Improvements relating to DC circuit breakers in power transfer networks

Abstract

There is provided a direct current circuit breaker system operable to interrupt direct current flowing through a direct current line, where the direct current line has a first potential relative to ground potential and is raised above ground to provide an electrical insulation gap, the direct current circuit breaker system comprising: one or more electrical subsystems, the electrical subsystem is raised above the ground and is configured to operate at a first potential; a first generator raised above the ground and configured to operate at a first potential, where the first generator is arranged to convert the received energy into electrical energy at the first potential, the electrical energy being used to power the one or more electrical subsystems; and an electric motor for generating received energy, where the electric motor is configured to operate at ground potential and is operably coupled to the first generator via a physical connection, where the physical connection is electrically insulated.

Description

Technical Field

[0001] The subject matter herein relates generally to the field of power transmission networks, and more particularly to DC circuit breakers in power transmission networks. Background Art

[0002] In a high-voltage direct current (HVDC) power transmission network, alternating current (AC) power is typically converted to direct current (DC) power for transmission via overhead lines, submarine cables, and / or underground cables; hereinafter referred to as DC lines or HVDC lines. This conversion eliminates the need to compensate for the AC reactive / capacitive loading effects imposed by the power transmission medium (i.e., transmission lines or cables), reduces the cost per kilometer of lines and / or cables, and therefore becomes cost-effective when power needs to be transmitted over long distances. For example, DC power can also be transmitted directly from an offshore wind farm to an onshore AC power transmission network.

[0003] Where it is necessary to interconnect DC and AC networks, conversion between DC power and AC power is utilized. In any such power transmission network, power conversion components, also called converters (i.e., power converters in converter stations), are required at each interface between AC and DC power to achieve the required conversion from AC to DC or from DC to AC.

[0004] The selection of the most suitable HVDC power transmission network or scheme depends on the application and scheme characteristics.Examples of power transmission networks include unipolar power transmission networks and bipolar power transmission networks.

[0005] HVDC lines typically operate at a high potential relative to the ground. For example, HVDC lines can typically operate at 500 kV relative to the ground. HVDC lines can include DC circuit breakers (DCCBs). DCCBs can include multiple electrical subsystems that require a significant amount of pre-charged energy before the DCCBs can operate.

[0006] There is still a continuous need for improvement in this area. Summary of the Invention

[0007] A direct current (DC) breaker system operable to interrupt direct current flowing through a DC line is provided, wherein the DC line has a first electrical potential relative to ground potential and is elevated above ground to provide an electrically insulating gap, the DC breaker system comprising: one or more electrical subsystems elevated above ground and configured to operate at the first electrical potential; a first generator elevated above ground and configured to operate at the first electrical potential, wherein the first generator is arranged to convert received energy into electrical energy at the first electrical potential, the electrical energy being used to power the one or more electrical subsystems; and an electric motor for generating the received energy, wherein the electric motor is configured to operate at ground potential and is operably coupled to the first generator via a physical connection, wherein the physical connection is electrically isolated.

[0008] A method of operating a DC circuit breaker system to interrupt DC flow through a DC line is provided, wherein the DC line comprises a first electrical potential relative to ground potential and is elevated above ground to provide an electrically insulating gap, the method comprising: converting received energy into electrical energy at the first electrical potential by a first generator, the electrical energy being used to power one or more electrical subsystems, wherein the one or more electrical subsystems and the first generator are elevated above ground and operate at the first electrical potential; and generating the received energy using an electric motor operating at ground potential, wherein the electric motor is operably coupled to the first generator via a physical connection, wherein the physical connection is electrically isolated.

[0009] It will be appreciated that specific features of different aspects share the technical effects and benefits of corresponding features of other aspects of the invention. More particularly, the controller, power converter, and power transmission network share the technical effects and benefits of the DC circuit breaker and method.

[0010] It will also be appreciated that the use of the terms "first," "second," etc., are merely intended to help distinguish similar features, and are not intended to indicate the relative importance of one feature to another, unless otherwise specified.

[0011] Within the scope of the present application, it is expressly intended that the various aspects, embodiments, examples and alternatives set forth in the preceding paragraphs and claims and / or the following description and drawings, as well as in particular individual features thereof, may be employed independently or in any combination. That is, all embodiments and all features of any embodiment may be combined in any manner and / or combination, unless such features are incompatible. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 An example of a power transmission network according to aspects of the present disclosure is generally shown; Figure 2 An embodiment of a controller for a power converter according to aspects of the present disclosure is shown; Figure 3 Components of a hybrid DCCB module according to aspects of the present disclosure are shown; Figure 4 illustrates components of a hybrid DCCB module according to aspects of the present disclosure; Figure 5 illustrates a plurality of hybrid DCCB modules connected in series according to aspects of the present disclosure; Figure 6 illustrates a DCCB system according to aspects of the present disclosure; Figure 7 illustrates a DCCB system according to aspects of the present disclosure; Figure 8 illustrates a DCCB system according to aspects of the present disclosure; Figure 9 illustrates a DCCB system according to aspects of the present disclosure; Figure 10 illustrates a DCCB system according to aspects of the present disclosure; Figure 11 illustrates a DCCB system according to aspects of the present disclosure; Figure 12 illustrates a transformer according to aspects of the present disclosure; Figure 13 A flow chart illustrating a method of operating a DCCB module is shown. DETAILED DESCRIPTION

[0013] The examples described herein may relate to a method for providing auxiliary power to live components of a high-voltage DC circuit breaker (DCCB), particularly a hybrid DCCB. This presents a significant engineering challenge for a DCCB because the DCCB contains multiple electrical subsystems, all of which normally operate at the potential of the HVDC line relative to ground (typically 500 kV), and some of these subsystems may be pre-charged with considerable energy (several kilojoules - and in some designs, several hundred kilojoules) before the DCCB can be operated.

[0014] Examples described herein may involve providing auxiliary power supplied from the ground to the energized components of a DCCB. Examples described herein may involve providing auxiliary power mechanically supplied from the ground to the energized components of the DCCB using an electric motor at ground potential coupled to an insulated drive shaft and, thereby, to a generator at the potential of the DCCB components. This generator may be used to pre-charge storage capacitors within the DCCB, which may serve as the primary energy source for the DCCB and may then be distributed to other components within the DCCB through other means.

[0015] The generator may be an AC synchronous generator feeding a diode rectifier. The generator may be a DC generator. One or more electric motors may drive two or more generators to supply power to two or more electrically isolated parts of a DCCB.

[0016] Auxiliary power can be supplied from ground to the live components of the DCCB in a two-stage process. In the first stage, auxiliary power can be supplied from ground potential across the high-voltage insulation barrier and used to precharge storage capacitors within the DCCB, which serve as the DCCB's primary energy source. The primary energy storage can be a storage capacitor for the actuator that operates the mechanical switches in the DCCB's main branch. Then, in the second stage, the energy can be distributed to other components in the DCCB. The energy transmission components used in the second stage (inside the DCCB) can be different from the energy transmission devices used in the first stage (transmission from ground).

[0017] The method for the second stage can involve connecting an inverter across the storage capacitor and using this inverter to drive a high-frequency current loop, which is fed through a bank of current transformers. This can be used to provide small amounts of power required by other systems at different potentials, such as insulated gate bipolar transistor (IGBT) gate drivers and control electronics.

[0018] Examples described herein may relate to methods of transferring energy from ground to live components of a DCCB.Examples described herein may relate to methods of distributing energy between different components at HVDC line potential.

[0019] Electrical isolation transformers can be used to electrically supply power to the DCCB. Optical power supply (using lasers and photodiodes) can be used to supply power to the DCCB. High-frequency circulating current capacitively coupled via high-voltage capacitors can be used to supply power to the DCCB. Pneumatic power supply can be used to supply power to the DCCB.

[0020] Mechanical power supply via the motor generator set may be used to supply power to the DCCB.

[0021] Energy can be distributed within the DCCB with the help of high-frequency current loops and current transformers.

[0022] Figure 1 An example of a power transmission network 100 is generally illustrated. The illustration is not intended to be limited to representing a particular power transmission scheme, such as a monopolar or bipolar HVDC transmission network, but is also provided as an illustration to aid in understanding the operating principles of the power transmission network of the present invention. In this manner, for example, the power transmission network 100 may generally represent a monopolar or bipolar scheme, or may represent a multi-terminal power transmission scheme. Thus, while certain features in the illustration are shown as being connected to one another using a particular number of connections, it will be understood that this is also not intended to be limiting, but rather is intended to illustrate the general connections between features / components. Relatedly, the relative sizes or distances between components perceived in the illustration are also not intended to be limiting. Thus, it will be understood that, for example, the principles and features discussed in network 100 and herein may be applied to a variety of power transmission schemes including Figure 2 The controller 200 of the network.

[0023] The power transmission network 100 illustrates a first power conversion component 110 (also referred to as a converter station) and a second power conversion component 120. The power conversion components 110, 120 convert AC power to DC power (and vice versa), essentially acting as rectifiers (when converting AC power to DC power for transmission) and inverters (when receiving DC power and converting it to AC power). In the case of a monopole system, the power conversion components 110, 120 can each include a single converter, or in the case of a bipole system, two converters. The power conversion components 110, 120 can represent multiple converter stations arranged as a multi-terminal power transmission system. Generally speaking, the first power conversion component 110 includes a first AC side 110a and a first DC side 110b. Generally speaking, the second power conversion component 120 includes a second AC side 120a and a second DC side 120b.

[0024] The first power conversion component 110 is connected to a first AC network 140. The first AC network 140 is connected to a first AC side 110a of the first power conversion component 110.

[0025] The second power conversion component 120 is connected to a second AC network 150. The second AC network 150 is connected to the second AC side 120a of the second power conversion component 120. The first AC network 140 and / or the second AC network 150 may be an electric power transmission system including power generation equipment, transmission equipment, distribution equipment, and power loads. The first AC network 140 and / or the second AC network 150 may include a renewable power generation network, such as a wind power generation network, a solar power generation network, or a biomass power generation network. The first AC network 140 or the second AC network 150 may be a consumer network. As a non-limiting example, for example, the first AC network 140 may be a power generation network, while the second AC network 150 may be a consumer network.

[0026] Also shown is a power transmission medium 130 interconnecting the first power conversion component 110 and the second power conversion component 120. The power transmission medium 130 is connected between the first DC side 110b of the first power conversion component 110 and the second DC side 120b of the second power conversion component 120. The power transmission medium 130 may include power cables and other electrical components that interconnect the first and second power conversion components 110 and 120. For example, the power transmission medium 130 may include a conductor that provides a first electrode; and / or a conductor that provides a second electrode. A neutral arrangement interconnecting the first and second power conversion components 110 and 120 may also be provided. The power transmission medium 130 provides a medium through which DC power is transmitted between the power conversion components 110 and 120.

[0027] The operation of the power transmission system 100 can be generally described as follows. A first AC power generation network 140 generates AC power that is provided to a first power conversion component 110 at a first AC side 110a. The first power conversion component 110 converts the received AC power into DC power for transmission to a second power conversion component 120. The DC power is transmitted from the first DC side 110b to the second DC side 120b of the second power conversion component 120 via a power transmission medium 130. The second power conversion component 120 converts the received DC power back into AC power. For example, the AC power is then provided from the second AC side 120a to a second AC network 150 for consumption. In some examples, the power conversion components 110 and 120 can be geographically remote. For example, the first power conversion component 110 can be located at an offshore wind farm, while the second power conversion component 120 can be located onshore.

[0028] It will be appreciated that various other electrical components may be located in any location or have any particular characteristics / components in example 100. These may include switches, transformers, resistors, reactors, surge arresters, harmonic filters, and other components known in the art.

[0029] It will be appreciated that a converter or power conversion component may comprise a variety of different technologies, such as a voltage source converter (e.g., using insulated gate bipolar transistor (IGBT) valves). Such a converter may generally be considered to use "power electronics." For example, a power electronics converter may comprise a multi-level voltage source converter.

[0030] It will be appreciated that cables used as power transmission media may include the following non-limiting examples of cross-linked polyethylene (XLPE) and / or heavily impregnated (MI) insulated cables. Such cables may include a conductor (such as copper or aluminum) surrounded by an insulating layer. The dimensions of the cable and its associated layers may vary depending on the specific application (and particularly the operating voltage requirements). In applications such as submarine installations, the cable may also include reinforcement or "armoring." The cable may also include a sheath / shield that is grounded at one or more locations.

[0031] Furthermore, it will be understood that the power transmission network 100 can be used with a three-phase power system. In a three-phase power system, three conductors supply first, second, and third phase AC power to consumers, respectively. Each of the first, second, and third phases will typically have a voltage or current of equal magnitude, which are 120° out of phase with each other.

[0032] In a three-phase power system, phase currents and voltages can be represented by three single-phase components: a positive-sequence component; a negative-sequence component; and a zero-sequence component. This is the positive-sequence component that rotates in phase with the power system. Therefore, in an ideal scenario, only positive-sequence voltages / currents would be present. It will be appreciated that imbalances in the magnitude or phase angle of the voltages or currents between the first, second, and third phases of a three-phase system can result in undesirable negative-sequence or zero-sequence components. Such imbalances may be caused, for example, by a fault condition in AC networks 140, 150.

[0033] The power transmission network 100 may operate using a method such as synchronized grid formation (SGFM), in which either or both of the power converters 110 , 120 act as a three-phase positive phase sequence AC voltage source after an impedance that operates at a frequency synchronized with the SGFM source connected to the power transmission network 100 .

[0034] The power transmission network 100 may also include a controller for controlling the operation of the components of the power transmission network 100. For example, a controller may be provided for performing the methods described herein. For example, such a controller may control the power conversion components 110, 120. Such a controller may be referred to as a controller component or a control component. The controller may be Figure 2 Controller 200.

[0035] Figure 2An embodiment of a controller 200 is illustrated that may be used to implement the invention described herein.

[0036] The controller 200 includes a memory 210 and at least one processor 220. The memory 210 includes computer-readable instructions that, when executed by the at least one processor 220, cause the controller 200 to perform one or more methods described herein.

[0037] The controller 200 is shown as including a transceiver arrangement 230, which may include a separate transmitter 231 and receiver 232. The transceiver arrangement 230 may be used to operatively communicate with other components or features of the embodiments described herein, either directly or via another interface such as a network interface. The transceiver arrangement 230 may, for example, use the transmitter 231 and receiver 232 to send and receive control signals. The control signals may include or define electrical control parameters, such as a reference current or a reference voltage.

[0038] At least one processor 220 is capable of executing computer-readable instructions and / or performing logical operations. The at least one processor 220 may be a microcontroller, a microprocessor, a central processing unit (CPU), a field programmable gate array (FPGA), or a similar programmable controller. The controller may also include user input devices and / or output devices. The processor 220 is communicatively coupled to the memory 210 and, in some embodiments, may be coupled to the transceiver 230.

[0039] The memory 210 may be a computer-readable storage medium. For example, the memory 210 may include a non-volatile computer storage medium. For example, the memory 210 may include a hard disk drive, a flash memory, etc.

[0040] Although not shown, the controller 200 may additionally include a user input device interface and / or a user output device interface that may allow visual, auditory, or tactile input / output. Examples include interfaces to electronic displays, touch screens, keyboards, mice, speakers, and microphones.

[0041] Figure 3 Components of a hybrid DCCB module 300 are shown, according to aspects of the present disclosure.

[0042] The hybrid DCCB module 300 includes the following electrical subsystems: an energy dissipation branch 312, a current commutation branch 314, and a main branch 316 connected in parallel in a DC line 311. The DC line 311 may be a DC line or a HVDC line.

[0043] The hybrid DCCB module 300 may be significantly more complex than an AC circuit breaker. The hybrid DCCB module 300 may include several electrical subsystems that can work together. During normal operation (e.g., when the DCCB is closed), current may flow through the main conducting branch 316. The energy dissipating branch 312 may include a surge arrester. When the main conducting branch 316 is open, the current commutating branch 314 may temporarily pass current.

[0044] The energy dissipation branch 312 may include a varistor. The main conduction branch 316 may include a mechanical switch 317 and a first power electronic switch (PE1). The current commutation branch 314 may include a second power electronic switch (PE2).

[0045] PE2 may be suitable for HVDC applications. PE2 may be suitable for use in a hybrid DCCB module 300. PE2 may be configured to withstand transient voltages generated across the hybrid DCCB module 300. PE2 may be configured to withstand the full voltage of the hybrid DCCB module 300. PE2 may be configured to withstand at least 500 kV. PE2 may include a large number of IGBTs connected in series. PE2 may include more than 100 IGBTs connected in series. The hybrid DCCB module 300 may generate transient voltages during operation.

[0046] PE1 may be suitable for HVDC applications. PE1 may be suitable for use in hybrid DCCB module 300. PE1 may be configured to generate a voltage to divert current from main conducting branch 316 into current commutating branch 314. PE1 may be configured to withstand several kV. PE1 may be configured to withstand less than 500 kV. PE1 may include fewer IGBTs than PE2. PE1 may include fewer series-connected IGBTs than PE2. PE1 may be smaller in size than PE2.

[0047] Figure 4 Components of a hybrid DCCB module 400 according to aspects of the present disclosure are illustrated.

[0048] The hybrid DCCB module 400 includes the following electrical subsystems: an energy dissipation branch 412, a current commutation branch 414, and a main branch 416 connected in parallel in a DC line 311. The DC line 311 may be an HVDC line.

[0049] The energy dissipation branch 412 may include a varistor. The main conduction branch 416 may include a mechanical switch 417 and a first power electronic switch (PE1). The current switching branch 414 may include a second power electronic switch (PE2). PE1 and PE2 may be the same as those described above. Figure 3 The description of PE1 and PE2 is the same.

[0050] Figure 5 Illustrated are a plurality of hybrid DCCB modules 500 connected in series according to aspects of the present disclosure.

[0051] Each hybrid DCCB module 500 includes the following electrical subsystems: energy dissipation branches 512a, 512b, 512c, 512d, current commutation branches 514a, 514b, 514c, 514d, and main branches 516a, 516b, 516c, 516d connected in parallel in a DC line 311. The DC line 311 can be a DC line or an HVDC line.

[0052] Each of the main branches 516a, 516b, 516c, 516d may include a mechanical switch 517a, 517b, 517c, 517d. Each mechanical switch 517a, 517b, 517c, 517d may require stored energy for its operation. One or more of the mechanical switches 517a, 517b, 517c, 517d may require or operate in conjunction with multiple electrical subsystems. One or more of the electrical subsystems may include an IGBT gate driver. One or more of the electrical subsystems may require power. The power of one or more of the electrical subsystems may be less than the power of one or more of the mechanical switches 517a, 517b, 517c, 517d.

[0053] The plurality of hybrid DCCB modules 500 are examples of a complete DCCB such that the voltage between the terminals of each subsystem or module is moderate (eg, in the range of 50-100 kV). For example, a DCCB may include ten hybrid DCCB modules 500.

[0054] Any one or more of the electrical subsystems 312, 314, 316, 412, 414, 416, 512a, 512b, 512c, 512d, 514a, 514b, 514c, 514d, 516a, 516b, 516c, or 516d may be at the potential of the HVDC line 311 (typically 500 kV). Similarly, the mechanical switches 317, 417, 517a, 517b, 517c, 517d may be at the potential of the HVDC line 311.

[0055] Any one or more of the electrical subsystems 312, 314, 316, 412, 414, 416, 512a, 512b, 512c, 512d, 514a, 514b, 514c, 514d, 516a, 516b, 516c, or 516d can be mounted on the bottom surface of one or more support insulators. Any one or more of the electrical subsystems 312, 314, 316, 412, 414, 416, 512a, 512b, 512c, 512d, 514a, 514b, 514c, 514d, 516a, 516b, 516c, or 516d can be suspended from a ceiling. The electrical subsystem can be suspended from a ceiling via one or more tension insulators.

[0056] The post insulator may be at least 4 meters. For a DC line of approximately 500 kV, the post insulator may be at least 4 meters. For a DC line of approximately 500 kV, the post insulator may be at least 4 meters. The tension insulator may be at least 4 meters. For a DC line of approximately 500 kV, the tension insulator may be at least 4 meters. For a DC line of approximately 500 kV, the tension insulator may be at least 4 meters.

[0057] Figure 6 Illustrated is a DCCB system 600 according to aspects of the present disclosure. The DCCB system 600 may be a mechanical arrangement of a DCCB.

[0058] The DCCB system 600 includes a DCCB 616 mounted on a support insulator 620. The support insulator 620 separates the DCCB 616 from a ground potential 670. The support insulator 620 can provide an insulating gap between the ground potential 670 and the electrical subsystems (e.g., live components) of the DCCB 616. The support insulator 620 can be a post insulator. The DCCB 616 can include one or more electrical subsystems. The DCCB 616 can include a main branch 616. The main branch 616 can include a mechanical switch 617. The DCCB 616 can be a hybrid DCCB module, such as those described above with respect to Figure 3 、 4 5. The DCCB 616 is connected via a DC line 311. The DC line 311 may be a HVDC line.

[0059] The DCCB 616 can be operated at the potential of the DC line 311. Operating the DCCB 616 often makes it very challenging to provide auxiliary power to the electrical subsystems from the ground. The mechanical switch 617 in the main current branch 616 is particularly challenging because it may need to be opened very quickly; for example, within a few milliseconds. Conventional methods of operating the mechanical switch 617, such as those used to operate mechanical switches in AC circuit breakers, are not fast enough. Methods used to operate mechanical switches in AC circuit breakers may include one or more of a mechanical operating lever, a spring, or a hydraulic system.

[0060] Mechanical switch 617 may use a high-performance electric actuator. The high-performance electric actuator may be a Thomson coil. The high-performance electric actuator may store several kilojoules of energy for operation. This energy storage may be implemented as a capacitor or storage capacitor. Other electrical subsystems may require auxiliary power, such as gate drivers for power semiconductor devices and control / communication printed circuit boards (PCBs).

[0061] The DCCB 616 may be a mechanical DCCB design. The DCCB 616 may use capacitor discharge to create an artificial current zero. The energy requirement for pre-charging the capacitor may be in the range of hundreds of kilojoules.

[0062] Figure 7 A DCCB system 700 according to aspects of the present disclosure is illustrated. The DCCB system 700 includes a DCCB 616 mounted on a support insulator 620. The DCCB 616 is connected via a DC line 311.

[0063] DCCB system 700 includes a DCCB 610. DCCB 610 includes a first mechanical switch 617 connected in series via a direct current (DC) line 311, which may be an HVDC line 311. DC line 311 can operate at a DC line potential. DCCB 610 can operate at the potential of DC line 311. DCCB 610 is mounted on a supporting insulator 620 to separate DCCB 610 from a ground potential 670 via an insulating gap.

[0064] DCCB system 700 includes an auxiliary power system 740. Auxiliary power system 740 includes an electric motor 742 and a generator 746. Generator 746 is elevated above ground and configured to operate at DC line potential. Electric motor 742 is configured to operate at ground potential 670. Electric motor 742 is operably coupled to generator 746 via a physical connection 744. Physical connection 744 is electrically isolated. Physical connection 744 may be a drive shaft 744. Drive shaft 744 may be electrically isolated.

[0065] Electric motor 742 is supplied at ground potential 670 and coupled to an insulated drive shaft 744, which spans the insulation gap between ground 670 and the live components of DCCB 616. The other end of drive shaft 744 is mechanically connected to a generator 746 at the potential of DC line 311. The output of this generator 746 is then used to pre-charge the energy storage system for the actuator of mechanical switch 617, for example, by arranging generator 746 as a synchronous AC generator coupled to a diode rectifier. In a second step, the stored energy is then used to provide electrical auxiliary power to the subsystems of DCCB 616. Figure 6 The electric motor 742 is shown positioned below the DCCB 616, with the drive shaft 744 extending vertically upward. The electric motor 742 can be mounted on the ceiling, with the drive shaft extending vertically downward. The electric motor 742 can also be mounted in some other grounded location, with the drive shaft 744 extending horizontally or at an angle. However, mounting the electric motor 742 on the floor may be too simplistic from a maintenance access perspective.

[0066] Electric motor 742 may be a DC motor. Electric motor 742 may be an AC induction motor. Electric motor 742 may be any other type of motor. Electric motor 742 may be capable of operating at variable speed to control the charging rate of the capacitor. Generator 746 may be a DC generator. Generator 746 may be a synchronous AC generator. Synchronous AC generators may be preferred for simplicity or reliability. Generator 746 may include permanent magnets for excitation. Generator 746 may be an AC generator.

[0067] The output of the generator 746 may be single phase. The output of the generator 746 may be multi-phase.

[0068] Figure 8 Illustrated is a DCCB system 800 according to aspects of the present disclosure.

[0069] DCCB system 800 includes DCCB 400. DCCB 400 includes a first mechanical switch 617 connected in series via a direct current (DC) line 311, which may be an HVDC line 311. DC line 311 may operate at a DC line potential. DCCB 400 operates at the potential of DC line 311. DCCB 400 may be mounted on a supporting insulator 620 to separate DCCB 400 from ground potential 670 via an insulating gap.

[0070] Auxiliary power system 740 includes an electric motor 742 and a generator 746. Generator 746 is elevated above ground level and configured to operate at DC line potential. Electric motor 742 is configured to operate at ground potential 670. Electric motor 742 is operably coupled to generator 746 via a physical connection 744. Physical connection 744 is electrically isolated. Physical connection 744 may be a drive shaft 744. Drive shaft 744 may be electrically isolated.

[0071] The DCCB 400 may be a hybrid DCCB module, which is similar to the above-mentioned Figure 4 The auxiliary power system 740 is the same as that described above with respect to the hybrid DCCB module 400. Figure 7 The auxiliary power system 740 described is the same.

[0072] The output of the generator 746 can be coupled to a diode bridge rectifier 841 to supply DC power to a storage capacitor 843. The storage capacitor 843 can be discharged to provide power to an actuator 845 for switching the mechanical switch 617. A typical alternator from a car can produce 1-2 kW, which can be sufficient to recharge the storage capacitor 843 in a few seconds.

[0073] The auxiliary power system 740 may operate for a predetermined duration. The auxiliary power system 740 may not operate continuously. The maximum power from the auxiliary power system 740 may rarely last only for a short time (a few seconds). The auxiliary power system 740 may operate after the DCCB 400 has been operated. Normal operation of the DCCB 400 may include operating the DCCB 400 once or twice per year. The auxiliary power system 740 may be operated intermittently or at a low speed to maximize its lifespan.

[0074] The auxiliary power system 740 may include two or more sets of electric motors 742 and generators 746. For reliability reasons, two or more redundant motor-generator sets may be provided so that even if one motor-generator set fails, the DCCB 400 can still be recharged.

[0075] Figure 9 Illustrated is a DCCB system 900 according to aspects of the present disclosure.

[0076] DCCB system 900 includes DCCB 910. DCCB 910 is connected via a direct current (DC) line 311, which may be an HVDC line 311. DC line 311 may operate at a DC line potential. DCCB 910 operates at the potential of DC line 311. DCCB 910 is mounted on a supporting insulator 620 to separate DCCB 910 from ground potential 670 via an insulating gap.

[0077] The DCCB 910 may include a first interruption unit 617a and a second interruption unit 617b connected in series. The first interruption unit 617a may be a mechanical switch. The second interruption unit 617b may be a mechanical switch.

[0078] The DCCB 910 includes an auxiliary power system 940; which may be similar to that described above with respect to Figure 7 and 8 Auxiliary power system 740 is described.

[0079] The auxiliary power system 940 includes an electric motor 942 , a first generator 946 a , and a second generator 946 b .

[0080] The first generator 946a is arranged to supply power to the first interruption unit 917a.The second generator 946b is arranged to supply power to the second interruption unit 917b.

[0081] The first generator 946a is elevated above the ground and is configured to operate at a first electrical potential. The second generator 946b is elevated above the ground and is configured to operate at a second electrical potential. The first interruption unit 617a can operate at a first DC line potential. The second interruption unit 617b can operate at a second DC line potential.

[0082] The first potential may be a first DC line potential. The second potential may be a second DC line potential. The first potential may be different from the second potential.

[0083] The electric motor 942 is configured to operate at ground potential 670. The electric motor 942 is operably coupled to a first generator 946a via a first physical connection 944a. The electric motor 942 is also operably coupled to a second generator 946b via a second physical connection 944b. The first physical connection 944a and the second physical connection 944b are electrically isolated.

[0084] The electric motor 942 may be connected to a first generator 946a via a gear arrangement.The electric motor 942 may be connected to a second generator 946b via a gear arrangement.

[0085] Figure 10 Illustrated is a DCCB system 1000 according to aspects of the present disclosure.

[0086] DCCB system 1000 includes DCCB 1010. DCCB 1010 is connected via a direct current (DC) line 311, which may be an HVDC line 311. DC line 311 may operate at a DC line potential. DCCB 1010 operates at the potential of DC line 311. DCCB 1010 is mounted on a supporting insulator 620 to separate DCCB 1010 from ground potential 670 via an insulating gap.

[0087] The DCCB 1010 may include a first interruption unit 1017a, a second interruption unit 1017b, and a third interruption unit 1017c connected in series. The first interruption unit 1017a may be a mechanical switch. The second interruption unit 1017b may be a mechanical switch. The third interruption unit 1017c may be a mechanical switch.

[0088] DCCB 1010 includes an auxiliary power system 1040; which may be similar to that described above with respect to Figure 7 、 8 9. The auxiliary power system 1040 includes an electric motor 1042, a first generator 1046a, a second generator 1046b, and a third generator 1046c.

[0089] The first generator 1046a is arranged to supply power to the first interruption unit 1017a. The second generator 1046b is arranged to supply power to the second interruption unit 1017b. The third generator 1046c is arranged to supply power to the third interruption unit 1017c.

[0090] The first generator 1046a is elevated above the ground and is configured to operate at a first electrical potential. The second generator 1046b is elevated above the ground and is configured to operate at a second electrical potential. The third generator 1046c is elevated above the ground and is configured to operate at a third electrical potential. The first interruption unit 1017a can operate at a first DC line potential. The second interruption unit 1017b can operate at a second DC line potential. The third interruption unit 1017b can operate at a third DC line potential.

[0091] The first potential may be a first DC line potential. The second potential may be a second DC line potential. The third potential may be a third DC line potential.

[0092] In the normally closed position of the DCCB 1010 , the first DC link potential, the second DC link potential, and the third DC link potential may be substantially equal.

[0093] After operation of DCCB 1010, the first DC line potential, the second DC line potential, and the third DC line potential may be significantly different. Operation of DCCB 1010 may involve opening DCCB 1010. Operation of DCCB 1010 may involve opening and then closing DCCB 1010. Operation of DCCB 1010 may involve clearing a fault. For example, the first potential may be different from the second potential, the first potential may be different from the third potential, and the second potential may be different from the third potential.

[0094] Electric motor 1042 is configured to operate at ground potential 670. Electric motor 1042 is operably coupled to first generator 1046a via first physical connection 1044a. Electric motor 1042 is also operably coupled to second generator 1046b via second physical connection 1044b. Electric motor 1042 is also operably coupled to third generator 1046c via third physical connection 1044c. First physical connection 1044a, second physical connection 1044b, and third physical connection 1044c are electrically isolated. First physical connection 1044a is connected to second physical connection 1044b and third physical connection 1044c via gear arrangement 1041.

[0095] Figure 11 Illustrated is a DCCB system 1100 according to aspects of the present disclosure.

[0096] The DCCB system 1100 includes a DCCB 1110. The DCCB 1110 may be a hybrid DCCB, which may be similar to the DCCB described above. Figure 4 and 8 A hybrid DCCB 400 is described.

[0097] The DCCB 1110 includes the following electrical subsystems: an energy dissipation branch 1112, a current commutation branch 1114, and a main branch 1116, which are connected in parallel in the DC line 311. The DC line 311 may be an HVDC line.

[0098] The energy dissipation branch 1112 may include a varistor. The main conduction branch 1116 may include a mechanical switch 617 and a first power electronic switch (PE1). The current switching branch 1114 may include a second power electronic switch (PE2). PE1 and PE2 may be connected as described above. Figure 3 The description of PE1 and PE2 is the same.

[0099] DCCB 1110 may include several (e.g., ten) mechanical switches 617, each requiring stored energy for its operation, as well as hundreds of other subsystems (e.g., IGBT gate drivers) that require smaller amounts of power. While all of these may be at the same potential (the potential of DC line 311) during normal operation, within the few milliseconds that DCCB 1110 is operating, the two main terminals of the DCCB may be at completely different potentials. For example, one end may be grounded (via a fault), while the other end is at 800 kV relative to ground. Consequently, all of these different subsystems may be insulated not only from ground but also from each other.

[0100] The DCCB system 1100 divides the problem of supplying energy to the subsystems of the DCCB 1110 into two parts: primary energy transmission from ground across the very high potential difference present in normal operation, and secondary energy distribution within the DCCB 1110 (or within each module of the DCCB 1110). The means of energy transmission / distribution between these two parts may be different.

[0101] An auxiliary power system 1140 may be used in the first phase. The auxiliary power system 1140 may include an isolation transformer to provide power across this high voltage isolation barrier. However, this can be very difficult in practice because of the very large voltages (e.g., 500 kV) that are constantly present. Even if designing an isolation transformer that will withstand this voltage for a short period of time is not particularly difficult, designing and manufacturing an isolation transformer for long-term reliable operation can be much more difficult. A significant problem is "partial discharge," in which small-scale discharges repeatedly occur in the insulation material, causing gradual degradation and eventual failure.

[0102] The auxiliary power system 1140 may include one or more of optical power supply, use of high frequency circulating current via capacitive coupling of high voltage capacitors, or pneumatic power supply. The auxiliary power system 1140 may include a motor generator set in which a motor at ground potential is coupled to an insulated drive shaft and thereby coupled to one or more generators at the live potential of the DCCB. Such an auxiliary power system 1140 may be similar to the one described above with respect to Figure 7 、 8 , 9 or 10 described in the auxiliary power system 740, 940 or 1040 is the same or similar.

[0103] Auxiliary power system 1140 may include an electric motor and a generator. The generator may be elevated above ground level and configured to operate at DC line 311 potential. The electric motor may be configured to operate at ground potential 670. The electric motor may be operably coupled to the generator via a physical connection. The physical connection may be electrically isolated. The physical connection may be a drive shaft. The drive shaft may be electrically isolated.

[0104] The generator(s) may be synchronous AC generators, the output of which may be coupled via a diode rectifier and used to provide charging power to the storage capacitor 841 of the actuator 845 of the DCCB mechanical switch 617 .

[0105] Thereafter, storage capacitor 841 serves as the energy source for the second-stage energy distribution system. This takes the form of an inverter 1147 connected across storage capacitor 841, which drives a high-frequency current (e.g., in the range of 1 kHz to 100 kHz) through a wire loop 1149. This wire loop 1149 passes through a plurality of current transformers (CTs), each of which provides isolated electrical power to one of the other subsystems of DCCB 1110, such as an IGBT gate driver. This system is effectively a type of isolation transformer.

[0106] An isolation transformer may be impractical for providing primary energy transfer from ground potential 670 to the auxiliary power system 1140 due to the difficulty in designing and manufacturing the isolation transformer to withstand the sustained high voltage present across this gap. However, one or more isolation transformers can be used in the second (distribution) stage because, first, there is no sustained voltage between the high-frequency current loop and the CT secondary winding; instead, only short-term (pulse) voltages are present, making the design of the insulation system much simpler. Second, the DCCB 1110 can be divided into several modules connected in series so that within each module, the peak voltage experienced between the wire loop 1149 (CT primary winding) and the CT secondary winding is only tens of kV.

[0107] In some examples, where the DCCB 1110 includes multiple modules connected in series, a separate generator and diode rectifier may be provided for charging the storage capacitor of each mechanical switch and driven via a single motor and drive shaft and gear arrangement (similar to Figure 9 and 10 as shown in ).

[0108] Figure 12 A transformer 1200 according to aspects of the present disclosure is illustrated.

[0109] The transformer 1200 may be as described above with respect to Figure 11 The transformer 1200 includes a portion of the isolation transformer that forms a wire loop (note that the rest of the loop is not shown). Figure 12 ) of the wire 1249, the wire loop can be the same as that described above Figure 11 The wire loop 1149 described is the same or similar.

[0110] The wire loop 1249 may include a primary conductor 1270. The wire loop may include an insulator 1271. The wire loop may not include an insulator 1271.

[0111] Wire loop 1249 passes through a first current transformer 1282 and a second current transformer 1284. First current transformer 1282 provides isolated electrical power to a first electronics board 1283 that is part of a first electrical subsystem of a DCCB (such as DCCB 1110), for example, to a first IGBT gate driver. Second current transformer 1284 provides isolated electrical power to a second electronics board 1285 that is part of a second electrical subsystem of a DCCB (such as DCCB 1110), for example, to a second IGBT gate driver.

[0112] Figure 13 A flow chart illustrating a method 1300 for operating a DC circuit breaker according to aspects of the present disclosure is provided. Method 1300 can be a method of operating a DC circuit breaker to interrupt a DC current flowing through a DC line, wherein the DC line comprises a first potential relative to ground potential and is elevated above ground to provide an electrical isolation gap. Operations of the method can be implemented by a DCCB system as described herein. In some implementations, the DCCB system can execute a set of instructions to control functional elements of the DCCB system to perform the described functions.

[0113] The first step 1302 includes converting the received energy into electrical energy at a first potential by a first generator, the electrical energy being used to power one or more electrical subsystems, wherein the one or more electrical subsystems and the first generator are elevated above the ground and operate at the first potential. The operations of step 1302 can be performed according to the examples described herein. In some implementations, aspects of the operations of step 1302 can be performed as described in reference to Figures 7 to 12 Any of the described DCCB systems can be implemented.

[0114] The second step 1304 includes generating the received energy using an electric motor operating at ground potential, wherein the electric motor is operatively coupled to the first generator via a physical connection, wherein the physical connection is electrically isolated. The operations of step 1304 can be performed according to the examples described herein. In some implementations, aspects of the operations of step 1304 can be performed as described with reference to Figures 7 to 12 Any of the described DCCB systems can be implemented.

[0115] Throughout this specification, reference to an example or similar language of a particular method or apparatus means that the particular feature, structure, or characteristic described in conjunction with the example is included in at least one implementation of the method and apparatus described herein. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms "a," "an," and "the" also mean "one or more," unless expressly specified otherwise.

[0116] As used herein, a list with the conjunction "and / or" includes any single item in the list or a combination of items in the list. For example, a list of A, B, and / or C includes only A, only B, only C, a combination of A and B, a combination of B and C, a combination of A and C, or a combination of A, B, and C. As used herein, a list using the term "one or more of..." includes any single item in the list or a combination of items in the list. For example, one or more of A, B, and C includes only A, only B, only C, a combination of A and B, a combination of B and C, a combination of A and C, or a combination of A, B, and C. As used herein, a list using the term "one of..." includes one and only one of any single item in the list. For example, "one of A, B, and C" includes only A, only B, or only C, but not a combination of A, B, and C. As used herein, "a member selected from the group consisting of A, B, and C" includes one and only one of A, B, or C, but not a combination of A, B, and C. As used herein, "a member selected from the group consisting of A, B, and C, and combinations thereof" includes only A, only B, only C, a combination of A and B, a combination of B and C, a combination of A and C, or a combination of A, B, and C.

[0117] Aspects of the disclosed methods and apparatus are described with reference to schematic flow charts and / or schematic block diagrams of methods, apparatus, systems, and program products. It will be understood that each block of the schematic flow charts and / or schematic block diagrams, as well as combinations of blocks in the schematic flow charts and / or schematic block diagrams, can be implemented by code. This code can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, such that instructions executed by the processor of the computer or other programmable data processing device create components for implementing the functions / actions specified in the schematic flow charts and / or schematic block diagrams.

[0118] The schematic flowcharts and / or schematic block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of devices, systems, methods, and program products. In this regard, each block in the schematic flowcharts and / or schematic block diagrams may represent a module, segment, or portion of code, which includes one or more executable instructions of the code for implementing (one or more) specified logical functions.

[0119] It will be appreciated that the numerical values recited herein are intended merely to help illustrate the operation of the invention and may vary depending on the requirements of a given power delivery network, its components, or power delivery application.

[0120] The listing or discussion of an apparently prior-published document or apparently prior-published information in this specification should not necessarily be taken as an admission that the document or information is part of the state of the art or is common general knowledge.

[0121] Unless the context dictates otherwise, preferences and options for a given aspect, feature or parameter of the invention should be considered disclosed in conjunction with any and all preferences and options for all other aspects, features and parameters of the invention.

[0122] The disclosure herein also provides a DC circuit breaker system operable to interrupt a DC current flowing through a DC line, wherein the DC line has a first electrical potential relative to ground potential and is elevated above the ground to provide an electrically insulating gap, the DC circuit breaker system comprising: one or more electrical subsystems elevated above the ground and configured to operate at the first electrical potential; a first generator elevated above the ground and configured to operate at the first electrical potential, wherein the first generator is arranged to convert received energy into electrical energy at the first electrical potential, the electrical energy being used to power the one or more electrical subsystems; and an electric motor for generating the received energy, wherein the electric motor is configured to operate at ground potential and is operably coupled to the first generator via a physical connection, wherein the physical connection is electrically isolated.

[0123] Such a DC breaker system tends to be simpler and more cost-effective than prior art DC breakers.

[0124] The physical connection may be sufficiently electrically insulating to withstand the potential difference between the first potential and ground potential.

[0125] The DC circuit breaker system may include a DC circuit breaker. The DC circuit breaker may include one or more electrical subsystems. The DC circuit breaker may be a hybrid DC circuit breaker. The DC circuit breaker may be a mechanical DC circuit breaker.

[0126] An electrical isolation gap may be between a DC line and ground. An electrical isolation gap may be between a DC line and an object on the ground.

[0127] The DC line may be a high voltage DC line.The first potential may be approximately 500 kV.

[0128] The DC circuit breaker system may include a support insulator. The DC circuit breaker system may include a suspension insulator. The DC circuit breaker may be mounted on the bottom surface of the support insulator. The DC circuit breaker may be mounted on a ceiling and supported by the suspension insulator.

[0129] At least one of the one or more electrical subsystems may be mounted on a bottom surface of the support insulator. At least one of the one or more electrical subsystems may be mounted on a ceiling and supported by the suspension insulator.

[0130] At least one of the one or more electrical subsystems may be a mechanical switch, a gate driver, or a printed circuit board. The gate driver may be part of a power semiconductor device. The printed circuit board may be used for control circuitry. The printed circuit board may be used for communication circuitry.

[0131] The first generator may be located at a first height. At least one of the one or more electrical subsystems may be located at a second height. The first height may be substantially the same as the second height.

[0132] The electric motor may be located on the ground. A physical connection may be arranged substantially vertically upwards from the electric motor to the first generator.

[0133] The electric motor may be located at a third height. The third height may be substantially the same as the first height. The physical connection may be arranged substantially horizontally from the third height to the first height. The third height may be higher than the first height. The physical connection may be arranged at an angle relative to the ground. The physical connection may be arranged substantially vertically downward from the electric motor to the first generator.

[0134] The electric motor may be configured to intermittently operate at maximum power.

[0135] The generator may be a DC generator. The generator may be a synchronous AC generator. The generator may include an AC generator.

[0136] The electric motor may include an air compressor.The electric motor may include a hydraulic pump.

[0137] The electrical energy may comprise a single phase.The electrical energy may comprise multiple phases.

[0138] The received energy may be mechanical energy. The received energy may be kinetic energy. The received energy may be kinetic energy or mechanical energy. The received energy may be non-electrical.

[0139] The DC circuit breaker may further comprise an energy storage system arranged to store electrical energy from the first generator.The energy storage system may comprise capacitors.

[0140] The first generator may include a synchronous AC generator. The synchronous AC generator may include permanent magnets for excitation. The synchronous AC generator may be coupled to a rectifier. The rectifier may be a diode rectifier. The rectifier may be a diode bridge rectifier. The rectifier may be configured to convert AC from the synchronous AC generator into DC.

[0141] The first generator may include a DC generator. The electric motor may be configured to generate the received energy at a variable rate. The first generator may be configured to generate electrical energy at a variable rate. The variable rate may be a variable rotational speed of the electric motor. The variable rate may be a variable air flow rate of the air compressor. The variable rate may be a variable hydraulic fluid flow rate of the hydraulic pump. The variable rate of the received energy may be determined by a desired charging rate of an energy storage system coupled to the generator. The variable rate of the received energy may be determined by a desired charging rate of a capacitor coupled to the generator.

[0142] At least one of the one or more subsystems may include an actuator for switching a mechanical switch from a closed state to an open state, or for switching the mechanical switch from an open state to a closed state. The mechanical switch may be in a main current branch of a DC circuit breaker. The mechanical switch may be operable to interrupt direct current flowing through a DC line. The mechanical switch may be operable to interrupt direct current flowing through the DC line by switching from a closed state to an open state. Electrical energy from a generator may be used to supply the actuator with electrical energy for switching the mechanical switch from a closed state to an open state.

[0143] The actuator may comprise a Thomson coil.

[0144] The physical connection may include a drive shaft.

[0145] The first generator may include an air turbine. The electric motor may include an air compressor. The physical connection may include an air duct. The first generator may include a water turbine. The electric motor may include a hydraulic pump. The physical connection may include a hydraulic duct.

[0146] The DC breaker system may further include one or more second generators coupled to the electric motor via a physical connection.

[0147] The DC circuit breaker may be a hybrid DC circuit breaker. The hybrid DC circuit breaker may include a main conducting branch through which current flows during normal operation (when the DCCB is closed). The hybrid DC circuit breaker may include an energy dissipating branch (surge arrester). The hybrid DC circuit breaker may include a current commutating branch whose function is to temporarily transfer current when the main conducting branch is open.

[0148] The first generator may further include an isolation transformer. The isolation transformer may be configured to convert electrical energy at the first potential into isolated electrical energy for the one or more electrical subsystems. The isolation transformer may include one or more of the following: an inverter, a storage capacitor, a conductor loop, or a current transformer (CT). The inverter may be connected across the storage capacitor to drive a high-frequency current through the conductor loop. The high-frequency current may be in the range of 1 kHz to 100 kHz. The conductor loop may pass through one or more current transformers (CT). Each of the one or more current transformers (CT) may be configured to provide isolated electrical energy to the one or more electrical subsystems.

[0149] A method of operating a DC circuit breaker system to interrupt direct current flowing through a DC line is provided, wherein the DC line comprises a first electrical potential relative to ground potential and is elevated above ground to provide an electrically insulating gap, the method comprising: converting received energy into electrical energy at the first electrical potential by a first generator, the electrical energy being used to power one or more electrical subsystems, wherein the one or more electrical subsystems and the first generator are elevated above ground and operated at the first electrical potential; and generating the received energy using an electric motor operating at ground potential, wherein the electric motor is operably coupled to the first generator via a physical connection, wherein the physical connection is electrically isolated.

[0150] Such a method of operating a DC circuit breaker system tends to be simpler and more cost-effective than prior art methods of operating a DC circuit breaker.

[0151] The method may further comprise storing electrical energy from the first generator in an energy storage system.The energy storage system may comprise a capacitor.

[0152] The first generator may include a synchronous AC generator. The synchronous AC generator may be coupled to a rectifier. The first generator may include a DC generator. The first generator may be configured to generate electrical energy at a variable rate.

[0153] At least one of the one or more electrical subsystems may include an actuator for switching the mechanical switch from a closed state to an open state or for switching the mechanical switch from an open state to a closed state. The actuator may include a Thomson coil.

[0154] The physical connection may include a drive shaft.

[0155] The first generator may include an air turbine, the electric motor may include an air compressor, and the physical connection may include an air duct. The first generator may include a water turbine, the electric motor may include a hydraulic pump, and the physical connection may include a hydraulic duct.

[0156] The method may further include coupling one or more second generators to the electric motor via a physical connection.

[0157] The first generator may further include an isolation transformer.

[0158] The present invention also provides a set of technical solutions, as follows.

[0159] Technical Solution 1. A DC circuit breaker system operable to interrupt a DC current flowing through a DC line, wherein the DC line has a first potential relative to ground potential and is elevated above ground to provide an electrical insulation gap, the DC circuit breaker system comprising:

[0160] one or more electrical subsystems elevated above ground level and configured to operate at the first electrical potential;

[0161] a first generator elevated above the ground and configured to operate at the first electrical potential, wherein the first generator is arranged to convert received energy into electrical energy at the first electrical potential, the electrical energy being used to power the one or more electrical subsystems; and

[0162] An electric motor for generating the received energy, wherein the electric motor is configured to operate at ground potential and is operatively coupled to the first generator via a physical connection, wherein the physical connection is electrically isolated.

[0163] Technical Solution 2. The DC circuit breaker system according to Technical Solution 1 further includes an energy storage system, which is arranged to store the electrical energy from the first generator.

[0164] Technical Solution 3. The DC circuit breaker system according to Technical Solution 2, wherein the energy storage system includes a capacitor.

[0165] Technical Solution 4. The DC circuit breaker system according to any of the preceding technical solutions, wherein the first generator comprises a synchronous AC generator.

[0166] Technical Solution 5. The DC circuit breaker system according to Technical Solution 4, wherein the synchronous AC generator is coupled to a rectifier.

[0167] Technical Solution 6. The DC circuit breaker system according to any one of Technical Solutions 1 to 3, wherein the first generator includes a DC generator.

[0168] Technical Solution 7. The DC circuit breaker system according to any of the preceding technical solutions, wherein the first generator is configured to generate the electrical energy at a variable rate.

[0169] Technical Solution 8. A DC circuit breaker system according to any of the foregoing technical solutions, wherein at least one of the one or more electrical subsystems includes an actuator for switching a mechanical switch from a closed state to an open state or for switching the mechanical switch from the open state to the closed state.

[0170] Technical Solution 9. The DC circuit breaker system according to Technical Solution 8, wherein the actuator includes a Thomson coil.

[0171] Technical Solution 10. The DC circuit breaker system according to any of the preceding technical solutions, wherein the physical connection includes a drive shaft.

[0172] Technical Solution 11. The DC circuit breaker system according to any one of Technical Solutions 1 to 9, wherein the first generator includes an air turbine, the electric motor includes an air compressor, and the physical connection includes an air duct.

[0173] Technical Solution 12. The DC circuit breaker system according to any one of Technical Solutions 1 to 9, wherein the first generator includes a turbine, the electric motor includes a hydraulic pump, and the physical connection includes a hydraulic pipeline.

[0174] Technical Solution 13. The DC circuit breaker system according to any of the preceding technical solutions further includes one or more second generators coupled to the electric motor via the physical connection.

[0175] Technical Solution 14. The DC circuit breaker system according to any of the foregoing technical solutions, wherein the first generator further includes an isolation transformer.

[0176] Technical Solution 15. A method of operating a DC circuit breaker system to interrupt a DC current flowing through a DC line, wherein the DC line comprises a first electrical potential relative to ground potential and is elevated above ground to provide an electrical insulation gap, the method comprising:

[0177] converting the received energy into electrical energy at the first electrical potential by a first generator, the electrical energy being used to power one or more electrical subsystems, wherein the one or more electrical subsystems and the first generator are elevated above ground and operated at the first electrical potential; and

[0178] The received energy is generated using an electric motor operating at ground potential, wherein the electric motor is operatively coupled to the first generator via a physical connection, wherein the physical connection is electrically isolated.

Claims

1. A DC circuit breaker system operable to interrupt a DC current flowing through a DC line, wherein: The DC line has a first potential relative to ground potential and is elevated above ground level to provide an electrical insulation gap, the DC circuit breaker system comprising: one or more electrical subsystems elevated above ground level and configured to operate at the first electrical potential; a first generator elevated above the ground and configured to operate at the first electrical potential, wherein the first generator is arranged to convert received energy into electrical energy at the first electrical potential, the electrical energy being used to power the one or more electrical subsystems; and An electric motor for generating the received energy, wherein the electric motor is configured to operate at ground potential and is operatively coupled to the first generator via a physical connection, wherein the physical connection is electrically isolated. 2 . The DC breaker system according to claim 1 , further comprising an energy storage system arranged to store the electrical energy from the first generator. 3 .

3. The DC circuit breaker system according to claim 2, wherein: The energy storage system includes a capacitor.

4. A DC circuit breaker system according to any preceding claim, wherein: The first generator comprises a synchronous alternator.

5. The DC circuit breaker system according to claim 4, wherein: The synchronous alternator is coupled to a rectifier.

6. The DC circuit breaker system according to any one of claims 1 to 3, wherein: The first generator includes a DC generator.

7. A DC circuit breaker system according to any preceding claim, wherein: The first generator is configured to generate the electrical energy at a variable rate.

8. A DC circuit breaker system according to any preceding claim, wherein: At least one of the one or more electrical subsystems includes an actuator for switching a mechanical switch from a closed state to an open state or for switching the mechanical switch from the open state to the closed state.

9. The DC circuit breaker system according to claim 8, wherein: The actuator includes a Thomson coil.

10. A DC circuit breaker system according to any preceding claim, wherein: The physical connection includes a drive shaft.

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