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Title:
ARRANGEMENT FOR A POWER SYSTEM
Document Type and Number:
WIPO Patent Application WO/2018/188750
Kind Code:
A1
Abstract:
An arrangement (10) is disclosed, comprising at least one first elongated element (1) and at least one second elongated element (2), each of the at least one first elongated element (1) and the at least one second elongated element (2) being movable, and each of the at least one first elongated element (1) and the at least one second elongated element (2) having at least one electrically conductive section (3, 5) and at least one electrically isolating section (4, 6). The arrangement (10) comprises at least one pair of grounding terminals (11, 12) arranged to be connected to at least one first portion or part (7) of electric equipment to be grounded and at least one pair of power supply terminals (14) arranged to be connected to at least one second portion or part (8) of electric equipment for supply of power thereto. The at least one first elongated element (1) and/or the at least one second elongated element (2) are movable at least into a first position of the at least one first elongated element (1) relatively to the at least one second elongated element (2) in which the at least one first elongated element (1) is in a position in which the at least one pair of grounding terminals (11, 12) are electrically connected by at least one electrically conductive section (3) of the at least one first elongated element (1) and in which the at least one electrically conductive section (3) of the at least one first elongated element (1) is connected to ground (17), and the at least one second elongated element (2) is in a position in which the at least one pair of power supply terminals (14) are electrically connected by at least one electrically conductive section (5) of the at least one second elongated element (2) and in which the at least one electrically conductive section (5) of the at least one second elongated element (2) is electrically connected to a power supply (U).

Inventors:
DORÉ, Erik (Bergsgatan 7A, Ludvika, 771 34, SE)
SJÖBERG, Christer (Tallstigen 10, Ludvika, 771 40, SE)
PAANANEN, Tommi (Kråkbärsgatan 12, Västerås, 722 23, SE)
SUNDSTEDT, Magnus (Medsvängen 12, 6 Borlänge, 784076, SE)
CHEN, Nan (Kopparbergsvägen 22 A, Västerås, 722 13, SE)
Application Number:
EP2017/058937
Publication Date:
October 18, 2018
Filing Date:
April 13, 2017
Export Citation:
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Assignee:
ABB SCHWEIZ AG (Brown Boveri Strasse 6, 5400 Baden, 5400, CH)
International Classes:
H02J3/36; H01H3/26; H02B1/16; H02B5/01; H02B11/28; H02B13/075; H02H7/10; H02M1/32
Domestic Patent References:
WO2014026469A12014-02-20
Foreign References:
US20110155698A12011-06-30
US20150131207A12015-05-14
US3801768A1974-04-02
US6268579B12001-07-31
Other References:
None
Attorney, Agent or Firm:
LUNDQVIST, Alida (ABB AB, Intellectual PropertyForskargränd 7, Västerås, 721 78, SE)
Download PDF:
Claims:
CLAIMS

1. An arrangement (10) comprising:

at least one first elongated element (1) and at least one second elongated element (2), each of the at least one first elongated element and the at least one second elongated element being movable and extending along a respective longitudinal axis, and each of the at least one first elongated element and the at least one second elongated element having at least one electrically conductive section (3, 5) and at least one electrically isolating section (4, 6) along the longitudinal axis;

at least one first electrical conductor (16) configured to be electrically connected to ground (17) and to the at least one first elongated element;

at least one second electrical conductor (18) configured to be electrically connected to a power supply (U) and to the at least one second elongated element;

at least one pair of grounding terminals (11, 12) arranged to be connected to at least one first portion or part (7) of electric equipment to be grounded;

at least one pair of power supply terminals (14) arranged to be connected to at least one second portion or part (8) of electric equipment for supply of power thereto; and an actuator (15) configured to move at least one of the at least one first elongated element and the at least one second elongated element at least into a first position of the at least one first elongated element relatively to the at least one second elongated element in which:

the at least one first elongated element is in a position in which the at least one pair of grounding terminals are electrically connected by at least one electrically conductive section of the at least one first elongated element, and in which the at least one electrically conductive section of the at least one first elongated element is connected to ground via the at least one first electrical conductor; and

the at least one second elongated element is in a position in which the at least one pair of power supply terminals are electrically connected by at least one electrically conductive section of the at least one second elongated element, and in which the at least one electrically conductive section of the at least one second elongated element is electrically connected to the power supply via the at least one second electrical conductor.

2. An arrangement according to claim 1, wherein the arrangement further comprises electrical isolation means (19), wherein the electrical isolation means are arranged such that, at least in the first position of the at least one first elongated element relatively to the at least one second elongated element, the at least one grounding terminal and the at least one power supply terminal are electrically isolated from each other.

3. An arrangement according to claim 1 or 2, wherein the actuator is configured to move at least one of the at least one first elongated element and the at least one second elongated element into the first position of the at least one first elongated element relatively to the at least one second elongated element from a second position of the at least one first elongated element relatively to the at least one second elongated element, in which second position:

the at least one first elongated element is in a position in which the at least one pair of grounding terminals are electrically isolated from the at least one first electrical conductor by means of at least one electrically isolating section of the at least one first elongated element; and

the at least one second elongated element is in a position in which the at least one pair of power supply terminals are electrically isolated from the at least one second electrical conductor by means of at least one electrically isolating section of the at least one second elongated element.

4. An arrangement according to any one of claims 1-3, wherein the actuator is configured to move the at least one first elongated element relatively to the at least one second elongated element, or vice versa, independently of each other, or jointly.

5. An arrangement according to any one of claims 1-4, wherein the actuator is configured to move the at least one first elongated element and the at least one second elongated element substantially simultaneously.

6. An arrangement according to any one of claims 1-5, wherein the actuator is configured to move at least one of the at least one first elongated element and the at least one second elongated element into the first position of the at least one first elongated element relatively to the at least one second elongated element such that the at least one first elongated element is brought into the position in which the at least one pair of grounding terminals are electrically connected by at least one electrically conductive section of the at least one first elongated element, and in which the at least one electrically conductive section of the at least one first elongated element is connected to ground via the at least one first electrical conductor, a selected period of time prior to the at least one second elongated element being brought into the position in which the at least one pair of power supply terminals are electrically connected by at least one electrically conductive section of the at least one second elongated element, and in which the at least one electrically conductive section of the at least one second elongated element is electrically connected to the power supply via the at least one second electrical conductor.

7. An arrangement according to claim 6, wherein the actuator is configured such that the selected period of time is 1 ms or less.

8. An arrangement according to any one of claims 1-7, wherein the at least one first elongated element is arranged to extend through at least one through-hole of each of the at least one pair of grounding terminals and to be movable in a longitudinal direction of the at least one first elongated element.

9. An arrangement according to any one of claims 1-8, wherein the at least one second elongated element is arranged to extend through at least one through-hole of each of the at least one pair of power supply terminals and to be movable in a longitudinal direction of the at least one second elongated element.

10. An arrangement according to any one of claims 1-9, wherein the actuator comprises a pneumatic, hydraulic and/or mechanical driving system configured to effect movement of at least one of the at least one first elongated element and the at least one second elongated element.

11. An arrangement according to any one of claims 1-10, wherein at least one of the at least one first elongated element or the at least one second elongated element is arranged such that the at least one electrically conductive section and the at least one electrically isolating section are arranged alternatingly along a longitudinal direction of the at least one of the at least one first elongated element or the at least one second elongated element, such that each electrically conductive section thereof is followed by an electrically isolating section, or vice versa. 12. An arrangement according to any one of claims 1-11, wherein the at least one first elongated element and the at least one second elongated element are arranged such that their respective longitudinal axes are substantially parallel to each other.

13. An arrangement according to any one of claims 1-12, wherein at least one of the at least one first elongated element or the at least one second elongated element comprises at least one rod element.

14. An arrangement according to any one of claims 1-13, wherein at least one of the at least one first elongated element or the at least one second elongated element comprises:

at least one elongated first member made of an electrically isolating material; and

at least one second member made of an electrically conductive material;

the at least one second member located on at least one circumferential surface portion of the at least one first member and being arranged to surround the at least one circumferential surface portion so as to form the at least one electrically conductive section and the at least one electrically isolating section along the longitudinal axis of the at least one of the at least one first elongated element or the at least one second elongated element.

15. An arrangement according to any one of claims 1-14, wherein at least one grounding terminal comprises at least one contact element (25) configured to be in contact with the at least one first elongated element.

16. An arrangement according to any one of claims 1-15, wherein at least one power supply terminal comprises at least one contact element (26) configured to be in contact with the at least one second elongated element.

17. A system (20) comprising:

an arrangement (10) according to any one of claims 1-16; and

electrical equipment (7, 8);

wherein the at least one pair of grounding terminals (11, 12) of the arrangement is arranged to be connected to at least one first portion or part (7) of electrical equipment for selectively grounding the at least one first portion or part, and the at least one pair of power supply terminals (14) is arranged to be connected to at least one second portion or part (8) of electrical equipment for selectively supplying power to the at least one second portion or part. 18. A system according to claim 17, wherein the at least one first portion or part and the at least one second part or portion are parts or portions of the same electrical equipment.

19. A system according to claim 17 or 18, wherein the electrical equipment comprises at least one converter cell, wherein the at least one first part or portion of the electrical equipment comprises at least one electrical energy storage element of at least one converter cell and the at least one second part or portion of the electrical equipment comprises a part or portion of the at least one converter cell different from the at least one electrical energy storage element.

Description:
ARRANGEMENT FOR A POWER SYSTEM

TECHNICAL FIELD

The present invention generally relates to the field of power systems, particularly power transmission systems, such as, for example, High Voltage Direct Current (HVDC) power transmission systems. Specifically, the present invention relates to an arrangement which for example may be used in conjunction with converter valves in a converter station, which converter valves in normal operation may be energized with power provided from the converter station. The arrangement is capable of grounding one or more parts or portions of the converter valve, e.g., capacitor(s) thereof, while at the same time permitting a supply of power to one or more other parts or portions of the converter valve.

BACKGROUND

HVDC power transmission has become increasingly important due to increasing need for power supply or delivery and interconnected power transmission and distribution systems. In a HVDC power system there is generally included an interface arrangement including or constituting a HVDC converter, or converter station, which is a type of converter or converter station configured to convert high voltage DC to AC, or vice versa, which interface arrangement configured to couple an AC power system with a DC power system, or vice versa. A HVDC converter station may comprise a plurality of elements such as the converter itself (or a plurality of converters connected in series or in parallel), one or more transformers, capacitors, filters, and/or other auxiliary elements. Converters may comprise a plurality of solid-state based devices such as semiconductor devices. HVDC technology may be classified as Current Source Converter (CSC) based HVDC and Voltage Source Converter (VSC) based HVDC. While CSC based HVDC converters employ thyristors as switches or switching elements (and/or other switches or switching elements that are not self-commutated), VSC based HVDC converters employ for example insulated gate bipolar transistors (IGBTs) as switches or switching elements (and/or other switches or switching elements that are self-commutated). A plurality of solid-state semiconductor devices such as thyristors or IGBTs may be connected together, for instance in series, to form a building block, or cell, of an HVDC converter. The converter cell may in alternative be referred to as a (HVDC) converter valve. Converter valves, such as HVDC converter valves, may be arranged indoors, in so called converter valve halls.

High voltage equipment, such as converter valves arranged in converter valve halls, may require regular maintenance and/or trouble-shooting. With reference to the particular example of converter valves, when a converter valve that is arranged in a converter valve hall is energized and in operation, personnel may not be permitted to be inside the converter valve hall due to risk of injury that may be caused for example by any electric discharges from the converter valves, such as surge current strokes or corona discharges originating from residual capacitor charges or static charge in insulating material. When the converter valve is energized and in operation, the converter valve is normally energized by means of phase power provided from the converter station. When the converter valve is energized and in operation, and when or whenever maintenance or trouble-shooting is to performed on the converter valve, the converter valve may need to be de-energized and to be electrically connected to ground prior to allowing for maintenance and/or trouble- shooting personnel to enter the converter valve hall in order to carry out maintenance or troubleshooting on the converter valve. The de-energization of the converter valve and the electrical connection thereof to ground prior to allowing for maintenance and/or trouble-shooting personnel to enter the converter valve hall in order to carry out maintenance or trouble- shooting on the converter valve is usually carried out for safety reasons. By electrically connecting the converter valve to ground, i.e. by grounding the converter valve, it may be ensured that any residual charges in the converter valve or in another part or portion of the converter station are not discharged while, e.g., maintenance and/or trouble- shooting personnel is within the converter valve hall. For example, by grounding the converter valve, capacitors of the converter valve (e.g., one or more capacitor banks of the converter valve) may be grounded and short-circuited, thereby preventing any discharge thereof during, e.g., maintenance and/or trouble-shooting.

In addition to capacitors a converter valve normally includes other types of electrical equipment. When the converter valve is energized and in operation, both the capacitors and other electric equipment of the converter valve are usually energized by means of phase power. However, in order to carry out any trouble-shooting on such other electric equipment that may be included in the converter valve, it may be required that the other electric equipment is energized. In order to energize the other electric equipment while the converter station is taken out of operation, an auxiliary power supply may be connected to the converter valve for supplying power to the other electric equipment. Existing auxiliary power supply solutions generally involve connecting each converter valve manually. However, such solutions may be hazardous and/or time consuming, in particular in case the converter station employs a modular multilevel converter (MMC) comprising a large number of converter cells, or converter valves, and may negatively impact RAM (Reliability, Availability and

Maintenance) of the converter station and even the overall power transmission system. SUMMARY

In view of the above, a concern of the present invention is to provide an arrangement which may facilitate carrying out maintenance or trouble-shooting on electrical equipment operating at a relatively high voltage in a relatively quick and safe manner.

To address at least one of this concerns and other concerns, an arrangement in accordance with the independent claim is provided. Preferred embodiments are defined by the dependent claims.

According to a first aspect, an arrangement is provided comprising at least one first elongated element and at least one second elongated element. Each of the at least one first elongated element and the at least one second elongated element is movable and is extending along a respective longitudinal axis. Each of the at least one first elongated element and the at least one second elongated element has at least one electrically conductive section and at least one electrically isolating section along the longitudinal axis thereof.

The arrangement comprises at least one first electrical conductor configured to be electrically connected to ground and to the at least one first elongated element, and at least one second electrical conductor configured to be electrically connected to a power supply and to the at least one second elongated element.

The arrangement comprises at least one pair of grounding terminals. The at least one pair of grounding terminals is arranged to be (possibly fixedly) connected to at least one first portion or part of electric equipment to be grounded.

The arrangement comprises at least one pair of power supply terminals. The at least one pair of power supply terminals is arranged to be (possibly fixedly) connected to at least one second portion or part of electric equipment for supply of power to the at least one second portion or part.

The arrangement comprises an actuator. The actuator is configured to move at least one of the at least one first elongated element and the at least one second elongated element at least into a first position of the at least one first elongated element relatively to the at least one second elongated element (i.e. a relative position of the at least one first elongated element and the at least one second elongated element), in which first position:

the at least one first elongated element is in a position in which the at least one pair of grounding terminals are electrically connected by at least one electrically conductive section of the at least one first elongated element, and in which the at least one electrically conductive section of the at least one first elongated element is connected to ground via the at least one first electrical conductor; and

the at least one second elongated element is in a position in which the at least one pair of power supply terminals are electrically connected by at least one electrically conductive section of the at least one second elongated element, and in which the at least one electrically conductive section of the at least one second elongated element is electrically connected to the power supply via the at least one second electrical conductor.

The position of the at least one first elongated element in which the at least one pair of grounding terminal is electrically connected by at least one electrically conductive section of the at least one first elongated element (the grounding terminals of a pair of grounding terminal may or may not be mechanically connected to a same electrically conductive section of the at least one first elongated element), and in which the at least one electrically conductive section of the at least one first elongated element is connected to ground via the at least one first electrical conductor, may be referred to as a grounding position of the at least one first elongated element. In the grounding position, the at least one first portion or part of electric equipment is grounded by its connection to ground via at least one electrically conductive section of the at least one first elongated element and the at least one pair of grounding terminals.

The position of the at least one second elongated element in which the at least one pair of power supply terminal is electrically connected by at least one electrically conductive section of the at least one second elongated element, and in which the at least one electrically conductive section of the at least one second elongated element is electrically connected to the power supply via the at least one second electrical conductor, may be referred to as a power supplying position, or as an auxiliary power supplying position, of the at least one second elongated element. In the power supplying position, there is a current path created between the at least one second electrical conductor, configured to be electrically connected to a power supply, and the at least one pair of power supply terminals, which is connected to the at least one second portion or part of electric equipment, which current path permits power to be supplied to the at least one second portion or part of electric equipment.

As described in the foregoing, the actuator is configured to move the at least one first elongated element and/or the at least one second elongated element into a relative position of the at least one first elongated element and the at least one second elongated element so that the at least one first elongated element is in the grounding position and the at least one second elongated element is in the power supplying position at the same time.

Thus, by means of the arrangement according to the first aspect, the at least one first portion or part of electric equipment may be grounded at the same time as the at least one second portion or part of electric equipment is supplied with power from a power supply. There may be several first portions or parts of electric equipment and several second portions or parts of electric equipment. By means of the arrangement according to the first aspect, all (or at least some) of the first portions or parts of electric equipment may be grounded at the same time as all (or at least some) of the second portions or parts of electric equipment may be supplied with power from a power supply. By means of the actuator being configured to move the at least one first elongated element and/or the at least one second elongated element into the first position, the at least one first elongated element and the at least one second elongated element can be brought into the grounding position and the power supplying position, respectively, without requiring any manual operations. In particular, the need for manually connecting the second portions or parts of electric equipment to the power supply may be reduced or even eliminated.

The at least one first portion or part and the at least one second part or portion may be different parts or portions, possibly of the same electrical equipment. For example, the electrical equipment may comprise a modular multilevel converter (MMC) comprising a plurality of converter cells, or converter valves, where the first portions or parts of electric equipment comprise one or more capacitors, or capacitor banks (and/or another type of electrical energy storage element) of the respective ones of the converter cells, and the second portions or parts of electric equipment comprise other parts of the respective ones of the converter cells. When the converter valves are energized and in operation, both the capacitors and the other parts of the respective converter valves are usually energized by means of phase power. When or whenever maintenance and/or trouble-shooting is needed to be carried out on the converter valves, the capacitors of the converter valves should be grounded so as to prevent any discharge thereof during the maintenance and/or trouble- shooting. However, in order to carry out any trouble-shooting on the other parts of the respective converter valves, it may be required that the other parts of the respective converter valves are energized. As indicated in the foregoing, the arrangement according to the first aspect can be used to connect the capacitors of the respective converter valves to ground while at the same time permit the above-mentioned other parts of the respective converter valves to be supplied with power from a power supply (e.g., an auxiliary power supply).

The at least two grounding terminals may comprise at least one pair of positive and negative grounding terminals arranged to be (possibly fixedly) connected to at least one first portion or part of electric equipment to be grounded.

The at least two power supply terminals may comprise at least one pair of positive and negative power supply terminals arranged to be (possibly fixedly) connected to at least one second portion or part of electric equipment for supply of power thereto.

The actuator may be configured to move at least one of the at least one first elongated element and the at least one second elongated element into the first position of the at least one first elongated element relatively to the at least one second elongated element wherein:

the at least one first elongated element is in a position in which the positive and negative grounding terminals are electrically connected to each other by means of at least one electrically conductive section of the at least one first elongated element, and in which the at least one electrically conductive section of the at least one first elongated element is connected to ground via the at least one first electrical conductor; and

the at least one second elongated element is in a position in which the positive and negative power supply terminals are electrically connected to each other by means of at least one electrically conductive section of the at least one second elongated element, and in which the at least one electrically conductive section of the at least one second elongated element is electrically connected to the power supply via the at least one second electrical conductor.

The arrangement may comprise electrical isolation means. The electrical isolation means may be arranged or configured such that, at least in the first position of the at least one first elongated element relatively to the at least one second elongated element, the at least one pair of grounding terminals and the at least one pair of power supply terminals are electrically isolated from each other. Thereby, it can be facilitated or even enabled that in the first position, the at least one first elongated element is electrically isolated from the at least one second elongated element, and that the at least one first portion or part of electric equipment is grounded while at the same time the at least one second portion or part of electric equipment can be supplied with power from a power supply. As mentioned in the foregoing, the arrangement may comprise at least one pair of positive and negative grounding terminals, and at least one pair of positive and negative power supply terminals. The electrical isolation means may be configured such that in the first position of the at least one first elongated element relatively to the at least one second elongated element, the at least one pair of positive and negative grounding terminals and the at least one pair of positive and negative power supply terminals are electrically isolated from each other.

The actuator may be configured to move at least one of the at least one first elongated element and the at least one second elongated element into the first position of the at least one first elongated element relatively to the at least one second elongated element from a second position of the at least one first elongated element relatively to the at least one second elongated element (i.e. a relative position of the at least one first elongated element and the at least one second elongated element), in which second position:

the at least one first elongated element is in a position in which the at least one pair of grounding terminals are electrically isolated from the at least one first electrical conductor by means of at least one electrically isolating section of the at least one first elongated element; and

the at least one second elongated element is in a position in which the at least one pair of power supply terminals are electrically isolated from the at least one second electrical conductor by means of at least one electrically isolating section of the at least one second elongated element. The position of the at least one first elongated element in which the at least one pair of grounding terminals are electrically isolated from the at least one first electrical conductor by means of at least one electrically isolating section of the at least one first elongated element may be referred to as a non-grounding position of the at least one first elongated element. In the non-grounding position, the at least one first portion or part of electric equipment is not grounded by a connection thereof to ground via at least one electrically conductive section of the at least one first elongated element and the at least one pair of grounding terminals.

The position of the at least one second elongated element in which the at least one pair of power supply terminals are electrically isolated from the at least one second electrical conductor by means of at least one electrically isolating section of the at least one second elongated element may be referred to as a non-power supplying position (with reference to power supplied from an auxiliary power supply) of the at least one second elongated element.

As mentioned in the foregoing, the electrical equipment may for example comprise an MMC comprising a plurality of converter cells, or converter valves, where the first portions or parts of electric equipment comprise one or more capacitors, or capacitor banks of the respective ones of the converter cells, and the second portions or parts of electric equipment comprise other parts of the respective ones of the converter cells.

When the relative position of the at least one first elongated element and the at least one second elongated element is in accordance with the second position, the capacitors of the respective converter valves are not grounded, and the other parts of the respective ones of the converter cells are not supplied with power from the power supply. Thus, the at least one first elongated element and the at least one second elongated element may be in the second position during 'normal' operation of the converter valves, when the converter valves are energized by means of phase power, which for example may be provided from the converter station in which the converter valve are comprised. The actuator may for example be configured to move the at least one first elongated element and/or the at least one second elongated element into the first position of the at least one first elongated element relatively to the at least one second elongated element from the second position of the at least one first elongated element relatively to the at least one second elongated element if maintenance and/or trouble- shooting on the converter valves is desired or required.

As mentioned in the foregoing, the arrangement may comprise at least one pair of positive and negative grounding terminals. In the second position of the at least one first elongated element relatively to the at least one second elongated element, the at least one first elongated element may be in a position in which the at least one pair of positive and negative grounding terminals are electrically isolated from each other by means of at least one electrically isolating section of the at least one first elongated element. The actuator may be configured to move the at least one first elongated element relatively to the at least one second elongated element, or vice versa, independently of each other, or jointly (i.e., together).

The actuator may be configured to move the at least one first elongated element and the at least one second elongated element substantially simultaneously.

The actuator may be configured to move the at least one first elongated element and the at least one second elongated element into the first position such that the at least one first elongated element is brought into the grounding position before the at least one second elongated element is brought into the power supplying position.

For example, the actuator may be configured to move at least one of the at least one first elongated element and the at least one second elongated element into the first position of the at least one first elongated element relatively to the at least one second elongated element such that the at least one first elongated element is brought into the position in which the at least one pair of grounding terminals are electrically connected by at least one electrically conductive section of the at least one first elongated element, and in which the at least one electrically conductive section of the at least one first elongated element is connected to ground via the at least one first electrical conductor, a selected period of time prior to the at least one second elongated element being brought into the position in which the at least one pair of power supply terminals are electrically connected by at least one electrically conductive section of the at least one second elongated element, and in which the at least one electrically conductive section of the at least one second elongated element is electrically connected to the power supply via the at least one second electrical conductor.

Thus, the actuator may be configured to move the at least one first elongated element and the at least one second elongated element into the first position such that the at least one first elongated element is brought into the grounding position a selected period of time before the at least one second elongated element is brought into the power supplying position. The selected period of time may for example be 1 ms, or about 1 ms, or less than 1 ms.

The actuator may for example comprise a pneumatic, hydraulic and/or mechanical driving system configured to (possibly controllably) effect movement of at least one of the at least one first elongated element and the at least one second elongated element.

Each of the at least one pair of grounding terminals may comprise at least one through-hole sized so as to permit the at least one first elongated element to extend through the at least one through-hole. The at least one first elongated element may for example be arranged to extend through the at least one through-hole of each of the at least one pair of grounding terminals and to be movable in a longitudinal direction of the at least one first elongated element. Similarly, each of the at least one pair of power supply terminals may comprise at least one through-hole sized so as to permit the at least one second elongated element to extend through the at least one through-hole. The at least one second elongated element may for example be arranged to extend through the at least one through-hole of each of the at least one pair of power supply terminals and to be movable in a longitudinal direction of the at least one second elongated element.

As mentioned in the foregoing, the arrangement may comprise at least one pair of positive and negative grounding terminals, and at least one pair of positive and negative power supply terminals. The at least one second elongated element may be arranged to extend through through-holes of the at least one pair of positive and negative power supply terminals and to be movable in a longitudinal direction of the at least one second elongated element. The at least one first elongated element may be arranged to extend through through-holes of the at least one pair of positive and negative grounding terminals and to be movable in a longitudinal direction of the at least one first elongated element.

At least one of the at least one first elongated element or the at least one second elongated element may for example comprise at least one rod element, or rod.

The at least one first elongated element and the at least one second elongated element may be arranged such that their respective longitudinal axes are parallel to each other, or at least substantially parallel to each other (e.g., allowing for an angle between the respective longitudinal axes of a few degrees).

The at least one first elongated element may be arranged such that the at least one electrically conductive section and the at least one electrically isolating section are arranged alternatingly along a longitudinal direction of the at least one of the at least one first elongated element such that each electrically conductive section thereof is followed by an electrically isolating section, or vice versa.

Similarly, and in alternative or in addition, the at least one second elongated element may be arranged such that the at least one electrically conductive section and the at least one electrically isolating section are arranged alternatingly along a longitudinal direction of the at least one of the at least one second elongated element such that each electrically conductive section thereof is followed by an electrically isolating section, or vice versa.

The arrangement of the at least one first elongated element or the at least one second elongated element with the electrically conductive section(s) and the electrically isolating section(s) may be realized in different ways.

For example, the at least one first elongated element and/or the at least one second elongated element may comprise at least one elongated first member which is made of an electrically isolating material, and at least one second member made of an electrically conductive material, wherein the at least one second member is located on at least one circumferential surface portion of the at least one first member and is arranged to surround the at least one circumferential surface portion so as to form the at least one electrically conductive section and the at least one electrically isolating section along the longitudinal axis of the at least one first elongated element and/or the at least one second elongated element. The at least one second member may for example be glued or force-fitted onto the at least one circumferential surface portion of the at least one first member.

The electrically isolating material of the at least one elongated first member may for example comprise glass fiber, a plastic or another type of electrically isolating material. The at least one elongated first member may for example comprise a rod element, or a rod. The rod element, or rod, may for example, be made of glass fiber, plastic or another type of electrically isolating material. The electrically conductive material of the at least one second member may for example comprise a metal or metallic material, such as, for example, Al, Cu, or an alloy including Al, Cu and/or another type of metal or metallic material.

At least one grounding terminal may for example comprise at least one contact element, which may be configured to be in contact with the at least one first elongated element. Similarly, and in alternative or in addition, at least one power supply terminal may comprise at least one contact element, which may be configured to be in contact with the at least one second elongated element.

Each or any one of the contact element(s) of the at least one pair of grounding terminals and/or the at least one pair of power supply terminals may for example comprise a spring contact element, but is not limited thereto, and could in alternative or in addition for example comprise a contact brush and/or a collector shoe.

Each or any one of the contact element(s) of the at least one pair of grounding terminals and/or the at least one pair of power supply terminals may be arranged so as to allow for movement of the at least one first elongated element and the at least one second elongated element, respectively, in a longitudinal direction thereof through the through-holes of the at least one pair of grounding terminals and/or the at least one pair of power supply terminals, respectively, while at the same time being sufficiently strong to be able to provide electrical contact with one or more of the conductive sections of the at least one first elongated element and the at least one second elongated element, respectively.

The contact element(s) may be for example be shaped similar to a clamp, claw or hook which may extend at least in part around (e.g., at least in part encircle) the at least one first elongated element and/or the at least one second elongated element.

As mentioned in the foregoing, the arrangement may comprise at least one pair of positive and negative grounding terminals, and at least one pair of positive and negative power supply terminals. Each of the positive and negative grounding terminals may comprise at least one contact element configured to be in contact with the at least one first elongated element. In alternative or in addition, each of the positive and negative power supply terminals may comprise at least one contact element configured to be in contact with the at least one second elongated element.

Each or any one of the grounding terminals may comprise at least two contact elements, whereby one contact element may be arranged close to one end of the grounding terminal and another contact element may be arranged close to the other end of the grounding terminal. In this manner the grounding terminal may provide for a bridging of, e.g., an electrically isolating section of the at least one first elongated element for example when the at least one first elongated element and the at least one second elongated element are in the first position.

Similarly, each or any one of the power supply terminals may comprise at least two contact elements, whereby one contact element may be arranged close to one end of the power supply terminal and another contact element may be arranged close to the other end of the power supply terminal. In this manner the power supply terminal may provide for a bridging of, e.g., an electrically isolating section of the at least one second elongated element for example when the at least one first elongated element and the at least one second elongated element are in the first position.

According to a second aspect there is provided a system comprising an arrangement according to the first aspect and electrical equipment. The at least one pair of grounding terminals of the arrangement may be arranged to be (possibly fixedly) connected to at least one first portion or part of electrical equipment for selectively grounding the at least one first portion or part. The at least one pair of power supply terminals may be arranged to be (possibly fixedly) connected to at least one second portion or part of electrical equipment for selectively supplying power to the at least one second portion or part.

As mentioned in the foregoing, the arrangement may comprise at least one pair of positive and negative grounding terminals, and at least one pair of positive and negative power supply terminals. The at least one pair of positive and negative grounding terminals of the arrangement may be arranged to be (possibly fixedly) connected to a first portion or part of the electrical equipment for grounding the first portion or part. The at least one pair of positive and negative power supply terminals may be arranged to be (possibly fixedly) connected to a second portion or part of the electrical equipment for supply of power to the second portion or part.

As already described in the foregoing, the at least one first portion or part and the at least one second part or portion may be parts or portions of the same electrical equipment. The electrical equipment may for example comprise at least one converter cell. The at least one first part or portion of the electrical equipment may comprise at least one electrical energy storage element of at least one converter cell, and the at least one second part or portion of the electrical equipment may comprise a part or portion of the at least one converter cell different from the at least one electrical energy storage element. The at least one electrical energy storage element may for example comprise one or more capacitors, or capacitor banks, and/or another type of electrical energy storage element.

Further objects and advantages of the present invention are described in the following by means of exemplifying embodiments. It is noted that the present invention relates to all possible combinations of features recited in the claims. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the description herein. Those skilled in the art realize that different features of the present invention can be combined to create embodiments other than those described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplifying embodiments of the present invention will be described below with reference to the accompanying drawings.

Figure 1 is a schematic side view of a system according to an embodiment of the present invention.

Figure 2 is a schematic sectional side view of an arrangement according to an embodiment of the present invention.

Figure 3 is a close-up view of a portion of Figure 2.

Figure 4 is similar to Figure 3 but illustrates the first elongated element and the second elongated element in a position relatively to each other that differs from the position of the first elongated element and the second elongated element relatively to each other illustrated in Figure 3.

Figures 5 to 8 are schematic side views of portions of arrangements in accordance with an embodiment of the present invention.

All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate embodiments of the present invention, wherein other parts may be omitted or merely suggested.

DETAILED DESCRIPTION

The present invention will now be described hereinafter with reference to the accompanying drawings, in which exemplifying embodiments of the present invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments of the present invention set forth herein;

rather, these embodiments are provided by way of example so that this disclosure will convey the scope of the present invention to those skilled in the art.

Figure 1 is a schematic side view of a system 20 according to an embodiment of the present invention. The system 20 comprises an arrangement 10. The arrangement 10 comprises a first elongated element 1 and a second elongated element 2, which in accordance with the illustrated embodiment of the present invention comprise rod elements 1 and 2, respectively, or rods. The first elongated element 1 and the second elongated element 2 will in the following be referred to as the first rod 1 and the second rod 2, without any loss of generality. It is to be understood that each of the first elongated element 1 and the second elongated element 2 may - in accordance with one or more other embodiments of the present invention - comprise in principle any suitable type of elongated element, such as, a pole, a bar, or a staff, for example.

Each of the first rod 1 and the second rod 2 is movable and is extending along a respective longitudinal axis. The first rod 1 has several electrically conductive sections 3 and several electrically isolating sections 4 along the longitudinal axis of the first rod 1. Only some of the electrically conductive sections 3 and the electrically isolating sections 4 are indicated by reference numerals in Figure 1. Similar to the first rod 1, the second rod 2 has several electrically conductive sections 5 and several electrically isolating sections 6 along the longitudinal axis of the second rod 2. Only some of the electrically conductive sections 5 and the electrically isolating sections 6 are indicated by reference numerals in Figure 1.

In accordance with the illustrated embodiment of the present invention, the first rod 1 and the second rod 2 are arranged such that their respective longitudinal axes are substantially parallel to each other. As illustrated in Figure 1, the first rod 1 and the second rod 2 may be straight, or substantially straight, and may be parallel to each other.

The first rod 1 and the second rod 2 may for example be arranged to be used in conjunction with a plurality of converter cells, or converter valves, which for example may be comprised in a modular multilevel converter (MMC). The first rod 1 and the second rod 2 can be used for grounding a plurality of first portions or parts 7 of the converter cells, which for example may comprise one or more capacitors 7 (or capacitor banks and/or another type of electrical energy storage element) of the respective ones of the converter cells, while at the same time permitting a supply of power to a plurality of second portions or parts 8 of the converter cells. The second portions or parts 8 of the converter cells may be different from the first portions or parts 7 of the converter cells. The second portions or parts 8 of the converter cells may for example comprise cell electronics, which for example may be configured to control operation of the respective converter cells. It is to be understood that the numbers of the first portions or parts 7 and the second portions or parts 8 illustrated in Figure 1 are exemplifying, and that the arrangement 10 could in principle include any number of first portions or parts 7 and second portions or parts 8.

The first rod 1 is arranged in conjunction with a plurality of pairs of positive and negative grounding terminals 11, 12. Only some of the pairs of positive and negative grounding terminals 11, 12 are indicated by reference numerals in Figure 1. The first rod 1 is arranged to extend through through-holes of the positive and negative grounding terminals 11, 12 and to be movable in a longitudinal direction of the first rod 1 (e.g., from the left to the right, and vice versa, in Figure 1). The second rod 2 is arranged in conjunction with a plurality of pairs of power supply terminals 14. Only some of the power supply terminals 14 are indicated by reference numerals in Figure 1. The second rod 2 is arranged to extend through through-holes of the power supply terminals 14 and to be movable in a longitudinal direction of the second rod 2 (e.g., from the left to the right, and vice versa, in Figure 1).

The arrangement 10 comprises an actuator 15 which is configured to move the first rod 1 and/or the second rod 2. The actuator 15 may for example comprise a pneumatic, hydraulic and/or mechanical driving system configured to (possibly controllably) effect movement of the first rod 1 and/or the second rod 2. Possibly, the operation of the actuator 15 may be controlled by means of a control unit or control device (not shown) connected to the actuator 15. The control unit or control device may be operated by an operator from a location that is remote in relation to the arrangement 10 and possibly the system 20, for example from the outside of a building or structure in which the converter cells are arranged.

The actuator 15 may for example comprise a piston 23 and a rod propulsion system. The first rod 1 and the second rod 2 may be configured to be propelled, or pushed and pulled, by a piston 23 connected to a rod propulsion system. The rod propulsion system may for example comprise an arrangement of pipes or tubes (not shown) for distributing air pressure or hydraulic pressure depending on if the rod propulsion system is pneumatic or hydraulic.

The actuator 15 may be configured to move the first rod 1 relatively to the second rod 2, or vice versa, independently of each other, or jointly (i.e. together). The actuator 15 may be configured to move the first rod 1 and the second rod 2 simultaneously, or substantially simultaneously.

The pairs of positive and negative grounding terminals 11, 12 are arranged to be connected to the first portions or parts 7 of the electric equipment to be selectively grounded (e.g., the capacitors(s) of the respective converter cells).

The power supply terminals 14 are arranged to be connected to the second portion or parts 8 of the electric equipment for selectively supplying power thereto.

The second rod 2 is additionally arranged in conjunction with a plurality of housings 13. Only some of the housings 13 are indicated by reference numerals in Figure 1. The second rod 2 is arranged to extend through through-holes of the housings 13 and, as mentioned in the foregoing, to be movable in a longitudinal direction of the second rod 2 (e.g., from the left to the right, and vice versa, in Figure 1). The housings 13, which may be made of an electrically conductive material, may be configured to keep at least one of the electrically conducting sections 5 of the second rod 2 at a selected voltage.

As illustrated in Figure 1, the positive and negative grounding terminals 11, 12 and possibly also the piston 23 of the actuator 15 may be arranged, or mounted, on a board, a substrate, or plate or the like 24. Furthermore, as illustrated in Figure 1, the power supply terminals 14 may for example be arranged on (e.g., supported by) the grounding terminals 12 via electrically isolating means 19. Only some of the electrically isolating means 19 are indicated by reference numerals. The electrically isolating means 19 may be made of any appropriate electrically isolating material. The electrically isolating means 19 may hence be arranged so as to be interposed between the power supply terminals 14 and the grounding terminals 12, and may provide for electrical isolation between the power supply terminals 14 and the grounding terminals 12 as well as support for the power supply terminals 14. It is to be understood that the board, substrate, or plate or the like 24 is not necessary and may be omitted. For example, the grounding terminals 12 and possibly also the piston 23 of the actuator 15 may be arranged, or mounted, directly on the electrical equipment (e.g., a plurality of converter cells) which the arrangement 10 may be used in conjunction with. Irrespective of whether the board, substrate, or plate or the like 24 is present or not, the arrangement 10 may include the electrically isolating means 19 arranged so as to be interposed between the power supply terminals 14 and the grounding terminals 12.

The arrangement 10 comprises a first electrical conductor configured to be electrically connected to ground and to the first rod 1. The first electrical conductor and ground are schematically indicated in Figure 1 by reference numerals 16 and 17, respectively. The first electrical conductor 16 may for example comprise a bus bar.

The arrangement 10 comprises a second electrical conductor configured to be electrically connected to a power supply and to the second rod 2. The second electrical conductor and the power supply are schematically indicated in Figure 1 by reference numeral 18 and reference sign U, respectively.

Although not shown in Figure 1, the arrangement 10 may comprise a plurality of first electrical conductors between the first rod 1 and ground 17, which for example be arranged at each of the grounding terminals 11. And the arrangement 10 may comprise a plurality of second electrical conductors between the second rod 2 and the power supply U (or to a respective one of a plurality of different power supplies), which for example be arranged at each of the power supply terminals 14. Possibly, the power supply or power supplies U may be electrically connected to the second rod 2 via one or more intermediate components. For example, the power supply or power supplies U may be electrically connected to the second rod 2 via a power converter, e.g., a DC/DC converter such as a buck converter.

The actuator 15 is configured to move the first rod 1 and/or the second rod 2 at least into a first position of the first rod 1 relatively to the second rod 2 in which the first rod 1 is in a position in which the first rod 1 is in a position in which the respective pairs of positive and negative grounding terminals 11, 12 are electrically connected to each other by means of at least one electrically conductive section 3 of the first rod 1, and in which the at least one electrically conductive section 3 of the first rod 1 is connected to ground 17 via the first electrical conductor 18, and the second rod 2 is in a position in which respective pairs of power supply terminals 14 are electrically connected by at least one electrically conductive section 5 of the at second rod 2, and in which the at least one electrically conductive section 5 of the second rod 2 is electrically connected to the power supply U via the second electrical conductor 18.

The position of the first rod 1 in which the respective pairs of positive and negative grounding terminals 11, 12 are electrically connected to each other by means of at least one electrically conductive section 3 of the first rod 1, and in which the at least one electrically conductive section 3 of the first rod 1 is connected to ground 17 via the first electrical conductor 18, may be referred to as a grounding position of the first rod 1. In the grounding position, first portions or parts 7 of the electric equipment (e.g., the capacitors(s) of the respective converter cells) are grounded by their connections to ground 17 via at least one electrically conductive section 3 of the at least one first rod 1 and the electrical

interconnection of the pairs of positive and negative grounding terminals 11, 12 by means of at least one electrically conductive section 3 of the first rod 1.

The position of the second rod 2 in which the respective pairs of power supply terminals 14 are electrically connected by at least one electrically conductive section 5 of the second rod 2, and in which the at least one electrically conductive section 5 of the second rod 2 is electrically connected to the power supply or power supplies U via the second electrical conductor 18, may be referred to as a power supplying position, or as an auxiliary power supplying position, of the second rod 2. In the power supplying position, there is a current path created between the second electrical conductor 18, configured to be electrically connected to a power supply or power supplies U, and the power supply terminals 14, which are connected to respective ones of the second portions or parts 8, which current path permits power to be supplied thereto.

The actuator 15 may be configured to move the first rod 1 and/or the second rod 2 into the above-mentioned first position of the first rod 1 relatively to the second rod 2 from a second relative position of the first rod 1 and the second rod 2, in which second position the first rod 1 is in a position in which the pairs of positive and negative grounding terminals 11, 12 are electrically isolated from each other by means of at least one electrically isolating section 4 of the first rod 1, and the second rod 2 is in a position in which the respective pairs of power supply terminals 14 are electrically isolated from the second electrical conductor 18 by means of at least one electrically isolating section 6 of the second rod 2. In the second relative position of the first rod 1 and the second rod 2, the first portions or parts 7 are hence not grounded, and the second portions or parts 8 are not supplied with power from the power supply or power supplies U. With respect to the example where the first portions or parts 7 and the second portions or parts 8 are portions or parts of respective ones of a plurality of converter cells, or converter valves (which for example may be comprised in an MMC), the second relative position of the first rod 1 and the second rod 2 may be used when the converter cells are in operation and are energized with phase power which for example may be provided from a converter station in which the converter cells are arranged.

According to one or more embodiments of the present invention, for example by choosing the lengths of the electrically isolating sections and the electrically conducting sections of the first rod and the second rod, respectively, the locations of the electrically isolating sections and the electrically conducting sections along the longitudinal axis of the first rod and the second rod, respectively, and their arrangement in relation to the grounding terminals and the power supply terminals, respectively, and possibly the lengths of the grounding terminals and the power supply terminals along the longitudinal axis of the first rod and the second rod, respectively, it may be possible to achieve a current path along the entire - or at least most of - the length of the first rod and the second rod, respectively, when the first rod and the second rod are arranged relatively to each other so that they are in the above- mentioned first (relative) position.

As illustrated in Figure 1, the arrangement 10 may comprise end terminals 21.

The end terminals 21 may be used to electrically connect an additional arrangement (not shown) to the arrangement 10, e.g., in series. Any number of arrangements, similar or identical to the arrangement 10 illustrated in Figure 1, may be electrically connected in this manner, e.g., in series.

Figure 2 is a schematic sectional side view of an arrangement 10 according to an embodiment of the present invention. The arrangement 10 illustrated in Figure 2 corresponds to a portion of the arrangement 10 illustrated in Figure 1. The same reference numerals in Figures 1 and 2 correspond to the same or similar components, having the same or similar function.

In accordance with the embodiment of the present invention illustrated in

Figure 2, each of the first rod 1 and the second rod 2 is made from a first member in the form of a rod made of an electrically isolating material, and several second members made of an electrically conductive material located on the circumferential surface portion of the first member and arranged to surround the circumferential surface portion, thereby forming a rod having electrically conductive sections and electrically isolating sections along the longitudinal axis. The second members may for example be glued or force fitted onto the circumferential surface portion of the first member. The electrically isolating material may for example comprise glass fiber, a plastic or another type of electrically isolating material. The electrically conductive material may for example comprise a metal or metallic material, such as, for example, Al or Cu, or an alloy including Al or Cu and/or another type of metal.

Figure 2 illustrates the first rod 1 and the second rod 2 when they are arranged relatively to each other so as to be in the above-mentioned second relative position, in which the first portions or parts 7 (not shown in Figure 2; cf. Figure 1) are not grounded, and the second portions or parts 8 (not shown in Figure 2; cf. Figure 1) are not supplied with power from the power supply or power supplies.

Figure 3 is a close-up view of a portion of Figure 2. Thus, the same reference numerals in Figures 2 and 3 correspond to the same or similar components, having the same or similar function.

The pair of grounding terminals 11, 12 may be connected to the first portions or parts 7 (not shown in Figure 2 or 3; cf. Figure 1). The power supply terminals 14 may be connected to the second portions or parts 8 (not shown in Figure 2 or 3; cf. Figure 1).

In the position of the first rod 1 illustrated in Figure 3, the pairs of grounding terminals 11, 12 are electrically isolated from each other by means of at least one electrically isolating section 4 of the first rod 1, and the second rod 2 is in a position in which the respective pairs of power supply terminals 14 are electrically isolated from the second electrical conductor 18 by means of at least one electrically isolating section 6 of the second rod 2.

With respect to the example where the first portions or parts 7 and the second portions or parts 8 (not shown in Figure 3; cf. Figure 1) are portions or parts of respective ones of a plurality of converter cells, or converter valves (which for example may be comprised in an MMC), the second relative position of the first rod 1 and the second rod 2 illustrated in Figure 3 may be used when the converter cells are energized with phase power, e.g., provided from a converter station in which the converter cells are arranged. Thus, Figure 3 illustrates the first rod 1 and the second rod 2 in a relative position which they may be in during 'normal' operation of the converter valves.

The electrically isolating sections 4 of the first rod 1 may ensure that the voltage between electrically conductive sections 3 of the first rod 1 interposed by one or more electrically isolating sections 4 not exceeds the voltage of one converter cell. Similarly, the electrically isolating section 6 of the second rod 2 may ensure that the voltage between electrically conductive sections 5 of the second rod 2 interposed by one or more electrically isolating section 6 not exceeds the voltage of one converter cell.

As illustrated for example in Figure 3, the grounding terminals 11, 12 may comprise one or more contact elements 25 which may be configured to be in contact with the first rod 1, in particular with the electrically conductive sections 3 thereof. Similarly, the power supply terminals 14 may comprise one or more contact element 26 which may be configured to be in contact with the second rod 2, in particular with the electrically conductive sections 5 thereof. In accordance with the embodiment of the present invention illustrated in Figure 3, the contact elements 25, 26 may for example comprise spring contact elements. The respective ones of the grounding terminals 11, 12 and power supply terminals 14 comprises two contact elements 25 and 26, respectively, with one contact element 25, 26 arranged close to one end of the terminal and the other contact element 25, 26 arranged close to the other end of the terminal. Only some contact elements 25, 26 are indicated by reference numerals in Figure 3.

As also illustrated for example in Figure 3, the housings 13 may comprise one or more contact element 27 which may be configured to be in contact with the second rod 2, in particular with the electrically conductive sections 5 thereof. As shown in Figure 3, each housing 13 may comprise two contact elements 27, with one contact element 27 arranged close to one end of the housing 13 and the other contact element 27 arranged close to the other end of the housing 13. The contact elements 27 may for example comprise spring contact elements. Only some contact elements 27 are indicated by reference numerals in Figure 3.

Figure 4 is similar to Figure 3, but illustrates the first rod 1 and the second rod 2 in a position relatively to each other that differs from the position of the first rod 1 and the second rod 2 relatively to each other that is illustrated in Figure 3. Thus, the same reference numerals in Figures 3 and 4 correspond to the same or similar components, having the same or similar function.

Figure 4 illustrates the first rod 1 and the second rod 2 when they are arranged relatively to each other so as to be in the above-mentioned first relative position, in which the first portions or parts 7 (not shown in Figure 4; cf. Figure 1) are grounded, and the second portions or parts 8 (not shown in Figure 4; cf. Figure 1) are supplied with power from the power supply or power supplies.

As illustrated in Figure 4, the electrically conducting sections 5 of the second rod 2 may have different thickness. For example, the second rod 2 may have a circular cross section along the longitudinal axis of the second rod 2, and the electrically conducting sections 5 of the second rod 2 may have different diameters. As illustrated for example in the middle portion of the rod 2 depicted in Figure 4, the transition between electrically conducting sections 5 of the second rod 2 having different thicknesses (e.g., different diameters) may be smooth, i.e. not abrupt.

Figure 4 illustrates how, by displacement of the first rod 1 in a longitudinal direction of the second rod 1 (from the left to the right in Figures 3 and 4), the pairs of grounding terminals 11, 12 may become electrically connected by at least one electrically conductive section 3 of the first rod 1. Figure 4 further illustrates how, by displacement of the first rod 2 in a longitudinal direction of the second rod 2 (from the left to the right in Figures 3 and 4), the power supply terminals 14 may become electrically connected by at least one electrically conductive section 5 of the first rod 2. Also, Figure 4 illustrates that by the displacement of the first rod 2 in a longitudinal direction of the second rod 2, the housings 13 - which as mentioned in the foregoing may be configured to keep at least one of the electrically conducting sections 5 of the second rod 2 at a selected voltage - are brought out of contact with an electrically conducting section 5 of the second rod 2 by way of a reduced thickness of the electrically conducting section 5 as compared to an adjoining electrically conducting section 5. For example, the electrically conducting section 5 of the second rod 2 that is brought out of contact with the housing 13 may have such a small thickness that the contact elements 27 of the housing 13 are not able to contact that particular electrically conducting section 5.

Figures 5 to 8 are schematic side views of portions of arrangements in accordance with an embodiment of the present invention, and illustrate different positions of the first rod 1 and the second rod 2 when moved in a longitudinal direction of the first rod 1 and the second rod 2, respectively. Figures 5 to 8 can hence be considered to illustrate the first rod 1 and the second rod 2 at different time instants during movement of the first rod 1 and the second rod 2, respectively, wherein Figure 5 may be considered as a starting position and Figure 8 may be considered as an end position, and with Figures 6 and 7 illustrating positions of the first rod 1 and the second rod 2 between the starting position and the end position of the respective ones of the first rod 1 and the second rod 2. The same reference numerals in Figures 5 to 8 and in Figures 1 to 4 correspond to the same or similar components, having the same or similar function. In Figures 5 to 8, the longitudinal direction of the respective ones of the first rod 1 and the second rod 2 is from left to right in Figures 5 to 8. According to the embodiment of the present invention illustrated in Figures 5 to 8, the first rod 1 and the second rod 2 are arranged such that their respective longitudinal axes are parallel to each other.

As indicated in Figures 5 to 8, the first rod 1 and the second rod 2 may be moved in the longitudinal direction of the respective ones of the first rod 1 and the second rod 2 by means of the actuator (not shown in Figures 5 to 8) at equal, or substantially equal, speeds. As indicated in the foregoing, the first rod 1 and the second rod 2 may be moved jointly, or together.

In Figures 5 to 8, a pair of negative and positive grounding terminals 11 and 12, respectively, is shown, which pair of negative and positive grounding terminals 11, 12 is arranged to be connected to a first portion or part 7 of electric equipment (not shown in Figures 5 to 8; cf. Figure 1) to be grounded. Figures 5 to 8 further show an additional negative grounding terminal 11 to the right of the pair of negative and positive grounding terminals 11 and 12. Furthermore, Figures 5 to 8 show a pair of power supply terminals 14 arranged to be connected to at least one second portion or part 8 of electric equipment (not shown in Figures 5 to 8; cf. Figure 1) for supply of power thereto.

In the positions of the first rod 1 and the second rod 2 illustrated in Figure 5, the pair of negative and positive grounding terminals 11, 12 are electrically isolated from each other by an electrically isolating section 4 of the first rod 1, and the pair of power supply terminals 14 are electrically isolated from each other by an electrically isolating section 6 of the second rod 2. With respect to the example where the first portions or parts 7 and the second portions or parts 8 (not shown in Figure 5; cf. Figure 1) are portions or parts of respective ones of a plurality of converter cells, or converter valves (which for example may be comprised in an MMC), the second relative position of the first rod 1 and the second rod 2 illustrated in Figure 5 may be used when the converter cells are energized with phase power that for example may be provided from a converter station in which the converter cells are arranged. Thus, Figure 5 illustrates the first rod 1 and the second rod 2 in a relative position which they may be in during 'normal' operation of the converter valves.

In the positions of the first rod 1 and the second rod 2 illustrated in Figure 6, the pair of negative and positive grounding terminals 11, 12 are electrically connected by an electrically conducting section 3 of the first rod 1. The first portion or part 7 to which the pair of negative and positive grounding terminals 11, 12 is arranged to be connected is short- circuited. The pair of power supply terminals 14 are electrically isolated from each other by the electrically isolating section 6 of the second rod 2. The positive grounding terminal 12 is electrically isolated from the negative grounding terminal 11 at the right-hand side in Figure 6 by an electrically isolating section 4 of the first rod 1.

In the positions of the first rod 1 and the second rod 2 illustrated in Figure 7, the pair of negative and positive grounding terminals 11, 12 are electrically connected by an electrically conducting section 3 of the first rod 1, and the positive grounding terminal 12 is further electrically connected by an electrically conducting section 3 of the first rod 1 to the negative grounding terminal 11 at the right-hand side in Figure 7. The first portion or part 7 to which the pair of negative and positive grounding terminals 11, 12 is arranged to be connected is short-circuited and grounded. The pair of power supply terminals 14 are electrically isolated from each other by the electrically isolating section 6 of the second rod 2.

In the positions of the first rod 1 and the second rod 2 illustrated in Figure 8, the pair of negative and positive grounding terminals 11, 12 are electrically connected by an electrically conducting section 3 of the first rod 1, and the positive grounding terminal 12 is further electrically connected by an electrically conducting section 3 of the first rod 1 to the negative grounding terminal 11 at the right-hand side in Figure 8. The first portion or part 7 to which the pair of negative and positive grounding terminals 11, 12 is arranged to be connected is short-circuited and grounded. The pair of power supply terminals 14 are now electrically connected by the electrically conducting section 5 of the second rod 2, whereby the second portion or part 8 to which the pair of power supply terminals 14 is arranged to be connected can be provided with power from a power supply.

While the present invention has been illustrated in the appended drawings and the foregoing description, such illustration is to be considered illustrative or exemplifying and not restrictive; the present invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the appended claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.