Electrical system for use in high-voltage DC multi-terminal switching stations

Abstract

This provides an electrical system for use in high-voltage DC multi-terminal switching stations. [Solution] The electrical system (300) comprises a first busbar (302a), a second busbar (302b), a resistor module (306) comprising one or more resistors and electrically coupled between the first busbar and the second busbar, a first switching element (307) electrically coupled between the first busbar and the second busbar and in series with the resistor module, and a plurality of power transmission media (304), wherein each power transmission media (304) of the plurality of power transmission media is electrically coupled to the first busbar via its respective second switching element (308), and each power transmission media of the plurality of power transmission media is electrically coupled to the second busbar via its respective third switching element (310).

Description

Technical Field

[0001] The subject matter of this specification generally relates to an electrical system for use in a high voltage direct current (HVDC) multiterminal switching station (MTSS).

Background Art

[0002] Introduction In recent years, the development of high voltage direct current (HVDC) power transmission systems has been increasingly shifting towards a multiterminal configuration in which multiple HVDC schemes are interconnected. Such a multiterminal HVDC system typically requires the implementation of a multiterminal switching station (MTSS) that functions as a hub for selectively connecting or disconnecting individual HVDC schemes.

[0003] When integrating a power transmission medium (e.g., an HVDC cable) into an active system, especially when the power transmission medium was previously grounded, it is usually necessary to first charge the power transmission medium before it can be connected. To control the inrush current during this charging process, a pre-insertion resistor (PIR) is typically used. The PIR limits the flow of current when the power transmission medium is charged from the MTSS. Similarly, when an HVDC converter goes online and is connected to the MTSS, charging via the PIR is usually performed even when the distance between the HVDC converter and the switching station is minimal.

[0004] For example, in scenarios where the power supply to the power transmission medium must be stopped during maintenance or fault removal, the power transmission medium must be safely discharged. This function is often performed by a dynamic braking system (DBS), but there are situations where the DBS cannot be utilized. In such cases, the PIR used for charging can be adapted for discharging as long as it is appropriately rated and equipped with an earth switch necessary to handle the discharging operation. [Overview of the project]

[0005] HVDC systems are being considered for use in urban areas and for connection to offshore wind farms that may only be accessible by floating offshore platforms. Therefore, the weight and volume of converter and switching stations may be subject to more stringent constraints than currently. The inventors realized that this could lead to the use of gas-insulated switchgear (GIS) instead of, for example, air-insulated switchgear (AIS) in some HVDC systems. The inventors further recognized that the need to dissipate the heat generated during charging or discharging via PIR may prevent the inclusion of the PIR device within the GIS itself.

[0006] It is desirable to provide an electrical system, such as MTSS, that mitigates these problems.

[0007] According to a first embodiment, an electrical system is provided comprising a first busbar, a second busbar, a resistor module comprising one or more resistors and electrically coupled between the first busbar and the second busbar, a first switching element electrically coupled between the first busbar and the second busbar and in series with the resistor module, and a plurality of power transmission media. Each of the plurality of power transmission media is electrically coupled to the first busbar via its respective second switching element. Each of the plurality of power transmission media is electrically coupled to the second busbar via its respective third switching element.

[0008] A resistor module may comprise multiple resistors and multiple switching elements, where each switching element is electrically coupled to one or more resistors. The multiple resistors may be selectively connected in series or parallel via the multiple switching elements.

[0009] A resistor module may include a first terminal electrically coupled to a first busbar and a second terminal electrically coupled to a second busbar. The electrical system may further include a fourth switching element electrically coupled to the first terminal. The first terminal may be configured to be selectively connected to ground through the fourth switching element.

[0010] A resistor module may include a first terminal electrically coupled to a first busbar and a second terminal electrically coupled to a second busbar. The electrical system may further include a fifth switching element electrically coupled to the second terminal. The second terminal may be configured to be selectively connected to ground through the fifth switching element.

[0011] Each of the multiple power transmission media may have terminals electrically coupled to a first busbar. The electrical system may further include a plurality of sixth switching elements. For each of the multiple power transmission media, the terminals of the power transmission media may be configured to be selectively connected to earth through their respective sixth switching elements.

[0012] The first busbar may include a first busbar terminal. The electrical system may further include a seventh switching element electrically coupled to the first busbar terminal. The first busbar terminal may be configured to be selectively connected to earth through the seventh switching element.

[0013] The electrical system may further include a further resistor module comprising one or more additional resistors and electrically coupled between a first busbar and a second busbar, and a further switching element electrically coupled between the first busbar and the second busbar and in series with the further resistor module.

[0014] The electrical system may further comprise an enclosure. A first busbar, a second busbar, each first switching element, and each second switching element may be enclosed within the enclosure. Resistor modules may be located outside the enclosure. The enclosure may house a gas-insulated switchgear (GIS) system.

[0015] The electrical system may be a multi-terminal switching station (MTSS). The electrical system may be a high-voltage direct current (HVDC) MTSS.

[0016] In a further embodiment, a first method is provided for operating an electrical system of any prior embodiment. The first method is for charging a first power transmission medium of a plurality of power transmission mediums. The first method includes opening a sixth switching element of the first power transmission medium, opening a fifth switching element, opening a fourth switching element, closing the first switching element, and closing a third switching element of the first power transmission medium, thereby charging the first power transmission medium via a resistor module.

[0017] The first method may further include closing a second switching element of a first power transmission medium, opening a third switching element of the first power transmission medium, and opening a first switching element.

[0018] The first method may further include closing a fourth switching element and / or closing a fifth switching element.

[0019] In a further embodiment, a second method is provided for operating an electrical system of any prior embodiment. The second method is for discharging a first power transmission medium of a plurality of power transmission mediums. The second method includes closing a fourth switching element and opening the second and third switching elements of the first power transmission medium to isolate the first power transmission medium from the first and second busbars, opening a fifth switching element and closing the third switching element of the first power transmission medium to discharge the first power transmission medium to ground via a resistor module.

[0020] The second method may further include closing the sixth switching element of the first power transmission medium, opening the third switching element of the first power transmission medium, and closing the fifth switching element.

[0021] In a further embodiment, a third switching element method is provided for operating an electrical system of any prior embodiment. The third method is for electrically isolating a first power transmission medium of a plurality of power transmission mediums from a first busbar and a second busbar. The third method includes opening a second switching element of the first power transmission medium and opening a third switching element of the first power transmission medium.

[0022] In a further embodiment, a fourth method is provided for operating an electrical system of any prior embodiment. The fourth method is for electrically isolating the first busbar. The fourth method includes opening each second switching element, opening each third switching element, and closing a seventh switching element with the second and third switching elements open, thereby connecting the first busbar to earth.

[0023] It will be understood that certain features of different embodiments share the technical effects and benefits of corresponding features of other embodiments of the present invention.

[0024] The use of terms such as "first" and "second" is only intended to help distinguish similar features and is understood not to be intended to indicate the relative importance of one feature over another, unless otherwise specified.

[0025] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples, and alternatives described in the previous paragraph, as well as in the claims and / or the following description and drawings, particularly their individual features, can be interpreted independently or in any combination. That is, all embodiments and all features of any embodiment can be combined in any way and / or combination, provided that such features are not mutually incompatible.

[0026] Here, embodiments of the present invention will be described by way of example only, with reference to the accompanying drawings.

Brief Description of the Drawings

[0027] [Figure 1] It is a schematic diagram showing a first example of a conventional electrical system. [Figure 2] It is a schematic diagram showing a second example of a conventional electrical system. [Figure 3] It is a diagram showing an electrical system for use in HVDC MTSS. [Figure 4] It is a first table showing the bay discharge process for an electrical system. [Figure 5] It is a second table showing the bay charging process for an electrical system. [Figure 6] It is a third table showing the bay insulation process for an electrical system. [Figure 7] It is a fourth table showing the busbar insulation process for an electrical system.

Modes for Carrying Out the Invention

[0028] Figure 1 is a schematic diagram showing a first example of a conventional electrical system 100 for use in MTSS. The first electrical system 100 is useful for understanding the present invention. Further details of the first electrical system 100 can be found in SHE Transmission, D15.1 Recommendations for Specifying DC GIS Systems, PROMOTioN-Progress on Meshed HVDC Offshore, 2018, the contents of which are incorporated herein by reference.

[0029] In this example, the first electrical system 100 comprises two busbars, namely a first busbar 102a for the positive terminal of the system and a second busbar 102b for the negative terminal of the system.

[0030] The first electrical system 100 further comprises a plurality of power transmission media 104a, 104b (for example, power supply units for an HVDC converter, or HVDC cables). Each of the power transmission media 104a, 104b is coupled to a first bus bar 102a or a second bus bar 102b via their respective PIRs 106a, 106b, their respective first switching elements 108a, 108b, and their respective second switching elements 110a, 110b.

[0031] For each power transmission medium 104a, 104b, the respective first switching elements 108a, 108b are electrically connected in series between the power transmission medium 104a, 104b and the busbars 102a, 102b to which the power transmission mediums 104a, 104b are coupled. For each power transmission medium 104a, 104b, the respective first switching elements 108a, 108b are configured to switchably connect or disconnect the power transmission medium 104a, 104b to the busbars 102a, 102b to which the power transmission mediums 104a, 104b are coupled.

[0032] For each power transmission medium 104a, 104b, the respective PIR 106a, 106b is electrically coupled in series between the power transmission medium 104a, 104b and the busbars 102a, 102b to which the power transmission medium 104a, 104b is coupled. Each PIR 106a, 106b is arranged in parallel with the respective second switching elements 110a, 110b. The second switching elements 110a, 110b are configured to either switchably bypass the PIR 106a, 106b or to connect the PIR 106a, 106b in series between the power transmission medium 104a, 104b and the busbars 102a, 102b.

[0033] In this example, the first exemplary electrical system 100 further comprises a plurality of earth switches 112a, 112b. Each pair of earth switches 112a, 112b is coupled to each PIR 106a, 106b, one on each side of the PIR 106a, 106b. Each earth switch 112a, 112b is configured to switchably connect or disconnect the terminals of the connected PIR 106a, 106b to earth. The earth switches 112a, 112b may be used to both enable safe maintenance of the PIR 106a, 106b while the MTSS is operating with the hub busbars 102a, 102b at high voltage, and to provide an earthing circuit for discharging the transmission medium 104a, 104b through the PIR 106a, 106b.

[0034] Figure 2 is a schematic diagram showing a second example of a conventional electrical system 200 for use in MTSS. The second electrical system 200 is useful for understanding the present invention.

[0035] In this example, the second electrical system 200 comprises a busbar 202 and a plurality of power transmission media 204 (e.g., power supply units for an HVDC converter, or HVDC cables). Each of the power transmission media 204 is coupled to the busbar 202 via its respective PIR 206, each first switching element 208, each second switching element 210, and each third switching element 211.

[0036] The second electrical system 200 has the same configuration as the first electrical system 100.

[0037] For each power transmission medium 204, each first switching element 208 is electrically connected in series between the power transmission medium 204 and the busbar 202. For each power transmission medium 204, each first switching element 208 is configured to switchably connect the power transmission medium 204 to the busbar 202 or disconnect it from the busbar 202. In this example, the first switching element 208 is connected in series between the busbar 202 and the second switching element 210.

[0038] For each power transmission medium 204, each PIR 206 is electrically connected in series between the power transmission medium 204 and the busbar 202. Each PIR 206 is arranged in parallel with each of the second switching elements 210. The second switching elements 210 are configured to either switchably bypass the PIR 206 or connect the PIR 206 in series between the power transmission medium 204 and the busbar 202. In this example, the second switching element 210 is connected in series between the first switching element 208 and the third switching element 211.

[0039] For each power transmission medium 204, each third switching element 211 is electrically connected in series between the power transmission medium 204 and the busbar 202. In this example, the third switching element 211 is connected in series between the second switching element 210 and the power transmission medium 204. The third switching element 211 and the first switching element 208 may be used to electrically isolate the PIR 206 connected between them from the busbar 202 and the power transmission medium 204 for safety during PIR maintenance.

[0040] In this example, the second exemplary electrical system 200 further comprises a plurality of earth switches 212a, 212b. Each pair of earth switches 212a, 212b is coupled to each second switching element 210, one on each side of the second switching element 210. Specifically, the first earth switch 212a is connected to the first terminal on the first side of the second switching element 210, and the second earth switch 212b is connected to the second terminal on the second side of the second switching element 210. The first earth switch 212a is on the same side of the second switching element 210 as the first switching element 208. The second earth switch 212b is on the same side of the second switching element 210 as the third switching element 211. Each earth switch 212a, 212b is configured to switchably connect or disconnect the terminal of the connected second switching element 210 to earth.

[0041] In this example, the second electrical system 200 is implemented in a GIS application. Specifically, the second electrical system 200 comprises a housing or enclosure 214 in which a pressurized gas, typically sulfur hexafluoride (SF6), is used as the insulating medium. This tends to allow HVDC systems to manage high voltages in confined spaces, which is particularly important in urban environments or offshore platforms.

[0042] In this example, the PIR206 is located outside the enclosure 214, i.e., outside the GIS. This is to facilitate the dissipation of heat generated during charging or discharging through the PIR206, which may be difficult or impossible if the PIR206 were located inside the enclosure 214. In this example, the electrical connections connecting each PIR206 to the electrical circuits of the second electrical system 200 pass through the walls of the enclosure 214 via each pair of bushings 216. In other words, each PIR206 is connected to the GIS using two bushings 216. The bushings may also be insulating conductors used to join through the barrier (i.e., the enclosure 214) to prevent or resist leakage or discharge. The bushings can be thought of as interfaces or gaskets. The bushings 216 can create an airtight seal around the electrical connections passing through the walls of the enclosure 214, thereby preventing or resisting gas leakage from the GIS.

[0043] In this example, each transmission medium 204 extends through the wall of the enclosure 214 via its respective additional bushing 218. The additional bushing 218 creates an airtight seal around the transmission medium 204 as it passes through the wall of the enclosure 214, thereby preventing or counteracting gas leakage from the GIS.

[0044] In this example, a given power transmission medium 204 can be charged from the busbar 202 by closing its first switching element 208 and its third switching element 211, but opening its second switching element 210. This connects the power transmission medium 204 to the busbar 202 via the PIR 206, thereby restricting the flow of current to the power transmission medium 204.

[0045] In this example, a given power transmission medium 204 can be discharged by opening its first switching element 208 and its third switching element 211 to disconnect the power transmission medium 204 from the busbar 202, opening the second switching element 210, closing the first earth switch 212a, and then closing the third switching element 211, thereby connecting the power transmission medium 204 to earth via the PIR 206.

[0046] The design of the second electrical system 200 uses a separate PIR 206 for each of the power transmission media 204. When a new power supply unit / power transmission media is added to station 200, a new PIR 206 must be included for that new power transmission media 204.

[0047] Furthermore, to support the charging and discharging functions of the circuit, three earth switches and three disconnectors may be implemented for each power supply unit. Specifically, a second earth switch 212b and a third switching element 211 may be used for isolation and maintenance. After discharge, the second earth switch 212b may be closed to connect the power supply unit directly to earth. Then, the third switching element 211 may be used to isolate the power supply unit from the bay (for example, for PIR maintenance), and a further earth switch 213 may be closed to maintain a direct earth connection to the power supply unit.

[0048] In a GIS system, such as the second electrical system 200 shown in Figure 2, at least two bushings are used to connect each external PIR 206 to the GIS.

[0049] Next, an embodiment of the improved electrical system will be described.

[0050] Figure 3 is a schematic diagram showing one embodiment of the electrical system 300. In this embodiment, the electrical system 300 is an MTSS, in particular an HVDC MTSS, or an MTSS, in particular an HVDC MTSS for use. The MTSS may be a modular design, for example, that allows a new HVDC system to be connected via a new bay without significant modifications to the original station.

[0051] In this example, the electrical system 300 comprises a first busbar 302a, a second busbar 302b, and a plurality of power transmission media 304 (for example, power supply units for an HVDC converter, or HVDC cables).

[0052] The electrical system 300 further comprises a resistor module 306 having one or more resistors which are PIRs in this embodiment. The resistor module 306 is electrically coupled between the first busbar 302a and the second busbar 302b.

[0053] The electrical system 300 further comprises a first switching element 307, for example, a first switch. The first switching element 307 is electrically coupled between a first busbar 302a and a second busbar 302b. The first switching element 307 is electrically connected in series with a resistor module 306 between the first busbar 302a and the second busbar 302b.

[0054] For each power transmission medium 304, each second switching element 308 (e.g., a second switch) is electrically coupled in series between the power transmission medium 304 and the first busbar 302a. Each second switching element 308 is configured to switchably connect the power transmission medium 304 to the first busbar 302a or disconnect it from the first busbar 302a.

[0055] For each power transmission medium 304, each third switching element 310 (e.g., a third switch) is electrically coupled in series between the power transmission medium 304 and the second busbar 302b. Each third switching element 310 is configured to switchably connect the power transmission medium 304 to the second busbar 302b or disconnect it from the second busbar 302b.

[0056] In some embodiments, the resistor module 306 comprises only a single resistor, i.e., a single PIR. However, in other embodiments, the resistor module 306 comprises multiple resistors (i.e., multiple PIRs) and multiple resistor module switches electrically coupled to the multiple resistors. The multiple resistors can be selectively connected in series or parallel configuration via the multiple resistor module switches. By controlling the resistor module switches, the configuration and overall resistance of the resistor module 306 can be changed. This tends to advantageously allow power supplies with different charge / discharge requirements (e.g., cables of significantly different lengths) to be charged / discharged. It also tends to allow multiple power supplies to be charged / discharged simultaneously.

[0057] In some embodiments, a resistor module may comprise a plurality of resistors, a plurality of switches, each electrically coupled to one or more of the resistors, and a control circuit operably coupled to the switches. The plurality of resistors can be selectively connected in series or parallel configuration via the plurality of switches. The control circuit is configured to dynamically switch one or more resistors in series or parallel configuration and out of series or parallel configuration based on operating requirements, thereby allowing the total resistance of the resistor module to be adjusted. The control circuit allows for the selective engagement of individual resistors to provide the desired overall resistance according to various load conditions.

[0058] The resistor module 306 includes a first terminal 312 electrically coupled to the first busbar 302a and a second terminal 314 electrically coupled to the second busbar 302b.

[0059] In this embodiment, the electrical system 300 further comprises a fourth switching element 316 (e.g., a fourth switch) electrically coupled to the first terminal 312 of the resistor module 306. The fourth switching element 316 is an earth switch connected between the first terminal 312 and ground.

[0060] In this embodiment, the electrical system 300 further comprises a fifth switching element 318 (e.g., a fifth switch) electrically coupled to the second terminal 314 of the resistor module 306. The fifth switching element 318 is an earth switch connected between the second terminal 314 and ground.

[0061] In this embodiment, each power transmission medium 304 has terminals electrically coupled to the first busbar 302a. The electrical system 300 further comprises a plurality of sixth switching elements 320 (i.e., sixth switches). For each power transmission medium 304, its terminals are configured to be selectively connected to earth through their respective sixth switching elements 320. The sixth switching elements 320 are earth switches, each connected between its respective power transmission medium 304 and earth.

[0062] In this embodiment, the first busbar 302a comprises a first busbar terminal 322. The electrical system further comprises a seventh switching element 324 (e.g., a seventh switch) electrically coupled to the first busbar terminal 322. The seventh switching element 324 is an earth switch connected between the first busbar terminal 322 and earth.

[0063] In this embodiment, the electrical system 300 is implemented in a GIS application. In particular, the electrical system 300 comprises a housing or enclosure 326 in which a pressurized gas, typically sulfur hexafluoride (SF6), is used as the insulating medium. This tends to allow the HVDC system to manage high voltages in a confined space, which is particularly important in urban environments or offshore platforms.

[0064] In this embodiment, the resistor module 306 is located outside the enclosure 326, i.e., outside the GIS. This is to facilitate the dissipation of heat generated during charging or discharging through the resistor module 306, which may be difficult or impossible if the resistor module 306 were located inside the enclosure 326. The electrical connection that connects the resistor module 306 to the electrical circuit of the electrical system 300 passes through the wall of the enclosure 326 via a pair of bushings 328. In other words, the resistor module 306 is connected to the GIS using two bushings 328. The bushings 328 create an airtight seal around the electrical connection passing through the wall of the enclosure 326, thereby preventing or counteracting gas leakage from the GIS.

[0065] In this embodiment, each transmission medium 304 extends through the wall of the enclosure 326 via its respective additional bushing 330. The additional bushing 330 creates an airtight seal around the transmission medium 304 as it passes through the wall of the enclosure 326, thereby preventing or counteracting gas leakage from the GIS.

[0066] Therefore, one embodiment of the electrical system 300 is provided.

[0067] Under the so-called "normal mode" of operation of the electrical system 300 when power is supplied to the transmission medium 304 via the electrical system 300, each transmission medium 304 is connected to the first busbar 302a and disconnected from the second busbar 302b. In particular, for a given transmission medium 304, the second switching element 308 connecting the transmission medium 304 to the first busbar 302a is closed, and the third switching element 310 connecting the transmission medium 304 to the second busbar 302b is open. The second busbar 302b is disconnected from the first busbar 302a by opening the first switching element 307. Also in this embodiment, when not in use, the resistor module 306 is grounded by closing either or both of the fourth switching element 316 and the fifth switching element 318. The sixth switching element 320 is also open. The seventh switching element 324 is also open.

[0068] In this "normal mode," one or more of the power transmission media 304 may be discharged.

[0069] Figure 4 shows Table 400, which illustrates a specific sequence of process steps in one embodiment of the process for discharging the power transmission medium 304.

[0070] In step 402, the power transmission medium 304 is operated in "normal mode" with the second switching element 308 closed and the third switching element 310 open. The first switching element 307 is open. The fourth switching element 316 and the fifth switching element 318 are closed.

[0071] In step 404, the power supply to the HVDC converter attached to the power transmission medium 304 is stopped.

[0072] In step 406, the second switching element 308 is opened. This electrically isolates the power transmission medium 304 from the first busbar 302a.

[0073] In step 408, the fifth switching element 318 is opened. This disconnects the ground connection of the second busbar 302b through the fifth switching element 318.

[0074] In step 410, the third switching element 310 is closed. This creates a path for current from the power transmission medium 304 to ground through the third switching element 310, the second busbar 302b, the resistor module 306, and the fourth switching element 316.

[0075] Therefore, the power transmission medium 304 is discharged to earth via the resistor module 306. The resistor module 306 limits or suppresses the flow of discharge current from the power transmission medium 304.

[0076] Optionally, in step 412, the sixth switching element 320 is closed. Thus, the discharged power transmission medium 304 is connected to ground via the sixth switching element 320.

[0077] Optionally, in step 414, the third switching element 310 is opened. Thus, the resistor module 306 is electrically isolated from the power transmission medium 304. Step 414 tends to allow other bays to utilize the resistor module 306 and the second busbar 302b without affecting, for example, a bay that is currently being discharged / maintained, and / or being affected by a bay that is currently being discharged / maintained.

[0078] Optionally, in step 416, the fifth switching element 318 is closed. Thus, the resistor module 306 is grounded. Step 416 tends to enable or facilitate maintenance of the resistor module 306 (e.g., PIR maintenance).

[0079] Accordingly, an embodiment of the process for discharging the power transmission medium 304 is provided. In this embodiment, in order to discharge the power transmission medium 304, the power transmission medium 304 is isolated from the first busbar 302a by opening the second switching element 308, and then discharged to ground via the resistor module 306 and the fourth switching module 316 by closing the third switching module 310. For this process, the third switching module 310 has current-passing capability. Since the resistor module 306 is disconnected from the first busbar 302a by the first switching element 307, this operation does not affect other power transmission mediums 304 connected to the hub.

[0080] From a state in which a given power transmission medium 304 has been discharged, for example, from the state of the electrical system 300 in step 416 of the process in Figure 4, the power transmission medium 304 can then be recharged.

[0081] Figure 5 shows a second Table 500 illustrating specific sequential process steps of one embodiment of the process for charging the power transmission medium 304.

[0082] In step 502, the power transmission medium 304 is in a discharged state and is isolated from the first busbar 302a and the second busbar 302b. In particular, both the second switching element 308 and the third switching element 310 are open. The first switching element 307 is open. The seventh switching element 324 is open. The fourth switching element 316 and the fifth switching element 318 are closed. The sixth switching element 320 is closed.

[0083] In step 504, the sixth switching element 320 is opened. As a result, the ground connection of the power transmission medium 304 via the sixth switching element 320 is released.

[0084] In step 506, the fifth switching element 318 is opened. Thus, the ground connection of the second busbar 302b via the fifth switching element 318 is released.

[0085] In step 508, the fourth switching element 316 is opened. Thus, the ground connection of the resistor module 306 is released.

[0086] In step 510, the first switching element 307 is closed. Thus, an electrical connection is established between the first busbar 302a and the second busbar 302b via the resistor module 306.

[0087] In step 512, the third switching element 310 is closed. Thus, the power transmission medium 304 is electrically connected to the second busbar 302b. As a result, the power transmission medium 304 is charged via the resistor module 306 and the secondary busbar 302b. The resistor module 306 limits or suppresses the flow of charging current to the power transmission medium 304.

[0088] Optionally, once the power transmission medium 304 is charged (for example, fully charged or charged to a threshold level), in step 514, the second switching element 308 is closed. This electrically connects the power transmission medium 304 directly to the primary busbar 302a.

[0089] Optionally, in step 516, the third switching element 310 is opened. This disconnects the power transmission medium 304 from the second busbar 302b and the resistor module 306.

[0090] Optionally, in step 518, the first switching element 307 is opened. This disconnects the first busbar 302a from the second busbar 302b and the resistor module 306.

[0091] Optionally, in step 520, the fourth switching element 316 is closed. This connects the resistor module 306 to ground via the fourth switching element 316. Thus, the resistor module 306 is grounded.

[0092] Optionally, in step 522, the fifth switching element 318 is closed. This connects the second busbar 302b to ground via the fifth switching element 318. Thus, the second busbar 302b is grounded. Advantageously, the second terminal 314 is grounded, which means that both terminals 312 and 314 of the resistor module 306 are grounded for safe maintenance of the resistor module 306.

[0093] Advantageously, some or all of steps 514-522 tend to return the switching station to "normal mode." This may allow maintenance of resistor module 306. This also frees up resistor module 306 for use by other power supply units, etc.

[0094] Accordingly, an embodiment of the process for charging the power transmission medium 304 is provided. In this embodiment, the power transmission medium 304 is charged by closing the first switching element 307, thereby connecting the first busbar 302a to the second busbar 302b via the resistor module 306. By leaving the second switching element 308 open, the direct connection of the power transmission medium 304 to the first busbar 302a is interrupted. All earth switches may be left open, and the third switching element 310 may be closed to connect the power transmission medium 304 to the second busbar 302b, allowing the first busbar 302a to charge the power transmission medium 304 via the resistor module 306.

[0095] In "normal mode," the first busbar 302a can be electrically isolated from the rest of the electrical system 300.

[0096] Figure 6 shows Table 600, which illustrates specific sequential process steps of one embodiment of the process for insulating the first busbar 302a.

[0097] In step 602, the power transmission medium 304 is operated in "normal mode" with the second switching element 308 closed and the third switching element 310 open. The first switching element 307 is open. The fourth switching element 316 and the fifth switching element 318 are closed.

[0098] In step 604, the second switching element 308 is opened. This electrically isolates the power transmission medium 304 from the first busbar 302a.

[0099] Therefore, the first busbar 302a is electrically isolated from the power transmission medium 304 and the second busbar 302b.

[0100] All bays / power supplies are isolated from the first busbar 302a in this manner (i.e., by opening their respective second switching elements 308). Alternatively, one or more bays / power supplies are discharged / grounded.

[0101] In step 606, the seventh switching element 324 is closed. Thus, the first busbar 302a is connected to ground via the seventh switching element 324.

[0102] One or more of the power transmission media 304 may still be operating independently and may still discharge through the second busbar 302b, the resistor module 306, and the fourth switching element 316 while the first busbar 302a remains isolated and grounded.

[0103] Therefore, an embodiment of the process for insulating the first busbar 302a is provided.

[0104] In "normal mode," the power transmission medium 304 can be electrically isolated from the rest of the electrical system 300.

[0105] Figure 7 shows Table 700, the fourth table, illustrating specific sequential process steps of one embodiment of the process for isolating the power transmission medium 304 from the GIS.

[0106] In step 702, the power transmission medium 304 is operated in "normal mode" with the second switching element 308 closed and the third switching element 310 open. The first switching element 307 is open. The fourth switching element 316 and the fifth switching element 318 are closed.

[0107] In step 704, the second switching element 308 is opened. This electrically isolates the power transmission medium 304 from the first bus bar 302a. Thus, the power transmission medium 304 is isolated from both the first bus bar 302a and the second bus bar 302b.

[0108] Therefore, one embodiment of the process for insulating the power transmission medium 304 is provided.

[0109] The electrical system 300 described above tends to have the advantage of reducing the complexity and number of components used for each power supply / transmission medium of the station compared to conventional systems 100, 200. In particular, the electrical system can individually charge or discharge any of the power supply units 304 using a single common resistor module 306 (i.e., one or more PIRs). This tends to be achieved by using a second busbar 302b connected to a first busbar via the resistor module 306, a switching element 307, and ground circuits 316, 318.

[0110] Advantageously, by placing the resistor module 306, the first switching element 307, the fourth switching element 316, and the fifth switching element 318 between the first busbar 302a and the second busbar 302b, and sharing this as a common circuit among all power transmission media 304, the need for these components (i.e., the resistor module 306, the first switching element 307, the fourth switching element 316, and the fifth switching element 318) for each bay, i.e., each individual power transmission medium, tends to be eliminated. This tends to reduce the overall number of components.

[0111] Furthermore, at the expense of including these four components in the hub circuit, each subsequent power transmission medium added to the system tends to use two fewer earth switches and one fewer current-on / off switch, and does not use an additional PIR.

[0112] Furthermore, there is a trend towards reducing the number of bushings in GIS.

[0113] Advantageously, in the electrical system 300 described above, opening the first switching element 307 tends to allow either the DC hub or any power transmission medium 304 to be isolated for maintenance while the other is still operating.

[0114] For maintenance of the power transmission medium 304, the sixth switching element 320 can be closed and the second switching element 308 can be opened while the other power transmission mediums 304 and the hub continue to operate. (The third switching element 310 is also open.)

[0115] For maintenance of the hub itself, the first busbar 302a can be grounded using the seventh switching element 324 while any of the power transmission media 304 continues to operate. For this purpose, all of the second switching elements 308 may be open.

[0116] Advantageously, the resistor module 306 (i.e., PIR) is isolated from the power transmission medium 304 and the hub and can be connected to ground by the fourth switching element 316 and the fifth switching element 318 for maintenance while the rest of the switching station continues to operate. If necessary, for example for further safety, a second disconnector can be placed to the right of the resistor module 306, i.e., between the second terminal 314 and the second busbar 302b.

[0117] In the embodiments described above, the electrical system comprises only a single resistor module and ground circuit. In these embodiments, this is connected between the first busbar and the second busbar. However, in other embodiments, one or more additional, or "backup," resistor modules and ground circuits may be added in parallel to the first resistor module and ground circuit. Such one or more additional resistor modules and ground circuits are connected between the first busbar and the second busbar. The one or more additional resistor modules and ground circuits tend to have the advantage of reducing the risk of energy loss during maintenance.

[0118] In other words, in some embodiments, the electrical system may further include a further resistor module comprising one or more additional resistors and electrically coupled between a first busbar and a second busbar, and a further switch electrically coupled between the first busbar and the second busbar and in series with the further resistor module.

[0119] In Example 100, it will be understood that various other electrical components may be located in any particular position or with any particular feature / component. These may include switches, transformers, resistors, reactors, surge arresters, harmonic filters, and other components well known in the art.

[0120] It will be understood that cables used as a power transmission medium may include the following non-limiting examples of cross-linked polyethylene (XLPE) and / or mass-impregnated (MI) insulated cables. Such cables may include a conductor (such as copper or aluminum) surrounded by an insulating layer. The dimensions of the cables and their associated layers may be modified depending on the specific application (and, in particular, the operating voltage requirements). Cables may further include reinforcement or "outer sheaths" in applications such as submerged installations. Cables may further include a grounded sheath / screen at one or more locations. The power transmission medium may refer to busbars, etc., without cables (e.g., directly connected to a converter station).

[0121] Throughout this specification, any reference to an example of a particular method or apparatus, or similar phrasing, means that the particular features, structure, or characteristics described in relation to that example are included in at least one implementation of the methods and apparatus described herein. The terms “including,” “comprising,” “having,” and their variations mean “including but not limited to,” unless otherwise specified. An enumerated list of items does not mean that any or all of the items are mutually exclusive unless otherwise specified. Also, the terms “a,” “an,” and “the” mean “one or more,” unless otherwise specified.

[0122] As used herein, a list containing the combination of "and / or" includes any single item in the list or any combination of items in the list. For example, the list A, B and / or C includes A only, B only, C only, 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 any combination of items in the list. For example, one or more of A, B and C includes A only, B only, C only, 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 only one of any single items in the list. For example, "one of A, B and C" includes A only, B only, or C only, and excludes the combination of A, B and C. As used herein, “members selected from the group consisting of A, B, and C” includes only one of A, B, or C, and excludes combinations of A, B, and C. As used herein, “members selected from the group consisting of A, B, and C, and combinations thereof” includes A only, B only, C only, 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.

[0123] The embodiments of the disclosed methods and apparatus will be described with reference to schematic flowcharts and / or schematic block diagrams of the methods, apparatus, systems, and program products. It will be understood that each block in the schematic flowcharts and / or schematic block diagrams, as well as any combination of blocks in the schematic flowcharts and / or schematic block diagrams, can be implemented by code. This code may be provided to a general-purpose computer processor, a dedicated computer processor, or other programmable data processing device for manufacturing a machine, thereby providing instructions executed via the computer processor or other programmable data processing device with means to perform the functions / actions specified in the schematic flowcharts and / or schematic block diagrams.

[0124] The schematic flowcharts and / or schematic block diagrams and / or schematic tables in the drawings illustrate the architecture, function, and operation of possible implementations of devices, systems, methods, and program products. In this regard, each block in the schematic flowchart and / or schematic block diagram may represent a module, segment, or portion of code that contains one or more executable instructions of code to implement a specified logical function.

[0125] The numerical values ​​listed herein are intended solely to aid in illustrating the function of the present invention and should be understood to vary depending on a given power transmission network, its components, or the requirements of the power transmission application.

[0126] Any list or discussion in this specification of documents or information that are clearly previously published should not necessarily be construed as an endorsement that such documents or information are part of the current technology or common general knowledge.

[0127] Any given aspect, feature, or parameter preference and choice of the present invention should be considered to be disclosed in combination with all other aspects, features, and parameter preferences and choices of the present invention, unless the context indicates otherwise. [Explanation of Symbols]

[0128] 100 Conventional electrical systems, first electrical systems, first exemplary electrical systems, conventional systems, examples 102a First bus bar, bus bar, hub bus bar 102b Second bus bar, bus bar, hub bus bar 104a Transmission medium 104b Transmission medium 106a PIR 106b PIR 108a First switching element 108b First switching element 110a Second switching element 110b Second switching element 112a Earth switch 112b Earth switch 200 Conventional electrical systems, second electrical systems, second exemplary electrical systems, stations 202 Bus Bar 204 Power transmission medium 206 PIR 208 First switching element 210 Second switching element 211 Third switching element 212a Earth switch, first earth switch 212b Earth switch, second earth switch 213 Further Earth Switches 214 Enclosure 216 Bushing 218 Further bushing 300 Electrical Systems 302a First bus bar, primary bus bar 302b Second bus bar, secondary bus bar 304 Power transmission medium, power supply unit 306 Resistor Module 307 First switching element, switching element 308 Second switching element 310 Third switching element, third switching module 312 First terminal 314 Second terminal 316. Fourth switching element, fourth switching module, ground circuit 318 Fifth switching element, ground circuit 320 The sixth switching element 322 First busbar terminal 324 The seventh switching element 326 Enclosure 328 Bushing 330 Further bushing 400 Table 1 500 Table 2 600 Table 3 700 Table 4

Claims

1. The first busbar (302a) and The second busbar (302b), A resistor module (306) comprising one or more resistors and electrically coupled between the first busbar (302a) and the second busbar (302b), A first switching element (307) is electrically coupled between the first busbar (302a) and the second busbar (302b) and is in series with the resistor module (306), Multiple power transmission media (304) and An electrical system (300) comprising, Each of the plurality of power transmission media (304) is electrically coupled to the first busbar (302a) via its respective second switching element (308). An electrical system (300) in which each of the plurality of power transmission media (304) is electrically coupled to the second busbar (302b) via its respective third switching element (310).

2. The resistor module (306) Multiple resistors, A plurality of switching elements, wherein each of the plurality of switching elements is electrically coupled to one or more of the plurality of resistors, and The electrical system (300) according to claim 1, comprising the plurality of resistors being selectively connectable in series or parallel configuration via the plurality of switching elements.

3. The resistor module (306) A first terminal (312) electrically coupled to the first busbar (302a), The second terminal (314) is electrically coupled to the second busbar (302b) and The electrical system (300) further comprises a fourth switching element (316) electrically coupled to the first terminal (312), The first terminal (312) is configured to be selectively connected to earth through the fourth switching element (316). The electrical system (300) according to claim 1 or 2.

4. The resistor module (306) A first terminal (312) electrically coupled to the first busbar (302a), The second terminal (314) is electrically coupled to the second busbar (302b) and The electrical system (300) further comprises a fifth switching element (318) electrically coupled to the second terminal (314), The second terminal (314) is configured to be selectively connected to earth through the fifth switching element (318). An electrical system (300) according to any one of claims 1 to 3.

5. Each of the plurality of power transmission media (304) is provided with terminals electrically coupled to the first busbar (302a), The electrical system (300) further comprises a plurality of sixth switching elements (320), Each of the multiple power transmission media (304) is configured such that each of its terminals is selectively connected to ground through its respective sixth switching element (320). An electrical system (300) according to any one of claims 1 to 4.

6. The first busbar (302a) is equipped with a first busbar terminal (322), The electrical system (300) further comprises a seventh switching element (324) electrically coupled to the first busbar terminal (322), The first busbar terminal (322) is configured to be selectively connected to earth through the seventh switching element (324). An electrical system (300) according to any one of claims 1 to 5.

7. A further resistor module comprising one or more additional resistors, electrically coupled between the first busbar (302a) and the second busbar (302b), A further switching element is electrically coupled between the first busbar (302a) and the second busbar (302b) and is in series with the further resistor module. An electrical system (300) according to any one of claims 1 to 6, further comprising:

8. Enclosure (326) The enclosure (326) further comprises the first busbar (302a), the second busbar (302b), each first switching element (307), and each second switching element (308), The resistor module (306) is located outside the enclosure (326). An electrical system (300) according to any one of claims 1 to 7.

9. The electrical system (300) according to claim 8, wherein the enclosure (326) houses a gas-insulated switchgear (GIS) system.

10. The electrical system (300) according to any one of claims 1 to 9, wherein the electrical system (300) is a multi-terminal switching station (MTSS).

11. The electrical system (300) according to claim 10, wherein the electrical system (300) is a high-voltage direct current (HVDC) MTSS.

12. This is for charging the first power transmission medium among the plurality of power transmission mediums (304), Opening the sixth switching element (320) of the first power transmission medium, Opening the fifth switching element (318), Opening the fourth switching element (316), Closing the first switching element (307), The third switching element (310) of the first power transmission medium is closed, thereby charging the first power transmission medium via the resistor module (306). A method for operating an electrical system (300) according to any one of claims 1 to 11, as dependent on claims 3, 4 and 5, including the above.

13. This is for discharging the first power transmission medium among the plurality of power transmission mediums (304), Closing the fourth switching element (316), By opening the second switching element (308) and the third switching element (310) of the first power transmission medium, the first power transmission medium is isolated from the first busbar (302a) and the second busbar (302b), Opening the fifth switching element (318), The third switching element (310) of the first power transmission medium is closed, thereby discharging the first power transmission medium to ground via the resistor module (306). A method for operating an electrical system (300) according to any one of claims 1 to 11, as dependent on claims 3 and 4, including the above.

14. This is for electrically insulating the first power transmission medium among the plurality of power transmission mediums (304) from the first busbar (302a) and the second busbar (302b). Opening the second switching element (308) of the first power transmission medium, Opening the third switching element (310) of the first power transmission medium and A method for operating an electrical system (300) according to any one of claims 1 to 11, including the following:

15. This is for electrically insulating the first busbar (302a), Opening each second switching element (308), Opening each third switching element (310), With the second switching element (308) and the third switching element (310) open, the seventh switching element (324) is closed, thereby connecting the first busbar (302a) to ground. A method for operating an electrical system (300) according to claim 6 or any claim dependent on claim 6, including the above.

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