Transformer life loss calculation method and device and storage medium

Abstract

The invention discloses a transformer life loss calculation method and device and a storage medium, transformer life calculation is transferred from engineering conservative design to electric heating load capacity essence, a transformer hot spot thermal circuit model based on bottom layer oil temperature is established, factors such as an oil flow path, oil viscosity and a transformer structure are fully considered, and the reliability of the transformer life loss calculation is improved. According to the method, the heat transfer process of the transformer can be described from the physical essence, the inconsistency of the hot-spot temperature and the current of the transformer is comprehensively shown, precise dynamic process calculation of the hot-spot temperature of the transformer is realized, and a long-time hot-spot temperature-time curve is divided into countless small intervals by utilizing a differential thought; the electrical quantity and the hot-spot temperature are regarded to be constant in the small interval, data are substituted into the transformer insulation life model, then the short-time overload capacity contained in the whole life period is released with the designed aging life as the constraint, and the operation state of the transformer is evaluated again; the invention provides an oil-immersed transformer thermal aging life loss calculation method considering the short-time overload capacity.

Description

Technical Field

[0001] The present application relates to the technical field of transformer life prediction, and in particular to a transformer life loss calculation method, device and storage medium. Background Art

[0002] With the rapid construction of new power systems, voltage levels and capacities are increasing. As a key component for power grid power transmission and voltage conversion, the failure rate of power transformers is also increasing. After years of practical experience, researchers have found that the main reason for the reduction in transformer life is the aging of insulation materials. As the highest temperature value of the transformer, once the hot spot temperature is higher than the rated value, the aging rate of the insulation material increases dramatically, seriously threatening the normal operation of the transformer. If the temperature is too low, the transformer operates at a low temperature and low load state, the insulation material life loss is lower than the rated value, a large amount of load potential is wasted, and there is a life surplus.

[0003] At present, there are two problems in the calculation of thermal aging life loss of transformers: 1. The hot spot temperature calculation method used in the current transformer life loss calculation has large errors and poor accuracy. It is generally obtained by simply superimposing the ambient temperature, the temperature difference between the top oil and the environment, and the temperature difference between the hot spot of the transformer and the top oil. The life loss is essentially the accumulation of insulation material aging caused by excessive physical temperature. The temperature rise process of the transformer is ignored, usually 30-90 minutes, and there is a lack of dynamic time-refined simulation of the heat transfer process, which leads to large errors in the calculation of thermal aging life loss. 2. The traditional method lacks consideration of short-term overload capacity, resulting in conservative life calculation, which is mainly reflected in the following two aspects. On the one hand, in traditional cases, the life of the transformer is estimated based on the maximum allowable temperature for long-term operation and conservative meteorological conditions. Due to the strong time-varying meteorological conditions, current fluctuations and thermal inertia, the short-term high load of the transformer does not necessarily lead to excessively high hot spot temperatures. If it is higher than the long-term maximum allowable operating temperature, the overall life loss is not within the allowable range. On the other hand, under the premise of ensuring the design life, the life loss under low temperature and low load is much lower than the maximum allowable temperature, which brings a large surplus to the operating life. In addition, the engineering allows the hot spot temperature of the transformer to be higher than the long-term maximum allowable operating temperature, and the short-term overload capacity needs to be further explored.

[0004] Therefore, the existing calculation method does not take into account the actual operating status of the transformer, resulting in conservative or aggressive calculation of transformer life loss, and equipment failure or waste of resources often occurs. Summary of the invention

[0005] The present application provides a transformer life loss calculation method, device and storage medium to solve the above problems.

[0006] In one aspect, the present application provides a method for calculating transformer life loss, the method comprising the following steps:

[0007] Step S1: Establishing a transformer hot spot thermal circuit model based on bottom oil temperature;

[0008] Step S2: Based on Kirchhoff's law, thermal resistance is analogous to resistance, loss is analogous to current source, bottom oil temperature and hot spot temperature are analogous to voltage, and transformer dielectric characteristics are analogous to capacitance, and the following formula is obtained:

[0009]

[0010] Where: is the heat capacity of the bottom oil; is the thermal resistance between the bottom oil and the external environment; is the bottom oil temperature; is the iron loss; is the load loss; is the thermal capacity of the winding; is the thermal resistance between the hot spot and the bottom oil; is the hot spot temperature; is the winding loss;

[0011] Step S3: using the Runge-Kutta method to solve the formula in step S2, and simulating the hot spot temperature change trajectory of the transformer;

[0012] Step S4: Express the insulation life as a function of the medium and temperature as shown in the following equation:

[0013]

[0014] Where: DP end DP is the insulation value at the end of the transformer's design life; start is the initial insulation value of the transformer; A is the constant of the chemical environment; L(θ hs ) is the operating life; E is the activation energy; R is the gas constant; θ hs is the hot spot temperature;

[0015] Step S5: Calculate the life loss percentage of the transformer based on the following formula:

[0016]

[0017] Step S6: Based on the following formula, the loss percentage of life within the operation period T is calculated as:

[0018]

[0019] The operation cycle T is divided into t 1 , t 2 ……tN There are N operating intervals in total, and each operating interval is divided into infinite subintervals dt;

[0020] Step S7: Determine whether the loss percentage of the transformer's life has reached an upper limit constraint.

[0021] In one implementation of the present application, in step S3, the Runge-Kutta method is of fourth order, and the expression of the fourth-order Runge-Kutta method is:

[0022]

[0023] The present application also provides a transformer life loss calculation device, the device comprising:

[0024] at least one processor; and,

[0025] a memory communicatively connected to the at least one processor; wherein,

[0026] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can complete the aforementioned transformer life loss calculation method.

[0027] The present application also provides a non-volatile computer storage medium for transformer life loss calculation, which stores computer executable instructions. The computer executable instructions are executed by a processor for the aforementioned transformer life loss calculation method.

[0028] The present application provides a transformer life loss calculation method, device and medium, which have the following beneficial effects:

[0029] (1) A transformer hot spot temperature thermal circuit model based on the bottom oil temperature is used to explore the heat transfer process under the complex structure of the transformer from the physical essence, and fully consider the type difference factors such as oil viscosity and cooling method. It can describe the dynamic process of the transformer hot spot temperature in real time and accurately, reducing the error of traditional calculation methods and providing accurate data support for life loss calculation;

[0030] (2) A method for calculating the life loss of oil-immersed transformers due to thermal aging taking into account the short-term overload capacity is proposed. This method fully considers the short-term overload capacity of the transformer under real-time operation conditions, greatly taps the short-term overcurrent capacity hidden in the thermal inertia process, and realizes the lean calculation of the transformer life loss. It provides an effective data support for transformer status assessment and fault analysis, which is in line with the application prospects of the new power system under the dual carbon goals. It establishes a theoretical framework and conducts useful discussions for further forming a standardized method for calculating the life loss of transformers, which is conducive to improving the investment efficiency of power grid construction and the utilization rate of substation equipment, thereby bringing considerable social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0032] Figure 1 A flow chart of a transformer life loss calculation method provided in an embodiment of the present application;

[0033] Figure 2 A schematic diagram of a thermal circuit model provided in an embodiment of the present application;

[0034] Figure 3 A transformer simulation result diagram provided in an embodiment of the present application;

[0035] Figure 4 A life loss curve diagram of the transformer in the first year provided in an embodiment of the present application;

[0036] Figure 5 A schematic diagram of a transformer life loss calculation device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0038] The embodiments of the present application provide a transformer life loss calculation method, device and storage medium. The technical solution proposed in the embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0039] Figure 1 A flow chart of a transformer life loss calculation method provided in an embodiment of the present application. Figure 1 As shown, the method mainly includes the following steps:

[0040] Step S1: Establish a transformer hot spot thermal circuit model based on the bottom oil temperature.

[0041] The hot spot temperature calculation of the transformer is divided into two heat transfer processes: ambient temperature-bottom oil temperature and bottom oil temperature-hot spot temperature. The thermal circuit model is constructed in the form of a circuit, such as Figure 2 shown.

[0042] Step S2: Based on Kirchhoff's law, thermal resistance is analogous to resistance, loss is analogous to current source, bottom oil temperature and hot spot temperature are analogous to voltage, and transformer dielectric characteristics are analogous to capacitance, and the following formula is obtained:

[0043]

[0044] Where: is the heat capacity of the bottom oil; is the thermal resistance between the bottom oil and the external environment; is the bottom oil temperature; is the iron loss; is the load loss; is the thermal capacity of the winding; is the thermal resistance between the hot spot and the bottom oil; is the hot spot temperature; is the winding loss.

[0045] Step S3: Use the Runge-Kutta method to solve the formula in step S2 and simulate the temperature change trajectory of the transformer hot spot.

[0046] During actual operation, the surrounding meteorological environment and current carrier change continuously over time, and the thermal equilibrium state of the transformer is broken. Due to the existence of thermal inertia, the current carrier can no longer fully describe the change process of the transformer hot spot temperature. The Runge-Kutta method is used to solve the formula in step S2 to simulate the change trajectory of the transformer hot spot temperature and explore the current carrying capacity contained in the thermal dynamic process of the transformer.

[0047] Step S4: Express the insulation life as a function of the medium and temperature as shown in the following equation:

[0048]

[0049] Where: DP end DP is the insulation value at the end of the transformer's design life; start is the initial insulation value of the transformer; A is the constant of the chemical environment; L(θ hs ) is the operating life; E is the activation energy; R is the gas constant; θ hs is the hot spot temperature;

[0050] Step S5: Calculate the life loss percentage of the transformer based on the following formula:

[0051]

[0052] The hot spot temperature is a constant setting based on conservative engineering operating conditions, ignoring the dynamic process of the actual operation of the transformer. In view of this situation, a reasonable and effective transformer thermal aging assessment method needs to be studied. This section intends to use the mathematical idea of ​​differentials to divide the operating cycle T into t 1 , t2 ……t N There are N operating intervals in total, and each operating interval is divided into infinite small intervals dt. In each small interval dt, the current and environmental conditions do not change in each interval, so the hot spot temperature of the transformer can also be regarded as a constant value.

[0053] Step S6: Based on the following formula, the loss percentage of life within the operation period T is calculated as:

[0054]

[0055] Step S7: Based on the formula: L loss ≤L limit , determine the loss percentage of transformer life L loss Whether the upper limit constraint is reached, L limit It is the upper limit of the loss percentage of the transformer life.

[0056] The transformer thermal circuit model can accurately simulate the dynamic process of current and temperature inconsistency (thermal inertia) on the hot spot temperature. The thermal inertia of the transformer is generally 30-90 minutes. If the current is used to calculate the corresponding hot spot temperature, it will lead to a large error. The temperature rise process of the transformer under rated load is solved using the Runge-Kutta method. The parameters of the transformer are shown in Table 1 below:

[0057] Table 1 Transformer parameters

[0058]

[0059] The simulation results are as follows Figure 3 As shown in the figure, it can be seen from the simulation results that the hotspot oil temperature rises very quickly during the startup period. Since the transformer starts in a cold start mode, the temperature is low, the oil viscosity is relatively high, the buoyancy and flow rate are small, and the heat dissipation speed is slow, resulting in a rapid rise in the hotspot temperature. The thermal inertia time constant of the bottom oil temperature is about 118 minutes, and the thermal inertia time constant of the hotspot temperature is about 8 minutes, which reflects that the transformer has typical thermal inertia characteristics and has huge short-term current carrying potential during the temperature rise process. The model can simulate the heat transfer process of the transformer in detail according to the actual situation, and the simulation calculation accuracy is high.

[0060] The normal operating design life of the transformer is calculated based on the rated maximum allowable temperature and conservative meteorological environment conditions. However, under actual operation, the transformer is in a low temperature and low load state. The probability of high temperature and full load conditions is low and the duration is short. Therefore, compared with the rated conditions, the life loss during this period is greatly reduced. In addition, the hot spot temperature is allowed to exceed the rated temperature for a short time in engineering applications, which provides great potential for short-term overload capacity.

[0061] Based on the 30-year operation data and meteorological environment data of a transformer in Shandong, and based on the transformer bottom oil temperature thermal circuit model, the transformer hot spot temperature time series and life loss time series obtained by simulation method are used to explore the aging law and characteristics of the transformer throughout its life cycle. Among them, the system reference voltage is 220kV, and the transformer life loss in the first year is as follows Figure 4 shown.

[0062] Since the hot spot temperature and meteorological environment of the transformer fluctuate in the actual operating environment, the accumulation process of the degree of life loss is unstable. In addition, the temperature duration dt of each hot spot is determined by the data resolution and historical data in the simulation method. In theory, the higher the data resolution, the more accurate the simulation results. Table 2 below shows the percentage of life loss of the transformer over the entire design life cycle.

[0063] Table 2 Percentage of transformer life loss during the entire design life cycle

[0064]

[0065] It can be seen from the table that using the simulation results of actual operating data, the life loss of the transformer presents a fluctuating accumulation process. When the design life is 30 years, it still has a large load potential, and the life loss is only 35.28%.

[0066] The above is a transformer life loss calculation system provided by an embodiment of the present application. Based on the same inventive concept, an embodiment of the present application also provides a transformer life loss calculation device. Figure 5 A schematic diagram of a transformer life loss calculation device provided in an embodiment of the present application, such as Figure 5 As shown, the device mainly includes: at least one processor 501; and a memory 502 that is communicatively connected to the at least one processor; wherein the memory 502 stores instructions that can be executed by the at least one processor 501, and the instructions are executed by the at least one processor 501 so that the at least one processor 501 can complete the aforementioned transformer life loss calculation method.

[0067] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1A device that provides the functions specified in a block or multiple blocks.

[0068] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0069] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0070] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0071] Each embodiment in this application is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0072] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0073] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for calculating transformer life loss, characterized in that: The method comprises the following steps: Step S1: Establishing a transformer hot spot thermal circuit model based on bottom oil temperature; Step S2: Based on Kirchhoff's law, thermal resistance is analogous to resistance, loss is analogous to current source, bottom oil temperature and hot spot temperature are analogous to voltage, and transformer dielectric characteristics are analogous to capacitance, and the following formula is obtained: Where: is the heat capacity of the bottom oil; is the thermal resistance between the bottom oil and the external environment; is the bottom oil temperature; is the iron loss; is the load loss; is the thermal capacity of the winding; is the thermal resistance between the hot spot and the bottom oil; is the hot spot temperature; is the winding loss; Step S3: using the Runge-Kutta method to solve the formula in step S2, and simulating the hot spot temperature change trajectory of the transformer; Step S4: Express the insulation life as a function of the medium and temperature as shown in the following equation: Where: DP end DP is the insulation value at the end of the transformer's design life; start is the initial insulation value of the transformer; A is the constant of the chemical environment; L(θ hs ) is the operating life; E is the activation energy; R is the gas constant; θ hs is the hot spot temperature; Step S5: Calculate the life loss percentage of the transformer based on the following formula: Step S6: Based on the following formula, the loss percentage of life within the operation period T is calculated as: The operation cycle T is divided into t1, t2...t N There are N operating intervals in total, and each operating interval is divided into infinite subintervals dt; Step S7: Determine whether the loss percentage of the transformer's life has reached an upper limit constraint.

2. A transformer life loss calculation method according to claim 1, characterized in that: In step S3, the Runge-Kutta method is of fourth order, and the expression of the fourth order Runge-Kutta method is:

3. A transformer life loss calculation device, characterized in that: The device comprises: at least one processor; and, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can complete the transformer life loss calculation method described in any one of claims 1-2.

4. A non-volatile computer storage medium for transformer life loss calculation, storing computer executable instructions, characterized in that: The computer executable instructions are executed by a processor to implement a transformer life loss calculation method as described in any one of claims 1-2.

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