Isolation transformer and dc high voltage isolation transformer system

Abstract

The present application provides an isolation transformer and a direct current high voltage isolation transformer system, wherein the isolation transformer comprises an isolation transformer unit and a voltage equalizing device built in a shell, in the isolation transformer unit, a core, a first insulator, a primary winding, a second insulator and a secondary winding are sequentially arranged from the inner periphery to the outer periphery, the second insulator comprises n (an integer greater than or equal to 2) sub-insulators sequentially arranged from the inner periphery to the outer periphery, a voltage equalizing shielding layer is arranged between each sub-insulator and the side of the secondary winding of the sub-insulator closest to the secondary winding, the voltage equalizing device is formed by connecting n voltage equalizing resistors in series, each voltage equalizing shielding layer is connected to the other end of each voltage equalizing resistor different from the end connected in series, so that the potential between each voltage equalizing shielding layer satisfies a specified proportional relationship. The isolation transformer and the direct current high voltage isolation transformer system of the present application have high reliability and can achieve higher isolation voltage.

Description

Technical Field

[0001] This invention relates to the field of transformer equipment technology, and more particularly to isolation transformers and DC high-voltage isolation transformer systems for powering DC high-voltage platforms. Background Technology

[0002] Isolation transformers are commonly used equipment in electrical systems, primarily for voltage transformation between different voltage levels, power transmission in electrical systems, and current transformation in systems with different transmission capacities. With the development of electrical technology, especially AC and high-voltage DC transmission, the function of isolation transformers has expanded beyond power transmission in electrical systems to other special applications, such as providing auxiliary power to equipment like radar, accelerators, and ion implanters. These applications require transformers to not only have power output capabilities but also highly reliable high-voltage isolation.

[0003] Currently, transformers above 50kV used in the electrical field are primarily oil-immersed transformers to achieve voltage isolation and provide necessary main insulation. For transformers of 50kV and below, various insulation types are available, including dry-type, oil-insulated, and gas-insulated transformers.

[0004] Figure 1 This is a schematic diagram of the internal structure of an existing isolation transformer. (For example...) Figure 1 As shown, an existing isolation transformer includes a core 101; a primary winding 102 and a secondary winding 103 coaxially arranged with the core 101; and an insulator (also known as an insulating barrier) 104 between the primary winding 102 and the secondary winding 103. The core 101, primary winding 102, insulator 104, and secondary winding 103 are arranged sequentially from the inner circumference to the outer circumference. The insulation design of this typical transformer mainly focuses on the insulation between the windings and is suitable for voltage levels ≤200kV (AC or DC). Summary of the Invention

[0005] The technical problem to be solved by the present invention

[0006] The biggest difference between designing transformers for high-voltage AC and DC withstand voltage is that the electric field distribution under AC voltage depends on the dielectric constant of the insulation material, while under DC withstand voltage conditions, the electric field distribution of the transformer insulation depends on the resistivity of the insulation material. However, it is difficult to achieve a uniform resistivity distribution relying solely on the insulation material. Furthermore, because the insulation material stores and accumulates charge under high DC voltage, it takes a long time for the transformer body alone to release this accumulated charge generated by the DC bias. In extreme cases, the DC bias can superimpose on the peak power frequency voltage, causing the voltage across the transformer winding insulation to exceed its rated withstand voltage, resulting in flashover or partial discharge, and in severe cases, insulation breakdown.

[0007] In addition, when there are local defects in the insulating material or the resistivity distribution is uneven, most of the DC voltage will be superimposed on the undamaged part or the insulating layer with good resistivity that is connected in series with the local defect. When this part of the insulating layer cannot withstand the applied electric field strength, flashover or partial discharge phenomena will also occur.

[0008] For the reasons mentioned above Figure 1 The typical existing transformer shown is suitable for voltage levels ≤200kV (AC or DC). Due to the difficulty in controlling internal partial discharge and flashover, it cannot operate stably if the voltage level is extended to 300kV (especially DC) and above.

[0009] With the continuous increase in voltage levels of electrical systems and technological advancements in fields such as radar, accelerators, and ion implanters, there is a demand for isolation transformers with higher voltage withstand capabilities. However, even with various improvements, the isolation voltage of a single isolation transformer assembly has a limit, making it difficult to exceed 1 mV (1 million volts). Therefore, some have proposed isolation transformer systems that combine multiple isolation transformers. This allows each of the multiple isolation transformers to withstand a portion of the total voltage, thereby increasing the overall isolation voltage level of the system.

[0010] However, in such isolation transformer systems, it cannot be guaranteed that all isolation transformers will bear the voltage evenly. There is a possibility that some isolation transformers may experience flashover or partial discharge due to being subjected to higher voltages, potentially leading to damage to those transformers. When one isolation transformer experiences a decrease in insulation resistance or even insulation breakdown, the higher voltage is applied to other isolation transformers, causing them to experience flashover or partial discharge, and in severe cases, damage. As a result, a failure or damage to one isolation transformer can lead to failures or damage to other isolation transformers and even the entire isolation transformer system.

[0011] In addition, for loads with complex operating conditions and large resistance fluctuations, overcurrent, overvoltage, and undervoltage caused by ultra-high voltage fluctuations can also lead to damage or even breakdown of the isolation transformer.

[0012] This invention was made to solve the above-mentioned technical problems, and its purpose is to provide an isolation transformer and a DC high-voltage isolation transformer system that have high reliability (can work more stably) and can achieve higher isolation voltage.

[0013] Technical means to solve technical problems

[0014] To address the aforementioned technical problems, the present invention provides an isolation transformer, comprising: a housing; an isolation transformer unit and a voltage equalization device housed within the housing.

[0015] The isolation transformer unit includes an iron core; a primary winding and a secondary winding coaxially arranged with the iron core; a first insulator between the iron core and the primary winding; and a second insulator between the primary winding and the secondary winding. The iron core, the first insulator, the primary winding, the second insulator, and the secondary winding are arranged sequentially from the inner periphery to the outer periphery.

[0016] The second insulator comprises n sub-insulators arranged sequentially from the inner periphery to the outer periphery, where n is an integer greater than or equal to 2.

[0017] When the sub-insulator closest to the primary winding is designated as the first sub-insulator, and the sub-insulator closest to the secondary winding is designated as the nth sub-insulator, a voltage-equalizing shielding layer made of conductive material is provided between each of the sub-insulators and on the secondary winding side of the nth sub-insulator.

[0018] The voltage equalization device consists of n voltage equalization resistors connected in series. When the voltage equalization resistor closest to the primary winding is designated as the first resistor, and the other voltage equalization resistors are designated as the second to nth resistors respectively, one end of the first resistor is grounded and the other end is connected to one end of the second resistor, and one end of the nth resistor is connected to the other end of the (n-1)th resistor.

[0019] Each of the voltage equalization shielding layers is connected to the other end of the first to nth resistors, so that the potentials of each voltage equalization shielding layer satisfy a specified proportional relationship.

[0020] Furthermore, this invention provides a DC high-voltage isolation transformer system, comprising n cascaded isolation transformers, where n is an integer greater than or equal to 2; multiple connection components for electrical connections between the isolation transformers and between the isolation transformers and the DC high-voltage platform; and n-1 graded protection power supplies respectively connected to n-1 cascaded nodes between every n adjacent pairs of the n isolation transformers.

[0021] Each of the isolation transformers includes a primary winding and a secondary winding.

[0022] Wherein, when the isolation transformer with the lowest DC potential is the first-stage isolation transformer and the isolation transformer with the highest DC potential is the nth-stage isolation transformer, the primary winding of the first-stage isolation transformer is connected to the mains power, the secondary winding of the first-stage isolation transformer is connected to the primary winding of the next-stage isolation transformer via the connecting assembly, the primary winding of the nth-stage isolation transformer is connected to the secondary winding of the (n-1)th-stage isolation transformer via the connecting assembly, and the secondary winding of the nth-stage isolation transformer is connected to a DC high-voltage platform with an absolute DC potential of VH via the connecting assembly.

[0023] The n isolation transformers are spatially spaced apart, and all isolation transformers except the first-stage isolation transformer are mounted on an insulating support.

[0024] The absolute value of the output DC potential of the graded protection power supply connected to each node increases sequentially from the first node to the (n-1)th node, and each of them satisfies a specified proportional relationship with VH.

[0025] Preferably, the DC high-voltage isolation transformer system of the present invention further includes a voltage and current measurement and control system and a safety interlock protection system. The voltage and current measurement and control system monitors at least the voltage and current of the high-voltage related equipment of the DC high-voltage platform and the voltage of each level of isolation transformer. The graded protection power supply controls its output DC potential according to the voltage monitored by the voltage and current measurement and control system. The safety interlock protection system outputs instructions according to the monitored voltage and current status. When it is judged to be normal, it outputs an "interlock on" instruction to enable the high-voltage related equipment to work normally. When it is judged to be abnormal, it outputs an "interlock off" instruction to shut down the high-voltage related equipment or prevent the high-voltage related equipment from starting.

[0026] Beneficial effects

[0027] (1) The isolation transformer of the present invention has multiple voltage-equalizing shielding layers connected to a voltage-equalizing device composed of multiple voltage-equalizing resistors connected in series in the winding insulation, so that the potentials of each voltage-equalizing shielding layer satisfy a specified proportional relationship. Therefore, it has high insulation withstand strength and low field strength distribution, which can effectively suppress partial discharge and realize the low partial discharge design of the transformer. At the same time, due to voltage grading and accumulated charge release, the above-mentioned technology of the present invention can effectively reduce the difficulty of transformer insulation design and manufacturing process.

[0028] (2) The DC high-voltage isolation transformer system of the present invention adopts a cascaded connection of multiple isolation transformers, which can achieve a multiplication or even several-fold increase in the maximum isolation voltage. By connecting graded protection power supplies to the cascade nodes of multiple isolation transformers respectively, a reasonable voltage distribution among multiple isolation transformers can be achieved to ensure the stable operation of the entire isolation transformer system under ultra-high voltage and extra-high voltage conditions. It is also possible to achieve the function of a large isolation transformer by cascading multiple miniaturized isolation transformers, which can increase the stability of the isolation transformer while reducing the size and production cost of the isolation transformer.

[0029] (3) For loads with complex operating conditions and large resistance fluctuations, overcurrent and overvoltage caused by high voltage fluctuations may damage or even break down the isolation transformer. Using a voltage and current measurement and control system, a graded protection power supply, and a safety interlock protection system to measure, control, and protect against the above situations can further enhance the reliability and stability of the system. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the internal structure of an existing isolation transformer;

[0031] Figure 2A and Figure 2B This is a schematic diagram illustrating the structure of an isolation transformer according to one embodiment of the present invention, wherein, Figure 2A This display shows the overall structure of the isolation transformer. Figure 2B This demonstrates the structure of a sub-insulator;

[0032] Figure 3 This is a schematic diagram illustrating the structure of a DC high-voltage isolation transformer system according to one embodiment of the present invention;

[0033] Figure 4 This is a schematic perspective view showing the structure of an isolation transformer according to an embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram illustrating the structure of a DC high-voltage isolation transformer system according to an embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram illustrating the structure of a connection component in a DC high-voltage isolation transformer system according to an embodiment of the present invention;

[0036] Figure 7 This is a schematic diagram illustrating the structure of another connecting component in a DC high-voltage isolation transformer system according to an embodiment of the present invention;

[0037] Figure 8 This is a schematic diagram illustrating the graded protection power supply and its connection relationship in a DC high-voltage isolation transformer system according to an embodiment of the present invention;

[0038] Figure 9 This is a schematic block diagram illustrating the functional architecture of a safety interlock protection system in a DC high-voltage isolation transformer system according to an embodiment of the present invention;

[0039] Figure 10 This is a schematic diagram illustrating the interlocking protection logic of a safety interlocking protection system in a DC high-voltage isolation transformer system according to an embodiment of the present invention. Detailed Implementation

[0040] To address the problems of flashover or partial discharge caused by accumulated charge and local defects or uneven resistivity distribution in the insulation material in existing DC high-voltage isolation transformers, the isolation transformer of this invention employs the following technical means: The required DC high voltage is graded, making each voltage level easily withstandable by conventional insulation materials, while simultaneously forming a conductive path for discharging accumulated charge. Specifically, a voltage equalization shielding layer combined with high-voltage resistors is used to evenly divide the required ultra-high voltage into n conventional withstand voltage levels. For example, for a DC 400kV withstand voltage level, it is divided into 4-5 levels, each level being 80-100kV. Due to the presence of the voltage equalization shielding layer, the electric field strength of each level in the insulation material is uniform, and the voltage increases gradually and controllably from ground (0V) to the DC 400kV level, thus solving the problem of flashover and partial discharge caused by unavoidable local defects in the insulation material.

[0041] Furthermore, the DC high-voltage isolation transformer system of this invention employs a cascaded connection of multiple isolation transformers, enabling a multiplication or even several-fold increase in the maximum isolation voltage. By connecting graded protection power supplies to the cascade nodes of the multiple isolation transformers, a reasonable voltage distribution among the multiple isolation transformers can be achieved, ensuring stable operation of the entire isolation transformer system under ultra-high voltage and extra-high voltage conditions. Moreover, the function of a large isolation transformer can be achieved by cascading multiple miniaturized isolation transformers, increasing the stability of the isolation transformer while reducing its size and production cost.

[0042] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0043] (An isolation transformer according to one embodiment of the present invention)

[0044] Figure 2A and Figure 2B This is a schematic diagram illustrating the structure of an isolation transformer according to one embodiment of the present invention, wherein, Figure 2A This display shows the overall structure of the isolation transformer. Figure 2B This demonstrates the structure of a sub-insulator. See below for reference. Figure 2A and Figure 2B This invention describes an isolation transformer according to one embodiment of the present invention.

[0045] An isolation transformer according to one embodiment of the present invention includes: a housing; an isolation transformer unit 21 and a voltage equalization device 22 built into the housing. For ease of explanation, in Figure 2A The illustration of the entire housing is omitted, and only the isolation transformer unit 21, the voltage equalization device 22, and the grounding part 23, which are part of the housing, are shown.

[0046] exist Figure 2A In the isolation transformer shown, the isolation transformer unit 21 includes an iron core 211; a primary winding 212 and a secondary winding 213 coaxially arranged with the iron core 211; a first insulator 214 between the iron core 211 and the primary winding 212; and a second insulator 215 between the primary winding 212 and the secondary winding 213. The iron core 211, the first insulator 214, the primary winding 212, the second insulator 215, and the secondary winding 213 are arranged sequentially from the inner periphery to the outer periphery.

[0047] The second insulator 215 includes n sub-insulators arranged sequentially from the inner periphery to the outer periphery, where n is an integer greater than or equal to 2. Figure 2A The example shown illustrates the case where n=3. That is, three sub-insulators are arranged sequentially from the inner perimeter to the outer perimeter: the first sub-insulator 215a closest to the primary winding 212, the second sub-insulator 215b in the middle, and the third sub-insulator 215c closest to the secondary winding 213. A voltage-equalizing shielding layer 215s made of conductive material is provided between each sub-insulator, as well as on the primary winding 212 side of the first sub-insulator 215a and the secondary winding 213 side of the third sub-insulator 215c.

[0048] However, Figure 2A The example shown with n=3 is merely an illustrative structure; the number of sub-insulators can be adjusted and modified according to different insulation classes. For example, if it is necessary to increase the insulation voltage class, one or more additional sub-insulators can be added.

[0049] The voltage equalization device 22 consists of n+1 voltage equalization resistors connected in series. Figure 2A The example shown illustrates the case where n=3. That is, the voltage equalization device consists of four voltage equalization resistors connected in series. The voltage equalization resistor closest to the primary winding 212 is resistor 221, and the others are resistors 222 through 224. One end of resistor 221 is connected to ground 23, and the other end is connected to one end of resistor 222. One end of resistor 223 is connected to the other end of resistor 222, and the other end of resistor 223 is connected to one end of resistor 224.

[0050] In an isolation transformer according to one embodiment of the present invention, each voltage-equalizing shielding layer 215s is connected to the other end of each of the first resistor 221 to the fourth resistor 224, thereby satisfying a predetermined proportional relationship between the potentials of each voltage-equalizing shielding layer. For example, the resistance values ​​of each of the first resistor 221 to the fourth resistor 224 may be equal, thereby satisfying a uniform voltage division relationship between the potentials of each voltage-equalizing shielding layer. That is, when the potential of the other end of the fourth resistor is V, the potential of the other end of the first resistor 221 is V*1 / 4, the potential of the other end of the second resistor 222 is V*2 / 4, and the potential of the other end of the third resistor 223 is V*3 / 4.

[0051] However, embodiments of the present invention are not limited to having equal resistance values ​​for the first resistor 221 to the fourth resistor 224; they can also have unequal resistance values. For example, the resistance values ​​can increase sequentially from the first resistor 221 to the fourth resistor 224. This reduces the voltage division ratio of the voltage-equalizing shielding layer on the inner periphery (a region with a larger electric field strength due to its smaller radius of curvature), thereby making the electric field distribution more uniform throughout the second insulator 215. Alternatively, the first resistor 221 can have a smaller first resistance value, while the second resistor 222 and the fourth resistor 224 can have larger second resistance values. This is because the primary winding 212 side of the first sub-insulator 215a has a lower potential, i.e., a smaller potential difference with ground potential, thus using the first resistor 221 with a smaller resistance value.

[0052] As described above, the isolation transformer of the present invention performs voltage grading on the DC high voltage to be borne, making each voltage level easily borne by conventional insulation materials, thus solving the problems of flashover and partial discharge caused by local defects in the insulation materials (which are unavoidable). At the same time, due to the presence of voltage equalizing resistors, they provide a release circuit or channel for the charge accumulated due to voltage storage under DC high voltage, greatly reducing or avoiding flashover or partial discharge caused by charge accumulation.

[0053] exist Figure 2AIn the isolation transformer of the illustrated embodiment, voltage-equalizing shielding layers 215s made of conductive material are respectively provided between each sub-insulator, on the side of the primary winding 212 of the first sub-insulator 215a, and on the side of the secondary winding 213 of the third sub-insulator 215c. However, the structure of the isolation transformer of the present invention is not limited to this. The voltage-equalizing shielding layer 215s on the side of the primary winding 212 of the first sub-insulator 215a can be omitted, i.e., only three voltage-equalizing shielding layers 215s, the same number as the number of sub-insulators, can be provided. Correspondingly, the voltage-equalizing device 22 is composed of n voltage-equalizing resistors connected in series. This is because the potential on the side of the primary winding 212 of the first sub-insulator 215a is inherently low, i.e., the potential difference with ground potential is small. Therefore, even without the voltage-equalizing shielding layers 215s and the corresponding voltage-equalizing resistors, the electric field distribution will not be significantly affected.

[0054] Preferably, the voltage equalizing resistors are arranged sequentially from the inner periphery to the outer periphery of the isolation transformer unit. This shortens the distance between each voltage equalizing shield and the corresponding voltage dividing resistor, thereby reducing the length of the connecting wires and creating a more uniform potential distribution within the housing. Both of these advantages contribute to improving the withstand voltage rating and reducing the size of the isolation transformer.

[0055] Preferably, a voltage equalization ring 225 is provided at the other end of each of the first to the (n+1)th resistors. The other end of each voltage equalization resistor is the highest potential point of the voltage level, and a wire from the voltage equalization shielding layer is connected to the other end of each voltage equalization resistor. In order to avoid electric field concentration at this point, a multi-ring-shaped voltage equalization ring is provided at this point to encircle the other end, thereby making the electric field distribution at this location more uniform.

[0056] Figure 2B This is a schematic diagram showing the structure of a sub-insulator. Figure 2B The sub-insulator shown in the diagram can be Figure 2A Any one of the first sub-insulator 215a, the second sub-insulator 215b, and the third sub-insulator 215c. For example... Figure 2B As shown, in an isolation transformer according to one embodiment of the present invention, preferably, each sub-insulator includes at least one insulator unit 2151. The insulator unit 2151 includes a first insulating layer 2151-1 having a predetermined first thickness and a second insulating layer 2151-2 having a second thickness smaller than the first thickness. The first insulating layer 2151-1 and the second insulating layer 2151-2 are stacked in a direction from the inner periphery to the outer periphery. In the axial direction of the iron core, the two ends of the second insulating layer 2151-2 protrude to the outside than the two ends of the first insulating layer 2151-1.

[0057] The phrase "at least one" here usually refers to multiple items, for example... Figure 2B The diagram shows three insulating units. However, the number of insulating units can be adjusted and modified according to different insulation levels. For example, if a higher insulation voltage level is required, one or more insulating units can be added. Each insulating unit includes a first insulating layer and a second insulating layer protruding to both sides along the axial direction of the iron core. This structure is similar to that of a high-voltage insulating terminal, and its function is to maximize the creepage distance while ensuring the basic withstand electric field strength (withstand voltage strength).

[0058] Preferably, the housing is an insulator filled with insulating oil. The first insulating layer 2151-1 is made of insulating paper with a first thickness of 15 mm or more, and the second insulating layer 2151-2 is made of insulating paper or high-voltage paperboard with a second thickness of 3-5 mm. This effectively improves the insulation strength and increases the creepage distance.

[0059] For example, 45# Karamay transformer oil can be used as an insulating oil.

[0060] Insulating paper is paper with insulating properties. The following types of insulating paper are commonly used in transformers: (1) DuPont paper, which is a meta-aramid fiber material, commercially known as Nomex. It is widely used as an insulating material in various electrical equipment and electronic fields. A common model of DuPont paper is NOMEXT410. (2) Miki insulating paper, also known as kraft paper, is yellow and has a thickness of 0.13mm to 0.5mm. (3) NMN insulating paper has a thickness of 0.1mm to 0.5mm.

[0061] High-voltage paperboard is short for high-voltage resistant insulating paperboard, such as Weidmann 0.5mm to 1mm high-voltage resistant insulating paperboard.

[0062] The first insulating layer 2151-1 is made of insulating paper, such as DuPont paper or cable paper, and its thickness and number of layers are determined by the required voltage level. As mentioned above, it is preferable that the first thickness is 15 mm or more. When the first thickness is less than 15 mm, the oil channel formed by it is not effective.

[0063] The second insulating layer 2151-2 serves as support and isolation. To ensure clear and visible oil channels between each layer and to guarantee the creepage distance of each sub-insulator, the second insulating layer 2151-2 is preferably made of DuPont paper with a thickness of 0.25 mm or high-voltage paperboard with a thickness of 0.5 mm, with a second thickness of 3-5 mm. Insulating paper that is too thin or insufficiently wound can easily cause collapse during later winding.

[0064] Figure 2AThe diagram shown depicts a structure with an isolation transformer unit and a voltage equalization device built into the housing; however, the isolation transformer of the present invention is not limited to this. Alternatively, the isolation transformer may be a three-phase isolation transformer, comprising three isolation transformer units and three voltage equalization devices respectively connected to each isolation transformer unit within the housing.

[0065] (A DC high-voltage isolation transformer system according to one embodiment of the present invention)

[0066] Figure 3 This is a schematic diagram illustrating the structure of a DC high-voltage isolation transformer system according to one embodiment of the present invention. Referring below... Figure 3 The structure of a DC high-voltage isolation transformer system according to one embodiment of the present invention will be described.

[0067] One embodiment of the present invention provides a DC high-voltage isolation transformer system comprising n cascaded isolation transformers, where n is an integer greater than or equal to 2; a plurality of connection components for electrical connections between the isolation transformers and between the isolation transformers and the DC high-voltage platform; and n-1 graded protection power supplies respectively connected to n-1 cascaded nodes of the n isolation transformers. Figure 3 The example shown is for the case where n=3. For example... Figure 3 As shown, the DC high-voltage isolation transformer system 300 includes a first-stage isolation transformer 301, a second-stage isolation transformer 302, and a third-stage isolation transformer 303. The first-stage isolation transformer 301 and the second-stage isolation transformer 302 are cascaded via a first connection component 304, and the second-stage isolation transformer 302 and the third-stage isolation transformer 303 are cascaded via a second connection component 305. The third-stage isolation transformer 303 is connected to the high-voltage platform via a third connection component 306. A first-level protection power supply 307 is connected to the cascade node of the first-stage isolation transformer 301 and the second-stage isolation transformer 302, and a second-level protection power supply 308 is connected to the cascade node of the second-stage isolation transformer 302 and the third-stage isolation transformer 303. Here, "cascade node" refers to a circuit-like location rather than an actual physical location. Figure 3 In the embodiment shown, the first-level protection power supply 307 is connected to the neutral line of the second-level isolation transformer 302, and the second-level protection power supply 308 is connected to the neutral line of the third-level isolation transformer 303. This will be explained in more detail in the embodiments described later.

[0068] exist Figure 3In the DC high-voltage isolation voltage transformation system 300 shown, three isolation transformers are arranged at spaced intervals in space, wherein the isolation transformer with the lowest DC potential (usually ground potential) is a first-stage isolation transformer 301, and the DC potential increases sequentially from the first-stage isolation transformer 301 to the third-stage isolation transformer 303. In order to achieve spatial isolation from ground potential, the second-stage isolation transformer and the third-stage isolation transformer are arranged on insulating supports 309 and 310.

[0069] In Figure 3 , the illustration is omitted. Each isolation transformer includes a primary winding and a secondary winding. The primary winding of the first-stage isolation transformer 301 is connected to mains power, the secondary winding of the first-stage isolation transformer 301 is connected to the primary winding of the second-stage isolation transformer 302 via a first connecting assembly 304, the primary winding of the third-stage isolation transformer 303 is connected to the secondary winding of the second-stage isolation transformer via a second connecting assembly 305, and the secondary winding of the third-stage isolation transformer 303 is connected to a DC high-voltage platform with an absolute DC potential value of VH via a third connecting assembly 306.

[0070] In the DC high-voltage isolation voltage transformation system according to an embodiment of the present invention, the absolute values of the output DC potentials of the graded protection power supplies connected to each node increase sequentially in the order from the first node to the n-1-th node, and each satisfies a predetermined proportional relationship with VH. Specifically, when the cascading node of the first-stage isolation transformer 301 and the second-stage isolation transformer 302 is designated as the first node, the cascading nodes between other isolation transformers are sequentially designated as the second node to the n-1-th node, and the absolute values of the output DC potentials of the n-1 graded protection power supplies connected to each node are V1, V2, ..., Vn-1 respectively, the relationship V1<V2<...<Vn-1<VH is satisfied, and V1, V2, ..., Vn-1 and VH satisfy a predetermined proportional relationship.

[0071] It should be noted that the relational expression V1<V2<...<Vn-1<VH is only schematic, and the number of DC potentials therein is not a fixed number. That is, since the number of graded protection power supplies is equal to the number of cascading nodes n-1, the maximum number of DC potentials is n-1. The number of DC potentials increases as the number of cascading nodes increases.

[0072] Specifically, in Figure 3In the embodiment having 2 nodes (i.e., n-1=2) as shown, since there are only 2 nodes, the relationship V1<V2<VH is satisfied, and a predetermined proportional relationship is satisfied between V1, V2 and VH. In the embodiment where n=2, that is, there is only 1 node (i.e., n-1=1), the relationship V1<VH is satisfied, and a predetermined proportional relationship is satisfied between V1 and VH. In the embodiment where n=4, that is, there are 3 nodes (i.e., n-1=3), since there are 3 nodes, the relationship V1<V2<V3<VH is satisfied, and a predetermined proportional relationship is satisfied among V1, V2, V3 and VH.

[0073] By adopting a multi-group cascading mode of isolating transformers, the maximum isolation voltage can be multiplied or even multiplied several times. By connecting graded protection power supplies to the cascading nodes of multiple isolating transformers respectively, reasonable voltage distribution among the multiple isolating transformers can be realized, so as to ensure the stable operation of the whole isolating voltage transformation system under ultra-high voltage and extra-high voltage conditions. The function of a large isolating transformer can also be realized by cascading a plurality of miniaturized isolating transformers, which can increase the stability of the isolating transformer and reduce the volume and production cost of the isolating voltage transformation.

[0074] Preferably, the n isolating transformers have the same structure, and the following proportional relationship is satisfied between V1, V2, ..., Vn-1 and VH: V1=VH*1 / n, V2=VH*2 / n, ..., Vn-1=VH*(n-1) / n. That is, preferably, when the n isolating transformers have the same structure, each isolating transformer equally shares the total isolation voltage to be borne. For example, in Figure 3 the case where n=3 as shown, V1=VH*1 / 3 and V2=VH*2 / 3.

[0075] Of course, in the DC high-voltage isolating voltage transformation system of the present invention, it is not limited that each isolating transformer equally shares the total isolation voltage to be borne. In some cases, a plurality of isolating transformers can each share different proportions of the isolation voltage.

[0076] As an example, there is a case where n isolating transformers have the same structure in the initial state, and after a period of time, internal damage occurs to a certain isolating transformer due to partial discharge and other causes. At this time, the upper limit of the voltage resistance of the isolating transformer will decrease, in other words, the voltage resistance cannot reach the design index, but it can still be used as an isolating transformer with a lower index. For example, after a serious arcing of an originally designed 200kV isolating transformer, it is tested that it can only withstand a maximum voltage of 180kV. Therefore, this isolating transformer can be used as an isolating transformer with a maximum voltage resistance of about 180kV (degraded use).

[0077] In this situation, the DC potential of the graded protection power supply can be adjusted to distribute the total voltage evenly across each isolation transformer instead of using a uniform voltage division method. Instead, a smaller voltage (not exceeding the upper limit voltage after damage) is applied to the damaged isolation transformer, while a relatively higher voltage (not exceeding the design specifications) is applied to the other isolation transformers. This voltage division method not only protects the damaged isolation transformer but also improves the stability of the entire system.

[0078] Preferably, the DC high-voltage isolation transformer system of the present invention further includes a voltage and current measurement and control system and a safety interlock protection system. The voltage and current measurement and control system monitors the voltage and current of the high-voltage related equipment of the DC high-voltage platform and the voltage of each level of isolation transformer. The graded protection power supply controls its output DC potential based on the voltage monitored by the voltage and current measurement and control system. The safety interlock protection system outputs commands based on the monitored voltage and current status. When the status is normal, it outputs an "interlock on" command to enable the high-voltage related equipment to operate normally. When the status is abnormal, it outputs an "interlock off" command to shut down the high-voltage related equipment or prevent its startup. The voltage and current measurement and control system and the safety interlock protection system in the DC high-voltage isolation transformer system of the present invention will be described in more detail in the embodiments section.

[0079] Preferably, in the DC high-voltage isolation transformer system of the present invention, the connection component includes: at least one live wire and one neutral wire connected between two cascaded isolation transformers or between the nth-stage isolation transformer and the high-voltage platform; the live wire connects the output-side live wire of the lower-stage isolation transformer to the corresponding input-side live wire of the higher-stage isolation transformer, or connects the output-side live wire of the nth-stage isolation transformer to the corresponding input-side live wire of the high-voltage platform; the neutral wire connects the output-side neutral wire of the lower-stage isolation transformer to the input-side neutral wire of the higher-stage isolation transformer, or connects the output-side neutral wire of the nth-stage isolation transformer to the input-side neutral wire of the high-voltage platform.

[0080] Preferably, the DC high-voltage isolation transformer system further includes: a low-level side equalizing ring disposed at the output end of the low-level isolation transformer in the two isolation transformers, or an nth-level output side equalizing ring disposed at the output end of the nth-level isolation transformer; and an advanced-level side equalizing ring disposed at the input end of the advanced-level isolation transformer, or a high-voltage platform equalizing ring disposed on the DC high-voltage platform. The low-level side equalizing ring is connected to the side of the low-level isolation transformer on the neutral wire connection line via a metal wire, or the nth-level output side equalizing ring is connected to the side of the nth-level isolation transformer on the neutral wire connection line via a metal wire, and the advanced-level side equalizing ring is connected to the side of the advanced-level isolation transformer on the neutral wire connection line via a metal wire, or the high-voltage platform equalizing ring is connected to the side of the DC high-voltage platform on the neutral wire connection line via a metal wire.

[0081] Preferably, in the DC high-voltage isolation transformer system of the present invention, the isolation transformer is an isolation transformer of the present invention having multiple voltage-equalizing shielding layers in the inter-winding insulator connected to a voltage-equalizing device formed by multiple voltage-equalizing resistors connected in series. By adopting this technical solution, the withstand voltage of each isolation transformer can be increased, thereby further improving the withstand voltage level of the DC high-voltage isolation transformer system and maximizing the function of the entire system.

[0082] (Example)

[0083] The specific embodiments and technical effects of the isolation transformer and DC high-voltage isolation transformer system of the present invention will be described below with reference to the accompanying drawings.

[0084] Figure 4 This is a schematic perspective view illustrating a three-phase isolation transformer according to an embodiment of the present invention. Figure 4 In the diagram, the three cylindrical objects 401 (only two are visible in the figure) are three isolation transformer units. Each transformer has an equalizing shielding layer, and each equalizing shielding layer is connected to a corresponding equalizing resistor via lead wires (not shown). In this embodiment, the equalizing shielding layer is formed by winding a layer of 0.5mm thick copper foil. Figure 4 In the three-phase isolation transformer shown, a voltage equalization device 402 is composed of six series-connected voltage equalization resistors. The withstand voltage of a single resistor is 30kV to 50kV (when oil-immersed), the resistance accuracy is 0.1%, and the resistance value is between 30MΩ and 50MΩ. However, the number of series-connected voltage equalization resistors is not limited to the six in the above embodiment, and the withstand voltage of a single resistor is not limited to 30kV to 50kV in the above embodiment. It can be adjusted according to different withstand voltage levels; for example, resistors with higher withstand voltage values ​​can be used.

[0085] The housing 403 is an insulator, made of epoxy resin (in... Figure 4In the diagram, the housing is shown as transparent to demonstrate the internal structure of the transformer. The low-voltage input terminal 404 is located at the bottom of the housing, and the high-voltage output terminal 405 is located at the top of the housing. A high-voltage equalizing ring 406 is provided above the top of the housing 403. It is roughly coaxial with the cylindrical housing and has a diameter roughly the same as the diameter of the housing.

[0086] An embodiment of the isolation transformer of the present invention has multiple voltage-equalizing shielding layers connected to a voltage-equalizing device composed of multiple voltage-equalizing resistors connected in series. This ensures that the potentials of each voltage-equalizing shielding layer satisfy a predetermined proportional relationship, thus exhibiting high insulation withstand strength and low electric field distribution. This effectively suppresses partial discharge, achieving a low partial discharge design for the transformer. The partial discharge quantity does not exceed 10 pC at voltage levels from DC 300kV to above 500kV. Furthermore, due to voltage grading and accumulated charge release, the above-mentioned technology of the present invention effectively reduces the difficulty of transformer insulation design and manufacturing processes.

[0087] Figure 5 This is a schematic diagram illustrating the structure of a DC high-voltage isolation transformer system according to an embodiment of the present invention. Figure 5 The embodiment shown is a DC high-voltage isolation transformer system with two-stage isolation transformers; however, the DC high-voltage isolation transformer system of the present invention is not limited to the form with two-stage isolation transformers.

[0088] like Figure 5 As shown, a DC high-voltage isolation transformer system according to an embodiment of the present invention includes: a first-stage isolation transformer 501, a second-stage isolation transformer 502, a first connection component 503 that cascades the first-stage isolation transformer 501 and the second-stage isolation transformer 502, a graded protection power supply 504 connected to the cascade node of the first-stage isolation transformer 501 and the second-stage isolation transformer 502, a voltage and current measurement and control system 505, and a safety interlock protection system 506.

[0089] exist Figure 5 In the illustrated embodiment, the first-stage isolation transformer 501 and the second-stage isolation transformer 502 are three-phase isolation transformers. A 380V three-phase AC power supply is input to the primary winding of the first-stage isolation transformer 501, and the secondary winding of the second-stage isolation transformer 502 is connected to a DC high-voltage platform, providing it with a 380V three-phase AC power supply.

[0090] like Figure 5 As shown, the first-stage isolation transformer 501 and the second-stage isolation transformer 502 are spatially separated, with the second-stage isolation transformer 502 mounted on an insulating support 507 made of insulating porcelain pillars.

[0091] exist Figure 5In the illustrated embodiment, the first-stage isolation transformer 501 and the second-stage isolation transformer 502 adopt the same structure, for example, they can be... Figure 4 The three-phase isolation transformer is shown. Since the first-stage isolation transformer 501 and the second-stage isolation transformer 502 adopt the same structure, the output voltage value of the graded protection power supply 504 is taken as 1 / 2 of the absolute value of the DC high-voltage platform voltage, that is, the first-stage isolation transformer 501 and the second-stage isolation transformer 502 each bear half of the DC high-voltage platform voltage value.

[0092] The voltage and current measurement and control system 505 includes a voltage sensor, a current sensor, a high-voltage isolated data communication line, and a measurement and control system terminal. Figure 5 Only the measurement and control system terminal is shown, while illustrations of other parts are omitted. The voltage and current measurement and control system 505 monitors the voltage and current of the high-voltage related equipment of the DC high-voltage platform and the voltage of each level of isolation transformer. The high-voltage related equipment of the DC high-voltage platform includes a high-voltage power supply that provides DC high voltage to the DC high-voltage platform, and at least one load in the DC high-voltage platform. As an example of a voltage sensor, a high-voltage probe is used to monitor the voltage through direct contact. As an example of a current sensor, a resistor with a known resistance value is used, and the current is detected by detecting the voltage across the resistor based on the basic principles of series voltage division and parallel current division.

[0093] For load currents that cannot be directly measured, the monitoring and control system terminal can compare the high-voltage power supply current monitored when the load is not operating with the current when the load is operating; the difference is the current flowing through the load. For the internal current of the isolation transformer that cannot be directly measured, the monitoring and control system terminal can calculate the internal current of the isolation transformer assembly by monitoring the total voltage and the voltage of each stage, using existing component resistance parameters, and current monitoring from other parts. For example, theoretically, the current inside the isolation transformer assembly can be obtained by subtracting the protection power supply current and the load current from the high-voltage power supply current.

[0094] Voltage and current sensors detect the voltage and current of high-voltage related equipment and the voltage of isolation transformers at each level, which are then input to the measurement and control system terminal via a high-voltage isolated data communication line. This high-voltage isolated data communication line can be constructed using existing opto-isolation or high-voltage isolation modules. Opto-isolation converts electrical signals into optical signals and transmits them via optical fiber, primarily used for isolation from the high-voltage platform to ground, suitable for signal isolation above tens of thousands of volts. High-voltage isolation modules are high-voltage isolation modules (withstanding hundreds to thousands of volts) inserted into the electrical signal transmission circuit, primarily used for zero-potential ground arcing isolation in high-voltage environments.

[0095] The hardware structure of the measurement and control system terminal includes: a CPU, memory, analog input units, analog output units, digital input units, digital output units, digital communication units, network communication units, and an uninterruptible power supply. These hardware components and circuits can be constructed using existing electronic parts and circuits; detailed descriptions are omitted here. The functional structure of the measurement and control system terminal includes: a voltage and current acquisition module for high-voltage related equipment, a signal denoising module, a load operating parameter acquisition module, a voltage and current control module for high-voltage related equipment, a load operating status control module, and a data export module. These modules can be implemented by a computer containing a CPU and memory running computer programs.

[0096] The voltage and current monitored by the voltage and current measurement and control system 505 are used for the output voltage control of the graded protection power supply 504, the operation control of high-voltage related equipment, and the interlocking protection provided by the safety interlocking protection system 506. For the safety interlocking protection system 506, reference will be made to... Figure 9 and Figure 10 This will explain its structure, function, and interlocking protection logic.

[0097] Figure 6 This is a schematic diagram illustrating the structure of a connection component in a DC high-voltage isolation transformer system according to an embodiment of the present invention, wherein the DC high-voltage isolation transformer system is... Figure 5 The diagram shows a DC high-voltage isolation transformer system with two-stage isolation transformers.

[0098] like Figure 6 As shown, the connection assembly 600 includes three live wires 601 and one neutral wire 602 connected between the first-stage isolation transformer 501 and the second-stage isolation transformer 502.

[0099] Among them, the three live wire connecting wires 601 connect the output side live wire of the first-stage isolation transformer 501 to the corresponding input side live wire of the second-stage isolation transformer 502, and the neutral wire connecting wire 602 connects the output side neutral wire of the first-stage isolation transformer 501 to the input side neutral wire of the second-stage isolation transformer 502.

[0100] Connecting the output neutral wire of the first-stage isolation transformer 501 to the input neutral wire of the second-stage isolation transformer 502 with the neutral wire 602 ensures that the ground potentials of all equipotential loads are physically connected and equal, thereby preventing discharge (i.e., arcing) between the connection wire and the isolation transformer.

[0101] As a preferred embodiment, such as Figure 6As shown, one equalizing ring 5011 is provided at the output terminal of the first-stage isolation transformer 501; two equalizing rings 5021 are provided at the input terminal of the second-stage isolation transformer 502. The equalizing ring 5011 is connected to the first-stage isolation transformer 501 side of the neutral connection line 602 via a metal wire, and the equalizing ring 5021 is connected to the second-stage isolation transformer 502 side of the neutral connection line 602 via a metal wire.

[0102] By installing equalizing rings near the input and output terminals of the isolation transformer and connecting them to the neutral wire as close as possible, electric field concentration can be avoided near the input and output terminals, thus making the potential distribution in these areas more uniform. These technical measures prevent discharge (i.e., arcing) near the input and output terminals of the isolation transformer.

[0103] Figure 6 The connection assembly shown is for cascading connections between two isolation transformers. However, the connection assembly in the DC high-voltage isolation transformer system of the present invention is not limited to cascading connections; it can also be used for electrical connections between isolation transformers and high-voltage platforms. Furthermore, depending on the type and structure of the connected high-voltage electrical equipment, the arrangement and number of equalizing rings are not limited to... Figure 6 As shown in the diagram.

[0104] Figure 7 This is a schematic diagram illustrating the structure of another connecting component in a DC high-voltage isolation transformer system according to an embodiment of the present invention. Figure 7 The connecting components shown are Figure 6 The difference in the connecting components shown is that, Figure 7 The connecting assembly 700 shown also includes a bellows and a metal support rod.

[0105] Specifically, for ease of explanation, in Figure 7 The diagram only shows the neutral wire connection and omits the three live wire connections. (See diagram for example.) Figure 7 As shown, the neutral wire 701 includes a conductive metal wire 702 and an insulating layer 703 covering the metal wire. A metal support rod 704 is arranged side-by-side with the neutral wire 701, most of which is surrounded by a metal bellows 705, with the portion for connection to the isolation transformer protruding from the bellows 705. The metal bellows 705, the metal support rod 704, and the neutral wire are connected together using highly conductive metal wires to ensure they have equal potential.

[0106] The metal support rod 704 provides physical support, preventing the entire connecting assembly 700 from bending due to its own weight. If the power transmission distance is short (e.g., less than 1 meter), the rigidity of the conductive metal wire 702 and the insulation layer 703 can prevent the connecting assembly 700 from bending excessively, thus eliminating the need for the metal support rod.

[0107] In a DC high-voltage isolation transformer system, since the entire connection assembly is at a high potential, the function of the metal bellows is to equalize the voltage, i.e., reduce the electric field strength near the connection assembly. Specifically, a large-diameter metal bellows surrounds multiple smaller-diameter connecting wires and metal support rods, and the metal bellows, metal support rods, and neutral wire are connected together using highly conductive metal wires to ensure that they are all at the same potential. Thus, from the outside, the entire connection assembly appears as a large-diameter bellows. Due to its large radius of curvature, the electric field strength on its surface and in the vicinity is reduced, thereby preventing the connection assembly from discharging into the air.

[0108] Figure 8 This is a schematic diagram illustrating the hierarchical protection power supply and its connection relationship in a DC high-voltage isolation transformer system according to an embodiment of the present invention, wherein the DC high-voltage isolation transformer system is... Figure 5 The diagram shows a DC high-voltage isolation transformer system with two-stage isolation transformers.

[0109] like Figure 8 As shown, the graded protection power supply 504 includes a power control section 5041 located on the lower side and a power boost section 5042 located on the upper side. A high DC voltage is output from the top of the graded protection power supply 504 and transmitted via a high DC voltage connection line 801 (e.g., ...). Figure 7 The connecting assembly 700 shown is connected to the neutral line of the second-stage isolation transformer 502. An equalizing ring 5043 is located near the output terminal of the DC high voltage. The equalizing ring 5043 is connected to the DC high voltage connection line 801 using a highly conductive metal wire.

[0110] In one embodiment of the present invention, the graded protection power supply in a DC high-voltage isolation transformer system has a variable output DC high voltage to ensure a predetermined proportional relationship between the voltage borne by the isolation transformer and the voltage of the high-voltage platform. For this purpose, data from the voltage and current measurement and control system 505 is input to the graded protection power supply 504 via the high-voltage isolation data communication line 802. This allows the output DC potential of the graded protection power supply to be controlled according to the measured voltage value, making it the desired voltage value, for example, half the absolute value of the DC high-voltage platform voltage.

[0111] Regarding the function and effect of graded protection power supplies, Figure 5 The following is a more detailed explanation using a DC high-voltage isolation transformer system with two-stage isolation transformers as an example.

[0112] When the high-voltage platform operates at a stable voltage, the protection power supply provides an intermediate voltage to equalize the voltage across the two isolation transformers, ensuring that the total voltage is evenly distributed across each isolation transformer component. As the total voltage (high-voltage power supply output) of the target voltage increases, the voltage parameters of the protection power supply are always set to 1 / 2 of the total voltage (if it is N stages, the second stage is 1 / n, the third stage is 2 / n, and so on), increasing synchronously with the total voltage.

[0113] In existing isolation transformer systems, the voltage across the isolation transformer is distributed based on the resistance ratio of its internal resistors. The magnitude of the distributed voltage is determined by the electrical and physical characteristics of each resistor segment and cannot be manually adjusted. If a resistor malfunctions, its electrical and physical characteristics change, affecting the stability of the entire system.

[0114] In the event of unstable conditions such as abnormal voltage fluctuations, the presence of the protective power supply ensures that the voltage between the two transformer stages remains equal, provided the power output does not exceed its capacity. Specifically, when abnormal voltage fluctuations occur due to load short circuits, open circuits, or other abnormalities, the protective power supply, with its large-capacity capacitors and other components, can absorb short-term surge voltages, maintaining its output voltage at the preset level and ensuring stable operation. For systems with two isolation transformers, this protective voltage is applied to the first-stage isolation transformer assembly; therefore, abnormal voltage fluctuations in the overall system voltage will not affect the first-stage isolation transformer assembly (similar to a seawall). Similarly, for DC high-voltage isolation transformer systems built using this model, voltage surges will be suppressed at the stage closest to the load (high-voltage platform), while other isolation transformer assemblies are protected by their respective protective power supplies.

[0115] In existing isolation transformer systems, the isolation transformer cannot stabilize abnormal voltage fluctuations within a uniform voltage state. Such abnormal voltage fluctuations can impact or even break down the weakest parts or components in the isolation transformer, potentially causing a breakdown interlocking reaction in severe cases.

[0116] Figure 9 This is a schematic block diagram illustrating the functional architecture of a safety interlocking protection system in a DC high-voltage isolation transformer system according to an embodiment of the present invention.

[0117] The core architecture of the safety interlock protection system is the safety interlock judgment logic. Its function is to output commands based on the monitored voltage and current status, load operating status, system authorization status, and emergency stop button status. When the judgment is normal, it outputs an "Interlock OK" command to allow the high-voltage power supply and related loads, which are related to high-voltage equipment, to operate normally. When the judgment is abnormal or a command is received from the emergency stop button, it outputs an "Interlock Disconnect" command, causing the high-voltage power supply or related load to shut down, or preventing the start-up of high-voltage related equipment.

[0118] As an embodiment of the present invention, the safety interlocking protection system in the DC high-voltage isolation transformer system, such as Figure 9 As shown, the operating status monitoring objects include: "high voltage power supply voltage / current over-limit", "load operating status over-limit", equipment "authorized status" and "emergency stop (button) status". However, the functional architecture of the safety interlock protection system in the DC high voltage isolation transformer system of the present invention is not limited to this. The operating status monitoring objects may only include a part of them, such as "high voltage power supply voltage / current over-limit" and "emergency stop (button) status".

[0119] Figure 10 This is a schematic diagram illustrating the interlocking protection logic of a safety interlocking protection system in a DC high-voltage isolation transformer system according to an embodiment of the present invention.

[0120] exist Figure 10 The input signals used for logical judgments in each logic gate include “voltage over-limit” and “current over-limit” for power supply status judgment, “operating parameter 1 over-limit” and “operating parameter n over-limit” for load status judgment, and “stop button pressed” and “unauthorized status” for operation authorization judgment.

[0121] Figure 10 In this system, the logical relationship between each logic gate is an "OR" operation. That is, if any logic gate is in an "overlimit" or "unauthorized" state, the final interlocking state judgment will be "NOT", i.e., "interlocking is open". In other words, only when all input signals used for logical judgment indicate that they are in a normal state will the final interlocking state judgment be "Yes", i.e., "interlocking is OK".

[0122] In actual operation of isolated transformer systems, if the interlock status is judged as "NOT", the output of high-risk loads such as the main high-voltage power supply will be stopped (output is not allowed to be started if it has not been started). This ensures that the entire system is safe and controllable before high-risk equipment is started. After the system is running, if a sudden abnormal operating state occurs, the output of high-risk loads such as the main high-voltage power supply can be stopped automatically according to the preset logic (automatic logic calculation of each safety interlock point). Alternatively, if the interlock setting threshold is not reached (an abnormal trend occurs, but the interlock setting threshold is not reached), the operator can use their operating experience to shut down the system with one click (emergency stop button), and then check for possible problems in the system, thus ensuring the overall safety of the system.

[0123] For example, in abnormal operating conditions such as high-voltage sparking, the safety interlock system can automatically stop dangerous outputs such as high-voltage power supply according to preset current limits and other conditions to protect the equipment.

[0124] Existing isolation transformer systems lack such protection, relying solely on the physical withstand voltage characteristics of the isolation transformer itself. If these characteristics are exceeded, damage may occur due to arcing or other reasons, potentially leading to insulation breakdown.

[0125] As can be seen from the above description, the isolation transformer and DC high-voltage isolation transformer system of the present invention have the following technical effects:

[0126] (1) The isolation transformer of the present invention has multiple voltage-equalizing shielding layers connected to a voltage-equalizing device composed of multiple voltage-equalizing resistors connected in series in the winding insulation, so that the potentials of each voltage-equalizing shielding layer satisfy a specified proportional relationship. Therefore, it has high insulation withstand strength and low field strength distribution, which can effectively suppress partial discharge and realize the low partial discharge design of the transformer. At the same time, due to voltage grading and accumulated charge release, the above-mentioned technology of the present invention can effectively reduce the difficulty of transformer insulation design and manufacturing process.

[0127] (2) The DC high-voltage isolation transformer system of the present invention adopts a cascaded connection of multiple isolation transformers, which can achieve a multiplication or even several-fold increase in the maximum isolation voltage. By connecting graded protection power supplies to the cascade nodes of multiple isolation transformers respectively, a reasonable voltage distribution among multiple isolation transformers can be achieved to ensure the stable operation of the entire isolation transformer system under ultra-high voltage and extra-high voltage conditions. It is also possible to achieve the function of a large isolation transformer by cascading multiple miniaturized isolation transformers, which can increase the stability of the isolation transformer while reducing the size and production cost of the isolation transformer.

[0128] (3) For loads with complex operating conditions and large resistance fluctuations, overcurrent and overvoltage caused by high voltage fluctuations may damage or even break down the isolation transformer. Using a voltage and current measurement and control system, a graded protection power supply, and a safety interlock protection system to measure, control, and protect against the above situations can further enhance the reliability and stability of the system.

Claims

1. An isolation transformer, characterized in that, include: case; The isolation transformer unit and voltage equalization device are built into the housing. The isolation transformer unit includes an iron core; a primary winding and a secondary winding arranged coaxially with the iron core; The first insulator between the iron core and the primary winding, and the second insulator between the primary winding and the secondary winding, are arranged sequentially from the inner periphery to the outer periphery. The second insulator comprises n sub-insulators arranged sequentially from the inner periphery to the outer periphery, where n is an integer greater than or equal to 2. When the sub-insulator closest to the primary winding is designated as the first sub-insulator, and the sub-insulator closest to the secondary winding is designated as the nth sub-insulator, a voltage-equalizing shielding layer made of conductive material is provided between each of the sub-insulators and on the secondary winding side of the nth sub-insulator. The voltage equalization device consists of n voltage equalization resistors connected in series. When the voltage-equalizing resistor closest to the primary winding is designated as the first resistor, and the other voltage-equalizing resistors are designated as the second to nth resistors respectively, one end of the first resistor is grounded and the other end is connected to one end of the second resistor, and one end of the nth resistor is connected to the other end of the (n-1)th resistor. Each of the voltage equalization shielding layers is connected to the other end of the first to nth resistors, so that the potentials of each voltage equalization shielding layer satisfy a specified proportional relationship.

2. The isolation transformer as described in claim 1, characterized in that, A voltage equalization ring is provided at the other end of each of the first to nth resistors. The n equalizing resistors are arranged sequentially in a direction from the inner periphery to the outer periphery of the isolation transformer unit.

3. The isolation transformer as described in claim 1 or 2, characterized in that, Each of the sub-insulators includes at least one insulator unit, the insulator unit including a first insulating layer having a predetermined first thickness and a second insulating layer having a second thickness smaller than the first thickness, the first insulating layer and the second insulating layer being stacked in a direction from the inner periphery to the outer periphery, and in the axial direction of the core, the two ends of the second insulating layer protrude outwards than the two ends of the first insulating layer.

4. The isolation transformer as described in claim 3, characterized in that, The housing is an insulator, and the housing is filled with insulating oil. The first insulating layer is made of stacked insulating paper, and its thickness is 15 mm or more. The second insulating layer is made of insulating paper or high-pressure paperboard, and the second thickness is 3~5mm.

5. The isolation transformer as described in claim 1 or 2, characterized in that, The isolation transformer is a three-phase isolation transformer, and the housing includes three isolation transformer units and three voltage equalization devices connected to each of the isolation transformer units.

6. The isolation transformer as described in claim 3, characterized in that, The isolation transformer is a three-phase isolation transformer, and the housing includes three isolation transformer units and three voltage equalization devices connected to each of the isolation transformer units.

7. The isolation transformer as described in claim 4, characterized in that, The isolation transformer is a three-phase isolation transformer, and the housing includes three isolation transformer units and three voltage equalization devices connected to each of the isolation transformer units.

8. A DC high-voltage isolation transformer system, characterized in that, include: n cascaded isolation transformers, where n is an integer greater than or equal to 2; Multiple connection components for electrical connections between the isolation transformers and between the isolation transformers and the DC high-voltage platform; and Each of the n isolation transformers is connected to one of the n-1 cascaded nodes between every two adjacent isolation transformers, and then to one of the n graded protection power supplies. Each of the isolation transformers includes a primary winding and a secondary winding. Wherein, when the isolation transformer with the lowest DC potential is the first-stage isolation transformer and the isolation transformer with the highest DC potential is the nth-stage isolation transformer, the primary winding of the first-stage isolation transformer is connected to the mains power, the secondary winding of the first-stage isolation transformer is connected to the primary winding of the next-stage isolation transformer via the connecting assembly, the primary winding of the nth-stage isolation transformer is connected to the secondary winding of the (n-1)th-stage isolation transformer via the connecting assembly, and the secondary winding of the nth-stage isolation transformer is connected to a DC high-voltage platform with an absolute DC potential of VH via the connecting assembly. The n isolation transformers are spatially spaced apart, and all isolation transformers except the first-stage isolation transformer are mounted on an insulating support. The absolute value of the output DC potential of the graded protection power supply connected to each node increases sequentially from the first node to the (n-1)th node, and each of them satisfies a specified proportional relationship with VH.

9. The DC high-voltage isolation transformer system as described in claim 8, characterized in that, It also includes voltage and current measurement and control systems and safety interlock protection systems. The voltage and current measurement and control system monitors at least the voltage and current of the high-voltage related equipment of the DC high-voltage platform and the voltage of each level of isolation transformer. The graded protection power supply controls its output DC potential based on the voltage monitored by the voltage and current measurement and control system. The safety interlock protection system outputs commands based on the monitored voltage and current status. When the status is normal, it outputs an "interlock on" command to enable the high-voltage related equipment to work normally. When the status is abnormal, it outputs an "interlock off" command to shut down the high-voltage related equipment or prevent the high-voltage related equipment from starting.

10. The DC high-voltage isolation transformer system as described in claim 8 or 9, characterized in that, The connection component includes: at least one live wire and one neutral wire connected between two cascaded isolation transformers or between the nth isolation transformer and the high-voltage platform; The live wire connection connects the output live wire of the lower-level isolation transformer to the corresponding input live wire of the higher-level isolation transformer, or connects the output live wire of the nth-level isolation transformer to the corresponding input live wire of the high-voltage platform. The neutral wire connection connects the output side neutral wire of the low-level isolation transformer to the input side neutral wire of the high-level isolation transformer, or connects the output side neutral wire of the nth-level isolation transformer to the input side neutral wire of the high-voltage platform.

11. The DC high-voltage isolation transformer system as described in claim 10, characterized in that, The DC high-voltage isolation transformer system further includes: a low-level side voltage equalization ring disposed at the output terminal of the low-level isolation transformer in the two isolation transformers, or an nth-level output side voltage equalization ring disposed at the output terminal of the nth-level isolation transformer; and an advanced-level voltage equalization ring disposed at the input terminal of the advanced-level isolation transformer, or a high-voltage platform voltage equalization ring disposed on the DC high-voltage platform. The low-level side equalizing ring is connected to the low-level side isolation transformer side of the neutral wire connection line via a metal wire, or the nth-stage output side equalizing ring is connected to the nth-stage isolation transformer side of the neutral wire connection line via a metal wire. The advanced-side equalizing ring is connected to the advanced-side isolation transformer side of the neutral wire connection line via a metal wire, or the high-voltage platform equalizing ring is connected to the DC high-voltage platform side of the neutral wire connection line via a metal wire.

12. The DC high-voltage isolation transformer system as described in claim 8 or 9, characterized in that, The isolation transformer is the isolation transformer described in any one of claims 1 to 7.

13. The DC high-voltage isolation transformer system as described in claim 10, characterized in that, The isolation transformer is the isolation transformer described in any one of claims 1 to 7.

14. The DC high-voltage isolation transformer system as described in claim 11, characterized in that, The isolation transformer is the isolation transformer described in any one of claims 1 to 7.

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