Electrical main wiring system and voltage boosting method of offshore photovoltaic 110kV box-type substation

Abstract

The application discloses a kind of offshore photovoltaic 110kV box-type substation electrical main wiring system and boosting method, belong to offshore photovoltaic power generation technical field, directly using 110kV double split oil-immersed transformer realizes voltage span, effectively reduce the number of power collection cable in photovoltaic field area and photovoltaic power generation unit, substantially reduce line transmission loss, innovatively use 110kV flexible cable between 110kV GIS equipment and transformer high voltage side instead of traditional GIL hard tube bus connection, effectively absorb and buffer mechanical stress, by 0.8kV electric energy at photovoltaic inverter outlet is directly boosted to 110kV by double split transformer, and high-voltage power collection network is constructed in T connection mode, the number of offshore power collection line and electric energy transmission loss are reduced, effectively improve the overall power generation benefit of large-scale offshore photovoltaic project.

Description

Technical Field

[0001] This invention belongs to the field of offshore photovoltaic power generation technology, specifically relating to an electrical main wiring system and voltage boosting method for an offshore photovoltaic 110kV box-type substation. Background Technology

[0002] Large-scale photovoltaic projects in coastal areas and nearshore waters generally use a 35kV or 66kV box-type substation as a power generation unit for a photovoltaic subarray. The power is then fed into the grid through a 35kV or 66kV collection line to a step-up substation. This scheme is relatively mature and common, and is a frequently used collection scheme for photovoltaic projects.

[0003] However, how to efficiently and efficiently transmit electricity in large-scale offshore photovoltaic projects is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide an electrical main wiring system and voltage boosting method for a 110kV box-type substation for offshore photovoltaic power generation, so as to overcome the technical problem of low power transmission efficiency in large-scale offshore photovoltaic projects in the prior art.

[0005] To solve the above problems, the present invention adopts the following technical solution: An electrical main wiring system for a 110kV prefabricated substation for offshore photovoltaic power includes a prefabricated substation base, an oil-immersed transformer, a 110kV gas-insulated metal-enclosed switchgear, and a 0.8kV low-voltage switchgear installed on the prefabricated substation base. The oil-immersed transformer is a three-phase double-split winding transformer with a low-voltage side of 0.8kV and a high-voltage side of 110kV. The 0.8kV low-voltage switchgear is connected to the low-voltage side of the oil-immersed transformer via a busbar; The high-voltage side of the oil-immersed transformer is flexibly connected to the 110kV gas-insulated metal-enclosed switchgear via a 110kV cable.

[0006] Furthermore, the 110kV gas-insulated metal-enclosed switchgear adopts a one-in-multiple-out wiring configuration, including at least one main transformer incoming line bay and multiple outgoing line bays.

[0007] Furthermore, the outgoing line bay is equipped with a three-position disconnect switch, and the main transformer incoming line bay is equipped with a three-position disconnect switch, a circuit breaker, and a maintenance grounding switch.

[0008] Furthermore, the busbar of the 110kV gas-insulated metal-enclosed switchgear is connected to a voltage transformer and a surge arrester.

[0009] Furthermore, the oil-immersed transformer is externally mounted on the upper platform of the base of the box-type substation, and the 0.8kV low-voltage switchgear and the 110kV gas-insulated metal-enclosed switchgear are integrated in the prefabricated cabin.

[0010] Furthermore, the 110kV cable flexible connection between the 110kV gas-insulated metal-enclosed switchgear and the high-voltage side of the oil-immersed transformer is a detachable connection.

[0011] Furthermore, a grounding maintenance switch is provided at the cable connection point.

[0012] Furthermore, the 110kV cable adopts a flexible structure cable.

[0013] Secondly, the present invention also provides a method for boosting and concentrating offshore photovoltaic power generation, comprising the following steps: The 0.8kV AC power output from the inverter of a single photovoltaic power generation unit is connected to the low-voltage side of the oil-immersed transformer through the busbar of the 0.8kV low-voltage switchgear. The voltage is directly stepped up from 0.8kV to 110kV via the oil-immersed transformer. Electrical energy is drawn to the 110kV collector cable through the intervals of the 110kV gas-insulated metal-enclosed switchgear; The 110kV collector cable is flexibly connected sequentially to the 110kV side of the box-type substation corresponding to multiple photovoltaic power generation units via a T-connection method.

[0014] Furthermore, during maintenance of the photovoltaic power collection lines, the three-position disconnecting switch inside the 110kV gas-insulated metal-enclosed switchgear can be operated to disconnect, isolate, or ground the electrical energy between the photovoltaic power generation units.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides an electrical main wiring system for a 110kV prefabricated substation for offshore photovoltaic power generation. It directly utilizes a 110kV double-split oil-immersed transformer to achieve voltage crossing, effectively reducing the number of collector cables and photovoltaic power generation units within the photovoltaic field, significantly reducing line transmission losses, and substantially improving power generation efficiency and investment economy. Addressing the vibration and uneven settlement issues that easily occur on offshore steel structure platforms under wind and wave surges, the system innovatively uses a 110kV flexible cable instead of the traditional GIL rigid conduit busbar connection between the 110kV GIS equipment and the high-voltage side of the transformer, effectively absorbing and buffering mechanical stress. Simultaneously, this modular and flexible connection structure allows for physical decoupling of the GIS and transformer after the equipment is in place at sea, enabling independent acceptance withstand voltage tests, significantly reducing the difficulty of offshore construction and the complexity of subsequent operation and maintenance. The entire system is highly integrated within a prefabricated base, facilitating overall transportation and hoisting, and providing reliable core technology support for the large-scale, low-cost development of offshore photovoltaic energy.

[0016] This invention also provides a method for boosting and collecting voltage for offshore photovoltaic power generation. By directly boosting the 0.8kV output voltage of the photovoltaic inverter to 110kV via a double-split transformer and constructing a high-voltage collection network using a T-connection, the number of offshore collection lines and power transmission losses are reduced, effectively improving the overall power generation efficiency of large-scale offshore photovoltaic projects. In actual installation, the dynamic connection method using 110kV flexible cables not only absorbs and offsets the mechanical stress on equipment connections caused by vibrations and uneven settlement of the offshore steel structure platform due to wind and waves in real time, but also simplifies the offshore construction process. Simple decoupling connections are all that's needed to conduct independent on-site handover withstand voltage tests on the GIS and transformer, significantly reducing the difficulty and risk of engineering implementation in harsh offshore environments. Furthermore, this method relies on the refined topology control of the three-position disconnector within the GIS to achieve safe isolation and rapid grounding of faulty units, providing reliable safety guarantees for daily maintenance and operation of collection lines under extreme sea conditions. This provides a practical and feasible method for the rapid construction and efficient operation of large-scale offshore photovoltaic power plants. Attached Figure Description

[0017] Figure 1 This is the main electrical wiring diagram for a 110kV prefabricated substation. Figure 2 Wiring system diagram for 110kV combined electrical equipment; Figure 3 Wiring diagram for transformer 110; Figure 4 This is a flowchart of a method for boosting and concentrating offshore photovoltaic power generation. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] This invention provides an electrical main wiring system for a 110kV prefabricated substation for offshore photovoltaic power, such as... Figure 1 As shown, the system is mounted on a prefabricated substation base, capable of accommodating the overall transportation and hoisting needs of offshore steel structure platforms. The system includes an oil-immersed transformer, a 110kV gas-insulated metal-enclosed switchgear (GIS), and a 0.8kV low-voltage switchgear.

[0021] In this embodiment, the oil-immersed transformer is a three-phase, double-split, no-load tap-changing oil-immersed transformer with a rated voltage of 110kV on the high-voltage side and 0.8kV on the low-voltage side. To improve compactness and meet heat dissipation requirements, the oil-immersed transformer is externally mounted on the upper platform of the prefabricated substation base; while the 0.8kV low-voltage switchgear and the 110kV GIS are respectively encapsulated in the prefabricated compartment of the prefabricated substation base. The 0.8kV low-voltage switchgear is connected to the low-voltage winding of the oil-immersed transformer via a low-voltage copper busbar to meet the inverter connection requirements. The high-voltage side of the oil-immersed transformer is flexibly connected to the 110kV GIS via a 110kV cross-linked polyethylene cable.

[0022] like Figure 3As shown, oil-immersed transformer T1 is a three-phase, double-split-winding, no-load tap-changing oil-immersed transformer with a rated capacity of 9600kVA, a voltage level of 115±2×2.5% / 0.8-0.8kV, a connection group of YN,d11-d11, and a half-pass-through impedance of 12%. The high-voltage side of the transformer has a 110kV star-connected winding with a neutral point lead-out; the low-voltage side has two independent 0.8kV delta-connected split windings, which respectively form two independent low-voltage busbars.

[0023] The high-voltage winding of the transformer is led out through a pluggable bushing and connected to a 110kV cable ERF-64 / 110kV-1×95 to achieve electrical connection with the GIS equipment. The pluggable bushing connection structure allows for a separable connection between the transformer and the GIS equipment. After the equipment is in place on site, the cable connector can be pulled out, physically disconnecting the transformer and the GIS equipment for independent withstand voltage testing, eliminating the need for overall pressurization and reducing the difficulty and risk of on-site testing.

[0024] The transformer neutral point is equipped with a main transformer neutral point grounding device, including a neutral point disconnect switch (GN8-40.5 / 630), a neutral point discharge resistor (YMF-51 / 131P), a surge arrester, and a neutral point current transformer (turn ratio 100 / 1A / 100 / 1A, accuracy class 5P20 / 5P20). The neutral point grounding device allows switching between direct grounding and resistor-grounded operation of the transformer neutral point via the disconnect switch, adapting to the system's single-phase ground fault current control requirements.

[0025] The two split windings on the low-voltage side are connected to two independent low-voltage busbars via low-voltage copper busbars. Each low-voltage busbar is equipped with multiple low-voltage feeder switchgear. Each feeder circuit is connected to the corresponding photovoltaic inverter, which collects the 0.8kV AC power output from the photovoltaic power generation unit and sends it to the low-voltage winding of the transformer. The low-voltage switchgear uses conventional low-voltage switchgear, equipped with circuit breakers, disconnect switches, current transformers, and other components to meet the requirements for inverter connection, protection, and metering.

[0026] Combination Figure 1 and Figure 2 As shown, the 110kV GIS equipment adopts gas-insulated metal-enclosed switchgear, with SF6 gas as the insulating medium inside. All high-voltage live parts are enclosed in a metal shell, which has the characteristics of small size, high reliability and strong corrosion resistance, and is particularly suitable for harsh operating environments with high salt spray and high humidity at sea.

[0027] The GIS equipment is equipped with a 110kV main busbar, which connects to the main transformer incoming line bay, multiple outgoing line bays, and PT bays. All bays are connected by aluminum conductors and are integrated within the GIS air chamber.

[0028] The main transformer incoming line bay is equipped with a three-position disconnector (DES), a circuit breaker (CB), and a maintenance grounding switch (ES) connected in series. The three-position disconnector (DES) has three operating positions: closed, open, and grounded, enabling switching between the main transformer circuit and the busbar for connection, disconnection, and maintenance grounding. The circuit breaker (CB) is an SF6 gas-insulated circuit breaker equipped with current transformers (CTs with P1 and P2 windings) for fault protection and current measurement of the main transformer circuit. The maintenance grounding switch (ES) is located between the circuit breaker and the cable terminal, ensuring reliable grounding of the main transformer incoming line side during maintenance and guaranteeing the safety of maintenance personnel.

[0029] The lower end of the main transformer incoming line bay is connected to a 110kV cable via a cable terminal SE (Cable SE), which then connects to the high-voltage side of the transformer. A live-line indicator (VD) is installed at the cable terminal to indicate in real time whether the cable circuit is energized, providing intuitive safety prompts for operation and maintenance.

[0030] Each outgoing line bay is equipped with a three-position disconnector (DES), with a 110kV cable leading out from the lower end via a cable terminal (CSE) for T-connection to the adjacent photovoltaic power generation unit's prefabricated substation. A live-line indicator (VD) is also installed at the cable terminal. The outgoing line bays are equipped with only three-position disconnectors instead of circuit breakers. This is because the protection functions of each photovoltaic power generation unit are centrally handled by the circuit breaker on the main transformer's incoming side. Furthermore, it effectively reduces the number of devices and compresses the GIS (Gas Insulated Gateway System) container volume, adapting to the compact layout requirements of offshore prefabricated substations.

[0031] The GIS equipment of this invention can be configured with various wiring configurations, such as one inlet and one outlet, one inlet and two outlets, or one inlet and three outlets, according to actual engineering needs. For example... Figure 1 The illustrated embodiment is a one-in-three-out scheme, which includes one main transformer incoming line bay and three outgoing line bays, enabling T-connection aggregation of multiple photovoltaic power generation units connected in series on a single 110kV collector line. By flexibly configuring the number of outgoing line bays, it can adapt to the aggregation needs of photovoltaic subarrays of different sizes.

[0032] The GIS main busbar is also equipped with PT bays, each containing a voltage transformer (PT) and a surge arrester (LA). The PTs are used for busbar voltage measurement and metering, providing voltage signals for system protection and monitoring. The surge arresters (LA) limit lightning overvoltages and switching overvoltages, protecting the GIS equipment and transformer insulation from overvoltage surge damage. The PT bays are connected to the main busbar via a three-position disconnect switch (DES), facilitating the maintenance and replacement of the PTs and surge arresters.

[0033] In another embodiment of the present invention, an electrical main wiring system scheme for a 110kV prefabricated substation suitable for large-scale offshore photovoltaic projects is provided, which is used to collect power from various photovoltaic power generation units via a 110kV collector line in the photovoltaic field. The low-voltage side of the photovoltaic field uses a 0.8kV voltage level, and the high-voltage side uses a 110kV voltage level. The transformer is a three-phase double-split winding no-load tap-changing oil-immersed transformer. The 110kV side uses gas-insulated metal-enclosed switchgear (GIS). To meet the different collection wiring requirements of the photovoltaic subarrays, the high-voltage side adopts wiring schemes such as one-in-one-out, one-in-two-out, and one-in-three-out. The 0.8kV side uses a low-voltage switchgear to meet the inverter connection requirements. The overall scheme of the prefabricated substation is as follows: the transformer is externally mounted, and the 0.8kV side low-voltage switchgear and 110kV GIS equipment are prefabricated and arranged in a prefabricated compartment, all placed on the base of the prefabricated substation for overall transportation and hoisting.

[0034] The 0.8kV side wiring scheme of the 110kV prefabricated substation adopts a conventional wiring method, with the low-voltage switchgear connected to the low-voltage winding of the main transformer via busbars. Considering the location of the prefabricated substation on an offshore steel structure platform, continuous wind disturbance and surges may cause platform vibration and uneven settlement. To improve the overall operational stability and reliability of the prefabricated substation, the 110kV GIS and the high-voltage side of the transformer are flexibly connected via 110kV cables, instead of a rigid connection using GIL (Gas Insulator) busbars. This effectively reduces the risk of failure at the equipment connection point due to platform vibration. It also allows for physical separation of the transformer and GIS equipment for withstand voltage testing after the equipment is in place, enabling separate withstand voltage tests. A grounding maintenance switch is installed at the connection point between the transformer and GIS to meet subsequent production, operation, and maintenance needs.

[0035] A 110kV collection line connects multiple photovoltaic power generation units in the photovoltaic field. Each power generation unit is equipped with a box-type substation. The box-type substations are connected by 110kV cables. There is a T-connection between the box-type substations. In order to meet the wiring connection requirements between photovoltaic power generation units, there is a one-in-multiple-out wiring configuration on the 110kV side. Each outgoing line bay is equipped with a three-position disconnect switch. The main transformer incoming line bay is equipped with a three-position disconnect switch + circuit breaker + maintenance grounding switch. The busbar is equipped with a PT bay including a surge arrester.

[0036] This solution meets the high-voltage collection line requirements of large-capacity power generation units in large-scale offshore photovoltaic projects. It reduces the number of photovoltaic power generation units and substations, improves power generation efficiency, and reduces line losses, effectively lowering investment costs and increasing power generation revenue. This patented technology represents a significant technological leap from 0.8kV at the photovoltaic inverter outlet to 110kV at the transformer, overcoming the challenges of limited space, strong corrosion, and harsh operating conditions at sea. It integrates the traditional onshore 110kV step-up substation into the confined space of an offshore platform. This solution reshapes the collection and transmission mode of power lines in offshore photovoltaic projects, providing indispensable key equipment and system solutions for large-scale, deep-sea photovoltaic energy development. It also provides a reference solution for power line collection and transmission for other new energy development projects.

[0037] This invention also provides a method for boosting and concentrating offshore photovoltaic power generation, such as... Figure 4 As shown, it includes the following steps: The 0.8kV AC power output from the inverter of a single photovoltaic power generation unit is connected to the low-voltage side of the oil-immersed transformer through the busbar of the 0.8kV low-voltage switchgear. The voltage is directly stepped up from 0.8kV to 110kV via an oil-immersed transformer; Electrical energy is drawn to 110kV collector cables through the bays of 110kV gas-insulated metal-enclosed switchgear. The 110kV collector cable is flexibly connected sequentially to the 110kV side of the box-type substation corresponding to multiple photovoltaic power generation units via a T-connection method.

[0038] In detail, firstly, the 0.8kV AC power output by the inverter of a single photovoltaic power generation unit is connected to the 0.8kV low-voltage switch cabinet through a low-voltage cable, and then connected to the low-voltage winding of the oil-immersed transformer through the low-voltage copper busbar. Next, the voltage is directly boosted from 0.8kV to 110kV in one step using a three-phase double-split oil-immersed transformer. This boosting step eliminates the 35kV or 66kV collection link in the traditional scheme, significantly reducing the number of collection lines in the entire photovoltaic field. Then, the boosted 110kV AC power is output to the 110kV collection cable through a 110kV GIS incoming circuit breaker and a three-position disconnect switch. Finally, using 110kV cross-linked polyethylene cables, the 110kV sides of the box-type substations corresponding to multiple adjacent photovoltaic power generation units are connected sequentially in a T-connection manner to form a 110kV collection line network for the photovoltaic field, ultimately transmitting the power to the main boosting station at sea or on land.

[0039] This embodiment focuses on the optimized design for the harsh operating conditions of offshore steel structure platforms. Due to the long-term impact of wind and wave disturbances on offshore platforms, they are prone to continuous minor vibrations and uneven settlement. Therefore, instead of the traditional rigid connection via GIL conduit between the 110kV GIS and the oil-immersed transformer, this system uses a 110kV cross-linked polyethylene flexible cable connection. This flexible cable effectively absorbs and buffers the mechanical stress generated at the GIS and transformer interface by platform vibrations and uneven settlement, significantly reducing the risk of air leakage or insulation failure due to damage to the rigid connection.

[0040] Furthermore, after the equipment is installed and positioned on the offshore platform, the flexible cable's detachable and bendable characteristics allow construction personnel to physically separate the 110kV GIS from the oil-immersed transformer, enabling separate acceptance withstand voltage tests on both the GIS and the transformer. This solves the problem of traditional combined equipment being unable to perform withstand voltage tests on the transformer independently. To ensure the safety of subsequent production and maintenance, a grounding maintenance switch is also installed at the 110kV cable terminal connecting the oil-immersed transformer and the GIS, facilitating the establishment of a reliable grounding point during maintenance.

[0041] When a fault occurs in a 110kV collection line or a photovoltaic power generation unit requires power outage maintenance, operators only need to operate the three-position isolating switch in the corresponding outgoing line bay to quickly isolate and ground that outgoing line bay, without affecting the normal operation of the main transformer incoming line bay and other outgoing line bays. Because the system uses a 110kV voltage level for collection, the transmission line cross-section is small and the number of lines is reduced. Compared with traditional 35kV or 66kV solutions, this significantly reduces line losses throughout the photovoltaic field, contributing to cost reduction and efficiency improvement for large-capacity offshore photovoltaic projects.

[0042] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An electrical main wiring system for a 110kV prefabricated substation for offshore photovoltaic power, characterized in that, It includes a prefabricated substation base, as well as an oil-immersed transformer, a 110kV gas-insulated metal-enclosed switchgear, and a 0.8kV low-voltage switchgear installed on the prefabricated substation base; The oil-immersed transformer is a three-phase double-split winding transformer with a low-voltage side of 0.8kV and a high-voltage side of 110kV. The 0.8kV low-voltage switchgear is connected to the low-voltage side of the oil-immersed transformer via a busbar; The high-voltage side of the oil-immersed transformer is flexibly connected to the 110kV gas-insulated metal-enclosed switchgear via a 110kV cable.

2. The electrical main wiring system of a 110kV prefabricated substation for offshore photovoltaic power according to claim 1, characterized in that, The 110kV gas-insulated metal-enclosed switchgear adopts a one-in-multiple-out wiring configuration, including at least one main transformer incoming line bay and multiple outgoing line bays.

3. The electrical main wiring system of a 110kV prefabricated substation for offshore photovoltaic power according to claim 2, characterized in that, The outgoing line bay is equipped with a three-position disconnect switch, and the main transformer incoming line bay is equipped with a three-position disconnect switch, a circuit breaker and a maintenance grounding switch.

4. The electrical main wiring system of a 110kV prefabricated substation for offshore photovoltaic power according to claim 2, characterized in that, The busbar of the 110kV gas-insulated metal-enclosed switchgear is connected to a voltage transformer and a surge arrester.

5. The electrical main wiring system for a 110kV prefabricated substation for offshore photovoltaic power according to claim 1, characterized in that, The oil-immersed transformer is externally mounted on the upper part of the platform of the prefabricated substation base, and the 0.8kV low-voltage switchgear and the 110kV gas-insulated metal-enclosed switchgear are integrated in the prefabricated cabin.

6. The electrical main wiring system of a 110kV prefabricated substation for offshore photovoltaic power according to claim 1, characterized in that, The 110kV cable flexible connection between the 110kV gas-insulated metal-enclosed switchgear and the high-voltage side of the oil-immersed transformer is a detachable connection.

7. The electrical main wiring system for a 110kV prefabricated substation for offshore photovoltaic power according to claim 6, characterized in that, A grounding maintenance switch is installed at the cable connection point.

8. The electrical main wiring system for a 110kV prefabricated substation for offshore photovoltaic power according to claim 6, characterized in that, The 110kV cable is a flexible structure cable.

9. A method for boosting and concentrating offshore photovoltaic power generation, characterized in that, The electrical main wiring system for a 110kV prefabricated substation for offshore photovoltaic power according to any one of claims 1-8 includes the following steps: The 0.8kV AC power output from the inverter of a single photovoltaic power generation unit is connected to the low-voltage side of the oil-immersed transformer through the busbar of the 0.8kV low-voltage switchgear. The voltage is directly stepped up from 0.8kV to 110kV via the oil-immersed transformer. Electrical energy is drawn to the 110kV collector cable through the intervals of the 110kV gas-insulated metal-enclosed switchgear; The 110kV collector cable is flexibly connected sequentially to the 110kV side of the box-type substation corresponding to multiple photovoltaic power generation units via a T-connection method.

10. A method for boosting and concentrating offshore photovoltaic power generation according to claim 9, characterized in that, When the power collection lines in the photovoltaic field are under maintenance, the three-position disconnecting switch in the 110kV gas-insulated metal-enclosed switchgear is operated to cut off, isolate or ground the power between the photovoltaic power generation units.

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