Non-uniformly distributed converter transformer oil paper insulation life estimation method, equipment and medium

Abstract

The invention relates to a non-uniformly distributed converter transformer oil paper insulation life estimation method, equipment and a medium, electric field, temperature and mechanical stress distribution of an oil paper insulation system at different positions is obtained in an electromagnetic-heat flow-mechanical stress multi-physics field coupling model, and aging rates at different positions are further obtained. Obtaining the local life through the aging rate, and obtaining and outputting the overall life of the oil-paper insulation system of the converter transformer through comprehensive processing. Various physical fields at different positions are accurately described in a non-uniform distribution model, and the actual complex operation condition of a power grid is met. Compared with the prior art, the method has the advantages of high accuracy, wide application range, capability of guaranteeing the safety of a power system and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer fault diagnosis and status assessment, and in particular to a method, device and medium for estimating the life of oil-paper insulation of a non-uniformly distributed converter transformer. Background Art

[0002] With the rapid development of high-voltage direct current transmission technology, converter transformers are increasingly used in power systems. Since the oil-paper insulation system inside the converter transformer is exposed to complex electrical and thermal stress environments for a long time, especially in an environment with AC / DC mixed electric fields, the aging process of the insulation system becomes more complicated and more difficult to predict. The aging of the oil-paper insulation system is not only affected by conventional factors such as voltage, temperature and humidity, but also by dynamic conditions such as load changes and partial discharges. The aging rate often shows an obvious non-uniform distribution. In the actual operation of the converter transformer, the electric field strength and temperature rise of the insulation materials at different positions are different, which makes the life state of the entire system show obvious temporal and spatial non-uniformity, increasing the difficulty of life assessment.

[0003] Chinese patent CN113884830B discloses a new model for evaluating insulation life based on transformer oil-paper polymerization degree DP value, water content, and average winding hot spot temperature. Since the patent is based on the uniform distribution assumption, it fails to fully consider the spatial and temporal non-uniformity of insulation system aging, making it difficult to accurately predict the actual life of the system under complex operating conditions. Therefore, how to reflect the non-uniform distribution of the life state of the oil-paper insulation system so as to make the life prediction more accurate is a technical problem that needs to be solved. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method, equipment and medium for predicting the life of oil-paper insulation of a non-uniformly distributed converter transformer. By constructing a non-uniform distribution model of electric field, temperature and mechanical stress and combining the results of multi-physical field analysis, the aging rate of non-uniform positions is obtained, and the overall life of the oil-paper insulation system is comprehensively obtained.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] According to one aspect of the present invention, a method for estimating the life of oil-paper insulation of a non-uniformly distributed converter transformer is provided, comprising the following steps:

[0007] S1. Obtaining state parameters of each spatial position from the commutation transformer winding model as input, wherein the state parameters include electric field intensity, temperature and mechanical stress value;

[0008] S2. Obtaining the aging rate of the oil-paper insulation system at different positions based on the input state parameters;

[0009] S3. The local life span is obtained through the aging rate at different positions. The overall life span of the oil-paper insulation system of the converter transformer is obtained by comprehensive processing of the local life span, and the overall life span is output.

[0010] Furthermore, the commutation transformer winding model in S1 is a non-uniform distribution model coupled with electromagnetic, thermal and solid force fields.

[0011] Furthermore, the aging rate expression of different positions of S2 is:

[0012]

[0013] Wherein, r(x,y,z) is the aging rate at position (x,y,z); T(x,y,z) is the temperature at position (x,y,z); E(x,y,z) is the electric field strength at position (x,y,z); σ(x,y,z) is the mechanical stress at position (x,y,z); α is the electric field coefficient; β is the stress coefficient.

[0014] Furthermore, the local lifespan expression of S3 is:

[0015]

[0016] Where r(x,y,z) is the aging rate at position (x,y,z).

[0017] Furthermore, the overall life expression of S3 is:

[0018]

[0019] Where R is the total aging rate of the entire model; r(x,y,z) is the aging rate at the position (x,y,z).

[0020] Furthermore, the electric field strength E(x, y, z) of S1 is obtained by Maxwell's equations, expressed as:

[0021]

[0022] Where E is the electric field intensity; H is the magnetic field intensity; J is the current density; D is the electric displacement field; and B is the magnetic induction intensity.

[0023] Furthermore, the distribution of the temperature of S1 at different positions is affected by the harmonic current by changing the conductor current density, and the thermal flow field expression is:

[0024]

[0025] Where r is the material density; c pis the specific heat capacity; T is the temperature field; k is the thermal conductivity; Q is the heat source term; t is the time.

[0026] Furthermore, the mechanical stress of S1 follows the law of elastic mechanics in solid mechanics, and the expression is:

[0027]

[0028] Among them, σ is the mechanical stress tensor; F is the body force; u is the displacement field; ρ is the density; t is the time.

[0029] According to a second aspect of the present invention, there is provided an electronic device, comprising a memory and a processor, wherein a computer program is stored in the memory, and the method described above is implemented when the processor executes the program.

[0030] According to a third aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon, wherein the program implements the method described above when executed by a processor.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) Improved accuracy: The non-uniformly distributed electric field, temperature and mechanical stress at different locations are taken into account to obtain the life prediction of each location and then comprehensively obtain the life prediction of the entire oil-paper insulation system, which improves the accuracy of the prediction.

[0033] (2) Improve the safety and reliability of power equipment: By predicting the life of the oil-paper insulation system in a complex and multi-location physical field, the converter transformer can accurately and timely respond to the equipment status, thereby improving the safety and reliability of power equipment operation.

[0034] (3) Wide range of applications: Taking into account multiple physical fields and the non-uniform distribution of each physical field, the differences in the aging rates of the insulation system at different locations and under different working conditions are fully considered. It is suitable for accurate prediction of the life of the oil-paper insulation system under the operating conditions of complex converter transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The flowchart of the method for estimating the life of oil-paper insulation of non-uniformly distributed commutation transformers is shown;

[0036] Figure 2 It is the structure diagram of the two-dimensional refined simulation model of the converter transformer winding;

[0037] Figure 3 It is the structural diagram of the two-dimensional refined simulation model of the grid-side winding of the converter transformer;

[0038] Figure 4 It is the structure diagram of the two-dimensional refined simulation model of the valve-side winding of the converter transformer;

[0039] Figure 5 is the electric field distribution diagram of the converter transformer;

[0040] Figure 6 The non-uniform distribution diagram of the converter transformer temperature field under 200kW loss;

[0041] Figure 7 The non-uniform distribution diagram of the converter transformer temperature field under 300kW loss;

[0042] Figure 8 The non-uniform distribution diagram of the converter transformer temperature field under 400kW loss;

[0043] Fig. 9 The non-uniform distribution diagram of the converter transformer temperature field under 500kW loss;

[0044] Fig.10 The non-uniform distribution diagram of converter transformer winding stress at t=0s;

[0045] Fig.11 The non-uniform distribution diagram of converter transformer winding stress at t = 0.05s;

[0046] Fig.12 The non-uniform distribution diagram of converter transformer winding stress at t = 0.1s;

[0047] Fig.13 The non-uniform distribution diagram of converter transformer winding stress at t = 0.15s;

[0048] Fig.14 The non-uniform distribution diagram of converter transformer winding stress at t = 0.2s;

[0049] Fig.15 The winding aging rate distribution diagram under 0MPa;

[0050] Fig.16 This is the distribution diagram of winding aging rate under 1MPa;

[0051] Fig.17 The distribution diagram of winding aging rate under 1.5MPa;

[0052] Fig.18 This is the distribution diagram of winding aging rate under 2MPa;

[0053] Fig.19 Life loss cloud diagram with 50% tension retained for insulation as end of life;

[0054] Fig. 20 Life loss contour diagram with a degree of polymerization of 200 as the end of life for insulation. DETAILED DESCRIPTION

[0055] 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 should fall within the scope of protection of the present invention.

[0056] Example 1

[0057] like Figure 1 As shown, a method for estimating the life of oil-paper insulation of a non-uniformly distributed converter transformer is provided, comprising the following steps:

[0058] S1. Obtaining state parameters of each spatial position from the commutation transformer winding model as input, wherein the state parameters include electric field intensity, temperature and mechanical stress value;

[0059] S2. Obtaining the aging rate of the oil-paper insulation system at different positions based on the input state parameters;

[0060] S3. The local life span is obtained through the aging rate at different positions. The overall life span of the oil-paper insulation system of the converter transformer is obtained by comprehensive processing of the local life span, and the overall life span is output.

[0061] The commutation transformer winding model is a non-uniform distribution model that couples electromagnetic, thermal and solid force fields.

[0062] The aging rate expression at different positions is:

[0063]

[0064] Wherein, r(x,y,z) is the aging rate at position (x,y,z); T(x,y,z) is the temperature at position (x,y,z); E(x,y,z) is the electric field strength at position (x,y,z); σ(x,y,z) is the mechanical stress at position (x,y,z); α is the electric field coefficient; β is the stress coefficient.

[0065] The local lifetime expression is:

[0066]

[0067] Where r(x,y,z) is the aging rate at position (x,y,z).

[0068] The overall lifetime expression in S3 is:

[0069]

[0070] Where R is the total aging rate of the entire model; r(x,y,z) is the aging rate at the position (x,y,z).

[0071] A non-uniform distribution model of electromagnetic-thermal flow-solid force field coupling is constructed to simulate the electric field, temperature and mechanical stress distribution of the converter transformer winding under actual operating conditions. The electric field, temperature and mechanical stress data at different positions are obtained by solving the electromagnetic-thermal flow multi-physics field model built according to the specific transformer type in the simulation software. Among them, the electric field intensity E(x, y, z) is obtained by Maxwell's equations, and the expression is:

[0072]

[0073] Among them, E is the electric field intensity; H is the magnetic field intensity; J is the current density; D is the electric displacement field; and B is the magnetic induction intensity.

[0074] The temperature distribution of S1 at different positions is affected by the harmonic current by changing the conductor current density. The thermal flow field expression is:

[0075]

[0076] Where r is the material density; c p is the specific heat capacity; T is the temperature field; k is the thermal conductivity; Q is the heat source term; t is the time.

[0077] The mechanical stress of S1 follows the law of elastic mechanics in solid mechanics, and the expression is:

[0078]

[0079] Among them, σ is the mechanical stress tensor; F is the body force; u is the displacement field; ρ is the density; t is the time.

[0080] This embodiment takes the UHV converter transformer model ZZDFPZ-405000 / 500-400 as an example to predict the oil-paper insulation life of the non-uniform distribution. The converter transformer is a 400kV converter transformer with Y / Y connection at the low end of the converter station pole 1, and its basic parameters are shown in Table 1.

[0081] Table 1 Basic parameters of UHV converter transformer

[0082] Parameter name Parameter Value Rated capacity 405MVA Voltage level Grid side 500kV Valve side ±400kV Rated phase voltage Grid side 530 / √3kV Valve side 171.88 / √3kV Rated phase current Grid side 2×662A Valve side 2×2041A Connection Ii Cooling method ODAF

[0083] The two-dimensional refined simulation model of the converter transformer winding is as follows: Figure 2 As shown in the figure, the two-dimensional refined simulation model of the grid-side winding is as follows: Figure 3 As shown in the figure, the two-dimensional refined simulation model of the valve side winding is as follows Figure 4As shown. The grid side and valve side voltage levels of the transformer are 500kV and 400kV respectively, and the cooling method is forced guided oil circulation air cooling. The rated current of the grid side winding is 2×662A, the winding width is about 130mm, and the height is about 2300mm; the grid side winding is divided into 8 areas from top to bottom by the oil baffle, the bottom area contains 18 coils, and each of the remaining areas contains 17 coils, totaling 137 coils. Each coil contains 5 turns of coil, and each turn of coil is composed of 12 strands of wire in parallel. The width of the horizontal oil channel between the grid side winding coils is 3mm, and the width of the vertical oil channel between the winding and the partition is 10mm. The rated current of the valve side winding is 2×2041A. The valve side winding has a total of 8 areas, the bottom area contains 23 coils, and each of the remaining areas contains 25 coils, totaling 198 coils. One coil is one turn, and each turn of coil is composed of 56 strands of wire in parallel. The width of the horizontal oil channel between the winding cakes on the valve side is 3mm, and the width of the vertical oil channel on the inner and outer diameter sides is different, the width of the oil channel on the inner diameter side is 16mm, and the width of the oil channel on the outer diameter side is 15mm.

[0084] The two-dimensional refined simulation model of the converter transformer winding is subjected to an electric-magnetic-thermal-mechanical multi-physics field coupling simulation to obtain the non-uniform distribution of the electric field, temperature field and solid force field of the converter transformer. Figure 5 The electric field of the converter transformer is unevenly distributed. From the overall electric field distribution diagram, it can be seen that the electric field strength inside the grid-side winding and the valve-side winding is relatively small, and the electric field strength in the oil channel between the windings is relatively large. The electric field strength of the oil channel between the windings is 3kV / mm to 4kV / mm, and the electric field strength of the winding partition is about 2kV / mm. The electric field strength at the top of the grid-side winding and the valve-side winding is also relatively large. Specifically, the maximum electric field strength of the grid-side winding is located at the electrostatic ring, which is 6.44kV / mm, and the maximum electric field strength of the valve-side winding is located at the top inner diameter side wire turn, which is about 6.13kV / mm. From the distribution of the electric field, the oil channel between the grid-side winding electrostatic ring and the corner ring is a weak point in insulation strength. Figure 6 , Figure 7 , Figure 8 and Fig. 9 The figure shows the non-uniform distribution of the temperature field of the converter transformer under different losses. As the loss increases, the winding temperature gradually increases, and the hot spot of the winding is located at the first strand turn on the inner diameter side of the second coil at the top of the first area above. Therefore, from the distribution of temperature, the hot spot of the grid-side winding is the weak insulation part. Fig.10 , Fig.11 , Fig.12 , Fig.13 and Fig.14The stress field of the converter transformer is non-uniformly distributed. As can be seen from the figure, as time goes by, the stress of the grid-side winding gradually shifts from the end to the middle, and the stress of the valve-side winding also shows a trend of gradual concentration, forming a stress peak area in the middle and lower part of the winding. Global calculations show that the winding stress reaches its maximum value at t=0.02s, the maximum stress value of the grid-side winding is 9.625MPa, and the maximum stress value of the valve-side winding is 2.346MPa. The overall stress value of the grid-side winding is greater than that of the valve-side winding.

[0085] Based on the electric field, temperature and mechanical stress data at different positions, the winding temperature and stress distribution data are used to obtain the non-uniform aging rate at different positions and under different working conditions. The aging rate distribution is as follows: Fig.16 , Fig.17 and Fig.18 As shown in the figure, the aging rate of the winding under the temperature, electric field and stress at different positions and working conditions is non-uniformly distributed. The maximum aging rate of the winding occurs at the upper end of the grid-side winding, and as the mechanical stress increases, the aging rate of the winding increases as a whole. Finally, taking the insulation retention of 50% tension as the end of life and the insulation retention degree of 200 as the end of life, the overall life distribution of the transformer oil-paper insulation system under different load rates is obtained as follows Fig.19 and Fig. 20 As shown, the life loss distribution is proportional to the winding aging rate distribution, and both present an uneven distribution. The life loss of the upper end of the grid-side winding is the most severe, and the overall life loss of the valve-side winding is less than that of the grid-side winding.

[0086] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the described module can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0087] Example 2

[0088] The electronic device of the present invention includes a central processing unit (CPU), which can perform various appropriate actions and processes according to computer program instructions stored in a read-only memory (ROM) or loaded from a storage unit into a random access memory (RAM). In the RAM, various programs and data required for device operation can also be stored. The CPU, ROM and RAM are connected to each other via a bus. An input / output (I / O) interface is also connected to the bus.

[0089] A plurality of components in the device are connected to the I / O interface, including: an input unit, such as a keyboard, a mouse, etc.; an output unit, such as various types of displays, speakers, etc.; a storage unit, such as a disk, an optical disk, etc.; and a communication unit, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit allows the device to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks. The processing unit performs the various methods and processes described above, such as the method of the present invention. For example, in some embodiments, the method of the present invention may be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as a storage unit. In some embodiments, part or all of the computer program may be loaded and / or installed on the device via a ROM and / or a communication unit. When the computer program is loaded into the RAM and executed by the CPU, one or more steps of the method of the present invention described above may be performed. Alternatively, in other embodiments, the CPU may be configured to perform the method of the present invention in any other appropriate manner (e.g., by means of firmware).

[0090] The functions described above herein may be performed at least in part by one or more hardware logic components. For example, without limitation, exemplary types of hardware logic components that may be used include: field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), complex programmable logic devices (CPLDs), and the like.

[0091] The program code for implementing the method of the present invention can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code can be executed entirely on the machine, partially on the machine, partially on the machine as a stand-alone software package and partially on a remote machine, or entirely on a remote machine or server.

[0092] In the context of the present invention, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0093] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for estimating the life of oil-paper insulation of non-uniformly distributed converter transformers, characterized in that: The following steps are involved: S1. Obtaining state parameters of each spatial position from the commutation transformer winding model as input, wherein the state parameters include electric field intensity, temperature and mechanical stress value; S2. Obtaining the aging rate of the oil-paper insulation system at different positions based on the input state parameters; S3. The local life span is obtained through the aging rate at different positions. The overall life span of the oil-paper insulation system of the converter transformer is obtained by comprehensive processing of the local life span, and the overall life span is output.

2. The method for estimating the life of oil-paper insulation of non-uniformly distributed converter transformers according to claim 1, characterized in that: The commutation transformer winding model in S1 is a non-uniform distribution model coupled with electromagnetic, thermal and solid force fields.

3. The method for estimating the life of oil-paper insulation of non-uniformly distributed converter transformers according to claim 1, characterized in that: The aging rate expression of different positions of S2 is: Wherein, r(x,y,z) is the aging rate at position (x,y,z); T(x,y,z) is the temperature at position (x,y,z); E(x,y,z) is the electric field strength at position (x,y,z); σ(x,y,z) is the mechanical stress at position (x,y,z); α is the electric field coefficient; β is the stress coefficient.

4. The method for estimating the life of oil-paper insulation of non-uniformly distributed converter transformers according to claim 1, characterized in that: The local life expression of S3 is: Where r(x,y,z) is the aging rate at position (x,y,z).

5. The method for estimating the life of oil-paper insulation of non-uniformly distributed converter transformers according to claim 1, characterized in that: The overall life expression of S3 is: Where R is the total aging rate of the entire model; r(x,y,z) is the aging rate at the position (x,y,z).

6. The method for estimating the life of oil-paper insulation of non-uniformly distributed converter transformers according to claim 1, characterized in that: The electric field strength E(x, y, z) of S1 is obtained by Maxwell equations, expressed as: Where E is the electric field intensity; H is the magnetic field intensity; J is the current density; D is the electric displacement field; and B is the magnetic induction intensity.

7. The method for estimating the life of oil-paper insulation of non-uniformly distributed converter transformers according to claim 1, characterized in that: The distribution of the temperature of S1 at different positions is affected by the harmonic current by changing the conductor current density. The thermal flow field expression is: Where r is the material density; c p is the specific heat capacity; T is the temperature field; k is the thermal conductivity; Q is the heat source term; t is the time.

8. The method for estimating the life of oil-paper insulation of non-uniformly distributed converter transformers according to claim 1, characterized in that: The mechanical stress of S1 follows the law of elastic mechanics in solid mechanics, and the expression is: Among them, σ is the mechanical stress tensor; F is the body force; u is the displacement field; ρ is the density; t is the time.

9. An electronic device comprising a memory and a processor, wherein a computer program is stored in the memory, wherein: When the processor executes the program, the method according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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