A method and system for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection

Abstract

This invention proposes a method and system for predicting the winding temperature of an oil-fired transformer at the instant of power disconnection, belonging to the field of winding temperature calculation. It obtains a set of winding resistance values ​​continuously measured at fixed time intervals after power disconnection and calculates the corresponding winding temperature. Based on the time interval, winding temperature, and cooling parameters, a cooling curve is fitted using MATLAB. Based on the cooling curve, the winding temperature at the instant of power disconnection is predicted. This invention calculates the winding temperature by continuously measuring a set of winding resistance values ​​at fixed time intervals after power disconnection, and fits a cooling curve based on the continuous winding temperature, thereby obtaining the winding temperature at the instant of power disconnection. This improves the efficiency and accuracy of winding temperature calculation and solves the problems of inaccuracy, lack of intuitiveness, and low efficiency in existing methods.

Description

Technical Field

[0001] This invention belongs to the field of winding temperature calculation, and in particular relates to a method and system for predicting the winding temperature of an oil-fired transformer at the instant the power supply is disconnected. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Temperature is the main cause of insulation aging in transformers. Due to uneven heat distribution inside the transformer, there are large temperature differences in different parts of the transformer. Therefore, it is necessary to measure the temperature rise of each part of the transformer under rated load to ensure that the temperature is within the allowable temperature rise range of the transformer.

[0004] The winding temperature at the instant the power is disconnected should ideally be measured at that moment. However, even if the two ends of the winding of the resistor under test are immediately connected to a DC measuring circuit after the power is cut off and the short-circuit connection is disconnected, there is still a time interval, making it impossible to measure at the instant of power disconnection. Therefore, the resistance value measured after power disconnection is converted into temperature to infer the resistance temperature at the instant of power disconnection. In other words, the winding temperature changes over time, and obtaining the winding temperature at the instant the power is disconnected is a difficult problem.

[0005] The calculation process of the existing winding temperature cooling curve is mostly carried out by computer programs, which fit a set of temperature readings into an analytical function. Common computer programs often use Excel spreadsheet function curve fitting, which is not intuitive and the curve fitted by the function has a certain deviation from the target curve. Furthermore, when multiple curves need to be fitted, the calculation is complicated and the image data cannot be effectively saved.

[0006] How to efficiently and accurately measure the winding temperature of an oil-fired transformer at the moment of power disconnection, and solve the problems of inaccuracy, lack of intuitiveness, and low efficiency in existing methods, is a topic worthy of further research. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention provides a method and system for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection. By continuously measuring a set of winding resistance values ​​at fixed time intervals after power disconnection, the winding temperature is calculated. Based on the continuous winding temperature, a cooling curve is fitted to obtain the winding temperature at the moment of power disconnection. This improves the efficiency and accuracy of winding temperature calculation and solves the problems of inaccuracy, lack of intuitiveness, and low efficiency in existing methods.

[0008] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0009] The first aspect of this invention provides a method for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection;

[0010] A method for predicting the winding temperature of an oil-fired transformer at the instant of power disconnection includes:

[0011] Obtain a set of winding resistance values ​​measured continuously at fixed time intervals after the power is disconnected, and calculate the winding temperature corresponding to the resistance values;

[0012] Based on the time interval, winding temperature, and cooling parameters, the cooling curve was fitted using MATLAB.

[0013] Based on the cooling curve, the winding temperature is predicted at the moment of power disconnection.

[0014] Furthermore, the set of winding resistance values ​​continuously measured at fixed time intervals is obtained by continuously measuring the winding resistance values ​​at fixed time intervals after the power is disconnected.

[0015] Preferably, the fixed time interval is set to 1 minute.

[0016] Furthermore, the specific method for calculating the winding temperature corresponding to the resistance value is as follows:

[0017] Obtain the winding resistance R0 and winding temperature θ0 of the transformer under stable ambient temperature;

[0018] According to the formula Calculate the winding resistance value R i The corresponding winding temperature θ i L is the winding coefficient.

[0019] Furthermore, the cooling parameters include cooling temperature per unit time and winding coefficient.

[0020] Furthermore, before fitting the cooling curve, the time interval and winding temperature are preprocessed, including the removal of abnormal data and the correction of winding temperature.

[0021] Furthermore, the winding temperature is corrected by multiplying the cooling temperature per unit time by the time interval.

[0022] Furthermore, the cooling curve is plotted with the time interval as the X-axis and the winding temperature as the Y-axis.

[0023] A second aspect of the present invention provides a winding temperature prediction system for oil-fired transformers at the moment of power disconnection.

[0024] A winding temperature prediction system for oil-fired transformers at the moment of power disconnection includes a data acquisition module, a curve fitting module, and a temperature prediction module.

[0025] The data acquisition module is configured to acquire a set of winding resistance values ​​measured continuously at fixed time intervals after the power is disconnected, and to calculate the winding temperature corresponding to the resistance values.

[0026] The curve fitting module is configured to fit the cooling curve using MATLAB based on the time interval, winding temperature, and cooling parameters.

[0027] The temperature prediction module is configured to predict the winding temperature at the moment of power disconnection based on the cooling curve.

[0028] A third aspect of the present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the steps of the method for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection as described in the first aspect of the present invention.

[0029] The fourth aspect of the present invention provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the method for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection as described in the first aspect of the present invention.

[0030] The above one or more technical solutions have the following beneficial effects:

[0031] This invention calculates the winding temperature by continuously measuring a set of winding resistance values ​​at fixed time intervals after the power is disconnected. Based on the continuous winding temperature, a cooling curve is fitted to obtain the winding temperature at the instant the power is disconnected. This improves the efficiency and accuracy of winding temperature calculation and solves the problems of inaccuracy, lack of intuitiveness, and low efficiency in existing methods.

[0032] The calculation method provided by this invention only requires a set of resistance values ​​to calculate the winding temperature, which is faster, simpler to use, and easier to understand.

[0033] This invention can meet the accuracy requirements of different devices. Some devices have an accuracy of 0.1 grade, displaying the temperature to one decimal place, while others have an accuracy of 0.01 grade, displaying the temperature to two decimal places. The winding temperature predicted by the calculation method of this invention can meet the accuracy requirements of different devices.

[0034] This invention calculates the rotor winding temperature based on dynamic parameters. It utilizes dynamic parameters collected during the operation of a doubly-fed asynchronous generator, including active power, reactive power, grid voltage, power factor, speed, and stator winding temperature, to calculate the dynamic rotor winding temperature. This allows for real-time monitoring of the rotor winding temperature without increasing hardware costs. Furthermore, this invention also provides a rotor winding temperature calculation system for a doubly-fed asynchronous generator and a computer-readable storage medium, which also possess the aforementioned beneficial effects.

[0035] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0037] Figure 1 This is a flowchart of the method in the first embodiment.

[0038] Figure 2 This is a schematic diagram of the cooling curve in the first embodiment.

[0039] Figure 3 This is a software interface design diagram from the first embodiment.

[0040] Figure 4 This is the final functional interface in the first embodiment.

[0041] Figure 5 This is a schematic diagram of the cooling curve prediction in the first embodiment.

[0042] Figure 6 This is a system structure diagram of the second embodiment. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0044] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0045] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] Example 1

[0047] This embodiment discloses a method for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection;

[0048] like Figure 1As shown, a method for predicting the winding temperature of an oil-fired transformer at the instant of power disconnection includes:

[0049] Step S1: Obtain a set of winding resistance values ​​measured continuously at fixed time intervals after the power is disconnected, and calculate the winding temperature corresponding to the resistance values.

[0050] Winding temperature is calculated by measuring resistance values. Therefore, after the power is disconnected, the winding resistance value should be measured first. For three-phase transformers, the resistance measurement should usually include the intermediate phase winding. For star junction or low-voltage and high-current windings, the measurement should be performed between the line terminals so that the neutral point lead can be removed from the test circuit. For transformers with a capacity of 800 kW or more, use the transformer test system LHR0006. For transformers with a capacity of less than 800 kW, use the transformer parameter comprehensive analyzer LHR0029.

[0051] Obtain a set of resistance values ​​[R1, R2, ... R] over time after the power is disconnected. n After that, calculate the winding temperature corresponding to each resistance value in this group. The specific calculation method is as follows:

[0052] Obtain the winding resistance R0 and winding temperature θ0 of the transformer under stable ambient temperature;

[0053] According to the formula in the transformer temperature rise standard Calculate the winding resistance value R i The corresponding winding temperature θ i L is the winding coefficient.

[0054] Step S2: Fit the cooling curve using MATLAB based on the time interval, winding temperature, and cooling parameters;

[0055] The cooling parameters include the cooling temperature per unit time and the winding coefficient.

[0056] The winding factor L for copper windings is 235, while the winding factor L for aluminum windings is 225. These are two relatively common winding materials.

[0057] In some cases, certain measurements taken at the initial stage after power disconnection may be inconsistent with subsequent values. These values ​​should be removed, i.e., abnormal data should be cleared. This abnormal data is usually caused by equipment usage issues or improper equipment operation, and is generally determined on-site by the testing personnel. The adopted effective values ​​are represented by θ. wval (i) indicates.

[0058] To ensure data integrity and prediction accuracy, the winding temperature is corrected. The specific formula for this correction is as follows:

[0059] θ w (i)=θ wval(i)+kt

[0060] Where, θ w (i) is the corrected winding temperature, k is the cooling temperature per unit time, and t is the time interval between the measurement of the i-th resistance value and the power supply being disconnected. For example, if k is 5℃ / minute and t is 10 minutes, 5℃ / minute means that the temperature decreases by 5℃ every minute.

[0061] Before fitting the cooling curve using MATLAB, the following data processing is required:

[0062] Calculate the difference between adjacent effective values ​​of winding temperature:

[0063] Δθ w (i)=θ w (i)-θ w (i-1)

[0064] Calculate the absolute value of the sum of the differences between adjacent effective values ​​of winding temperature:

[0065] S a =|∑[Δθ w (i)]|

[0066] Calculate the absolute value of the sum of the differences between the effective values ​​of the winding temperatures:

[0067] S b =|∑θ w (i)|

[0068] Calculate the absolute value of the sum of the products of the effective value of the winding temperature and the differences between adjacent effective values ​​of the corrected and confirmed winding temperature:

[0069] S d =∑|[θ w (i)Δθ w (i)]|

[0070] Calculate the sum of squares of the effective values ​​of the winding temperature:

[0071] S d =∑[θ w (i)] 2

[0072] Calculate auxiliary variables:

[0073]

[0074]

[0075] Calculate winding time parameters:

[0076] T w =Δt / ln(1+t) e )

[0077] Calculate parameters A0 and g:

[0078] S e =∑e (-i / Tw)

[0079] A0 = -t c / t e

[0080] g=(S b -n*A0) / S e

[0081] Calculate the winding temperature at the instant the power is disconnected:

[0082] θ W (t=0)=A0+g

[0083] Use MATLAB to fit the curve and obtain θ. w (t)=A0-kt+g*e -t / Tw The resulting curve is as follows Figure 2 As shown.

[0084] Step S3: Based on the cooling curve, predict the winding temperature at the moment the power is disconnected.

[0085] Based on the fitted cooling curve, the winding temperature at the instant the power is disconnected is predicted. The winding temperature at t=0 is the winding temperature at the instant the power is disconnected.

[0086] To facilitate easier prediction of winding temperature, a temperature prediction interface is provided. This interface uses a set of measured resistance values ​​as input to fit and display a cooling curve. The program is designed using MATLAB, and the software interface design is as follows. Figure 3 As shown, during the design process, graphical programming was used to select the required buttons and outline the necessary functional interface. The final functional interface is as follows. Figure 4 As shown in the diagram. Callback functions are created for the "Draw Curve" and "Save Image" buttons. The calculation program is then implemented in these callback functions, and finally, the "Save Image" button's callback function saves the drawn curve. Simply enter the corresponding parameters in the appropriate locations, and then click the "Draw Curve" button. The result is as shown in the diagram. Figure 5 As shown.

[0087] Example 2

[0088] This embodiment discloses a winding temperature prediction system for an oil-fired transformer at the moment of power disconnection;

[0089] like Figure 6As shown, a winding temperature prediction system for an oil-fired transformer at the moment of power disconnection includes a data acquisition module, a curve fitting module, and a temperature prediction module.

[0090] The data acquisition module is configured to acquire a set of winding resistance values ​​measured continuously at fixed time intervals after the power is disconnected, and to calculate the winding temperature corresponding to the resistance values.

[0091] The curve fitting module is configured to fit the cooling curve using MATLAB based on the time interval, winding temperature, and cooling parameters.

[0092] The temperature prediction module is configured to predict the winding temperature at the moment of power disconnection based on the cooling curve.

[0093] Example 3

[0094] The purpose of this embodiment is to provide a computer-readable storage medium.

[0095] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in a method for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection as described in Embodiment 1 of this disclosure.

[0096] Example 4

[0097] The purpose of this embodiment is to provide an electronic device.

[0098] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the method for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection as described in Embodiment 1 of this disclosure.

[0099] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for predicting the winding temperature of an oil-fired transformer at the instant of power disconnection, characterized in that, include: Obtain a set of winding resistance values ​​measured continuously at fixed time intervals after the power is disconnected, and calculate the winding temperature corresponding to the resistance values; The specific method for calculating the winding temperature corresponding to the resistance value is as follows: Obtain the winding resistance value of the transformer under stable ambient temperature. and winding temperature ; According to the formula Calculate the winding resistance value Corresponding winding temperature L is the winding coefficient; Based on the time interval, winding temperature, and cooling parameters, the cooling curve was fitted using MATLAB. The cooling parameters include the cooling temperature per unit time and the winding coefficient; Based on the cooling curve, the winding temperature is predicted at the moment of power disconnection.

2. The method for predicting the winding temperature of an oil-fired transformer at the instant of power disconnection as described in claim 1, characterized in that, The set of winding resistance values ​​measured continuously at fixed time intervals is obtained by measuring the winding resistance values ​​continuously at fixed time intervals after the power is disconnected.

3. The method for predicting the winding temperature of an oil-fired transformer at the instant of power disconnection as described in claim 1, characterized in that, Before fitting the cooling curve, the time interval and winding temperature are preprocessed, including the removal of abnormal data and the correction of winding temperature.

4. The method for predicting the winding temperature of an oil-fired transformer at the instant of power disconnection as described in claim 3, characterized in that, The winding temperature is corrected by multiplying the cooling temperature per unit time by the time interval.

5. The method for predicting the winding temperature of an oil-fired transformer at the instant of power disconnection as described in claim 1, characterized in that, The cooling curve is plotted with time interval as the X-axis and winding temperature as the Y-axis.

6. A winding temperature prediction system for an oil-fired transformer at the instant of power disconnection, characterized in that: It includes a data acquisition module, a curve fitting module, and a temperature prediction module; The data acquisition module is configured to acquire a set of winding resistance values ​​measured continuously at fixed time intervals after the power is disconnected, and to calculate the winding temperature corresponding to the resistance values. The specific method for calculating the winding temperature corresponding to the resistance value is as follows: Obtain the winding resistance value of the transformer under stable ambient temperature. and winding temperature ; According to the formula Calculate the winding resistance value Corresponding winding temperature L is the winding coefficient; The curve fitting module is configured to fit the cooling curve using MATLAB based on the time interval, winding temperature, and cooling parameters. The cooling parameters include the cooling temperature per unit time and the winding coefficient; The temperature prediction module is configured to predict the winding temperature at the moment of power disconnection based on the cooling curve.

7. A computer-readable storage medium having a program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the method for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection as described in any one of claims 1-5.

8. An electronic device, comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the method for predicting the winding temperature of an oil-fired transformer at the moment of power disconnection as described in any one of claims 1-5.

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