Neutral grounding protection device and method for dual voltage class of floating power plant

Abstract

The application provides a neutral point grounding protection device and method for a floating power station double-voltage level, which comprises the following steps: controlling a first electric operating mechanism to close, controlling a grounding switch to close, controlling the first electric operating mechanism to open, controlling the grounding switch to open, controlling a second electric operating mechanism to close, and controlling the second electric operating mechanism to open. The application can meet the grounding requirements of the main transformer of two voltage levels, realize remote flexible switching, and solve the problems of compact transformer area and difficult equipment arrangement of the power generation ship.

Description

Technical Field

[0001] This invention belongs to the field of neutral point grounding protection technology, and relates to a neutral point grounding protection device and method for dual voltage levels in floating power plants. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] The floating power generation vessel project consists of a floating liquefied natural gas regasification unit (FSRU) and a combined cycle natural gas power generation barge. The FSRU regasifies LNG and transports it to the power generation barge for use as fuel, then transmits the generated electricity to the power grid. Because potential customers in different countries have varying voltage requirements, the floating power generation vessel needs to meet the grid connection requirements at different locations, operating at both 230kV and 115kV voltage levels (the two voltages cannot operate simultaneously).

[0004] 110kV and above power systems are effectively grounded neutral systems. An effectively grounded system requires at least one point of effective neutral grounding (direct grounding or grounding via a small reactor) to ensure the system's grounding method is effective. However, the number of neutral grounding points cannot be too large, otherwise it will cause the system's zero-sequence impedance voltage to be too low, resulting in excessively large single-phase ground fault currents, even exceeding the three-phase short-circuit currents. This creates difficulties in equipment selection and may even require large-capacity equipment, which is uneconomical. Therefore, the number and location of transformer neutral grounding points need to be determined based on the power grid structure and parameters. Once the grounding point is determined, it is fixedly grounded, and the remaining transformer neutral points operate ungrounded. When a transformer operates with an ungrounded neutral point, to prevent excessive neutral point overvoltage, a surge arrester and gap-coordinated overvoltage protection are installed at the transformer neutral point. To allow for the selection of two different operating modes—grounded or ungrounded neutral point operation—and to meet the requirements of dispatch flexibility, the main transformer neutral point typically uses a neutral point gap grounding protection device.

[0005] Neutral point gap grounding protection devices are generally installed on the neutral point side of the transformer, connected by steel-cored aluminum stranded wire or copper busbars. The installation must meet the requirements for energized distance between equipment and safe clearance to ground. For floating power generation vessels, the low-voltage side of the main transformer is equipped with enclosed busbars and supports, cable conduits, firewalls, and escape routes, while the high-voltage side is equipped with high-voltage cables and supports, and a GIS building. The overall space on board is limited. If the traditional solution is followed, multiple single-voltage level neutral point grounding devices would need to be installed, which is difficult and cannot meet the installation requirements. Furthermore, the method of manually changing the connection wires to achieve dual-voltage grounding switching has low reliability, poor safety, and poor flexibility. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a neutral point grounding protection device and method for dual voltage levels in floating power plants. This invention can meet the grounding requirements of the main transformer for two voltage levels, enabling flexible remote switching without requiring manual on-site wiring changes. It also solves the problems of compact transformer areas and difficult equipment layout on power generation vessels.

[0007] According to some embodiments, the present invention adopts the following technical solution:

[0008] A neutral point grounding protection device for dual voltage levels in a floating power station includes a grounding switch, a switching mechanism, a first surge arrester, a second surge arrester, a first discharge gap, a second discharge gap, and a zero-sequence current transformer, wherein the transformer neutral point is connected to the grounding switch via a conductor. By operating the grounding switch, the opening or closing of the switching mechanism is controlled to determine the grounding mode of the transformer neutral point.

[0009] The operating switching system includes two mechanically interlocked disconnect switches, with their incoming lines connected in parallel and in parallel with the incoming line of the grounding switch;

[0010] One of the disconnecting switches has its outgoing line connected to the first surge arrester and the first discharge gap on the first voltage level side; the other switch has its outgoing line connected to the second surge arrester and the second discharge gap on the second voltage level side.

[0011] The corresponding voltage level gap equipment is put into operation by operating the switching switch;

[0012] The first and second discharge gaps are connected in parallel to the grounding sides and then connected to the incoming side of the zero-sequence current transformer. The outgoing side of the zero-sequence current transformer is connected to the system ground.

[0013] As an alternative implementation, the two disconnect switches are arranged in parallel, and the contacts of the two disconnect switches are mechanically interlocked with each other, so that when one side is open, the other side is closed.

[0014] As an alternative implementation, the grounding switch corresponds to the first electric operating mechanism;

[0015] The operation switching switch corresponds to a second electric operating mechanism.

[0016] As a further limitation, by controlling the first electric operating mechanism to close, the grounding switch is closed, and the transformer neutral point is directly grounded; by controlling the first electric operating mechanism to open, the grounding switch is opened, and the transformer neutral point is gap grounded.

[0017] As a further limitation, by controlling the second electric operating mechanism to close at the first voltage level, the surge arrester and discharge gap corresponding to the first voltage level side are put into operation; by controlling the second electric operating mechanism to close at the second voltage level, the surge arrester and discharge gap corresponding to the second voltage level side are put into operation.

[0018] As an alternative implementation, the first voltage level is 230kV; the second voltage level is 115kV.

[0019] As an alternative implementation, the neutral points of the two voltage levels are integrated into one unit.

[0020] The working method of the above-mentioned device includes the following steps:

[0021] When it is necessary to switch the neutral point grounding method, switch the opening and closing of the grounding switch to switch the transformer neutral point to direct grounding or grounding through a gap;

[0022] When it is necessary to switch voltage levels, the switching switch is opened and closed to switch and select the surge arrester and discharge gap corresponding to different voltage levels.

[0023] As an alternative implementation, by controlling the first electric operating mechanism to close, the grounding switch is closed, and the transformer neutral point is directly grounded; by controlling the first electric operating mechanism to open, the grounding switch is disconnected, and the transformer neutral point is gap grounded.

[0024] As an alternative implementation, by controlling the second electric operating mechanism to close at the first voltage level, the surge arrester and discharge gap corresponding to the first voltage level side are put into operation; by controlling the second electric operating mechanism to close at the second voltage level, the surge arrester and discharge gap corresponding to the second voltage level side are put into operation.

[0025] A floating power generation vessel, including the aforementioned protective device.

[0026] As an alternative implementation, the floating power generation vessel includes several gas turbine dual-winding main transformers and several steam turbine dual-winding main transformers, with the high-voltage side of the transformers connected to a GIS power distribution device.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The dual-voltage-level integrated neutral point grounding protection device configuration scheme provided by this invention breaks through the traditional neutral point grounding configuration scheme. A single device can flexibly switch between two voltage-level grounding or ungrounded operation modes simultaneously, reducing the number of gap grounding protection devices and correspondingly reducing equipment layout space. It features small size, convenient installation, and high reliability. Based on the hull layout and operation characteristics of floating power generation vessels, it meets the flexible grounding requirements of transformers at different locations and voltage levels. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 This is a schematic diagram of the grounding methods for each transformer on a floating power generation vessel.

[0031] Figure 2 This is a schematic diagram of the main wiring circuit and parameter configuration;

[0032] Figure 3 This is a schematic diagram of the grounding method switching of the transformer neutral point;

[0033] Figure 4 This is a schematic diagram showing the operation of gap equipment at two different voltage levels. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] Example 1

[0038] like Figure 1 As shown in the figure, this embodiment provides a dual-voltage-level integrated neutral point grounding protection device, which can meet the grounding requirements of the main transformer at two voltage levels of 115 / 230kV, realize flexible remote switching, and eliminate the need for manual on-site wiring changes. It can also solve the problems of compact transformer areas and difficult equipment layout on power generation ships.

[0039] The neutral-point grounding operation mode of transformers should meet the neutral-point insulation requirements of transformers and keep the zero-sequence impedance of the power plant basically unchanged as much as possible, so as to keep the distribution of zero-sequence current in the system constant and ensure that the zero-sequence current voltage protection has sufficient sensitivity. In power plants with multiple transformers operating in parallel, a portion of the transformers are typically operated with their neutral points grounded, while the other portion are operated with their neutral points ungrounded.

[0040] This embodiment of the floating power generation vessel uses two gas turbine double-winding main transformers and one steam turbine double-winding main transformer. The high-voltage side of the transformers is connected to a GIS power distribution system, which uses a double busbar connection. Given the limited space on the power generation vessel and the need for flexible layout and space constraints, the neutral point grounding of the three main transformers is arranged as follows: the two gas turbine main transformers use direct neutral point grounding, and the one steam turbine main transformer uses gap-grounded neutral point grounding. Figure 1 As shown.

[0041] To meet the grounding requirements of the 115kV / 230kV dual voltage levels on the high-voltage side of the main transformer and to save equipment layout space, the neutral point gap grounding protection device adopts an integrated set of equipment for both 115kV and 230kV neutral points, enabling the transformer neutral point to operate in either grounded or ungrounded mode at both voltage levels. The main wiring circuit and parameter configuration are as follows: Figure 2 As shown.

[0042] This complete set of equipment consists of two sets of neutral point gap grounding devices for different voltage levels: 115kV and 230kV. It is an integrated neutral point system, comprising a grounding switch K1 (with an electric operating mechanism C1), a 115 / 230kV operation switching switch K2 (with an electric operating mechanism C2), surge arresters LA1 and LA2, discharge gaps JX1 and JX2, and a zero-sequence current transformer CT (shared). It is suitable for transformers operating at different voltage levels. The specific configuration is as follows:

[0043] Grounding switch K1 (shared by all): Located at the very beginning of the entire equipment, the transformer neutral point is connected to its top incoming copper busbar terminal via a conductor. The grounding method of the transformer neutral point is achieved by operating its associated operating mechanism C1: pressing the open command on operating mechanism C1 remotely opens K1, enabling gap grounding; pressing the close command on operating mechanism C1 remotely closes K1, enabling direct grounding. Figure 3 As shown.

[0044] Changeover switch K2 (shared by both switches): consists of two parallel single-pole GW4 type disconnect switches. The contacts of the two single-pole disconnect switches are mechanically interlocked, and when one side opens (closes), the other side closes (opens). The incoming lines of the two single-pole disconnect switches are connected in parallel, and in parallel with the incoming line of the grounding disconnect switch, together forming the incoming point O of the neutral point gap grounding equipment for two voltage levels.

[0045] One of the units has its outgoing line connected to the 115kV surge arrester LA2 and the 115kV discharge gap; the other unit has its outgoing line connected to the 230kV surge arrester LA1 and the 230kV discharge gap.

[0046] The voltage level of the gap equipment is selected for operation by operating the associated operating mechanism C2: When the 230kV closing command is pressed remotely on operating mechanism C2, the 230kV side contacts of the GW4 disconnector close, and the 115kV side contacts open, putting the 230kV voltage level into operation; when the 115kV closing command is pressed on operating mechanism C2, the 115kV side contacts of the GW4 disconnector close, and the 230kV side contacts open, putting the 115kV voltage level into operation. For example... Figure 4 As shown.

[0047] Current transformer (CT) (shared by this device): The 115kV discharge gap and the 230kV discharge gap are connected in parallel to the grounding side and then connected to the incoming side of the CT. The outgoing side of the CT is connected to the system ground for gap protection.

[0048] If the high-voltage output voltage level of the transformer on the floating power ship is changed when the operating location is changed, it is only necessary to switch the opening and closing of the grounding switch K1 by operating mechanism C1 in the transformer neutral point gap grounding protection device to switch the transformer neutral point to be directly grounded or grounded through the gap; and switch the opening and closing of the switch K2 by controlling operating mechanism C2 to switch the surge arrester and discharge gap to be connected to different voltage levels.

[0049] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A neutral point grounding protection device for dual voltage levels in floating power plants, characterized in that, It includes a grounding switch, a running switch, a first surge arrester, a second surge arrester, a first discharge gap, a second discharge gap, and a zero-sequence current transformer. The neutral point of the transformer is connected to the grounding switch via a conductor. By operating the grounding switch, the opening or closing of the running switch is controlled to determine the grounding method of the transformer neutral point. The operating switching system includes two mechanically interlocked disconnect switches, with their incoming lines connected in parallel and in parallel with the incoming line of the grounding switch; One of the disconnecting switches has its outgoing line connected to the first surge arrester and the first discharge gap on the first voltage level side; the other disconnecting switch has its outgoing line connected to the second surge arrester and the second discharge gap on the second voltage level side. The corresponding voltage level gap equipment is put into operation by operating the switching switch; The first discharge gap and the second discharge gap are connected in parallel to the grounding side and then connected to the incoming side of the zero-sequence current transformer. The outgoing side of the zero-sequence current transformer is connected to the system ground. The first surge arrester is connected to the system ground through the first surge arrester monitor, and the second surge arrester is connected to the system ground through the second surge arrester monitor.

2. The neutral grounding protection device for dual voltage levels in floating power plants as described in claim 1, characterized in that, The two disconnect switches are arranged in parallel, and the contacts of the two disconnect switches are mechanically interlocked with each other, so that when one side is open, the other side is closed.

3. The neutral grounding protection device for dual voltage levels in floating power plants as described in claim 1, characterized in that, The grounding switch corresponds to the first electric operating mechanism; The operation switching switch corresponds to a second electric operating mechanism.

4. The neutral grounding protection device for dual voltage levels in floating power plants as described in claim 3, characterized in that, When the first electric operating mechanism is closed, the grounding switch is closed, and the transformer neutral point is directly grounded. When the first electric operating mechanism is opened, the grounding switch is opened, and the transformer neutral point is gap grounded.

5. A neutral grounding protection device for dual voltage levels in floating power plants as described in claim 4, characterized in that, By controlling the second electric operating mechanism to close the first voltage level, the surge arrester and discharge gap corresponding to the first voltage level side are put into operation; by controlling the second electric operating mechanism to close the second voltage level, the surge arrester and discharge gap corresponding to the second voltage level side are put into operation.

6. The method of operating the protection device according to claim 5, characterized in that, Includes the following steps: When it is necessary to switch the neutral point grounding method, switch the opening and closing of the grounding switch to switch the transformer neutral point to direct grounding or grounding through a gap; When it is necessary to switch voltage levels, the switching switch is controlled to select and switch the surge arrester and discharge gap corresponding to different voltage levels.

7. The working method as described in claim 6, characterized in that, When the first electric operating mechanism is closed, the grounding switch is closed, and the transformer neutral point is directly grounded. When the first electric operating mechanism is opened, the grounding switch is opened, and the transformer neutral point is gap grounded.

8. The working method as described in claim 6, characterized in that, By controlling the second electric operating mechanism to close the first voltage level, the surge arrester and discharge gap corresponding to the first voltage level side are put into operation; by controlling the second electric operating mechanism to close the second voltage level, the surge arrester and discharge gap corresponding to the second voltage level side are put into operation.

9. A floating power generation vessel, characterized in that, The protective device includes any one of claims 1-5.

10. The floating power generation vessel as described in claim 9, characterized in that, The floating power generation vessel includes several gas turbine dual-winding main transformers and several steam turbine dual-winding main transformers, with the high-voltage side of each transformer connected to a GIS power distribution system.

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