Transformer internal oil temperature high-precision detection method for power distribution network equipment inspection

Abstract

The application relates to the technical field of temperature measurement, in particular to a transformer internal oil temperature high-precision detection method for power distribution network equipment inspection, which comprises the following steps: acquiring temperature data of a transformer oil inlet and an oil outlet and heat data released by the transformer in real time; obtaining an up-floating lag time of insulating oil flowing from the transformer oil inlet to the oil outlet for a preset initial period after the transformer is operated; acquiring temperature difference data of the insulating oil from the oil inlet to the oil outlet and correcting the temperature difference data for the insulating oil to be measured, which is measured at a single time point as an oil outlet time point and at a time point moving forward by the up-floating lag time as an oil inlet time point in the initial period; obtaining the transformer center oil temperature at the time when the insulating oil to be measured reaches the transformer center; and further calculating the transformer center oil temperature at each collection time point. The application aims to improve the detection precision of the transformer center oil temperature.

Description

Technical Field

[0001] This application relates to the field of temperature measurement technology, specifically to a high-precision method for detecting the internal oil temperature of transformers for the inspection of power distribution network equipment. Background Technology

[0002] In power distribution networks, electrical energy output from power plants needs to be transmitted to users over long distances. To reduce line losses, high-voltage transmission is typically used. However, before connecting the energy to the user side, a transformer is needed to convert the high-voltage state in the line to a low-voltage state. During the transformation process, the transformer incurs energy losses, including copper and iron losses. These energy losses are converted into heat, causing the transformer temperature to rise. To prevent the transformer temperature from exceeding a safe range, insulating oil is usually filled inside the transformer. The heat is dissipated to the outside through the circulation of the insulating oil. Therefore, the transformer temperature can be indirectly monitored by detecting the temperature of the insulating oil inside the transformer.

[0003] Existing technologies generally use temperature sensors to measure the internal temperature of transformers. However, since the heat of a transformer comes from the current passing through the internal resistance of the transformer, and the insulation requirements of the high-voltage winding area inside the transformer are extremely high and the space structure is limited, it is impossible to directly install temperature sensors. The temperature sensors conventionally deployed at the oil inlet and outlet of the transformer can only measure the boundary oil temperature and cannot accurately reflect the true oil temperature in the central area inside the transformer, that is, the true oil temperature in the heat source area. Summary of the Invention

[0004] In view of the above, it is necessary to provide a high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection, which improves the detection accuracy of transformer center oil temperature compared with traditional transformer internal oil temperature detection methods.

[0005] The high-precision method for detecting the internal oil temperature of transformers for power distribution network equipment inspection in this application adopts the following technical solution:

[0006] One embodiment of this application provides a high-precision method for detecting the internal oil temperature of a transformer for inspection of power distribution network equipment. The method includes the following steps:

[0007] Real-time acquisition of temperature data at the transformer's oil inlet and outlet, as well as data on the heat released during transformer operation;

[0008] For the initial period after the transformer starts operating, the temperature difference data between the oil outlet and the oil inlet is obtained at each preset time offset, and similarity analysis is performed with the heat data to obtain the lag time of the insulating oil flowing from the transformer inlet to the oil outlet.

[0009] For the insulating oil under test, which takes a single moment as the oil outlet moment and the moment of the upward lag time as the oil inlet moment during the initial period, the temperature difference data and heat accumulation data of the insulating oil under test from the oil inlet to the oil outlet are obtained. By analyzing the changes in the temperature difference data and heat accumulation data of the insulating oil under test and its neighboring insulating oils, the temperature difference data of the insulating oil under test is corrected.

[0010] The timing of the insulating oil reaching the transformer center is determined by the lag time. The transformer center oil temperature at the moment the insulating oil reaches the transformer center is obtained by comparing the heat absorbed by the insulating oil in the first half of its journey from the inlet to the transformer center with the heat absorbed in the second half of its journey from the transformer center to the outlet, and by combining the corrected temperature difference data with the inlet temperature data. The transformer center oil temperature at each acquisition time is then calculated.

[0011] In one embodiment, the process of obtaining the buoyancy lag time is as follows:

[0012] The inlet temperature data, outlet temperature data, and heat data within the initial time period are arranged in chronological order to form the inlet temperature sequence, outlet temperature sequence, and heat sequence, respectively.

[0013] Calculate the difference sequence between the outlet temperature sequence and the inlet temperature sequence at each time offset;

[0014] Using the starting element of the heat sequence as the starting point, extract heat subsequences of the same length as the difference sequence at each time offset;

[0015] The difference sequence and the heat subsequence are normalized separately. By calculating the similarity between the normalized difference sequence and the heat subsequence at each time offset, the time offset used as the lag time is extracted from all time offsets.

[0016] In one embodiment, the extraction process of the buoyancy lag time is as follows:

[0017] Calculate the mean of the similarity across all time offsets;

[0018] Sort all time offsets in ascending order, and take the first time offset in the sorted result that satisfies the similarity greater than the mean as the upward lag duration.

[0019] In one embodiment, the temperature difference data is calculated by taking the difference between the temperature data of the oil outlet at the time of oil discharge from the insulating oil to be tested and the temperature data of the oil inlet at the time of oil inlet from the insulating oil to be tested as the temperature difference data of the insulating oil to be tested.

[0020] In one embodiment, the method for calculating the heat accumulation data is as follows: the sum of all heat data within a time interval including the oil inlet and outlet times of the insulating oil to be tested is used as the heat accumulation data of the insulating oil to be tested.

[0021] In one embodiment, the process of correcting the temperature difference data of the insulating oil to be tested is as follows:

[0022] The normalized values ​​of the temperature difference data of the insulating oil under test and its neighboring insulating oils are nonlinearly fitted over time to obtain the slope of the temperature difference data of the insulating oil under test.

[0023] The normalized values ​​of the heat accumulation data of the insulating oil under test and its neighboring insulating oils are nonlinearly fitted over time to obtain the slope of the heat accumulation data of the insulating oil under test.

[0024] The temperature difference data of the insulating oil under test is corrected by comparing the slope of the temperature difference data with the slope of the heat accumulation data.

[0025] In one embodiment, the step of correcting the temperature difference data of the insulating oil under test by comparing the slope of the temperature difference data with the slope of the heat accumulation data includes:

[0026] Calculate the ratio of the slope of the heat accumulation data of the insulating oil to the slope of the temperature difference data, and multiply the ratio by the temperature difference data of the insulating oil to be tested, and use the corrected temperature difference data of the insulating oil to be tested.

[0027] In one embodiment, obtaining the transformer center oil temperature at the moment the insulating oil to be tested reaches the transformer center includes:

[0028] Calculate the percentage of the heat absorbed in the first half of the process in the sum of the heat absorbed in the first half and the heat absorbed in the second half.

[0029] The temperature increment of the insulating oil under test from the inlet to the center of the transformer is calculated by using the numerical ratio and the corrected temperature difference data of the insulating oil under test.

[0030] By using the temperature increment and the temperature data of the insulating oil to be tested at the oil inlet, the transformer center oil temperature at the moment when the insulating oil to be tested reaches the transformer center can be obtained.

[0031] In one embodiment, the temperature increment is the product of the numerical percentage and the corrected temperature difference data of the insulating oil to be tested.

[0032] In one embodiment, the transformer center oil temperature at the moment the insulating oil to be tested reaches the transformer center is: the sum of the temperature data of the insulating oil to be tested at the oil inlet and the temperature increment.

[0033] This application has at least the following beneficial effects:

[0034] This application obtains the temperature difference data between the oil outlet and the oil inlet at various time offsets within the initial time period and performs similarity analysis with the heat data. This effectively identifies the temporal correlation between the temperature change of insulating oil and the heating of resistance. Furthermore, based on the similarity analysis results, the upward lag time is determined, which can accurately reflect the actual time taken for the insulating oil to flow from the bottom to the top of the transformer. Establishing a unified temporal correspondence between the positions of the insulating oil clump at the oil inlet and the oil outlet helps to track the thermal evolution process of a specific insulating oil inside the transformer, providing a reliable time reference for accurately calculating the temperature increment of the insulating oil inside the transformer.

[0035] Furthermore, by using the oil outlet time of the insulating oil under test and the oil inlet time with the forward floating lag time as time boundaries, temperature difference data and heat accumulation data are obtained, which can completely characterize the temperature change and heat absorption process of the insulating oil mass under test inside the transformer. Then, by analyzing the temperature difference data and heat accumulation data changes of the insulating oil under test and its neighboring insulating oils, the noise intensity in the temperature difference data can be evaluated. The changing trend of the heat accumulation data is used as a reference standard to correct the temperature difference data of the insulating oil under test, so that the corrected temperature difference data can more accurately characterize the temperature change of the insulating oil under test inside the transformer.

[0036] Furthermore, by determining the time when the insulating oil under test reaches the center of the transformer through the upward lag time, and comparing the heat absorbed in the first half and the heat absorbed in the second half, it is possible to measure the proportion of heat absorbed by the insulating oil under test from the oil inlet to the center of the transformer compared to the proportion absorbed from the oil inlet to the oil outlet. Then, by combining the corrected temperature difference data and the oil inlet temperature data, the transformer center oil temperature can be obtained. This overcomes the limitation that simple boundary averaging cannot reflect the true temperature of the internal heat source area. By reasonably distributing the temperature increment through the actual heat distribution, the estimated transformer center oil temperature results are more consistent with the actual physical process of heat generation and transfer inside the transformer, significantly improving the detection accuracy of transformer center oil temperature. Attached Figure Description

[0037] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1A flowchart illustrating the steps of the high-precision transformer internal oil temperature detection method for power distribution network equipment inspection provided in this application;

[0039] Figure 2 This is a schematic diagram illustrating the process of obtaining the buoyancy delay time.

[0040] Figure 3 This is a schematic diagram illustrating the calculation process for the center oil temperature of a transformer. Detailed Implementation

[0041] In the description of the embodiments in this application, the words "exemplary," "or," and "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "exemplary," "or," and "for example" is intended to present the relevant concepts in a specific manner.

[0042] Unless otherwise defined, 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. It should be understood that, unless otherwise stated, " / " in this application means "or".

[0043] It should also be noted that the terms "first" and "second" in this application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0044] The following description, in conjunction with the accompanying drawings, details the specific scheme of the high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection provided in this application.

[0045] This application provides an embodiment of a high-precision method for detecting the internal oil temperature of a transformer for power distribution network equipment inspection. Specifically, the method is described below. Please refer to [link to relevant documentation]. Figure 1 The method includes the following steps:

[0046] Step 1: Real-time acquisition of temperature data at the transformer's oil inlet and outlet, as well as data on the heat released during transformer operation.

[0047] Temperature sensors are installed at the oil inlet at the bottom and the oil outlet at the top of the transformer to collect real-time temperature data of the insulating oil inside the transformer. Simultaneously, a smart meter collects real-time current data from inside the transformer. The transformer's internal resistance value is obtained through its factory settings.

[0048] The resistance value and the current data at each acquisition moment are used as inputs to the resistance heat calculation formula, and the output is the heat released by the transformer at each acquisition moment. The resistance heat calculation formula is a known technique and will not be elaborated upon in this application.

[0049] In this embodiment, the acquisition frequency of both temperature data and current data is 10Hz. The acquisition frequency is preset by the user and can be set by the implementer according to the actual situation. This application does not impose any special restrictions.

[0050] Step 2: For the preset initial period after the transformer starts operating, obtain the temperature difference data between the oil outlet and the oil inlet at each preset time offset, and perform similarity analysis with the heat data to obtain the floating lag time of the insulating oil flowing from the transformer inlet to the oil outlet.

[0051] High-voltage electricity from power plants is transmitted to transformers via transmission lines. Through electromagnetic conversion within the transformer, the high voltage is reduced to a usable level for users. During this electromagnetic energy conversion process, heat is generated due to line losses. This heat is absorbed by the insulating oil inside the transformer, causing its temperature to rise. As the temperature increases, the density of the insulating oil decreases, causing it to rise and enter the radiator or cooler through the oil outlet at the top of the transformer, releasing the heat into the air. The cooled insulating oil then becomes denser and re-enters the transformer through the oil inlet at the bottom.

[0052] Based on the above analysis, the oil temperature inside the transformer exhibits a distribution characteristic of increasing from bottom to top. The reason for the temperature change of the insulating oil is the heat loss caused by the current passing through the resistance. Since it takes time for the insulating oil to travel from the bottom to the top of the transformer, there is a time lag between the arrival time of the same portion of insulating oil at the inlet and outlet; at the same time, the transformer load current changes dynamically with user demand, and the change in resistive heat generated at different times is also different, resulting in differences in the heat absorbed by the insulating oil entering the transformer at different times.

[0053] Based on the above analysis, for the preset initial period after the transformer starts operating, the temperature difference data between the oil outlet and the oil inlet at each preset time offset is obtained, and similarity analysis is performed with the heat data to obtain the upward lag time of the insulating oil flowing from the transformer inlet to the oil outlet. The specific process is as follows:

[0054] The inlet temperature data, outlet temperature data, and heat data within the initial time period are arranged in chronological order to form the inlet temperature sequence, outlet temperature sequence, and heat sequence, respectively.

[0055] Calculate the difference sequence between the outlet temperature sequence and the inlet temperature sequence at each time offset;

[0056] Using the starting element of the heat sequence as the starting point, extract heat subsequences of the same length as the difference sequence at each time offset;

[0057] Normalize the difference sequence and the heat subsequence separately, calculate the similarity between the normalized difference sequence and the heat subsequence at each time offset, and calculate the mean of the similarity at all time offsets.

[0058] All time offsets are sorted in ascending order. The first time offset in the sorted result that satisfies the similarity value greater than the mean is taken as the upward lag time. The specific calculation method for the difference sequence is: the temperature data at the oil outlet time t minus the oil inlet temperature data at the forward time offset time. A schematic diagram of the process for obtaining the upward lag time is shown below. Figure 2 As shown.

[0059] In this embodiment, the length of the initial time period is 1 minute. The length of the initial time period is preset by human intervention. Based on the premise that the initial time period covers the time it takes for at least one complete insulating oil of the transformer to move from the oil inlet to the oil outlet, the implementer can set it according to the actual situation. This application does not impose any special restrictions.

[0060] In this embodiment, the maximum value normalization method is used to normalize the difference sequence and the heat subsequence respectively. The maximum value normalization method is a well-known technique and will not be described in detail in this application.

[0061] In this embodiment, the similarity between the normalized difference sequence and the heat subsequence is the cosine similarity. The calculation of the cosine similarity is a well-known technique and will not be described in detail here. As other implementation methods, based on the ability to measure the similarity between the normalized difference sequence and the heat subsequence, the implementer may use other existing feasible techniques, such as the reciprocal of the Euclidean distance, etc. This application does not impose any special restrictions.

[0062] It should be noted that in existing technologies, the overlap position of two sequences can be determined by calculating the similarity between subsequences within the two sequences. In this embodiment, since the temperature rise of the insulating oil is caused by current flowing through a resistor, a heat sequence generated by current flowing through the resistor is introduced as a reference standard. Simultaneously, temperature data at the transformer inlet and outlet are monitored and a difference sequence is calculated. Then, by measuring the similarity between the difference sequence and the thermal quantum sequence extracted from the heat sequence, a higher similarity indicates that the temperature rise of the insulating oil is more likely caused by resistive heating. This determines the lag time of the insulating oil flowing from the transformer inlet to the outlet, helping to more accurately assess the temperature change of the insulating oil inside the transformer.

[0063] Step 3: For the insulating oil to be tested, with a single moment as the oil outlet moment and the moment of the upward lag time as the oil inlet moment within the initial time period, acquire the temperature difference data and heat accumulation data of the insulating oil to be tested from the oil inlet to the oil outlet. By analyzing the changes in the temperature difference data and heat accumulation data of the insulating oil to be tested and its neighboring insulating oils, the temperature difference data of the insulating oil to be tested is corrected.

[0064] For the insulating oil under test, with a single moment as the oil outlet moment within the initial time period and the moment shifted forward by the aforementioned upward lag time as the oil inlet moment, temperature difference data and heat accumulation data of the insulating oil under test from the oil inlet to the oil outlet are acquired. Specifically, the difference between the temperature data at the oil outlet moment of the oil's oil outlet and the temperature data at the oil inlet moment of the oil's oil inlet is used as the temperature difference data of the insulating oil under test, characterizing the temperature change of the insulating oil under test inside the transformer. The sum of all heat data within the time interval, including the oil inlet and outlet moments of the insulating oil under test, is used as the heat accumulation data of the insulating oil under test, characterizing the total heat absorbed by the insulating oil under test inside the transformer.

[0065] Since the temperature change of the insulating oil under test is related to the heat absorbed, under ideal conditions, the temperature difference data between the insulating oil under test and its neighboring insulating oils is almost identical to the heat accumulation data of the insulating oil under test and its neighboring insulating oils. Therefore, by analyzing the temperature difference data and heat accumulation data of the insulating oil under test and its neighboring insulating oils, the temperature difference data of the insulating oil under test is corrected to accurately reflect the temperature change of the insulating oil under test inside the transformer. The specific process is as follows:

[0066] The normalized values ​​of the temperature difference data of the insulating oil under test and its neighboring insulating oils are nonlinearly fitted over time to obtain the slope of the temperature difference data of the insulating oil under test, which is used to characterize the change state of the temperature difference data of the insulating oil under test.

[0067] The normalized values ​​of the heat accumulation data of the insulating oil under test and its neighboring insulating oils are nonlinearly fitted over time to obtain the slope of the heat accumulation data of the insulating oil under test, which is used to characterize the change state of the heat accumulation data of the insulating oil under test.

[0068] Calculate the ratio of the slope of the heat accumulation data of the insulating oil to the slope of the temperature difference data, and multiply the ratio by the temperature difference data of the insulating oil to be tested, and use the corrected temperature difference data of the insulating oil to be tested.

[0069] In this embodiment, the neighboring insulating oil of the insulating oil to be tested is specifically the insulating oil whose oil discharge time is within the initial time period.

[0070] In this embodiment, the maximum value normalization method is used to normalize the temperature difference data and the heat accumulation data respectively.

[0071] In this embodiment, the least squares method is used to perform nonlinear fitting on the normalized values ​​of temperature difference data and heat accumulation data, respectively. A cubic polynomial function is used as the target fitting function. According to the definition of the fitting curve and the derivative, the slope of the temperature difference data and the slope of the heat accumulation data of the insulating oil under test are obtained. The least squares method is a well-known technique and will not be described in detail in this application. As other implementation methods, based on the ability to measure the time-series changes of the normalized values ​​of temperature difference data and the time-series changes of the normalized values ​​of heat accumulation data, implementers may use other existing feasible techniques. This application does not impose any special restrictions.

[0072] It should be added that: In this application, when calculating the ratio, if there is a case where the denominator is 0, the denominator is first mapped to a positive number before subsequent calculations are performed. There are many methods to map data to a positive number, and implementers can choose existing feasible methods according to the actual situation. In this embodiment, the purpose of mapping the data to a positive number is achieved by calculating the sum of the data and a preset value greater than 0. The value of the preset value greater than 0 is preset by the user, and implementers can set it according to the actual situation. This application does not impose any special restrictions. In this embodiment, the value of the preset value greater than 0 is 0.01, and it is the same as the unit of the data that needs to be mapped to a positive number.

[0073] It should be noted that in existing technologies, data can be corrected by assessing the noise intensity. In this embodiment, the noise intensity in the temperature difference data is assessed by comparing the rate of change between the normalized heat accumulation data and the normalized temperature difference data, and then the temperature difference data is corrected to obtain corrected temperature difference data. This corrected temperature difference data can more accurately characterize the temperature change of the insulating oil under test inside the transformer, and helps to more accurately measure the temperature of the insulating oil in the center of the transformer.

[0074] Step 4: Determine the time when the insulating oil to be tested reaches the center of the transformer by the floating lag time; by comparing the heat absorbed by the insulating oil to be tested in the first half of the journey from the oil inlet to the center of the transformer with the heat absorbed in the second half of the journey from the center of the transformer to the oil outlet, and combining the corrected temperature difference data with the oil inlet temperature data, obtain the transformer center oil temperature at the time when the insulating oil to be tested reaches the center of the transformer.

[0075] Since the current transmitted in the power distribution network is not a fixed value but dynamically changes, the heat absorbed by the insulating oil under test is different at different times. The heat absorbed by the insulating oil under test in the first half from the oil inlet to the center of the transformer is different from the heat absorbed in the second half from the center of the transformer to the oil outlet.

[0076] The arrival time of the insulating oil under test at the transformer center is determined by the upward lag time. Specifically, the moment after the oil inlet of the insulating oil, with an interval of half the upward lag time, is taken as the arrival time of the insulating oil at the transformer center, used to represent the intermediate state of equivalent heat conduction. Therefore, the heat absorbed by the insulating oil in the first half of its journey from the inlet to the transformer center is the sum of all heat data within the time interval including both the oil inlet and arrival times. The heat absorbed by the insulating oil in the second half of its journey from the transformer center to the outlet is the sum of all heat data within the time interval including both the arrival times and outlet times.

[0077] By comparing the heat absorbed by the insulating oil in the first half of its journey from the inlet to the center of the transformer with the heat absorbed in the second half of its journey from the center of the transformer to the outlet, and combining this with corrected temperature difference data and inlet temperature data, the transformer center oil temperature at the moment the insulating oil reaches the transformer center is obtained. Specifically:

[0078] Calculate the percentage of the heat absorbed in the first half of the process in the sum of the heat absorbed in the first half and the heat absorbed in the second half.

[0079] The temperature increment of the insulating oil under test from the inlet to the center of the transformer is calculated by using the numerical ratio and the corrected temperature difference data of the insulating oil under test.

[0080] The transformer center oil temperature is obtained by combining the temperature increment with the temperature data of the insulating oil at the inlet. The calculation process for the transformer center oil temperature is illustrated in the diagram below. Figure 3 As shown.

[0081] The temperature increment of the insulating oil under test from the oil inlet to the center of the transformer is: the product of the stated value and the corrected temperature difference data of the insulating oil under test.

[0082] The transformer center oil temperature at the moment the insulating oil to be tested reaches the transformer center is: the sum of the temperature data of the insulating oil to be tested at the oil inlet and the temperature increment.

[0083] It should be noted that, in existing technologies, the average temperature at the center of an object can be used to characterize the temperature at both ends. In this embodiment, the change in heat generated by the insulating oil under test in the first and second halves is used to measure the proportion of heat absorbed by the insulating oil as it moves from the inlet to the center of the transformer compared to its movement from the inlet to the outlet. The increase in temperature of the insulating oil as it moves from the inlet to the center of the transformer is obtained by multiplying the proportion of absorbed heat by the corrected temperature difference data of the insulating oil under test. This increase is then summed with the temperature data of the insulating oil under test at the inlet to obtain the temperature of the insulating oil under test at the center of the transformer, thus providing a more accurate characterization of the temperature of the insulating oil under test at the center of the transformer.

[0084] It should be noted that: in the initial period after the transformer starts operating, there is insufficient data in the first half of the upward lag time, so it cannot be calculated. Therefore, the average value of the oil inlet and outlet temperature data at each collection time in the first half of the upward lag time is taken as the transformer center oil temperature at each collection time in the first half of the upward lag time.

[0085] Step 5: Calculate the transformer center oil temperature at each data acquisition time.

[0086] The preceding steps have yielded the time required for the insulating oil to travel from the inlet to the outlet during the initial period. However, due to varying power requirements at different times, the heat generated inside the transformer during the same time period differs, resulting in varying insulating oil temperatures. Consequently, the rate at which the insulating oil rises varies. Higher temperatures lead to lower viscosity and density of the insulating oil, resulting in a faster rate of rise, while lower temperatures result in a slower rate of rise. Therefore, it is necessary to update the lag time for the insulating oil to flow from the transformer inlet to the outlet.

[0087] In this embodiment, starting from the beginning of the initial time period, the upward lag duration is updated every 5 minutes. Here, 5 minutes is just one embodiment of this application, and implementers can set it according to the actual situation. This application does not impose any special restrictions.

[0088] Outside of the initial time period, for each additional data collection time, the transformer center oil temperature is calculated at a historical time before the new data collection time and after a half-floating lag time between the new data collection time and the new data collection time. This allows us to calculate the transformer center oil temperature at each data collection time.

[0089] In summary, this application, by acquiring the temperature difference data between the oil outlet and the oil inlet at various time offsets within the initial time period and performing similarity analysis with the heat data, can effectively identify the temporal correlation between the temperature change of insulating oil and the heating of resistance. Furthermore, based on the similarity analysis results, the upward lag time can be determined, accurately reflecting the actual time taken for the insulating oil to flow from the bottom to the top of the transformer. Establishing a unified temporal correspondence between the positions of the insulating oil clump at the oil inlet and outlet helps track the thermal evolution process of a specific insulating oil inside the transformer, providing a reliable time reference for accurately calculating the temperature increment of the insulating oil inside the transformer.

[0090] Furthermore, by using the oil outlet time of the insulating oil under test and the oil inlet time with the forward floating lag time as time boundaries, temperature difference data and heat accumulation data are obtained, which can completely characterize the temperature change and heat absorption process of the insulating oil mass under test inside the transformer. Then, by analyzing the temperature difference data and heat accumulation data changes of the insulating oil under test and its neighboring insulating oils, the noise intensity in the temperature difference data can be evaluated. The changing trend of the heat accumulation data is used as a reference standard to correct the temperature difference data of the insulating oil under test, so that the corrected temperature difference data can more accurately characterize the temperature change of the insulating oil under test inside the transformer.

[0091] Furthermore, by determining the time when the insulating oil under test reaches the center of the transformer through the upward lag time, and comparing the heat absorbed in the first half and the heat absorbed in the second half, it is possible to measure the proportion of heat absorbed by the insulating oil under test from the oil inlet to the center of the transformer compared to the proportion absorbed from the oil inlet to the oil outlet. Then, by combining the corrected temperature difference data and the oil inlet temperature data, the transformer center oil temperature can be obtained. This overcomes the limitation that simple boundary averaging cannot reflect the true temperature of the internal heat source area. By reasonably distributing the temperature increment through the actual heat distribution, the estimated transformer center oil temperature results are more consistent with the actual physical process of heat generation and transfer inside the transformer, significantly improving the detection accuracy of transformer center oil temperature.

[0092] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than that shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. In the descriptions corresponding to the flowcharts and block diagrams in the accompanying drawings, the operations or steps corresponding to different blocks may also occur in a different order than disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. Each block in a block diagram and / or flowchart, and combinations of blocks in a block diagram and / or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0093] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from its essential characteristics. Therefore, the embodiments described above should be considered exemplary and non-limiting in all respects.

Claims

1. A high-precision method for detecting the internal oil temperature of transformers for power distribution network equipment inspection, characterized in that, The method includes the following steps: Real-time acquisition of temperature data at the transformer's oil inlet and outlet, as well as data on the heat released during transformer operation; For the initial period after the transformer starts operating, the temperature difference data between the oil outlet and the oil inlet at each preset time offset is obtained, and similarity analysis is performed with the heat data to obtain the lag time of the insulating oil flowing from the transformer inlet to the oil outlet. For the insulating oil under test, which takes a single moment as the oil outlet moment and the moment of the upward lag time as the oil inlet moment during the initial period, the temperature difference data and heat accumulation data of the insulating oil under test from the oil inlet to the oil outlet are obtained. By analyzing the changes in the temperature difference data and heat accumulation data of the insulating oil under test and its neighboring insulating oils, the temperature difference data of the insulating oil under test is corrected. The timing of the insulating oil reaching the transformer center is determined by the lag time. The transformer center oil temperature at the moment the insulating oil reaches the transformer center is obtained by comparing the heat absorbed by the insulating oil in the first half of its journey from the inlet to the transformer center with the heat absorbed in the second half of its journey from the transformer center to the outlet, and by combining the corrected temperature difference data with the inlet temperature data. The transformer center oil temperature at each acquisition time is then calculated.

2. The high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection as described in claim 1, characterized in that, The process for obtaining the buoyancy delay time is as follows: The inlet temperature data, outlet temperature data, and heat data within the initial time period are arranged in chronological order to form the inlet temperature sequence, outlet temperature sequence, and heat sequence, respectively. Calculate the difference sequence between the outlet temperature sequence and the inlet temperature sequence at each time offset; Using the starting element of the heat sequence as the starting point, extract heat subsequences of the same length as the difference sequence at each time offset; The difference sequence and the heat subsequence are normalized separately. By calculating the similarity between the normalized difference sequence and the heat subsequence at each time offset, the time offset used as the levitation lag time is extracted from all time offsets.

3. The high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection as described in claim 2, characterized in that, The process for extracting the buoyancy lag time is as follows: Calculate the mean of the similarity across all time offsets; Sort all time offsets in ascending order, and take the first time offset in the sorted result that satisfies the similarity greater than the mean as the upward lag duration.

4. The high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection as described in claim 2, characterized in that, The method for calculating the temperature difference data is as follows: the difference between the temperature data of the oil outlet at the time of oil discharge of the insulating oil to be tested and the temperature data of the oil inlet at the time of oil inlet of the insulating oil to be tested is used as the temperature difference data of the insulating oil to be tested.

5. The high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection as described in claim 1, characterized in that, The method for calculating the heat accumulation data is as follows: the sum of all heat data within the time interval including the oil inlet and outlet times of the insulating oil to be tested is taken as the heat accumulation data of the insulating oil to be tested.

6. The high-precision method for detecting the internal oil temperature of transformers for power distribution network equipment inspection as described in claim 1, characterized in that, The process of correcting the temperature difference data of the insulating oil to be tested is as follows: The normalized values ​​of the temperature difference data of the insulating oil under test and its neighboring insulating oils are nonlinearly fitted over time to obtain the slope of the temperature difference data of the insulating oil under test. The normalized values ​​of the heat accumulation data of the insulating oil under test and its neighboring insulating oils are nonlinearly fitted over time to obtain the slope of the heat accumulation data of the insulating oil under test. The temperature difference data of the insulating oil under test is corrected by comparing the slope of the temperature difference data with the slope of the heat accumulation data.

7. The high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection as described in claim 6, characterized in that, The correction of the temperature difference data of the insulating oil under test by comparing the slope of the temperature difference data with the slope of the heat accumulation data includes: Calculate the ratio of the slope of the heat accumulation data of the insulating oil to the slope of the temperature difference data, and multiply the ratio by the temperature difference data of the insulating oil to be tested, and use the corrected temperature difference data of the insulating oil to be tested.

8. The high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection as described in claim 1, characterized in that, Obtain the transformer center oil temperature at the moment the insulating oil to be tested reaches the transformer center, including: Calculate the percentage of the heat absorbed in the first half of the process in the sum of the heat absorbed in the first half and the heat absorbed in the second half. The temperature increment of the insulating oil under test from the inlet to the center of the transformer is calculated by using the numerical ratio and the corrected temperature difference data of the insulating oil under test. By using the temperature increment and the temperature data of the insulating oil to be tested at the oil inlet, the transformer center oil temperature at the moment when the insulating oil to be tested reaches the transformer center can be obtained.

9. The high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection as described in claim 8, characterized in that, The temperature increment is the product of the numerical percentage and the corrected temperature difference data of the insulating oil to be tested.

10. The high-precision detection method for transformer internal oil temperature for power distribution network equipment inspection as described in claim 8, characterized in that, The transformer center oil temperature at the moment the insulating oil to be tested reaches the transformer center is: the sum of the temperature data of the insulating oil to be tested at the oil inlet and the temperature increment.

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