitable for use in a HV installation, for example any of the HV installations according to Figures 1 to 5 .

The waveguide 600 comprises a first hollow conductor 601 and a second hollow conductor 602 . In the described embodiment , the hollow conductors 601 and 602 have a circular crosssection . The hollow conductors 601 and 602 each end in a respective termination area 603 and 604 . The two termination areas 603 and 604 face each other, so as to enable an electromagnetic wave travelling within the first hollow conductor 601 to continue to travel through the second hollow conductor 602 and vice versa . The two termination areas 603 and 604 are held in place by an insulation element 605 , such that their ends are aligned with respect to a central axis of the waveguide . The insulation element 605 at least partially encloses the first termination area 603 and second termination area 604 . The insulation element 605 thus provides an improved dielectric strength in an area of an insulating gap 606 formed between the two termination areas 603 and 604 , which is superior, for example , to that of an air- filled gap . This assists in having a suf ficiently small gap width for electromagnetic waves to travel without signi ficant losses or reflections through the waveguide 600 . The insulation element 605 may also provide protection for the insulating gap 606 . In particular, the insulation element 605 may protect the insulation gap 606 from moisture and other unwanted influences associated with an outdoor environment .

In the described embodiment , the first hollow conductor 601 and the second hollow conductor 602 are made from a metal material . The insulation element 605 is formed, for example , from a non-conductive polymer material .

The waveguide 600 shown in Figure 6 includes a number of features that make it particularly useful for use in HV installations , in an outdoor environment and/or for transmitting high- frequency, high bandwidth signals .

For example , each of the termination areas 603 and 604 comprises corresponding, rounded field shaping elements 607 and 608 . The field shaping elements 607 and 608 reduce a local electrical field strength and shapes the electrical field at the termination areas 603 and 604 . This helps to avoid critical field strength caused by potentially high di f ferences in an electrical potential of the connected cells , working, for example , at a relatively low frequency of 50 or 60 Hz . They may also improve the electromagnetic coupling between the two hollow conductors 601 and 602 . Among other things , the presence of the rounded, outwardly protruding field shaping elements 607 and 608 at the frontal faces of the termination areas 603 and 604 enables maximi zing the radius of their ends for minimi zing electrical field enhancement , while avoiding signal reflections of an electromagnetic wave travelling through the inside of the waveguide 600 .

Moreover, as also shown in Figure 6 , each of the hollow conductors 601 and 602 comprises a step 609 and 610 in its diameter for impedance matching . In particular, the steps 609 and 610 of the hollow elements 601 and 602 are located at a beginning of the termination areas 603 and 604 , and at predefined distance from the open ends of the respective hollow conductors 601 and 602 .

The insulation element 605 of Figure 6 is configured to increase a creepage distance between the two hollow conductors 601 and 602 . For this purpose , the insulation element 605 comprises an insulating cover 611 with multiple baf fles or sheds to increase an outside creepage distance d _O ut • Moreover, the insulation element 605 comprises an insulating core 612 which extends on the inside of the hollow conductors 601 and 602 . In the described embodiment , the insulating core extends all the way through the termination areas 603 and 604 to the steps 609 and 610 , respectively . Thus , the insulating core 612 provides an inside creepage distance di _n which extends all the way from the first step 609 to the second step 610 . However, depending on the voltage and other parameters , the insulating core 612 may also be shorter or longer in an axial direction . The insulating cover 611 and the insulating core 612 are connected to each other by a circular insulating rib 613 to form one integrated insulation element 605 . The insulating rib 613 also electrically separates the first and second field shaping elements 607 and 608 . Depending on the speci fic application, the described waveguide 600 may have the following dimensions : an inner radius of the hollow conductors 601 and 602 may lie between 1 and 50 mm; a thickness of the insulating core 612 may lie between 0 . 1 and 10 mm; a width of the insulating gap 606 between the first and second field shaping elements 607 and

608 may lie between 0 . 1 and 10 mm; a radius of the field shaping elements 607 and 608 may lie between 0 . 5 and 10 mm; a length of the middle waveguide section between the first step

609 and the second step 610 may lie between 10 and 300 mm; a di f ference in a radius between the outer waveguide sections and the middle waveguide section may lie between 0 and 20 mm . With these dimension, a typical blocking voltages for the described waveguide 600 are in the range between 1 and 100 kV . The potential operating frequency range for transmitting control signal through the waveguide 600 may extend from 100 MHz to several hundreds of GHz .

For example , Figure 7 shows a snapshot of a simulated electric field of a travelling wave at 5 . 5 GHz for a certain phase in the waveguide 600 . The termination area of the speci fic waveguide was designed for a signal transmission between 5 and 6 GHz .

In another embodiment , not shown in the Figures , an insulation element forms an outer skeleton for aligning first and second hollow conductors . In this case , the first termination area may be electrically insulated from the second termination area by air or vacuum, an insulating gas , such as sul fur hexafluoride ( SF6 ) , or another non-conductive filling material of the waveguide . According to di f ferent embodiments , the waveguide 600 can have the following variations . Some of these are shown in Figures 8 to 14 . In particular, Figures 9 to 11 show three di f ferent details A to C of a cross section through one of the walls of the waveguide 600 . Moreover, Figures 12 to 14 show di f ferent types of field shaping elements . Other variations , such as those described later with respect to the waveguide 700 of Figure 17 , are also applicable to corresponding parts of the waveguide 600 .

- The cross section of the hollow conductors 601 and 602 may be square , rectangular, circular, elliptical , or any other shape .

- The hollow conductors 601 and 602 may comprise one or several notches 651 in the outer insulation cover 611 as shown in Figure 9 . The provision of notches 651 within the termination areas 603 and 604 may also improve the RF properties of the waveguide 600 by impedance matching .

- The insulation gap 606 might be surrounded by a metal ring 661 as shown in Figure 10 . The ring 661 may act as shielding element to reduce the coupling of external fields into the waveguide 600 and/or as grading electrode to improve the coupling of the hollow conductors 601 and 602 .

- Multiple insulation gaps 606a and 606a may be implemented in the same waveguide 600 to distribute the overall potential di f ference between the first hollow conductor 601 and second hollow conductor 602 as shown in Figure 11 . The provision of multiple gaps 606 may also improve the RF performance of the waveguide 600 .

- As further shown in Figures 12 to 14 , the field shaping elements 607 and 608 may take the form of circular field shaping element 671, elliptical field shaping element 681, or hockey stick shaped field shaping element 691. Other rounded shapes are also possible.

- The overall shape of the waveguide 600 may be straight as shown in the Figures or bent.

- The outside of the waveguide 600 may be partially or fully protected by sheds of insulating material to increase the outside creepage distance between the two hollow conductors 601 and 602.

- The specific creepage distance, which in general depends on a pollution level in a respective environment such as an outdoor environment, can be obtained by adjusting the length, thickness, shape and position of the various parts of the insulation element 605.

Figures 15 and 16 show reflection and transmission characteristics of the termination areas 603 and 604 of three prototype waveguides 600 with different gap widths of 1, 2 and 3 mm, respectively. The waveguides 600 are designed to be operated between 5 and 6 GHz. The prototypes have been manufactured according to the design described above with regard to Figure 6. The insulation material of the insulation element 605 is epoxy.

Figure 15 illustrates the simulated and measured reflections of the prototypes in an RF measurement setup. The measured reflection coefficient is below -25 dB in the frequency range between 5.1 GHz and 5.8 GHz for a gap size of 1 mm, and only slightly higher for the other gap sizes. The agreement with simulations used for the design was observed to be very good. The transmission coefficient as shown in Figure 16 is around -0.25 dB for the entire range of frequencies for the gap size of 1 mm and only slightly lower for the other gap sizes. The measurement results shown in Figures 15 and 16 prove the validity of the design of the prototype as well as the superior RF performance of the waveguide 600 .

The described waveguide 600 has the following advantages and benefits :

- The terminal areas 603 and 604 facilitate the use of waveguide based communication in HV converters .

- The proposed design provides a nearly non distortive propagation path for RF communication signals due to the high transmission and very low reflection properties .

- The design of the waveguide 600 is simple compared with other structures used for DC blocking .

- The described waveguide design can be implemented using only one type of conductive material and one type of insulating material . Alternative , a combination of di f ferent materials , such as two di f ferent plastic materials may be used .

- The design can easily be adapted for other frequency bands by varying the dimensions indicated above .

- The design described above can be easily adapted for other voltage levels by varying the dimensions as indicated above .

- The design described above allows extreme modulari zation, as waveguide segments with insulation segments can be easily combined to build di f ferent types of waveguide networks for di f ferent types of converters .

- The described design can be reliably used in outdoor environments , in polluted indoor environments and any climate zone around the world as it provides excellent resistance to pollution and UV irradiation . Figure 17 shows a further implementation of a waveguide 700 with a built-in insulation section 702 . The waveguide 700 comprises an insulating core 704 partially covered in a first and second surface area with an outer conductive layer 706 . The conductive layer 706 has a gap 708 to provide electric insulation between the left and right parts of the outer conductive layer 706 . Accordingly, electrical devices connected to the right hand side and left hand side of the waveguide 700 may be at di f ferent electric potentials without creating a short-circuit and a corresponding electrical disturbance .

The length of the gap 708 is chosen long enough to ensure electric insulation at a rated voltage level , such as a voltage level at or above 10 kV, and as short as possible for maintaining good electromagnetic transmission and low reflections of the waveguide 700 .

In the described embodiment , the gap 708 is filled with an insulating material to enhance the breakdown field strength . A shed-like structure 710 on an external part of the wave guide 700 may be used at least in the area of the insulation section 702 to enhance the creepage distance for an electrical potential in an outdoor environment as described with regard to the previous embodiment .

The design of the waveguide 700 with built-in insulation section 702 shown in Figure 17 may be varied as detailed above with respect to the wave guide 600 and as detailed below and shown partially in Figures 18 to 21 . In particular, Figures 18 and 19 show two di f ferent multi-gap configurations . Moreover, Figure 20 shows a waveguide with integrated grading electrode, and Figure 21 shows a waveguide with integrated coaxial-to-waveguide transition structure.

- The waveguide cross section may be rectangular or elliptical or any shape suitable for wave propagation.

- The waveguide 700 can be straight or show bent sections.

- The insulating core 704 may be solid, like a rod or bar, or hollow, like a tube, pipe, or profile.

- The insulating core 704 may be made out of dielectric material, e.g. polymeric material, ceramic, glass, or a combination thereof.

- The core material may be a low-loss material at GHz to hundreds of GHz frequencies. In particular, the core may be made of Polytetrafluoroethylene (PTFE) .

- The outer conductive layer 706 may be made from a metal or a conductive polymer.

- The core 704 and the outer conductive layer 706 may be manufactured by co-extrusion .

- The conductive layer 706 may be applied onto the core 704 by extrusion, chemical or physical vapor deposition, electrolytic plating, electroless plating, arc or flame spraying, wrapping with conductive tape. If required, the corresponding core surface may be activated using a primer, corona or plasma discharges before deposition of the conductive layer 706 to ensure improved adhesion.

- The insulating section 702 may be formed by local removing of parts of the conductive layer 706 mechanically, e.g. by machining, knife cutting, or blasting, or thermally, e.g. by laser removal, or chemically, e.g. using an acid.

- The insulating section 702 may be obtained by locally avoiding the application of a conductive layer 706, for example using a mask or an anti-adhesion means before a conductive material is applied onto the core 704 .

- The location of the insulating section 702 can be predefined, e . g . during manufacturing in a factory, or custom-made , e . g . decided on-site .

- Multiple , serial insulating sections 702 with corresponding gaps 708 may be formed to connect multiple , di f ferent potentials Vi, V2 , ..., V _N as shown in Figure 18 .

- One insulating section 702 may be composed of multiple gaps 708 as shown in Figure 19 . Multiple gaps 708 might also be advantageous for RF performance .

- The gap region may be filled with an electrically field grading material 722 as shown in Figure 20 .

- The field grading material may have a high permittivity and/or a nonlinear conductivity .

- The insulating material filling the gap 708 may be a mastic, a gel , a grease , a hot melt polymer, a thermoplastic or a thermoset .

- Field shaping elements may be implemented in the insulating section 702 at the end of each conductive layer 706 to avoid local field enhancements .

- The waveguide 700 may be covered by an outer insulation 724 as also shown in Figure 20 , at least in the region of the insulating sections 702 . For example the outer insulation material 724 may cover an insulating material filling the gap 708 , such as the field grading material 722 .

- The waveguide 700 may be suitable for outdoor environment . To increase a creepage distance the outer insulation may include multiple sheds 712 as shown in Figure 19 . - The outer insulation 724 may be composed of more than one layer as also shown in Figure 20 . A grading electrode 720 may be enclosed in the outer insulation 724 itsel f or in the field grading material 724 as shown . The use of a co-axial grading electrode 720 allows gaps 708 of longer length while maintaining good electromagnetic shielding . This may be beneficial from a manufacturing point , as it improved a dimensional tolerance for the gap 708 .

- The external insulating material 724 may be premanufactured, e . g . a cold or heat shrink sleeve .

- The external insulating material 724 can be manufactured by taping, casting, inj ection or trans fer molding on the waveguide 700 . This manufacturing can take place in a factory or on-site .

- The materials used for filling the gap 708 and the external insulation may be UV curing .

- Coaxial-to-waveguide transition structures 730 may be integrated into one or both of the conductive layers 706 as shown in Figure 21 . Such a coaxial-to-waveguide transition structure 730 may be used, for example , to connect the waveguide 700 to individual devices or di f ferent segments of di f ferent waveguides by means of coaxial cables .

- The waveguide 700 can form a whole continuous waveguide system including complex shapes .

Insulating sections 702 may be located at suitable positions .

- The continuous waveguide system can be produced in one piece by suitable methods like inj ection molding .

In case the insulating core 704 is hollow, it may be filled with di f ferent insulating material such as foam or gel . - The insulating material used to fill a hollow insulating core 704 may be selected to increase permitted frequencies or to prevent the ingress of moisture and dirt .

Depending on the application, the described waveguide can have the following indicative dimensions : a cross-section of 10 mm ² to 1000 mm ² ; a thickness of the conductive layer 706 of 10 nm to 2 mm; a gap width of 0 . 1 mm to 10 mm .

The typical voltages di f ference over the gap 708 may be in the range 1 kV to 100 kV; a potential frequency range may extend from 100 MHz to several hundreds of GHz .

The key benefits of the waveguide 700 according to the described embodiments comprise the following :

- The waveguide 700 with built-in insulation section 702 facilitates the use of waveguide based communication in HV converters .

- The waveguide 700 can be manufactured in a simple manner compared with known devices for blocking DC voltages .

- Because no flanges are needed to connect the di f ferent functional parts of the waveguide 700 , e . g . to connect a fully conductive waveguide segment with an insulation segment , the waveguide 700 is fully sealed and therefore less susceptible to disturbance in an uncontrolled outdoor environment .

In case a solid insulating core 704 is used, no humidity can get into the communication network . Moreover, water condensation inside the waveguide 700 is completely avoided, thereby obliterating the danger of short circuits between di f ferent segments of a communication network .

- The described design is useful for providing mechanical flexibility . For example , the waveguide 700 can be bent in case a hollow polymeric insulation core 704 is used .

- Compared with a hollow metallic waveguide , a cross section of a waveguide 700 with a polymeric core , in particular a filled polymeric core , can be reduced .

- One or more insulating sections 702 may be formed at any axial position along the waveguide 700 as desired, which improves design flexibility .

- The weight of a waveguide 700 with a polymeric core 704 is lower than the weight of a corresponding metal waveguide without supporting core .

Figure 22 shows steps of a method for manufacturing a waveguide such as the waveguide 600 of Figure 6 or the waveguide 700 of Figure 17 .

In an optional step S I , an insulating core is formed . The insulating core may be hollow as the insulating core 612 shown in Fig . 6 or completely filled as the insulating core 704 shown in Fig . 17 and may be formed by extrusion or similar manufacturing techniques .

In a step S2 , a hollow conductive structure is formed, such as the hollow conductors 601 and 602 or the conductive layer 706a conductive layer 706 . The conductive structure may be metallic or formed on a conductive polymer . The conductive structure may be applied on an insulating core 612 or 704 by extrusion, chemical or physical vapor deposition, electrolytic plating, electroless plating, arc of flame spraying, wrapping with conductive tape or other suitable manufacturing methods . Optionally, a core surface may be activated using a primer, corona or plasma discharge before deposition a conductive layer 706 on an insulating core to ensure improved adhesion .

In a further step S3 , one or more insulating gaps 708 are formed . Attention is drawn to the fact that steps S2 and S3 may be combined in case a conductive layer 706 is only formed in certain areas of an insulating core 704 , i . e . by additive manufacturing . Alternatively, an entire surface of an insulating core 704 can be covered with a conductive layer 706 first , before individual gaps 708 are formed in the conductive layer 706 , i . e . by subtractive manufacturing . Thus , step S3 may comprise avoiding the application of conductive material in certain areas of the outer surface of the insulating core 708 , for example by using a mask or anti adhesion means , before a conductive layer 706 is applied onto the core 704 . Alternatively, the insulating gap 708 may be formed by local removal of the conductive layer material , e . g . by mechanical removal such as machining, cutting or blasting, or by thermal removal , such as laser removal , or chemical removal , such as etching .

In an optional step S4 , one or more field shaping elements 607 and 608 may be formed . For example , the field shaping elements 671 , 681 and 691 described with regard to Figures 12 to 14 may be formed at an end of respective parts of a conductive structure . Again, steps S4 and S2 may be integrated with one another .

In a further optional step S5 , one or more grading electrodes , such as the metal ring 661 shown in Figure 10 or the grading electrode 720 of Figure 20 may be formed in an area of the gap 606 or 708 .

Before , during or after forming the grading electrodes , in a further optional step S 6 , the gap 606 or 708 between the respective ends of the conductive structures may be filled with an insulating material .

In a further optional step S7 , an outer insulating cover 611 may be formed in the area of the gap 708 . For example , the shed-like structure 710 may be formed by application of further insulating material on an outside of the waveguide .

The embodiments shown in Figures 1 to 21 as stated represent exemplary embodiments of improved waveguide elements and communication networks formed thereof . They may be formed by the method shown in Figure 22 . They do not constitute a complete list of all embodiments according to the claims . Actual arrangements and methods for the manufacturing may vary from the embodiments shown in terms of arrangements , devices , dimensions and materials , for example . Reference signs

100 HV installation

110 first cell

112 first electrical device

120 second cell

122 second electrical device

130 waveguide

132 conductive segment

134 insulation segment

200 HV installation

212 central control hub

222 HV switching device

230 segmented bus structure

300 HV installation

330 continuous bus structure

332 conductive bus segment

334 conductive branch segment

400 HV installation

430 daisy chain structure

432 conductive uplink segment

434 conductive downlink segment

500 HV installation

510 control hub cell

512 control unit

520 switching cell

522 HV switching unit

530 mesh structure

532 conductive cell segment waveguide , 602 hollow conductor , 604 termination area insulation element insulation gap , 608 field shaping element , 610 step insulating cover insulating core insulating rib notch metal ring circular field shaping element elliptical field shaping element hockey stick shaped field shaping element waveguide (built-in) insulating section insulating core ( outer ) conductive layer gap shed-like structure sheds grading electrode field grading material outer insulation material coaxial-to-waveguide transition structure