Winding for grounding transformer and grounding transformer
By optimizing the winding and core structure of the grounding transformer, including designing insulation distance and airway size, the problem of high local discharge caused by its own structure is solved, and higher voltage resistance and equipment life are achieved.
Patent Information
- Application Number
- CN202311872081.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-29
- Publication Date
- 2025-07-01
AI Technical Summary
The existing grounding transformers have high local discharge caused by their own structure, which affects their life and safety.
By designing the insulation distance between the windings is 15 to 25 mm, the minimum distance between adjacent airways is 3 to 10 mm, the airway size between the inner and outer windings is 10 to 25 mm, and cooling is used with heating equipment at high temperatures, optimizing the insulation distance between the iron core and the windings to ensure mechanical strength and insulation effect.
It effectively reduces the local discharge of the grounding transformer, improves the voltage withstand performance and structural performance, extends the equipment life, and reduces the risk of local discharge.
Smart Images
Figure CN120236874A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a winding for a grounding transformer and a grounding transformer, belonging to the technical field of transformers. Background Art
[0002] The partial discharge level is a key indicator for measuring the casting process and production quality of the insulating material of a dry-type grounding transformer.
[0003] For ease of reading, the grounding transformer in this article is abbreviated as grounding transformer; partial discharge is abbreviated as PD.
[0004] There are various discharge types of PD in the grounding transformer, including the form of partial discharge occurring on the insulating surface. If the energy is large and discharge marks are left on the insulator surface, it will affect the life of the test grounding transformer; it also includes the form of partial discharge with a higher discharge intensity, occurring in air cavities or sharp-corner electrodes, concentrated at a few points. This discharge can penetrate into the layers and depths of the insulating cardboard, ultimately leading to breakdown.
[0005] The direct cause of PD in the grounding transformer includes defective products produced by poor production processes.
[0006] PD in the grounding transformer is the main cause of the aging of insulating parts and their breakdown. Short-term discharge will not damage the medium of the entire channel. Once the discharge continues, the electrolytic action of the discharge will accelerate the oxidation of the insulation and corrode the insulation effect, thereby shortening the life of the grounding transformer. The degree of damage depends on the discharge performance and the breakdown mechanism of the insulation under the action of the discharge.
[0007] Existing measures: Try to conduct the test in a shielding room. The grounding must be independent, that is, the grounding must be grounded at one point and cannot form a large loop with other metals and the outside world. The test object, filter, coupling capacitor voltage divider, and PD tester should also be grounded; on this basis, if there is a metal room, it should also be grounded. In addition, before the test, it is necessary to check and confirm whether all the insulating parts of the test object are fastened, and clean and purge the test object. The purging should be carried out from top to bottom; when purging with an air pipe, the gas should not contain water mist and water droplets; before the test, attention should also be paid to the operation of frequency conversion equipment that affects the test, such as overhead traveling cranes.
[0008] The above measures are only for the test and do not target the grounding transformer itself. Burnouts or explosions of existing grounding transformers due to poor production processes occur frequently. In summary, the present invention provides an iron core for a grounding transformer, a coil for a grounding transformer, and a grounding transformer, which make improvements to the structure of the grounding transformer itself to solve the problem of high partial discharge caused by its own structure in existing grounding transformers. Summary of the Invention
[0009] The object of the present invention is to provide a winding for a grounding transformer and a grounding transformer, so as to solve the problem of high partial discharge caused by the self-structure of the existing grounding transformer.
[0010] To achieve the above object, the solution of the present invention includes:
[0011] A winding for a grounding transformer of the present invention includes a winding sleeved on an iron core. The winding includes an inner winding and an outer winding. A plurality of air ducts for heat dissipation are provided between the inner winding and the outer winding. The insulation distance between the windings is 15 to 25 mm, the minimum distance between adjacent air ducts is 3 to 10 mm, the size of the air duct between the inner winding and the outer winding is 10 to 25 mm, and the insulation distance between the connection of the inner winding and the outer winding is 10 to 25 mm.
[0012] Further, between the windings includes between high-voltage windings and / or between high- and low-voltage windings; the high-voltage winding is used as the outer winding, and the low-voltage winding is used as the inner winding.
[0013] Further, when the winding temperature is higher than the set value, the winding is cooled by a heating device at a set cooling rate.
[0014] A grounding transformer of the present invention includes an iron core and a winding. The winding is sleeved on the iron core. The winding includes an inner winding and an outer winding. A plurality of air ducts for heat dissipation are provided between the inner winding and the outer winding. The insulation distance between the windings is 15 to 25 mm, and the insulation distance between the terminal of the grounding transformer and the inner winding is 35 to 45 mm.
[0015] Further, the minimum distance between adjacent air ducts is 3 to 10 mm, the size of the air duct between the inner winding and the outer winding is 10 to 25 mm, and the insulation distance between the connection of the inner winding and the outer winding is 10 to 25 mm.
[0016] Further, between the windings includes between high-voltage windings and / or between high- and low-voltage windings; the high-voltage winding is used as the outer winding, and the low-voltage winding is used as the inner winding.
[0017] Further, when the winding temperature is higher than the set value, the winding is cooled by a heating device at a set cooling rate.
[0018] Further, the iron core includes a core column for sleeving the winding and a yoke for closing the magnetic circuit. The insulation distance between the end of the core column and the outer surface of the yoke provided at the end of the core column is 40 to 60 mm.
[0019] Further, the insulation distance between the end of the winding sleeved on the core column and the outer surface of the yoke provided at the end of the core column is 40 to 60 mm.
[0020] The beneficial effects of the present invention:
[0021] The present invention makes improvements to the structure of the grounding transformer, which can effectively reduce partial discharge. Specifically, the windings of the grounding transformer are designed as follows: the insulation distance between windings is designed to be 15 to 25 mm, the minimum distance between adjacent air ducts is designed to be 3 to 10 mm, the size of the air duct between the inner winding and the outer winding is designed to be 10 to 25 mm, and the insulation distance between the connection between the inner winding and the outer winding is designed to be 10 to 25 mm.
[0022] The present invention also makes improvements to the structure of the grounding transformer, which can effectively reduce partial discharge. Specifically, the grounding transformer is designed as follows: the insulation distance between windings is designed to be 15 to 25 mm, and the insulation distance between the terminal of the grounding transformer and the inner winding is designed to be 35 to 45 mm.
[0023] The present invention improves the withstand voltage performance of the grounding transformer by designing the size of the air duct, and improves the structural performance of the grounding transformer by designing the minimum distance between adjacent air ducts and / or the insulation distance between the connection between the inner and outer windings, which can effectively reduce partial discharge. Description of the Drawings
[0024] Figure 1 is a schematic diagram of the external connection of the inner and outer coils of the embodiment of the present invention;
[0025] Figure 2 is a schematic diagram of the connection of the inner and outer coils of the embodiment of the present invention;
[0026] Figure 3 is a schematic diagram of the position of the iron core coil of the embodiment of the present invention;
[0027] Figure 4 is a top view of the coil air duct of the embodiment of the present invention;
[0028] Figure 5 is a stress distribution diagram of the simulation test of the grounding transformer of the embodiment of the present invention;
[0029] Figure 6 is the partial discharge test device and its waveform diagram of the embodiment of the present invention;
[0030] Figure 7 is the partial discharge detection system obtained by simulation of the embodiment of the present invention;
[0031] Figure 8 is a relationship diagram between the winding temperature and the partial discharge voltage of the embodiment of the present invention.
[0032] Description of the Reference Numerals:
[0033] 1. Core column; 10. Yoke; 2. Inner winding; 3. Outer winding; d1. Air duct size between the inner winding and the outer winding; d2. Minimum distance between adjacent air ducts; d3. Insulation distance of the connection between the inner winding and the outer winding. Detailed implementation mode
[0034] To make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments.
[0035] To solve the problems in the background technology, the present invention improves the structure of the grounding transformer itself, which can effectively reduce partial discharge. Specifically, the withstand voltage performance of the grounding transformer is improved by designing the air duct size, and the structural performance of the grounding transformer is improved by the minimum distance between adjacent air ducts and / or the insulation distance of the connection between the inner and outer windings, which can effectively reduce partial discharge.
[0036] An embodiment of a grounding transformer:
[0037] A grounding transformer includes an iron core and windings, and the windings are sleeved on the iron core. Among them, the windings are the windings used for the grounding transformer, specifically as Figure 4 shown. The windings include an inner winding 2 and an outer winding 3. A plurality of air ducts for heat dissipation are provided between the inner winding 2 and the outer winding 3. The insulation distance between the windings is 15 to 25 mm, and the insulation distance between the terminal of the grounding transformer and the inner winding is 35 to 45 mm.
[0038] Among them, the insulation distance between the windings refers to the average insulation distance between the windings, that is, the average value of the insulation distances between the windings. Among them, the insulation distance between the terminal of the grounding transformer and the inner winding refers to the average value of the insulation distances between all terminals and the inner winding, that is, the average value of the insulation distances between all terminals on the grounding transformer and the inner winding; the insulation distance between any one of all terminals and the inner winding is the average value of the insulation distance between the terminal and the inner winding.
[0039] Among them, as Figure 4 shown, the minimum distance d2 between adjacent air ducts is 3 to 10 mm, the air duct size d1 between the inner winding and the outer winding is 10 to 25 mm, and the insulation distance d3 of the connection between the inner winding and the outer winding is 10 to 25 mm.
[0040] Among them, the air duct size d1 between the inner winding and the outer winding takes the average value of the air duct sizes between the inner and outer windings; the insulation distance d3 of the connection between the inner and outer windings takes the average value of the insulation distances of the connection between the inner and outer windings.
[0041] Preferably, the minimum distance d2 between adjacent air ducts is 5 to 8 mm, the size d1 of the air duct between the inner winding and the outer winding is 15 to 25 mm, and the insulation distance d3 between the inner winding and the outer winding is 15 to 25 mm.
[0042] Among them, between windings includes between high-voltage windings and / or between high- and low-voltage windings; the high-voltage winding is used as the outer winding, and the low-voltage winding is used as the inner winding. That is, the insulation distance between high-voltage windings is 15 to 25 mm, and the insulation distance between high- and low-voltage windings is 15 to 25 mm.
[0043] Among them, the insulation distance between high-voltage windings refers to the average insulation distance between high-voltage windings, that is, the average value of the insulation distance between high-voltage windings; the insulation distance between high- and low-voltage windings refers to the average insulation distance between high- and low-voltage windings, that is, the average value of the insulation distance between high- and low-voltage windings.
[0044] Among them, when the winding temperature is higher than the set value, the winding is cooled by a heating device at a set cooling rate.
[0045] Among them, referring to Figure 3 , the iron core includes a core column 1 for sleeving the winding and a yoke 10 for closing the magnetic circuit, and the insulation distance M between the end of the core column 1 and the outer surface of the yoke 10 provided at the end of the core column is 40 to 60 mm.
[0046] Among them, the insulation distance M between the end of the core column 1 and the outer surface of the yoke 10 provided at the end of the core column refers to the average value of the insulation distance between the end of the core column and the outer surface of the yoke.
[0047] Among them, as Figure 3 shown, the insulation distance between the end of the winding sleeved on the core column and the outer surface of the yoke provided at the end of the core column is 40 to 60 mm.
[0048] Among them, the insulation distance between the end of the winding sleeved on the core column and the outer surface of the yoke provided at the end of the core column refers to the average value of the insulation distance between the end of the winding and the outer surface of the yoke.
[0049] Referring to Figure 1 shown, for example, the average insulation distance between the terminal A1 of the grounding transformer and the inner winding is 35 to 45 mm.
[0050] Specifically, during the test, any value is taken within the insulation distance between windings of 15 to 25 mm, any value is taken within the air duct size between the inner and outer windings of 10 to 25 mm, any value is taken within the insulation distance of the connection between the inner and outer windings of 10 to 25 mm. On the basis that the above values remain unchanged, simulation tests are respectively carried out on windings with different minimum distances between adjacent air ducts. Test conclusion: On the basis that the above values remain unchanged, the partial discharge of the winding with the minimum distance between adjacent air ducts of 3 to 10 mm is low. The partial discharge of the winding with the minimum distance between adjacent air ducts of 5 to 8 mm is even lower.
[0051] As other embodiments, during the specific test, any value is taken within the insulation distance between windings of 15 to 25 mm. On the basis that the above value remains unchanged, simulation tests are respectively carried out on earthing transformers with different insulation distances between the terminals of the earthing transformer and the inner winding. Test conclusion: Under the same insulation distance between windings, the partial discharge of the earthing transformer with the insulation distance between the terminals of the earthing transformer and the inner winding of 35 to 45 mm is low. The partial discharge of the earthing transformer with the insulation distance between the earthing transformer terminal and the inner winding of 40 mm is even lower.
[0052] As other embodiments, during the specific test, any value is taken within the insulation distance between windings of 15 to 25 mm, any value is taken within the insulation distance between the terminals of the earthing transformer and the inner winding of 35 to 45 mm, any value is taken within the air duct size between the inner and outer windings of 10 to 25 mm, any value is taken within the insulation distance of the connection between the inner and outer windings of 10 to 25 mm. On the basis that the above values remain unchanged, simulation tests are respectively carried out on earthing transformers with different minimum distances between adjacent air ducts. Test conclusion: On the basis that the above values remain unchanged, the partial discharge of the earthing transformer with the minimum distance between adjacent air ducts of 3 to 10 mm is low. The partial discharge of the earthing transformer with the minimum distance between adjacent air ducts of 5 to 8 mm is even lower.
[0053] As other embodiments, during specific tests, any value is taken within the insulation distance between windings of 15 to 25 mm, any value is taken within the minimum distance between adjacent air ducts of 3 to 10 mm, any value is taken within the air duct size between the inner and outer windings of 10 to 25 mm, any value is taken within the insulation distance of the connection between the inner and outer windings of 10 to 25 mm, and any value is taken within the insulation distance between the terminal of the earthing transformer with different values and the inner winding. Based on the above unchanged values, simulation tests are respectively carried out on earthing transformers with different values of the insulation distance between the terminal of the earthing transformer and the inner winding. Test conclusion: Based on the above unchanged values, the partial discharge of the earthing transformer with the insulation distance between the terminal of the earthing transformer and the inner winding taking values of 35 to 45 mm is low. The partial discharge of the earthing transformer with the insulation distance between the terminal of the earthing transformer and the inner winding taking a value of 40 mm is even lower.
[0054] As other embodiments, during specific tests, any value is taken within the insulation distance between windings of 15 to 25 mm, any value is taken within the minimum distance between adjacent air ducts of 3 to 10 mm, any value is taken within the air duct size between the inner and outer windings of 10 to 25 mm, any value is taken within the insulation distance of the connection between the inner and outer windings of 10 to 25 mm, any value is taken within the insulation distance between the terminal of the earthing transformer and the inner winding of 35 to 45 mm, and based on the above unchanged values, simulation tests are respectively carried out on earthing transformers with different values of the insulation distance between the end of the iron core column and the outer surface of the yoke provided at the end of the iron core column. Test conclusion: Based on the above unchanged values, the partial discharge of the earthing transformer with the insulation distance between the terminal of the earthing transformer and the inner winding taking values of 40 to 60 mm is low.
[0055] As other embodiments, during specific tests, any value is taken within the insulation distance between windings of 15 to 25 mm, any value is taken within the minimum distance between adjacent air ducts of 3 to 10 mm, any value is taken within the air duct size between the inner and outer windings of 10 to 25 mm, any value is taken within the insulation distance of the connection between the inner and outer windings of 10 to 25 mm, any value is taken within the insulation distance between the terminal of the earthing transformer and the inner winding of 35 to 45 mm, and based on the above unchanged values, simulation tests are respectively carried out on earthing transformers with different values of the insulation distance between the end of the winding sleeved on the iron core column and the outer surface of the yoke provided at the end of the iron core column. Test conclusion: Based on the above unchanged values, the partial discharge of the earthing transformer with the insulation distance between the end of the winding sleeved on the iron core column and the outer surface of the yoke provided at the end of the iron core column taking values of 40 to 60 mm is low.
[0056] Among them, when designing the main insulation distance for the grounding transformer winding, it is necessary to ensure and consider sufficient insulation distances between the high- and low-voltage coils, between the high-voltage coils in different phases, and between the high-voltage coil and the ground. At the same time, sufficient mechanical strength should also be guaranteed to avoid cracks on the surface and inside air ducts of the coil, which may lead to an increase in partial discharge.
[0057] Compared with ordinary epoxy cast dry-type transformers, the grounding transformer winding of the Z-junction method has its particularity. The schematic diagram of the winding leads is as Figure 1 shown, and the internal structure connection of the coil is as Figure 2 shown. Figure 1 The distances between the first and last ends A, B, C and O, and between A1, B1, C1 and X1, Y1, Z1 of the grounding transformer in
[0058] are much smaller than those of epoxy cast dry-type transformers. Since the inner and outer windings are separated by air ducts, cracks are generated in the air duct connection area under stress, forming creepage and resulting in a very high partial discharge. Therefore, certain measures must be taken to control the stress.
[0059]
[0060] In the formula: H - stress;
[0061] α R 、α M - linear expansion coefficients of resin and embedded objects;
[0062] E R 、E M - elastic moduli of resin and embedded objects;
[0063] A R 、A M - cross-sectional areas of resin and embedded objects perpendicular to shrinkage;
[0064] t2 - the highest heating temperature during curing;
[0065] t1 - cooling temperature.
[0066] It can be seen from the calculation formula that the value of (t1 - t2) plays a very important role in whether the winding is cracked.
[0067] Adopt such as Figure 7 The partial discharge detection system shown in the figure is used to conduct simulation tests on the grounding transformer with a high-voltage capacity of 630 kVA and no low voltage, and coils with the same volume and mass. Taking the normal temperature of 50 °C as the reference value, the airway width d1 is set to 20 mm. According to different d2 sizes, the following results are obtained. The partial discharge test device and its waveform diagram used are as shown in Figure 6 the figure. It can be seen from Table 1 below that the higher the temperature, the higher the partial discharge.
[0068] Table 1: Relationship between partial discharge and temperature of dry-type transformers
[0069]
[0070] However, the thermal expansion coefficient of the wire of the dry-type transformer is different from that of the epoxy resin. When the temperature changes, due to different deformations, air gaps may appear in the internal insulation, which will also lead to the generation of partial discharge. At the same time, as shown in Figure 8 the figure, due to the increase in temperature, the decrease in the inception voltage of partial discharge causes some large air bubbles existing in the insulator to start discharging, and the increase in the number of discharges will cause the superposition of discharge pulses and increase the discharge amplitude, which will also increase the discharge amount.
[0071] According to the simulation test, the stress distribution diagram shown in Figure 5 the figure is obtained, and then the comparison table of simulation results is shown in Table 2 below.
[0072] Table 2: Comparison table of simulation results of temperature, stress and partial discharge
[0073] d2 Thickness (mm) 3 5 8 10 Partial Discharge (pC) 4.8 4.3 4.6 4.7 Temperature (°C) -5 1 5 12
[0074] Under general conventional conditions, the insulation distance selected between the high- and low-voltage coils and the high-voltage coil of the 10 kV earthing transformer is between 15 and 25 mm. The insulation distance M between windings A, B, and C, which are high-voltage conductors, and the transformer yoke can be controlled between 40 and 60 mm. The distance between the terminals of the earthing transformer and the inner winding is controlled at about 40 mm. The connection dimension d2 between the air ducts is not less than 5 mm. However, if the thickness of d2 is too large, the cost and temperature rise will increase accordingly. Therefore, it should not be too large to ensure the overall safety of the earthing transformer. The value range of d2 is taken as 5 mm to 8 mm. When d2 is 5 mm, the partial discharge is the lowest. Here, the connection dimension d2 between the air ducts refers to the minimum value of the connection dimensions between adjacent air ducts, that is, the minimum value of the connection between adjacent air ducts is not less than 5 mm and not higher than 8 mm. Optimizing different air duct specifications and methods has guiding significance for the partial discharge of the product. When designing the product, carefully analyze the electric field distribution of the insulation structure, leave an insulation margin, and improve the insulation structure and process level.
[0075] In view of the possible defects (such as drawing structure defects, on-site environmental defects, manufacturing process defects, etc.) that may occur during the whole process of product design and manufacturing of the earthing transformer, the present invention optimizes the design of the self-structure of the earthing transformer to reduce partial discharge.
[0076] An embodiment of a winding for an earthing transformer:
[0077] A winding for an earthing transformer has been specifically described in detail in an embodiment of an earthing transformer and will not be elaborated here.
Claims
1. A winding for a grounding transformer, comprising a winding for sleeving on an iron core, the winding including an inner winding and an outer winding, and a plurality of air ducts for heat dissipation are arranged between the inner winding and the outer winding, characterized in that, The insulation distance between windings is 15 to 25 millimeters, the minimum distance between adjacent air ducts is 3 to 10 millimeters, the size of the air duct between the inner winding and the outer winding is 10 to 25 millimeters, and the insulation distance between the connection between the inner winding and the outer winding is 10 to 25 millimeters.
2. The winding for a grounding transformer according to claim 1, wherein, Between the windings include between high-voltage windings and / or between high- and low-voltage windings; the high-voltage winding serves as the outer winding, and the low-voltage winding serves as the inner winding.
3. The winding for a grounding transformer according to claim 1, characterized in that, When the winding temperature is higher than the set value, the winding is cooled by a heating device at a set cooling rate.
4. A grounding transformer, comprising an iron core and windings, the windings being sleeved on the iron core, the windings including an inner winding and an outer winding, and a plurality of air channels for heat dissipation being provided between the inner winding and the outer winding, characterized in that, The insulation distance between windings is 15 to 25 millimeters, and the insulation distance between the terminal of the grounding transformer and the inner winding is 35 to 45 millimeters.
5. The earthing transformer according to claim 4, characterized in that, The minimum distance between adjacent air ducts is 3 to 10 millimeters, the size of the air duct between the inner winding and the outer winding is 10 to 25 millimeters, and the insulation distance between the connection between the inner winding and the outer winding is 10 to 25 millimeters.
6. The earthing transformer according to claim 4, wherein, Between the windings include between high-voltage windings and / or between high- and low-voltage windings; the high-voltage winding serves as the outer winding, and the low-voltage winding serves as the inner winding.
7. The earthing transformer according to claim 4, characterized in that, When the winding temperature is higher than the set value, the winding is cooled by a heating device at a set cooling rate.
8. The earthing transformer according to claim 4, characterized in that, The iron core includes a core column for sleeving the winding and a yoke for closing the magnetic circuit, and the insulation distance between the end of the core column and the outer surface of the yoke provided at the end of the core column is 40 to 60 millimeters.
9. The earthing transformer according to claim 8, characterized in that, The insulation distance between the end of the winding sleeved on the core column and the outer surface of the yoke provided at the end of the core column is 40 to 60 millimeters.