Axial pre-tightening force adjusting device and method for transformer in short-circuit state
By using transformer pretension parts and axial pretension oil bags in the transformer, combined with the calculation of the number of short-circuit impacts and real-time adjustment of the pressure sensor, the problem of insufficient axial pretension force in the short-circuit state is solved, and the transformation is realized The stable operation and service life of the transformer in a short circuit state.
Patent Information
- Application Number
- CN202411348337.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-26
- Publication Date
- 2025-02-07
AI Technical Summary
The prior art cannot adjust the axial preload force of the transformer in a short-circuit state in time, resulting in the transformer being easily damaged.
A device including a transformer pretension member and an axial pretension oil bag is provided, and the axial pretension force is adjusted by calculating the number of short-circuit impacts and is adjusted in real time using a pressure sensor to ensure constant pretension force.
Effectively ensure that the axial preload of the transformer is always maintained at the preset value in the short-circuit state, preventing the winding and core from moving relative to each other, reducing mechanical vibration and noise, and extending the service life of the transformer.
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Figure CN119400549A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of transformers, and in particular to an axial preload adjustment device and method for a transformer in a short-circuit state. Background Art
[0002] A transformer is an electrical device used to change AC voltage. It is widely used in power systems and various electronic devices. Its basic principle is to use the principle of electromagnetic induction to change the voltage through mutual induction while keeping the power basically unchanged. The transformer consists of two or more coils (generally coils wound with wires, called windings) and an iron core. The iron core is usually stacked with silicon steel sheets to concentrate the magnetic field and reduce energy loss. The basic working principle of the transformer is that the magnetic field generated by the AC current in one winding is induced into another winding connected to it, thereby generating an electromotive force in the winding, that is, the original electromagnetic induction law of the transformer. When the transformer is in a short-circuit condition, the transformer winding will produce an axial displacement corresponding to it. At this time, the axial preload plays an important role. The role of this preload is to ensure that the internal components of the transformer, such as the winding and the iron core, can be firmly fixed together to resist the huge force and thermal stress brought by the short-circuit current. Insufficient axial preload may cause the winding and the iron core to move relative to each other under the action of electromagnetic force. This movement will increase the mechanical vibration and noise inside the transformer, thereby affecting the stability and safety of the equipment. Especially in the case of short circuit, due to the sudden increase of current, if there is not enough preload support, the winding may be abnormally displaced, and even cause the breakage of insulation materials and damage to the winding. Insufficient axial preload may also affect the electrical performance of the transformer. In the case of short circuit, the transformer needs to withstand the impact of large current to ensure normal operation and the stability of the electrical system. If the preload is insufficient, the winding may experience local current overload and form hot spots, which not only affects the efficiency and power factor of the transformer, but also may cause overheating and damage to the equipment. Insufficient axial preload may shorten the service life of the transformer. In the case of frequent short circuits, due to the lack of sufficient preload support, the windings and cores may be subjected to greater stress and thermal stress, resulting in increased material aging, which will cause equipment failure and damage in advance and increase the cost of repair and replacement. Summary of the invention
[0003] The embodiment of the present invention provides an axial preload adjustment device and method for a transformer in a short-circuit state, so as to solve the problem that the prior art cannot adjust the axial preload in time, resulting in easy damage to the transformer.
[0004] In a first aspect, an axial preload force adjustment device for a transformer in a short-circuit state is provided, comprising: at least one set of transformer preload members and at least one axial preload oil bag, wherein the transformer preload members comprise: two transformer clamps and two axial preload rods;
[0005] The two transformer clamps are respectively arranged at the upper end and the lower end of the transformer winding coil, one axial pre-tightening rod connects one end of the two transformer clamps, and the other axial pre-tightening rod connects the other end of the two transformer clamps. The upper and lower ends of each axial pre-tightening rod are engaged with a nut, and the axial pre-tightening oil bag is arranged between the transformer clamp located at the upper end and the upper end of the transformer winding coil. The axial pre-tightening oil bag is connected to the transformer oil storage tank through an oil pipeline, and a flow rate sensor is arranged in the axial pre-tightening oil bag, and a pressure sensor is arranged between the lower end of the axial pre-tightening oil bag and the upper end of the transformer winding.
[0006] In a second aspect, a method for adjusting an axial preload force in a transformer short-circuit state is provided, wherein the axial preload force adjusting device for a transformer short-circuit state as described in the first aspect is used, and the axial preload force adjusting method comprises:
[0007] If the transformer is in a short-circuit condition, the axial preload of the transformer winding is calculated based on the number of short-circuit impacts;
[0008] According to the calculated axial preload force of the transformer winding, the transformer oil in the transformer oil storage tank is transported to the axial preload oil bag or the transformer oil in the axial preload oil bag is extracted into the transformer oil storage tank, so that the axial preload force of the transformer winding reaches a preset preload force value;
[0009] A pressure sensor is used to measure the axial preload of transformer windings;
[0010] According to the measured axial preload force of the transformer winding, the transformer oil in the transformer oil storage tank is transported to the axial preload oil bag or the transformer oil in the axial preload oil bag is extracted into the transformer oil storage tank, so that the axial preload force of the transformer winding reaches a preset preload force value.
[0011] In this way, in the embodiment of the present invention, the axial preload force obtained by calculating the number of short-circuit impacts is used to feed or pump oil to the axial preload oil bag, thereby pre-adjusting the axial preload force to a preset preload force value, and then the actual axial preload force is detected by the pressure sensor, and the axial preload oil bag is again fed or pumped to make the axial preload oil bag more sensitive, thereby ensuring that the axial preload force of the transformer is constant; both methods also ensure that the adjustment of the axial preload force is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.
[0013] Figure 1 1 is a schematic structural diagram of an axial preload force adjustment device for a transformer in a short-circuit state according to an embodiment of the present invention;
[0014] Figure 2 is a flow chart of an axial preload adjustment method for a transformer in a short-circuit state according to an embodiment of the present invention;
[0015] Figure 3 is a schematic diagram of a compression force-displacement loop under a simulated cumulative short-circuit impact according to an embodiment of the present invention;
[0016] Figure 4 is a schematic diagram of the relationship between the number of simulated impacts and deformation of an insulating spacer according to an embodiment of the present invention;
[0017] Figure 5 is a schematic diagram of the relationship between the number of simulated impacts and the elastic coefficient of the insulating spacer according to an embodiment of the present invention;
[0018] Figure 6 It is a schematic diagram of a test curve of short-circuit impact times and axial preload force according to an embodiment of the present invention. DETAILED DESCRIPTION
[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0020] The embodiment of the present invention discloses an axial preload adjustment device for a transformer in a short-circuit state. Figure 1 As shown, the transformer is composed of a transformer winding bobbin 1 and an iron core. Each transformer winding bobbin 1 surrounds each iron core. Multiple iron cores can be installed in sequence and spaced apart on an iron yoke 2 for support. Insulating spacers 3 are arranged between adjacent coils of the transformer winding bobbin 1.
[0021] like Figure 1 As shown, the axial preload force adjustment device includes the following structure:
[0022] At least one set of transformer preload and at least one axial preload oil bag 4. The number of axial preload oil bags 4 is the same as the number of transformer winding coils 1, that is, one transformer winding coil 1 is equipped with one axial preload oil bag 4. The transformer preload includes: two transformer clamps 5 and two axial preload rods 6.
[0023] Two transformer clamps 5 are respectively arranged at the upper and lower ends of the transformer winding coil 1. An axial preload rod 6 connects one end of the two transformer clamps 5, and another axial preload rod 6 connects the other end of the two transformer clamps 5. Specifically, a through hole is provided at the corresponding position of the transformer clamp 5 for the axial preload rod 6 to pass through. A nut 7 is engaged and sleeved at the upper and lower ends of each axial preload rod 6. The nut 7 at the upper end is located above the transformer clamp 5 at the upper end, and the nut 7 at the lower end is located below the transformer clamp 5 at the lower end. By rotating the nut 7, the transformer clamp 5 is applied with force, so that the axial preload force on the transformer winding coil 1 is a preset preload force value. An axial preload oil bag 4 is provided between the transformer clamp 5 at the upper end and the upper end of the transformer winding coil 1. The axial preload oil bag 4 is connected to the transformer oil storage tank through an oil pipeline. The axial preload oil bag 4 is used to transfer oil or extract oil to the transformer oil storage tank to control the axial preload force of the transformer when the transformer is short-circuited, ensuring the constant axial preload force when the transformer is short-circuited. The transportation of transformer oil can be powered by the oil transfer motor connected to the transformer oil storage tank. A flow rate sensor is provided in the axial preload oil bag 4 to monitor the oil transportation of the transformer to the axial preload oil bag 4. When the flow rate is positive, it indicates that the transformer oil in the transformer oil storage tank flows into the axial preload oil bag 4; when the flow rate is negative, it indicates that the transformer oil in the axial preload oil bag 4 flows back to the transformer oil storage tank. A pressure sensor is provided between the lower end of the axial preload oil bag 4 and the upper end of the transformer winding 1. The pressure sensor is in close contact with the axial preload oil bag 4 and the transformer winding 1. The pressure sensor is used to collect the axial preload force of the transformer winding.
[0024] In addition, a monitoring terminal may be provided to communicate with the flow velocity sensor and the pressure sensor to display data collected by the flow velocity sensor and the pressure sensor.
[0025] Specifically, the axial preload oil bag 4 is annular and surrounds the outside of the core.
[0026] Specifically, the material of the axial preload oil bag 4 is rubber, which generally has good sealing performance and chemical corrosion resistance, and can withstand certain pressure and temperature changes to ensure the stability and safety of the axial preload oil bag 4 during operation.
[0027] Preferably, there are two groups of transformer preload members, which are symmetrically located on both sides of the central axis of the transformer winding bobbin 1, for example, symmetrically located on both sides of the iron yoke 2 of the iron core, which is more conducive to uniform stress on the transformer winding bobbin 1.
[0028] When in use, the nut 7 is twisted by using a torque wrench to reach the preset preload value. When the transformer is short-circuited, the axial displacement of the transformer winding coil 1 is large, which seriously affects the axial preload of the transformer, making it impossible to maintain the preset preload value, causing the transformer winding coil 1 to axially move and fall off. The axial preload adjustment device of the embodiment of the present invention adopts an axial preload oil bag 4. When the transformer is short-circuited, the transformer oil in the transformer oil storage tank is transported to or extracted from the axial preload oil bag 4 to adjust the axial preload, so that the axial preload of the transformer during short circuit is maintained at the preset preload value.
[0029] Since the short-circuit time of the transformer is short, the oil delivery motor takes a long time to deliver oil to the axial preload oil bag, which will cause deviations in the correction of the axial preload. To solve this problem, the embodiment of the present invention also discloses an axial preload adjustment method for the transformer short-circuit state. The axial preload adjustment method adopts the axial preload adjustment device for the transformer short-circuit state described in the above example. The present invention predicts oil delivery / oil extraction based on the test curve of the number of short-circuit impacts and the size of the axial preload when the transformer is short-circuited, and predicts the size of the axial preload generated by the number of transformer winding impacts, so as to perform oil delivery or oil extraction in advance, make the axial preload oil bag more sensitive, and ensure the constant axial preload of the transformer.
[0030] Specifically, Figure 2 As shown, the axial preload force adjustment method includes the following steps:
[0031] Step S201: If a short-circuit condition occurs in the transformer, the axial preload force of the transformer winding is calculated based on the number of short-circuit impacts.
[0032] When a transformer is hit by a short-circuit impact fault, a short-circuit force will occur in the axial direction of the winding, which will periodically squeeze the center from both sides. The stress is mainly concentrated in the middle of the winding. Because the transformer winding is mainly composed of windings and insulating pads in the axial direction, the short-circuit force will not cause elastic deformation of the metal (copper, aluminum) windings, but will only affect the physical properties of the insulating pads, including the thickness of the insulating pads, elastic modulus and other key parameters. When a short-circuit impact occurs in the transformer, the axial force of the winding will repeatedly compress the insulating pads to cause them to undergo plastic deformation, thereby affecting the axial preload of the winding.
[0033] Based on this, the transformer is subjected to a simulated short-circuit impact test in advance, such as Figure 3As shown in the figure, the compression force-displacement loop of the insulating pad consists of a linear region and a nonlinear region. In the nonlinear region, the maximum and minimum values of the loop of the 60th simulated short-circuit impact are significantly greater than the deformation displacement during the first simulated short-circuit impact. This shows that with the continuous increase in the cumulative number of compressions, the test specimen has obviously undergone plastic deformation, and the thickness has become significantly thinner without applying external force. In the linear region, the slopes of the two tests can be compared, K1 = 6261.54 N / mm, K60 = 11737.21 N / mm, it can be seen that the elastic coefficient during the first simulated short-circuit impact is much smaller than the elastic coefficient during the 60th simulation, which shows that with the continuous increase in the cumulative number of compressions, the elastic coefficient of the insulating pad continues to increase, and it is less likely to deform.
[0034] like Figure 4 As shown in the figure, it is the full life model of the aging of the insulating pad. With the increase of the number of simulated short-circuit impacts, the plastic deformation variable X of the insulating pad continues to increase, and the two are nonlinear. The growth of plastic deformation goes through 5 stages, and each plastic stage is divided into a rapid growth process and a slow growth process. When the insulating pad simulates short-circuit force aging for more than 70 times (plastic stage 5), its plastic deformation will no longer change, reaching the end of the mechanical performance life of the insulating pad. Through curve fitting, the following calculation formula for the plastic deformation variable of the insulating pad corresponding to the number of short-circuit impacts is obtained:
[0035]
[0036] Among them, X (n) is the plastic deformation of the insulating spacer corresponding to the number of short-circuit impacts, A1, A2, n0 and p are constants, and n is the number of short-circuit impacts.
[0037] like Figure 5 As shown in the figure, with the increase of the number of simulated short-circuit impacts, the elastic coefficient k of the insulating pad increases continuously, and the two are in a nonlinear relationship. Through Logistic curve fitting, the following calculation formula for the elastic coefficient of the insulating pad corresponding to the number of short-circuit impacts is obtained:
[0038]
[0039] Among them, k (n) is the elastic coefficient of the insulating spacer corresponding to the number of short-circuit impacts, B1, B2, n1 and q are constants, and n is the number of short-circuit impacts.
[0040] A1, A2, n0, p, B1, B2, n1 and q are all obtained by fitting. In a specific embodiment, the specific values obtained by fitting are shown in Table 1.
[0041] Table 1 Fitting results
[0042] <![CDATA[A1]]> <![CDATA[A2]]> <![CDATA[n0]]> p <![CDATA[B1]]> <![CDATA[B2]]> <![CDATA[n1]]> q 1.26 1.68 37.52 2.04 5982.52 11775.45 10.44 2.3
[0043] Substituting the above formulas (1) and (2) into the following formula for calculating the axial preload of the transformer winding based on the number of short-circuit impacts, the axial preload of the transformer winding under the current number of short-circuit impacts can be calculated:
[0044] F (n) =k (n) ×(hX (n) -h′) (3)
[0045] Among them, F (n) is the axial preload of the transformer winding. h is the original height of the insulating spacer, which can be measured. h′ is the design value of the axial preload compression of the insulating spacer during transformer assembly, which is generally determined by the preset preload value and can be measured after applying the preset preload value in advance.
[0046] like Figure 6 As shown, the short-circuit impact number and axial preload test curve are used to predict the oil delivery / pumping test curve when the transformer is short-circuited. The axial preload generated by the transformer winding impact number is predicted, and oil delivery or pumping is performed in advance to make the axial preload oil bag more sensitive and ensure the constant axial preload of the transformer.
[0047] Step S202: According to the calculated axial preload force of the transformer winding, the transformer oil in the transformer oil storage tank is transported to the axial preload oil bag or the transformer oil in the axial preload oil bag is extracted into the transformer oil storage tank, so that the axial preload force of the transformer winding reaches a preset preload force value.
[0048] Through the above steps, the axial preload force generated by the number of short-circuit impacts can be predicted so that oil can be transported or pumped in advance, making the axial preload oil bag more sensitive and ensuring the constant axial preload force of the transformer.
[0049] Specifically, when the calculated axial preload force of the transformer winding is less than the preset preload force value, the transformer oil in the transformer oil storage tank is transported to the axial preload oil bag; when the calculated axial preload force of the transformer winding is greater than the preset preload force value, the transformer oil in the axial preload oil bag is drawn out into the transformer oil storage tank.
[0050] Step S203: using a pressure sensor to measure the axial preload force of the transformer winding.
[0051] Step S204: according to the measured axial preload force of the transformer winding, the transformer oil in the transformer oil storage tank is transported to the axial preload oil bag or the transformer oil in the axial preload oil bag is extracted into the transformer oil storage tank, so that the axial preload force of the transformer winding reaches a preset preload force value.
[0052] Specifically, when the measured axial preload force of the transformer winding is less than the preset preload force value, the transformer oil in the transformer oil storage tank is transported to the axial preload oil bag; when the measured axial preload force of the transformer winding is greater than the preset preload force value, the transformer oil in the axial preload oil bag is drawn out into the transformer oil storage tank.
[0053] Preferably, before step S201, the method of the embodiment of the present invention further includes:
[0054] 1. When it is detected that the transformer current is greater than a preset current value, the flow rate of the transformer oil detected by the flow rate sensor is obtained.
[0055] Specifically, the transformer current may be collected by arranging a current sensor on the current line.
[0056] 2. If the flow rate is negative, it is determined that the transformer is in a short-circuit condition.
[0057] Monitor whether the transformer is in a short-circuit condition, and monitor it through short-circuit current test and flow rate sensor. When the transformer is in a short-circuit condition, the transformer current will increase instantly, and the transformer winding will be affected by the short-circuit current and have different degrees of axial displacement. The transformer winding will be displaced and squeeze the axial preload oil bag. The flow rate sensor will show a negative value, indicating that the transformer oil in the axial preload oil bag flows back into the transformer oil storage tank. Based on this, it is judged that the transformer has been short-circuited.
[0058] In summary, in the embodiments of the present invention, the axial preload force obtained by calculating the number of short-circuit impacts is used in advance to transport or pump oil to the axial preload oil bag, thereby pre-adjusting the axial preload force to a preset preload force value, and then the actual axial preload force is detected by a pressure sensor, and the axial preload oil bag is transported or pumped again to make the axial preload oil bag more sensitive, thereby ensuring that the axial preload force of the transformer is constant; both methods also ensure that the adjustment of the axial preload force is more accurate.
[0059] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.
Claims
1. An axial preload adjustment device for a transformer in a short-circuit state, characterized in that: include: At least one set of transformer preload members and at least one axial preload oil bag, wherein the transformer preload members include: two transformer clamps and two axial preload rods; The two transformer clamps are respectively arranged at the upper end and the lower end of the transformer winding coil, one axial pre-tightening rod connects one end of the two transformer clamps, and the other axial pre-tightening rod connects the other end of the two transformer clamps. The upper and lower ends of each axial pre-tightening rod are engaged with a nut, and the axial pre-tightening oil bag is arranged between the transformer clamp located at the upper end and the upper end of the transformer winding coil. The axial pre-tightening oil bag is connected to the transformer oil storage tank through an oil pipeline, and a flow rate sensor is arranged in the axial pre-tightening oil bag, and a pressure sensor is arranged between the lower end of the axial pre-tightening oil bag and the upper end of the transformer winding.
2. The axial preload adjustment device for transformer short circuit state according to claim 1 is characterized in that: The material of the axial preload oil bag is rubber.
3. The axial preload adjustment device for transformer short circuit state according to claim 1, characterized in that: The axial preload oil bag is annular and surrounds the outside of the core.
4. The axial preload adjustment device for transformer short circuit state according to claim 1, characterized in that: The transformer pre-tightening members are in two groups, which are symmetrically located on both sides of the central axis of the transformer winding coil.
5. The axial preload adjustment device for transformer short circuit state according to claim 1, characterized in that: The number of the axial preload oil bags is the same as the number of the transformer winding coils.
6. A method for adjusting the axial preload force of a transformer in a short-circuit state, characterized in that: The axial preload force adjustment device for a transformer in a short-circuit state according to any one of claims 1 to 5 is adopted, and the axial preload force adjustment method comprises: If the transformer is in a short-circuit condition, the axial preload of the transformer winding is calculated based on the number of short-circuit impacts; According to the calculated axial preload force of the transformer winding, the transformer oil in the transformer oil storage tank is transported to the axial preload oil bag or the transformer oil in the axial preload oil bag is extracted into the transformer oil storage tank, so that the axial preload force of the transformer winding reaches a preset preload force value; A pressure sensor is used to measure the axial preload of transformer windings; According to the measured axial preload force of the transformer winding, the transformer oil in the transformer oil storage tank is transported to the axial preload oil bag or the transformer oil in the axial preload oil bag is extracted into the transformer oil storage tank, so that the axial preload force of the transformer winding reaches a preset preload force value.
7. The method for adjusting the axial preload force in a transformer short-circuit state according to claim 6, characterized in that: The calculation formula for calculating the axial preload force of the transformer winding based on the number of short-circuit impacts includes: F (n) =k (n) ×(h-X (n) -h′); Among them, F (n) is the axial preload of transformer winding, k (n) is the elastic coefficient of the insulating pad corresponding to the number of short-circuit impacts, h is the original height of the insulating pad, and X (n) is the plastic deformation of the insulating spacer corresponding to the number of short-circuit impacts, and h′ is the design value of the axial preload compression of the insulating spacer during transformer assembly.
8. The method for adjusting the axial preload force of a transformer in a short-circuit state according to claim 7, characterized in that: The calculation formula of the plastic deformation amount of the insulating spacer corresponding to the number of short-circuit impacts includes: Among them, A1, A2, n0 and p are constants, and n is the number of short-circuit impacts.
9. The method for adjusting the axial preload force in a transformer short-circuit state according to claim 7, characterized in that: The calculation formula of the elastic coefficient of the insulating pad corresponding to the number of short-circuit impacts includes: Among them, B1, B2, n1 and q are constants, and n is the number of short-circuit impacts.
10. The method for adjusting the axial preload force in a transformer short-circuit state according to claim 6, characterized in that: Before the step of calculating the axial preload force of the transformer winding based on the number of short-circuit impacts, the method further includes: When it is detected that the transformer current is greater than a preset current value, the flow rate of the transformer oil detected by the flow rate sensor is obtained; If the flow rate is a negative value, it is determined that a short circuit condition occurs in the transformer.