Abstract: An AC/DC converter includes an AC circuit breaker, configured as a hybrid circuit or semiconductor circuit breaker; a rectifier; a smoothing capacitor; a semiconductor switch connected in series with the smoothing capacitor; and a first isolation relay for galvanic isolation. One input of the AC circuit breaker forms an AC input of the converter. One output of the AC circuit breaker is connected with an input of the rectifier. The smoothing capacitor, and the first semiconductor switch, connect a first output of the rectifier with its second output. The first output of the rectifier is connected with one input of the first isolation relay. The one output of the first isolation relay forms a first DC output of the AC/DC converter. The AC circuit breaker, the first semiconductor switch, and the first isolation relay are interconnected.

Abstract: A motor drive comprises a rectifier arranged to receive an externally supplied AC voltage and to generate a DC bus voltage. An inverter is arranged to receive the DC bus voltage and to generate an AC output voltage for supply to an external load. A DC bus portion is connected between the rectifier and the inverter. The DC bus comprises first and second conductors, wherein an inductor is connected in series along the first conductor between the rectifier and the inverter. A DC link capacitor is connected in parallel between the conductors. A controller is arranged to supply a plurality of perturbation signals at a first node between the rectifier circuit portion and the DC bus portion, to measure a respective response signal at a second node between the DC bus and the inverter and is is arranged to generate a parameterised model of a transfer function of the DC.

Abstract: The disclosure discloses a commutation failure prediction method, device and storage medium based on energy accumulation features of inverter. The method includes the following steps: collecting instantaneous values of three-phase valve side current and calculating the derivatives of the three-phase valve side current according to the instantaneous values of three-phase valve side current; the derivative includes positive, negative and zero states; according to the derivatives of the three-phase valve side current, determining the locations of incoming valve and ongoing valve; based on the valve side current of the incoming valve and ongoing valve, calculating energy accumulation features of the 12-pulse inverter; predicting whether the commutation failure from the incoming valve to the ongoing valve will happen according to the states of the derivatives of the three-phase valve side current and the energy accumulation features of the 12-pulse inverter.

Abstract: A solid-state circuit breaker and breaking method are disclosed. In an embodiment, the solid-state circuit breaker includes a semiconductor switch; a controller, connected to the semiconductor switch; and an energy absorber, connected in parallel with the semiconductor switch. The controller is configured to obtain an equivalent inductance of a circuit of the solid-state circuit breaker upon a fault occurring in a line. Further, upon the equivalent inductance being greater than an inductance estimated value, the controller is configured to set a second current fault threshold. Finally, upon a fault current of the line reaching the second current fault threshold, the semiconductor switch is controlled to execute a closing operation.

Abstract: Various examples are provided related to semiconductor topologies and devices that can be used for soft starting and active fault protection of power converters. In one example, an active switch device includes an active switch having a gating control input; and a thyristor having a gating control input. The thyristor is coupled in parallel with the active switch. The active switch can be an IGBT, MOSFET, or other appropriate device. In another example, a power converter can include the active switch devices and switching control circuitry coupled to gating control inputs of the active switch devices.

Abstract: In the field of high voltage direct current (HVDC) power transmission there is provided a power converter assembly (10) comprising a line-commutated power converter (12) that is configured to transfer power from a DC network (14) to a corresponding receiving AC network (16). The power converter assembly (10) also includes a control unit which is operatively associated with the line-commutated power converter (12) and is programmed, in response to the receiving AC network (16) exhibiting a reduced AC voltage (Va, Vb, Vc), to cause a reduction in the operating DC voltage (VDC) of the line-commutated power converter (12) by the DC network (14).

Abstract: A mechanism for travelling wave protection of a transmission line and a method for acquiring information of both voltage and current polarities from two ends of a transmission line. The method includes comparing the voltage and current polarities of both ends of the transmission line to each other. The method also includes making a trip decision based on the comparison.

Abstract: One aspect of the disclosure includes a submodule topology for a modular multilevel converter. The submodule topology includes two electronic switches connected together with a first series connection terminal connecting the electronic switches in series, the series connected switches being connected in parallel with two capacitors connected together with a second series connection terminal connecting the capacitors in series. A bidirectional electronic switch connects the first series connection terminal with the second series connected terminal. An output voltage is obtained across the first series connected terminal and a common terminal formed by the parallel connection of the series connected switches with the series connected capacitors.

Abstract: A device switches a direct current. The device contains an operating current branch in which a mechanical switch is arranged, a protective switch connected to the operating current branch for interrupting the current flow in the operating current branch, a capacitor branch connected in parallel with the operating current branch in which capacitor branch a capacitor is arranged, and a damping apparatus which has a resistance element. The damping apparatus is arranged in the capacitor branch in series with the capacitor or in the operating current branch in series with the mechanical switch, which damping apparatus can be bypassed by a bypass switch connected in parallel with the damping apparatus.

Abstract: A converter control arrangement (18) for regulating the output current of a dc source power converter (16) comprises a current regulator (20) for regulating the output current based on a comparison of an output current value (Iout) of the dc source power converter (16) with a desired target current value (Itgt). When the output voltage value (Vout) of the dc source power converter (16) is within a normal operating voltage range between minimum and maximum voltage values (Vmin, Vmax) defined with respect to a voltage reference value (Vref) of the dc source power converter (16), the converter control arrangement (18) controls the target current value (Itgt) so that it is equal to a desired reference current value (Iref).

Abstract: Protection of an electric motor drive controller from a transient voltage is described herein. The transient voltage is provided by an alternating current (AC) power line that includes a line conductor, a neutral conductor, and a ground conductor. The transient voltage protection system includes a first stage protection device coupled to an input of a rectifier of the motor drive controller. The first stage protection device is configured to suppress the transient voltage to prevent damage to the motor drive controller. The transient voltage protection system also includes a second stage protection device coupled between the rectifier and an inverter of the motor drive controller. The second stage protection device is configured to further suppress the transient voltage to prevent damage to the inverter.

Abstract: An inverter-charger integrated device for an electric vehicle is provided. The inverter-charger integrated device for the electric vehicle includes a motor; a power input unit; a rectifying unit; an inverter; and a control unit, wherein the inverter comprises a first group of switches including first and second switches, a second group of switches including third and fourth switches, and a third group of switches including fifth and sixth switches, the rectifying unit is directly connected to the first of the first to third groups of switches, and phases of the motor are respectively connected to the first to third group of switches.

Abstract: Positive-side DC terminals P1? and P? connected to a positive-side DC bus of a chopper 4 are provided in the chopper 4 and the positive-side DC terminals P1? and P? are connected to positive-side DC terminals P1 and P, respectively. With this configuration, a current of a DC bus of an inverter 2 is drawn via the positive-side DC terminal P1? into the chopper 4 and is returned via the positive-side DC terminal P? to the DC bus of the inverter 2.

Abstract: To provide a fault detection device for an inverter system, that detects a fault in the inverter system including an inverter circuit 2 that converts DC power into AC power and a motor 5 driven thereby. When a driving start signal Sig1 of the inverter circuit 2 is input, a test voltage applying unit 20 applies a predetermined first test voltage to a current measuring unit 10 that measures current flowing in the inverter circuit 2, and it is determined whether the current measuring unit 10 has failed, based on the first test voltage. A control unit 30 applies a predetermined second test voltage to the inverter circuit 2 and the motor 5, and it is determined whether the inverter circuit 2 and a motor coil have failed, based on the second test voltage.

Abstract: A method for operating a power generation system coupled to a power grid during a grid unbalance event, a method for determining an injection current to be supplied into a power grid by a power generation system, and a method for addressing an asymmetric grid fault in a power grid connected to a power generation system are provided. The methods may be carried out based on a reactive or an active power/current priority.

Abstract: An arrangement for controlling the electric power transmission in a high voltage direct current, HVDC, power transmission system includes at least one HVDC transmission or distribution line for carrying direct current, DC, and the arrangement includes an apparatus connectable to the HVDC transmission or distribution line, the apparatus being arranged to control the direct current of the HVDC transmission or distribution line by introducing a DC voltage in series with the HVDC transmission or distribution line. The arrangement includes a protection device for protecting the apparatus against over-current or overvoltage occurrences. The protection device includes a bypass device connectable to the HVDC transmission or distribution line and connected in parallel with the apparatus. The bypass device is arranged to be in a non-conducting mode and arranged to be set to a conducting mode.

Abstract: Multi-terminal HVDC systems and control methods therefore are disclosed. Methods for controlling multi-terminal HVDC systems having a plurality of converter stations may include receiving a plurality of measurements from a plurality of measurement units disposed on the HVDC system, identifying from the measurements a disruption within the HVDC system, monitoring the measurements to identify a steady-state disrupted condition for the HVDC system, calculating a new set point for at least one of the plurality of converter stations, which new set point may be based on the steady-state disrupted condition and the measurements, and transmitting the new set point to the at least one of the plurality of converter stations. In some examples, the HVDC systems may include an HVDC grid interconnecting the plurality of converter stations and a controller communicatively linked to the plurality of measurement units and the plurality of converter stations.

Abstract: A converter, and in particular a current source converter, including a bridge having an AC terminal for each of one or more AC lines, and first and second DC terminals. A converter arm is connected between each respective AC terminal and the first DC terminal, and between each respective AC terminal and the second DC terminal. Each converter arm includes a first power semiconductor switching device capable of being turned ‘on’ and ‘off’ by gate control and having a recovery time. The converter is adapted to be operated in one or more inverting modes.

Abstract: In a frequency converter operated for safety of personnel and/or fire protection via a ground fault interrupter is frequently not able to distinguish between an actual fault current and an operationally generated leakage current. The proposed method addresses this problem by determining a course of a magnitude of a current flowing through the frequency converter, predefining a signal portion which is independent of switching processes within the frequency converter while the frequency converter operates fault-free, checking whether the determined course satisfies a criterion that is predetermined depending on the signal portion, and interrupting the current the determined course fails to satisfy the predetermined criterion.

Abstract: Active front end power conversion systems are presented having a peak detector with adjustable decay providing a signal to an overload protection component to selectively discontinue rectifier switching control signals for protection of active rectifier switches during unbalanced line voltage conditions.

Abstract: An inverter apparatus having a power supply circuit includes a converter circuit for rectifying AC power into DC power, a smoothening circuit for smoothening the rectified DC power, an inverter circuit for converting the smoothened DC into AC at a variable frequency through a plurality of switches to control a load, and a current detection circuit for detecting overcurrent from the smoothened DC supplied from the inverter circuit, wherein the inverter circuit applies bootstrap power for driving the switches to the current detection circuit to use the bootstrap power as power of the current detection circuit. When bootstrap power for driving switch gates is used, it is possible to use the bootstrap power as the power of the current detection circuit by adding the auxiliary circuit composed of a small number of passive elements.

Abstract: A Voltage Sourced Converter, VSC, for a High Voitage Direct Current, HVDC, power converter, the VSC comprises a bridge circuit for each of one or more phases of an AG network. The bridge circuit has two arms, each arm connecting the supply to a pole of a DC terminal, wherein each arm of the bridge circuit has one or more semiconductor modules capable of being switched between an on-condition, in which a capacitor of the module is in-line in the arm of the bridge circuit, and an off-condition, in which the capacitor is out of line. A DC current fault detection arrangement detects a fault arising at one or the other of the poles of the DC terminal within the DC converter or the DC grid. A controller responsive to the detection of the DC current fault switches one or more of the semiconductor modules in one of the arms of the bridge to the on and one or more of the semiconductor modules of the other arm of the bridge circuit to the off-condition.

Abstract: A power-saving driving device is provided for a same load pattern device 23 that is driven by a motor 21 receiving electric power from an inverter 19 and repeatedly operated in a same load pattern. The power-saving driving device includes: an electric power amount calculator 81 that calculates an electric power amount W received by the inverter in the same load pattern; and a parameter selection and command device 83 that makes a parameter of the inverter change to a plurality of values, compares the received electric power amounts corresponding to the values of the parameter, selects the parameter value minimizing the received electric power amount and issues the selected value as a command to the inverter.

Abstract: A DC voltage source converter for use in high voltage DC power transmission comprising at least one chain-link converter connected between first and second DC terminals. The or each chain-link converter includes a chain of modules connected in series and each module including at least one pair of semiconductor switches connected in parallel with an energy storage device. The or each chain-link converter is operable when DC networks are connected to the first and second DC terminals to control switching of the modules to selectively charge or discharge the energy storage device of one or more of the modules, as required, to offset any difference in the DC voltage levels of the DC networks.

Abstract: A high voltage controller configured to drive a high voltage generator. The high voltage controller includes a voltage select input and a current select input, an actual voltage input and an actual current input. First circuitry is configured to generate an alternating current (AC) drive signal. Second circuitry configured to generate a direct current (DC) drive signal. Closed loop control circuitry is configured to adjust the DC drive signal based on at least one of the voltage select and current select inputs and at least one of the actual voltage and actual current inputs. The first circuitry may include a push-pull circuit. The second circuitry may include a pulse width modulation (PWM) controller. A high voltage generator may be coupled to the AC and DC drive signals. The high voltage generator may include a high voltage transformer having a pair of primary windings and center tap. The AC drive signal may be coupled to the primary windings and the DC drive signal may be coupled to the center tap.

Abstract: In one aspect, a method for over-voltage protection is provided. The method includes connecting a first winding of a saturable reactor to a direct current (DC) source; connecting at least one phase of an alternating current (AC) electrical system to ground through a second winding of the saturable reactor; and controlling DC current flow from the DC source to the first winding of the saturable reactor in response to an over-voltage event, wherein energy is shunted to ground from the at least one phase of the alternating current electrical system through the second winding of the saturable reactor.

Abstract: A method, voltage source converter and computer program product for limiting the current in a DC power transmission system are disclosed. The voltage source converter has an AC side and a DC side and a fault current path between these sides. It furthermore includes a control unit and at least one switching unit of a first type provided in the fault current path and that includes a primary switching element together with an anti-parallel secondary controllable rectifying element. Based on a fault being detected in the DC power system when the primary switching elements of the converter are blocked, the control unit changes the control of the controllable rectifying element from acting as a non-controllable rectifying to acting as a controllable rectifying element.

Abstract: The present invention relates to an HVDC switchyard arranged to interconnect a first part of a DC grid with a second part of the DC grid. By means of the invention, a first part of the DC grid is connected to the busbars of the HVDC switchyard via a fast DC breaker, while further part(s) of the DC grid are connected to the busbars of the HVDC switchyard by means of switchyard DC breakers of lower breaking speed. By use of the inventive HVDC switchyard arrangement, the cost for the HVDC switchyard can be considerably reduced, while adequate protection can be provided. In one embodiment, the fast DC breaker is an HVDC station DC breaker forming part of an HVDC station. In another embodiment, the fast DC breaker is a switchyard DC breaker.

Abstract: An interface arrangement for connection between an AC system and a DC system and to a method of disconnecting a DC system from an AC system are disclosed. The arrangement includes a converter for conversion between AC and DC having a DC side for connection to the DC system and an AC side for being coupled to the AC system, a set of circuit breakers coupled between the AC side of the converter and the AC system and a breaker assisting unit including a set of branches connected between the AC side of the converter and ground, where each branch includes a switch in series with an impedance element.

Abstract: To prevent demagnetization of a permanent magnet synchronous rotating machine, a rotating machine control device according to the present invention is a rotating machine control device comprising: a power converter having a switch part on each of a positive side and a negative side for each phase; and short circuit detection unit for detecting a short circuit of the switch part, wherein a command to turn on positive-side switches and negative-side switches of a plurality of phases of the switch part is issued in the case where the short circuit detection unit detects the short circuit.

Abstract: A method to control a voltage source converter in a HVDC system includes controlling a frequency and a voltage amplitude of an AC voltage generated by the voltage source converter independently of the conditions in an AC network connected to the voltage source converter. The method is performed by a control unit of an HVDC system. The method may form a basis of a method to black start an AC network. The AC network includes transmission lines and is connected to at least two AC power stations. One of the at least two AC power stations is connected via a HVDC system to the AC network.

Abstract: Losses are reduced in a current supply circuit including an inverter having a switching element. The dynamic losses in an IGBT element including a free wheeling diode are proportional to the product of turn-on losses and a switching frequency, and the static losses are proportional to the product of a current flowing through the IGBT element and a saturation voltage across a collector and an emitter of the IGBT element. When the breakdown voltage of the IGBT element is increased twice, the saturation voltage across a collector and an emitter does not reach twice as much. Therefore, the static losses can be reduced by increasing a voltage twice and reducing a current by half that are supplied to a load to attain the same power to supplied to the load, with the same dynamic losses.

Abstract: The present invention concerns a projection system for providing a distributed manifestation within an environment. The projection system includes a data generator for generating a plurality of data sets of associated state data and spatial coordinate data. The projection system also includes a projector in communication with the data generator for receiving the data sets. The projector is provided with a signal generating module for generating a plurality of electromagnetic signals, and a projecting module for projecting each of the electromagnetic signals towards a target location within the environment. The projection system also includes a plurality of receiving units distributed within the environment, each receiving unit having a receiver for receiving one of the electromagnetic signals when the receiving unit is positioned in the corresponding target location, each receiving unit being adapted to perform a change of state in response to the state data.

Abstract: A HVDC power grid including a multiplicity of voltage sourced converters arranged in a symmetrical monopole transmission configuration to transmit DC power over a DC power grid of transmission lines connected between the voltage sourced converters, and circuitry implemented for sensing and identifying a fault occurred on a section of a DC transmission line. In response to the sensing, the current on the faulted DC transmission line is controllably drawn down to a target current level, e.g., 50 amp, which will accommodate clearing of the faulted transmission line section by allowing switches located at each end of the faulted transmission line section to be able to open against such level of current without triggering an non-extinguishable or sustained arc across one of the switches. At least one of the switches is capable of opening when the current is reduced to the drawn down level to isolate the transmission line.

Abstract: A contact-input circuit for a power system device is described for processing a higher voltage signal from power system equipment or another power system device for use by a lower voltage circuit. The contact-input circuit generally includes a voltage threshold detection device adapted to allow current to flow therefrom when it detects that the higher voltage signal reaches a select threshold. An opto-isolator device, which is coupled to the voltage threshold detection device, provides a voltage signal suitable for use by the lower voltage circuit when the threshold detection device allows the current-flow through the opto-isolator.

Abstract: There is provided an apparatus and methods for a power conversion device. The method includes rectifying a mains voltage to produce a dc voltage and placing the dc voltage on a bus. The bus is coupled to an output converter and has a switch. The method also includes monitoring the bus voltage using voltage sensing circuitry and determining whether the voltage on the bus exceeds a threshold. If the voltage exceeds a threshold, the switch is turned off.

Abstract: A high voltage DC breaker apparatus configured to interrupt a fault current occurring in a high voltage DC conductor comprises a mechanical interrupter, at least one semiconductor device connected in series with the interrupter, an arrester connected in parallel with the semiconductor device and an LC-circuit connected in parallel with the series connection of the semiconductor device and the interrupter. A control unit is configured to, upon detection of a fault current, control switching of the semiconductor device at a frequency adapted to the values of an inductance and a capacitance of the LC-circuit for charging the capacitance by the fault current while making the current through the interrupter oscillating with an increasing amplitude and the interrupter to open for having the mechanical contacts thereof separated when current zero-crossing is reached for obtaining interruption of the fault current through the interrupter.

Abstract: A current control circuit (active element) is provided that is connected between a rectifier of a DC power source and a smoothing capacitor in a power frequency converter and that controls a variation in the rectified current caused by a variation in the instantaneous power consumption of the load device. When the rectified current increases, the current control circuit limits the current to have a reference current value or lower and, when the rectified current decreases, the current control circuit increases the current to have a value close to the reference current to thereby suppress the rectified current from the rectifier to a substantially-constant value. This consequently mitigates the influence on the primary power source by the variation in the instantaneous power consumption of the load device, thus clearing the Load Demand Variation specification required for the power source to be used in an aircraft.

Abstract: A control device for rectifier stations in a high-voltage DC transmission system has a rectifier drive unit and an inverter drive unit for driving power rectifier stations that are working either as a rectifier or as an inverter. The trigger angles for the rectifier or for the inverter can be adjusted and regulated by way of the rectifier drive unit and the inverter drive unit respectively. A delay element is placed between the rectifier drive unit and the inverter drive unit with which the start time for regulating the trigger angle for the inverter relative to the start time for regulating the trigger angle for the rectifier can be delayed by a predetermined delay time. Because of less mutual interaction of the trigger angle control processes, a relatively faster transition from an initial operating state into a new stationary state results.

Abstract: A method and device for providing redundant control of a controllable current valve in a converter of a power transmission system. A first converter control unit sends a first valve control signal. A first active/standby indicator is associated with the first converter. A second converter control unit sends a second valve control signal. A second active/standby indicator is associated with the second converter control unit. The device also includes a valve control unit. An active/standby indicator indicates if a corresponding converter control unit is active or standby. Only one indicator indicates an active unit at a given point in time. The valve control unit receives the active/standby indicators and valve control signals, selects a valve control signal to be applied if the corresponding active/standby indicator indicates an active converter control unit and controls the current valve using the selected valve control signal.

Abstract: An HVDC transmission system including a rectifier station and an inverter station each having a series connection of at least two converters. A by-pass DC breaker is connected in parallel with each converter. A control device is adapted to deblock a blocked converter by starting to control the converter at high delay angle and gradually decreasing the delay angle until substantially all DC current flows through the converter and to then control the by-pass breaker to open at substantially zero current, and to stop the operation of a converter by controlling the converter at gradually increasing delay angle until the voltage across the converter is substantially zero and to then control the converter to be blocked by firing a by-pass pair thereof and to then control the by-pass breaker to close for taking over all the DC current when the voltage between a neutral bus and a pole of a transmission line between the stations is to be increased and reduced, respectively.

Abstract: An electric power transmission system includes at each end of a high voltage direct current transmission line including three conductors, a converter station for conversion of an alternating voltage into a direct voltage for transmitting direct current between the stations in all three conductors. Each station has a voltage source converter and an extra phase leg connected between the two pole conductors of the direct voltage side of the converter. A third of the conductors is connected to a midpoint between current valves of the extra phase leg. An arrangement is adapted to control the current valves of the extra phase leg to switch for connecting the third conductor either to the first pole conductor or the second pole conductor for utilizing the third conductor for conducting current between the stations.

Abstract: An energy storage device includes buck and boost switches that charge and discharge a charge storage element (e.g. a supercapacitor or ultracapacitor) over a broad voltage range. Integrated charge limiting prevents the storage element from sinking a potentially damaging level of current. Pulse-width modulated control signals are combined with higher-frequency signals to allow the resulting modulated control signals to pass through relatively small, inexpensive isolation transformers. Pairs of control signals may be combined to produce composite control signals that turn power switches on and off, or may be used to separately turn the power switches on and off.

Abstract: A converter station an element adapted to determine a value of an actual temperature of any critical component of the station and an element adapted to determine a value of an actual temperature of any media used to cool the critical component. An arrangement is adapted to utilize these temperature values and information about actual cooling capacity of any cooling equipment present to cool the critical component and information about the thermal behavior of the critical component and the possible cooling media upon a possible change of the power actually transmitted through the station in a mathematical model for calculating the present overload capabilities of the converter station for use in the control of converters of the station upon a possible request of utilizing an overload capability of the station.

Abstract: A voltage source converter for high voltage DC power transmission is disclosed. According to one aspect, the voltage source converter is connectable between a DC network and another electrical network to interconnect the DC network and the other electrical network. The voltage source converter includes a converter unit configured to convert power flowing between the DC network and the other electrical network and at least one fault unit. One or more of the fault units includes at least one fault module having a voltage source that is operable, in the event of a short circuit in a DC network connected to the voltage source converter, to produce a voltage that acts to reduce current flowing through the voltage source converter and the short circuit.

Abstract: An electric energy exchange system between at least one motor-generator system and at least one storage member determining a continuous storage voltage between two branches of a bus circuit on which are connected in parallel a DC/DC converter, a filtering capacity, and a DC/AC converter connected on at least one motor-generator system. The system includes at least one thyristor connected as a bypass on the positive bus between the storage member and the output of the converter-voltage raiser to short-cut the converter, and a thyristor priming device to, based on the required voltage at the filtering capacity, determine at least in discharge the shorting of the converter-voltage raiser with direct passage of the current through the thyristor as long as the voltage of the filtering capacity, which is substantially equal to the storage member voltage, is sufficient for the electric machines to provide requested torque.

Abstract: The invention relates to distribution of electrical power, supervision and security. The invention comprises a power feeding station PFS for delivering electrical power. The PFS comprises a low voltage side LVS, a high voltage side HVS and a transformer TF which is configured to deliver high voltage single phase alternating current on the high voltage side, The power can be distributed, via a cable, to one or more power receiving stations PRS. The cable is configured to distribute current-symmetrical single phase current delivered by the power feeding station. The cable can preferable be a coaxial cable with the shield as current return path. The invention also comprises a current sensor unit CSU which is situated on the high voltage side. The means for measuring characteristics of the current CD can comprise a coil without galvanic contact with the high voltage side. A circuit break unit CBU suitable for breaking the current is situated on the low voltage side.

Abstract: A converter station for connecting an AC system to a bipolar HVDC transmission line. A DC neutral arrangement includes first DC breakers enabling breaking of a first current path from the neutral bus of one pole to the neutral bus of the other pole at bipolar operation of the station for changing to monopolar operation thereof for isolation of a faulty section of the system while establishing a current path to electrode line connecting members for diverting the current from the one pole thereto. A separate connecting member is provided for each of the electrode lines. A connector is configured to connect each neutral bus to an optional of the two electrode line connecting members.

Abstract: A converter station for connecting an AC system to a bipolar HVDC transmission line. A DC neutral arrangement is provided with first DC breakers enabling breaking of a first current path from a neutral bus of one pole of the transmission line to a neutral bus of another pole at bipolar operation of the station for isolation of a faulty section and changing to monopolar operation/metallic return thereof. The DC neutral arrangement has in the first current path at least two first DC breakers connected in series and adapted to act as a backup for each other would the other thereof fail to break the first current path upon a control to isolate a faulty section by changing from bipolar to monopolar operation.

Abstract: A HVDC transmission system including at one end of a bipolar HVDC transmission line a converter station for connecting the transmission line to an AC system. The station has two converters and a DC neutral arrangement in common to the converters. The DC neutral arrangement has a separate electrode line connecting member connecting to electrode lines. The electrode lines are dimensioned to be able to at monopolar operation of the converter station transmit substantially full current to an electrode station through the remaining one or ones of the electrode lines at disconnection of an arbitrary of the electrode lines.