Power transformer winding temperature on-line monitoring system and method

Abstract

The invention discloses a power transformer winding temperature on-line monitoring system. The system comprises a temperature analyzer, and an infrared thermal imager, an environment sensor group and an operation data acquisition module which are connected with the temperature analyzer; the thermal infrared imager is aligned with a monitoring area, corresponding to a winding, of a preset oil tank on the power transformer so as to collect a corresponding thermal infrared image in real time; the environment sensor group collects surrounding environment parameters of the power transformer in real time; the operation data acquisition module is arranged on an external connection cable of the power transformer so as to acquire operation data of the power transformer in real time; and the temperature analyzer receives the infrared thermogram of the monitoring area and carries out image processing so as to extract the average temperature of the monitoring area, and the average temperature is combined with the surrounding environment parameters and the operation data of the power transformer and is imported into a heat conduction model to calculate the on-line temperature of the power transformer winding. According to the invention, the problems of inconvenient installation, low precision, incapability of accurately monitoring the winding temperature in real time and the like of the existing power transformer winding temperature monitoring method can be solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system, and particularly relates to a winding temperature on-line monitoring system and method of power transformer. BACKGROUND

[0002] The power transformer is a core equipment of the power system, and the winding temperature is a key parameter for evaluating the running state and thermal aging life of the power transformer (according to the IEEE C57.91 standard, the life is shortened by 50% when the winding hotspot temperature is increased by 6℃).

[0003] At present, the existing winding temperature monitoring methods of the power transformer include a pre-embedded sensor method and an infrared thermal imaging technology. The pre-embedded sensor method needs to install a platinum resistance sensor and the like under power-off, can only monitor the local winding, is also susceptible to electromagnetic interference, and cannot reflect the overall temperature distribution. The infrared thermal imaging technology cannot accurately aim at the monitoring area corresponding to the oil tank and the winding of the power transformer, has low measurement accuracy, lacks an environmental compensation mechanism and a special heat conduction model, cannot accurately convert the actual temperature of the winding, and results in large monitoring error, so that the online monitoring demand cannot be met.

[0004] In order to solve the problems of the existing winding temperature monitoring methods of the power transformer, such as inconvenient installation, low accuracy, and inability to accurately monitor the winding temperature in real time, a new winding temperature monitoring method of the power transformer is urgently needed. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a winding temperature on-line monitoring system and method of power transformer, which can solve the problems of the existing winding temperature monitoring methods of the power transformer, such as inconvenient installation, low accuracy, and inability to accurately monitor the winding temperature in real time.

[0006] In order to solve the above technical problems, the embodiment of the present application provides a winding temperature on-line monitoring system of power transformer, which comprises a temperature analyzer and infrared thermal imager, an environmental sensor group and a running data acquisition module connected to the temperature analyzer.

[0007] The infrared thermal imager is arranged at a specified distance from the power transformer, and aims at the monitoring area corresponding to the oil tank and the winding on the outer wall of the power transformer, and is used for real-time acquisition of the infrared thermal image of the monitoring area.

[0008] The environmental sensor group is arranged at a specified distance from the power transformer, and is used for real-time acquisition of the environmental parameters of the power transformer.

[0009] The running data acquisition module is arranged on the external connecting cable of the power transformer, and is used for real-time acquisition of the running data of the power transformer.

[0010] The temperature analyzer is arranged away from the power transformer, and is configured to receive the infrared thermal image of the monitoring area collected by the infrared thermal imager in real time and perform image processing to extract the average temperature of the monitoring area. Furthermore, the ambient environmental parameters of the power transformer collected by the ambient sensor group and the operation data of the power transformer collected by the operation data collection module are combined, and are introduced into a preset heat conduction model to calculate the online temperature of the power transformer winding. The heat conduction model is a relational model for mapping the average temperature of the monitoring area, the ambient environmental parameters of the power transformer and the operation data into the temperature of the power transformer winding.

[0011] The infrared thermal imager is arranged at the same height as the central axis of the power transformer winding, and the field of view covers more than 95% of the area of the monitoring area.

[0012] The monitoring area includes a winding projection area and an unloaded high-temperature supplementary area. The monitoring area is marked on the outer wall of the power transformer by a laser positioner based on a preset transformer winding structure drawing and an unloaded thermal image.

[0013] The infrared thermal image of the monitoring area is first denoised by a db4 wavelet base three-layer soft threshold, and then is subjected to image enhancement processing by histogram equalization to eliminate oil film and dust interference. The histogram equalization is implemented by using an adaptive CLAHE algorithm.

[0014] The ambient sensor group includes a humidity sensor, a temperature sensor and a wind speed sensor. The ambient environmental parameters of the power transformer include ambient humidity, ambient temperature and wind speed.

[0015] The operation data collection module includes a current transformer. The operation data is a load current.

[0016] The expression of the heat conduction model is wherein,

[0017] T w is the online temperature of the power transformer winding; T avg is the average temperature of the monitoring area; I is the load current; I o is the rated current of the power transformer; T a is the ambient temperature; R H is the ambient humidity; v is the wind speed; and α, β and λ are fixed constants. k1, k2, k3 and k4 are preset coefficients and are constants, and are obtained by fitting experimental data.

[0018] The embodiment of the present application also provides a power transformer winding temperature on-line monitoring method, which is implemented on the power transformer winding temperature on-line monitoring system, and comprises the following steps:

[0019] The infrared thermal imager collects the infrared thermal image of the monitoring area corresponding to the winding of the oil tank in real time.

[0020] The environment sensor group collects the surrounding environment parameters of the power transformer in real time.

[0021] The operation data collection module collects the operation data of the power transformer in real time.

[0022] The temperature analyzer receives the infrared thermal image of the monitoring area collected by the infrared thermal imager in real time and performs image processing to extract the average temperature of the monitoring area, and further combines the surrounding environment parameters of the power transformer collected by the environment sensor group and the operation data of the power transformer collected by the operation data collection module, and introduces them into a preset heat conduction model to calculate the power transformer winding on-line temperature; wherein the heat conduction model is a relationship model for combining and mapping the average temperature of the monitoring area, the surrounding environment parameters of the power transformer and the operation data into the power transformer winding temperature.

[0023] The method further comprises:

[0024] If the calculated power transformer winding on-line temperature is greater than the preset temperature threshold, the temperature analyzer triggers an audible and light alarm and generates an alarm information to be sent to the power system SCADA platform.

[0025] The method further comprises:

[0026] The temperature analyzer periodically stores the average temperature of the monitoring area, the surrounding environment parameters of the power transformer and the operation data, and synchronously uploads them to the cloud.

[0027] The embodiment of the present application has the following beneficial effects:

[0028] In the present application, the temperature analyzer, the infrared thermal imager, the environment sensor group and the operation data collection module are all designed in a non-contact manner, and can be installed on the power transformer without power-off, which can avoid the influence of the traditional pre-embedded sensor on the operation and maintenance of the transformer, and the temperature analyzer can eliminate interference by image pre-processing the infrared thermal image of the monitoring area, and combine the special heat conduction model of the environment multi-parameter compensation and the operation data to quickly realize the on-line temperature measurement of the power transformer winding, so as to solve the problems of the existing power transformer winding temperature monitoring method, such as inconvenient installation, low precision, and inability to monitor the winding temperature in real time and accurately. BRIEF DESCRIPTION OF DRAWINGS

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0030] Figure 1 This is a schematic diagram of the structure of an online monitoring system for the winding temperature of a power transformer provided in an embodiment of the present invention;

[0031] Figure 2 A flowchart of an online monitoring method for the winding temperature of a power transformer provided in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] like Figure 1 As shown in the figure, an online monitoring system for the winding temperature of a power transformer, as proposed in this embodiment of the invention, includes a temperature analyzer 1 and its connected infrared thermal imager 2, an environmental sensor group 3, and an operational data acquisition module 4; wherein,

[0034] An infrared thermal imager 2 (resolution ≥ 640×512) is set at a certain distance (e.g., 1.5m to 3m) from a specified power transformer (not shown), and is aligned with a pre-defined monitoring area (including the winding projection area and the no-load high-temperature supplementary area) on the outer wall of the power transformer corresponding to the oil tank and windings. It is used to collect infrared thermal images of the monitoring area in real time (frame rate ≥ 1fps). The infrared thermal imager 2 is installed at the same height as the central axis of the power transformer windings, and its field of view covers more than 95% of the area occupied by the monitoring area. At this time, the monitoring area is marked on the outer wall of the power transformer by a laser positioning device after simulation calculation based on the preset transformer winding structure drawing and no-load thermal image.

[0035] The environmental sensor group 3 (including but not limited to humidity sensor, temperature sensor and wind speed sensor, etc.) is set at a certain distance from the power transformer to collect the surrounding environmental parameters of the power transformer in real time (including ambient humidity, ambient temperature and wind speed, etc.).

[0036] The operation data acquisition module 4 (including but not limited to a current transformer) is arranged on an external connecting cable (not shown) of the power transformer, and is used for acquiring operation data (including a load current, etc.) of the power transformer in real time;

[0037] The temperature analyzer 1 is arranged away from the power transformer, and is used for receiving an infrared thermal image of the monitoring area acquired by the infrared thermal imager 2 in real time and performing image processing to extract an average temperature of the monitoring area, and further combining peripheral environment parameters of the power transformer acquired by the environment sensor group 2 in real time and operation data of the power transformer acquired by the operation data acquisition module 3 in real time, and introducing into a preset heat conduction model to calculate an online temperature of the winding of the power transformer; wherein the heat conduction model is a relational model for mapping the average temperature of the monitoring area, the peripheral environment parameters of the power transformer and the operation data into the winding temperature of the power transformer. It should be noted that the infrared thermal image of the monitoring area is first denoised by a db4 wavelet base three-layer soft threshold, and then image enhancement processing is performed by histogram equalization to eliminate oil film and dust interference; wherein the image enhancement by histogram equalization is realized by using an adaptive CLAHE algorithm; and an expression of the heat conduction model is T w is the online temperature of the winding of the power transformer; T avg is the average temperature of the monitoring area; I is the load current; I o is the rated current of the power transformer; T a is the ambient temperature; R H is the ambient humidity; v is the wind speed; and alpha, beta and lambda are fixed constants; k1, k2, k3 and k4 are preset coefficients and are constants, and are obtained by fitting experimental data.

[0038] It can be understood that the peripheral environment parameters can further include atmospheric pressure acquired by using an atmospheric pressure sensor, and the operation data can further include load voltage acquired by using a voltage transformer, and the atmospheric pressure and the load voltage are combined with the other peripheral environment parameters and operation data to revise the expression of the heat conduction model, so as to further adapt to different scene applications and improve the calculation precision of the winding temperature of the power transformer.

[0039] In the embodiment of the application, the temperature analyzer 1 and the infrared thermal imager 2, the environment sensor group 3 and the operation data acquisition module 4 connected thereto are designed in a non-contact manner, and all do not need to be installed on the power transformer during power-off, so that the influence of the traditional pre-embedded sensor on the operation and maintenance of the transformer can be avoided, and the installation time is reduced by 80%.

[0040] In addition, the temperature analyzer 1 eliminates interference by monitoring the infrared thermal image of the monitoring area through image preprocessing, and combines environmental multi-parameter compensation and a special heat conduction model of operation data to quickly realize online temperature measurement of the power transformer winding, so that the winding temperature monitoring error is ≤2℃, which is reduced by 60% compared with the existing infrared method.

[0041] It can be understood that the temperature analyzer 1 can also perform multi-level threshold alarm and remote communication, so that the operation and maintenance personnel can receive abnormal information in real time, and the fault response time is shortened to within 5 minutes; at the same time, the temperature analyzer 1 forms a historical database of the average temperature of the monitoring area, the surrounding environmental parameters and operation data of the power transformer, and the winding temperature of the power transformer, to support temperature trend analysis, which can be combined with the IEEE C57.91 standard to evaluate the remaining life of the transformer, to provide a basis for condition-based maintenance, and to reduce operation and maintenance costs by 30%.

[0042] As shown in Figure 2 , a power transformer winding temperature online monitoring method provided in the embodiment of the present application is implemented on the power transformer winding temperature online monitoring system in the embodiment of the present application, and the method comprises the following steps:

[0043] Step S1, an infrared thermal imager acquires in real time an infrared thermal image of a monitoring area corresponding to an oil tank and a winding on an outer wall of a power transformer;

[0044] Step S2, an environmental sensor group acquires in real time surrounding environmental parameters of the power transformer;

[0045] Step S3, an operation data acquisition module acquires in real time operation data of the power transformer;

[0046] Step S4, a temperature analyzer receives the infrared thermal image of the monitoring area acquired in real time by the infrared thermal imager and performs image processing to extract the average temperature of the monitoring area, and further combines the surrounding environmental parameters of the power transformer acquired in real time by the environmental sensor group and the operation data of the power transformer acquired in real time by the operation data acquisition module, and imports a preset heat conduction model to calculate the online temperature of the power transformer winding; wherein the heat conduction model is a relationship model for combining and mapping the average temperature of the monitoring area, the surrounding environmental parameters and operation data of the power transformer into the winding temperature of the power transformer.

[0047] The method further comprises:

[0048] If the temperature analyzer judges that the calculated online temperature of the power transformer winding is greater than a preset temperature threshold (such as 110℃), an audible and light alarm is triggered, and alarm information is sent to the power system SCADA platform.

[0049] The method further comprises:

[0050] The temperature analyzer periodically stores the average temperature of the monitoring area, the peripheral environment parameters and operation data of the power transformer, and synchronously uploads to the cloud.

[0051] The embodiment of the present application has the following beneficial effects:

[0052] In the present application, the temperature analyzer, the infrared thermal imager, the environmental sensor group and the operation data acquisition module are all designed in a non-contact manner, and do not need to be installed on the power transformer during power-off, so that the influence of the traditional pre-embedded sensor on the operation and maintenance of the transformer can be avoided, and the temperature analyzer can eliminate interference by monitoring the infrared thermal image of the monitoring area through image preprocessing, and can quickly realize online temperature measurement of the winding of the power transformer by combining with the special heat conduction model of the environmental multi-parameter compensation and the operation data, so that the problems of the existing power transformer winding temperature monitoring method, such as inconvenient installation, low precision and inability to realize real-time and accurate monitoring of the winding temperature, can be solved.

[0053] Those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment methods can be completed by programs instructing related hardware, and the programs can be stored in a computer readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc.

[0054] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An online monitoring system for the winding temperature of a power transformer, characterized in that, This includes a temperature analyzer and its connected infrared thermal imager, environmental sensor array, and operational data acquisition module; among which, The infrared thermal imager is set at a certain distance from the specified power transformer and is aligned with the monitoring area corresponding to the oil tank and windings pre-set on the outer wall of the power transformer, for real-time acquisition of infrared thermal images of the monitoring area; The environmental sensor array is set at a certain distance from the power transformer to collect the surrounding environmental parameters of the power transformer in real time. The operation data acquisition module is installed on the external connection cable of the power transformer and is used to collect the operation data of the power transformer in real time. The temperature analyzer is positioned away from the power transformer and is used to receive and process the infrared thermal images of the monitored area collected in real time by the infrared thermal imager to extract the average temperature of the monitored area. Furthermore, it combines the environmental parameters of the power transformer's surrounding environment collected in real time by the environmental sensor group and the operating data of the power transformer collected in real time by the operating data acquisition module, importing these data into a preset heat conduction model to calculate the online temperature of the power transformer windings. The heat conduction model is a relationship model that maps the average temperature of the monitored area, the environmental parameters of the power transformer's surrounding environment, and the operating data to the winding temperature of the power transformer.

2. The online monitoring system for power transformer winding temperature as described in claim 1, characterized in that, The infrared thermal imager is installed at the same height as the central axis of the power transformer winding, and its field of view covers more than 95% of the area of ​​the monitored area.

3. The online monitoring system for power transformer winding temperature as described in claim 2, characterized in that, The monitoring area includes a winding projection area and an unloaded high-temperature supplementary area; wherein, the monitoring area is marked on the outer wall of the power transformer by a laser positioning device after simulation calculation based on a preset transformer winding structure drawing and an unloaded thermal image.

4. The online monitoring system for power transformer winding temperature as described in claim 3, characterized in that, The infrared thermal image of the monitored area is first denoised using a three-layer soft thresholding method based on db4 wavelet basis, and then enhanced by histogram equalization to eliminate oil film and dust interference. The histogram equalization for image enhancement is implemented using the adaptive CLAHE algorithm.

5. The online monitoring system for power transformer winding temperature as described in claim 4, characterized in that, The environmental sensor group includes a humidity sensor, a temperature sensor, and a wind speed sensor; the surrounding environmental parameters of the power transformer include ambient humidity, ambient temperature, and wind speed.

6. The online monitoring system for power transformer winding temperature as described in claim 5, characterized in that, The operational data acquisition module includes a current transformer; the operational data is the load current.

7. The online monitoring system for power transformer winding temperature as described in claim 6, characterized in that, The expression for the heat conduction model is: in, T w T represents the online temperature of the power transformer windings. avg I represents the average temperature of the monitored area; I represents the load current; I0 o T is the rated current of the power transformer; a R represents ambient temperature. H λ represents ambient humidity; v represents wind speed; α, β, and λ are all fixed constants; k1, k2, k3, and k4 are preset coefficients and are constants obtained by fitting experimental data.

8. A method for online monitoring of the winding temperature of a power transformer, characterized in that, It is implemented on the online monitoring system for the winding temperature of a power transformer as described in claim 7, and the method includes the following steps: Infrared thermal imagers acquire real-time infrared thermal images of the monitoring areas corresponding to the oil tank and windings on the outer wall of power transformers. The environmental sensor array collects the surrounding environmental parameters of the power transformer in real time; The data acquisition module collects the operating data of the power transformer in real time. The temperature analyzer receives the infrared thermal image of the monitored area acquired in real time by the infrared thermal imager and performs image processing to extract the average temperature of the monitored area. Furthermore, it combines the ambient environmental parameters of the power transformer acquired in real time by the environmental sensor group and the operating data of the power transformer acquired in real time by the operating data acquisition module, importing them into a preset heat conduction model to calculate the online temperature of the power transformer windings. The heat conduction model is a relationship model that maps the average temperature of the monitored area, the ambient environmental parameters of the power transformer, and the operating data to the winding temperature of the power transformer.

9. The online monitoring method for the winding temperature of a power transformer as described in claim 8, characterized in that, The method further includes: If the temperature analyzer determines that the calculated online temperature of the power transformer winding is greater than the preset temperature threshold, it triggers an audible and visual alarm and generates alarm information which is remotely sent to the power system SCADA platform.

10. The online monitoring method for the winding temperature of a power transformer as described in claim 9, characterized in that, The method further includes: The temperature analyzer periodically stores the average temperature of the monitored area, the surrounding environmental parameters of the power transformer, and operating data, and uploads them to the cloud simultaneously.

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