Oil level monitoring method and device for current transformer

Abstract

The present application discloses a method and device for monitoring the oil level of a current transformer. The method comprises: obtaining the initial height, axial displacement, and radial displacement of an expander, performing calculations based on the initial height and axial displacement of the expander to obtain the initial oil level of the current transformer; correcting the oil level of the current transformer based on the radial displacement and initial oil level of the expander to obtain the corrected oil level of the current transformer; and evaluating the effectiveness of the corrected oil level of the current transformer, and obtaining the monitored oil level of the current transformer based on the evaluation results. The present application takes into account the non-ideal axial deformation of the expander of the current transformer during expansion, corrects the oil level monitoring value of the current transformer based on the axial displacement and radial displacement of the expander, and determines the monitored oil level of the current transformer based on the expansion characteristics of the current transformer expander, thereby improving the accuracy of the current transformer oil level monitoring and providing highly reliable data support for the reliable operation of the current transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of oil level monitoring of current transformers, and in particular to a method and device for monitoring the oil level of a current transformer. Background Art

[0002] Current transformers are primarily used to convert high currents into low currents for measurement, protection, and control. They play a vital role in power systems and are widely used in power distribution, energy metering, current protection, and other applications. Current transformers require excellent insulation performance during use to prevent current leakage and equipment damage. They use oil as an insulating medium, which isolates the potential between the windings and between the windings and ground, preventing problems such as electric shock and discharge. To maintain the normal operation and insulation performance of the current transformer, the oil level must be monitored. Abnormal oil levels may indicate an internal fault in the equipment, such as a short circuit or insulation overheating, which requires prompt attention.

[0003] Existing methods for monitoring the oil level of current transformers are mainly through manual inspections or remote monitoring using camera videos, but these two methods have many limitations. Regular manual inspections require a lot of manpower and time resources, and are easily affected by factors such as human negligence or field of view limitations. The observed oil level is inaccurate, and the oil level monitoring of the observation window is intermittent, which cannot understand the oil level changes of the equipment in real time. This may miss important status changes and delay fault detection and processing; the video monitoring method cannot obtain detailed data and can only provide a general understanding of the oil level. It cannot provide specific oil level values, oil level change trends and other information, which limits the comprehensive understanding of the equipment status.

[0004] In summary, the existing oil level monitoring method for the current transformer cannot accurately monitor the oil level of the current transformer. Summary of the Invention

[0005] In view of this, the present invention provides a method and device for monitoring the oil level of a current transformer, the main purpose of which is to solve the problem that the existing method for monitoring the oil level of a current transformer cannot accurately monitor the oil level of the current transformer.

[0006] According to one aspect of the present application, a method for monitoring the oil level of a current transformer is provided. The method is applied to an oil level monitoring device of a current transformer based on an oil level sensor, comprising:

[0007] Obtaining an initial height, an axial displacement, and a radial displacement of the expander, and performing calculations based on the initial height and the axial displacement of the expander to obtain an initial oil level of the current transformer;

[0008] Correcting the oil level of the current transformer based on the radial displacement of the expander and the initial oil level to obtain a corrected oil level of the current transformer;

[0009] The effectiveness of the calibrated oil level of the current transformer is evaluated, and the monitoring oil level of the current transformer is obtained according to the evaluation result.

[0010] Optionally, the performing effectiveness evaluation on the correction oil level of the current transformer and obtaining the monitoring oil level of the current transformer according to the evaluation result includes:

[0011] calculating the degree of instability of the expander during expansion based on the corrected oil level and the initial oil level of the current transformer;

[0012] If the instability is less than or equal to a preset instability threshold, the correction oil level of the current transformer is the monitoring oil level of the current transformer.

[0013] Optionally, the degree of instability during the expansion process of the expander is obtained by the following method:

[0014]

[0015] Among them, ε is the instability, q0 is the initial wave distance, h′ is the correction oil level of the current transformer, and N is the number of expansion joints of the expander.

[0016] Optionally, the following method is used to obtain the corrected oil level of the current transformer:

[0017]

[0018] Where h′ is the calibration oil level of the current transformer, h is the initial oil level of the current transformer, and D m is the average diameter of the expander, q0 is the initial wave distance, α is the stress coefficient of the expander when the plane is unstable; A cu is the average cross-sectional area of ​​the expander metal, K r is the expander circumferential stress coefficient, satisfying the formula

[0019] K r =max(K r1 ,1);

[0020]

[0021] Among them, K r1 is the expander circumferential stress coefficient, e y is the radial displacement of the expander, N is the number of expansion joints of the expander, and x is the axial displacement of the expander.

[0022] Optionally, the calculating the initial oil level of the current transformer based on the initial height and axial displacement of the expander includes:

[0023] The sum of the initial height and the axial displacement of the expander is taken as the initial oil level of the current transformer.

[0024] According to another aspect of the present application, an oil level monitoring device of a current transformer based on an oil level sensor is provided, comprising:

[0025] Oil level sensor: The oil level sensor is used to collect the axial displacement and radial displacement of the expander of the current transformer;

[0026] a repeater, the repeater being connected to the oil level sensor via radio, and the repeater being used to transmit the axial displacement and radial displacement of the expander collected by the oil level sensor to a controller;

[0027] The controller is electrically connected to the repeater, and is used to execute operations corresponding to the above-mentioned oil level monitoring method for the current transformer.

[0028] Optionally, the oil level sensor is arranged on the top of the expander housing of the current transformer.

[0029] Optionally, a groove is provided at the top center of the expander cover, and the oil level sensor is embedded in the groove.

[0030] Optionally, the repeater is arranged on a supporting column at the lower end of the current transformer.

[0031] By means of the above technical solution, the technical solution provided by the embodiment of the present invention has at least the following advantages:

[0032] The present application provides a method and device for monitoring the oil level of a current transformer. The method and device obtain the initial oil level of the current transformer by collecting the initial height and axial displacement of the expander through the oil level sensor. The non-ideal axial deformation occurring during the expansion process of the expander of the current transformer is taken into account. The initial oil level of the current transformer is corrected based on the radial displacement of the expander, and the effectiveness of the corrected oil level is evaluated based on the expansion characteristics of the current transformer expander. The monitoring oil level of the current transformer is determined based on the evaluation results, thereby improving the accuracy of the current transformer oil level monitoring, providing highly reliable data support for the judgment of the oil level status of the current transformer, and having important significance for the reliable and stable operation of the current transformer.

[0033] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to denote the same components. In the drawings:

[0035] Figure 1 A flow chart of a method for monitoring the oil level of a current transformer provided in an embodiment of the present application is shown;

[0036] Figure 2 A connection diagram of an oil level monitoring device based on a current transformer of an oil level sensor provided in an embodiment of the present application is shown;

[0037] Figure 3 Another connection diagram of an oil level monitoring device based on a current transformer of an oil level sensor provided in an embodiment of the present application is shown;

[0038] Figure 4 A diagram showing the installation position of an oil level sensor of an oil level monitoring device based on a current transformer of an oil level sensor provided in an embodiment of the present application is shown;

[0039] in,

[0040] In the figure: 1- oil level sensor; 2- repeater; 3- controller; 4- expander housing of phase A current transformer; 5- expander housing of phase B current transformer; 6- expander housing of phase C current transformer; 7- support column; 8- data transmission cable. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0042] To further illustrate the technical means and effects employed by the present invention to achieve its intended objectives, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention is provided in conjunction with the accompanying drawings and preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0043] In view of the problem that the existing oil level monitoring method for monitoring the current transformer cannot accurately monitor the oil level of the current transformer, the embodiment of the present application provides an oil level monitoring method for the current transformer, such as Figure 1 As shown, the method includes:

[0044] 102: Obtaining an initial height, axial displacement, and radial displacement of the expander, and performing calculations based on the initial height and axial displacement of the expander to obtain an initial oil level of the current transformer;

[0045] 104: Based on the radial displacement of the expander and the initial oil level, the oil level of the current transformer is corrected to obtain a corrected oil level of the current transformer;

[0046] 106: Evaluate the effectiveness of the calibrated oil level of the current transformer, and obtain the monitoring oil level of the current transformer based on the evaluation result.

[0047] Specifically, because current transformers are fully enclosed electrical equipment, the insulating oil level cannot be directly measured. Manual or video measurements of the oil level are inaccurate. Due to the unique structure of current transformers, the oil level can be monitored by monitoring the height of the expander. The expander is a key component of a current transformer, typically placed on top of the transformer or within an oil storage cabinet. Its function is to compensate for changes in transformer oil volume due to temperature fluctuations, ensuring safe operation of the current transformer in a fully sealed state. Specifically, the expander utilizes the expansion and contraction of corrugated plates to compensate for changes in oil volume and maintain stable internal pressure within the current transformer. When the oil temperature inside the current transformer rises, the oil volume increases, causing the corrugated plates to expand to accommodate more oil. Conversely, when the oil temperature drops, the corrugated plates contract, reducing the amount of oil and maintaining internal pressure balance. To protect the expander structure, an expander cover is placed over the expander. This cover not only protects the expander from impurities and improves safety, but also facilitates observation and monitoring of the expander's operating status, ensuring stable system operation.

[0048] A high-precision oil level sensor is installed on top of the expander housing. It measures the expander's axial and radial displacements. Axial displacement is the distance traveled along the expander's axis, while radial displacement is the distance traveled perpendicular to the axis. Positive values ​​indicate expansion, while negative values ​​indicate contraction.

[0049] The initial oil level monitored by the oil level sensor is calculated based on the expander's initial height and axial displacement. The expander will deform due to expansion. Based on the non-ideal axial deformation characteristics that occur during the expansion process, the current transformer's oil level is corrected based on the expander's radial displacement and the initial oil level to obtain the corrected oil level. Due to the expander's deformation, the corrected oil level may not necessarily be a valid detection result. Therefore, the effectiveness of the corrected oil level of the current transformer is evaluated. The expansion characteristics of the current transformer expander are quantified, and the effectiveness of the current transformer expander deformation is evaluated. The effectiveness of the monitored corrected oil level is then assessed based on the evaluation results.

[0050] Compared with the prior art, the present application provides an oil level monitoring method for a current transformer, which obtains the initial oil level of the current transformer by collecting the initial height and axial displacement of the expander through the oil level sensor, takes into account the non-ideal axial deformation of the expander of the current transformer during the expansion process, corrects the initial oil level of the current transformer based on the radial displacement of the expander, and evaluates whether the corrected oil level is effective based on the expansion characteristics of the current transformer expander. The monitoring oil level of the current transformer is determined based on the evaluation results, which improves the accuracy of the current transformer oil level monitoring, provides highly reliable data support for the judgment of the oil level status of the current transformer, and is of great significance to the reliable and stable operation of the current transformer.

[0051] In one embodiment of the present invention, the effectiveness of the calibrated oil level of the current transformer is evaluated, and the monitoring oil level of the current transformer is obtained according to the evaluation result, including:

[0052] Based on the corrected oil level and initial oil level of the current transformer, the instability of the expander during expansion is calculated;

[0053] If the instability is less than or equal to a preset instability threshold, the correction oil level of the current transformer is the monitoring oil level of the current transformer.

[0054] Specifically, the instability degree of the expander during expansion is calculated using the following method:

[0055]

[0056] Among them, ε is the instability, q0 is the initial wave distance, h′ is the correction oil level of the current transformer, and N is the number of expansion joints of the expander.

[0057] When the instability is greater than the preset instability threshold, it indicates that the current transformer's expander is at risk of severe, irreversible deformation, and the monitored transformer oil level is invalid. When the instability is less than or equal to the preset instability threshold, it indicates that the current transformer's expander is not severely deformed, and the monitored transformer oil level is valid. The corrected oil level is used as the current transformer's monitored oil level.

[0058] In one embodiment, the preset instability threshold is 40%. When the instability ε>40%, it indicates that the expander of the current transformer is at risk of severe irreversible deformation, the pressure compensation performance drops sharply, and the current transformer oil level monitoring method is considered to be failed, requiring manual inspection.

[0059] In one embodiment of the present invention, the following method is used to obtain the corrected oil level of the current transformer:

[0060]

[0061] Where h′ is the calibration oil level of the current transformer, h is the initial oil level of the current transformer, and D m is the average diameter of the expander, q0 is the initial wave distance, α is the stress coefficient of the expander when the plane is unstable; A cu is the average cross-sectional area of ​​the expander metal, K r is the expander circumferential stress coefficient, satisfying the formula

[0062] K r =max(K r1 , 1);

[0063]

[0064] Among them, K r1 is the expander circumferential stress coefficient, e y is the radial displacement of the expander, N is the number of expansion joints of the expander, and x is the axial displacement of the expander.

[0065] Specifically, considering the non-ideal axial deformation that occurs during the expansion process of the expander, the corrected current transformer oil level h′ satisfies the formula:

[0066]

[0067] D m is the average diameter of the expander, in mm; q0 is the initial wave distance, in mm; α is the stress coefficient of the expander when the plane is unstable; A cu is the average cross-sectional area of ​​the expander metal, in mm 2 ;

[0068] K r is the circumferential stress coefficient of the expander, satisfying the formula K r =max(K r1 , 1);

[0069]

[0070] K r1 is the expander circumferential stress coefficient, e y is the radial displacement monitored by the oil level sensor, in mm; N is the number of expansion joints of the expander, and x is the axial displacement of the expander.

[0071] In one embodiment of the present invention, the initial oil level of the current transformer is calculated based on the initial height and axial displacement of the expander, including:

[0072] The sum of the initial height and axial displacement of the expander is taken as the initial oil level of the current transformer.

[0073] Specifically, the initial data monitored by the high-precision oil level sensor (also the initial height of the expander) and the axial displacement of the expander are calculated to obtain the initial oil level h of the current transformer. The calculation formula is:

[0074] h=l+x

[0075] l is the initial height of the expander, in mm; x is the axial displacement of the expander monitored by the high-precision oil level sensor, in mm.

[0076] Furthermore, as a response to the above Figure 1 The embodiment of the present invention provides an oil level monitoring device based on a current transformer of an oil level sensor, such as Figure 2 As shown, the device includes:

[0077] Oil level sensor 1, oil level sensor 1 is used to collect the axial displacement and radial displacement of the expander of the current transformer;

[0078] Repeater 2, which is connected to the oil level sensor 1 by radio. Repeater 2 is used to transmit the axial displacement and radial displacement of the expander collected by the oil level sensor 1 to the controller 3;

[0079] The controller 3 is electrically connected to the repeater 2 , and the controller 3 is used to execute operations corresponding to the above-mentioned oil level monitoring method for the current transformer.

[0080] Specifically, an oil level sensor is installed on top of the expander housing of the current transformer. The oil level sensor collects the axial and radial displacements of the expander. A repeater is mounted on the support column at the lower end of the current transformer and wirelessly connects to the oil level sensor. The repeater receives the expander's initial height, axial displacement, and radial displacement monitored by the oil level sensor via a wireless antenna. The repeater is connected to the controller via a data transmission cable, which transmits the data collected by the oil level sensor to the controller. If the data collected by the oil level sensor is directly transmitted wirelessly to the controller, the transmitted signal power will gradually attenuate. At a certain level of attenuation, this will cause signal distortion and reception errors. The repeater completes the physical connection, amplifies the attenuated signal, and maintains the same data as the original, accurately transmitting the expander's initial height, axial displacement, and radial displacement to the controller.

[0081] The controller calculates the initial oil level of the current transformer based on the initial oil level and axial displacement of the expander, corrects the initial oil level of the current transformer based on the radial displacement and initial oil level of the expander to obtain the corrected oil level of the current transformer, and evaluates the effectiveness of the corrected oil level of the current transformer based on the non-ideal axial deformation characteristics that occur during the expansion process of the expander. Whether the monitored corrected oil level is valid is determined based on the evaluation result. When the evaluation result is valid, the corrected oil level of the current transformer is used as the monitored oil level of the current transformer.

[0082] like Figure 3 As shown, when the current transformer is a three-phase current transformer, the oil level of each phase current transformer is monitored. High-precision oil level sensor 1 No. 1, high-precision oil level sensor 1 No. 2, and high-precision oil level sensor 1 No. 3 are respectively embedded in the top center of the expander housing 4 of the A-phase current transformer, the expander housing 5 of the B-phase current transformer, and the expander housing 6 of the C-phase current transformer. Repeater 2 is installed on the lower end support column 7 of the B-phase current transformer. Repeater 2 receives the axial displacement and radial displacement of the expander monitored by the three high-precision oil level sensors based on a wireless antenna. Repeater 2 is connected to the host computer or controller 3 via a data transmission cable 8.

[0083] Turn on the power of the high-precision oil level sensor and repeater, set the transceiver frequency and automatic save frequency of the high-precision oil level sensor and repeater in the host computer serial port connection program, click data collection, and the repeater will transmit the axial displacement and radial displacement of the expander collected by the oil level sensor to the host computer.

[0084] The host computer or controller 3 performs initial oil level calculation, correction oil level calculation and effectiveness evaluation of the correction oil level for the current of each phase current transformer based on the axial displacement and radial displacement of the expander of each phase current transformer, and obtains the monitoring oil level corresponding to each phase current transformer according to the evaluation results of each phase.

[0085] The present application provides an oil level monitoring device for a current transformer. Compared with the prior art, the initial oil level of the current transformer is obtained by collecting the initial height and axial displacement of the expander through the oil level sensor. The non-ideal axial deformation occurring during the expansion process of the expander of the current transformer is taken into account. The initial oil level of the current transformer is corrected based on the radial displacement of the expander, and the effectiveness of the corrected oil level is evaluated based on the expansion characteristics of the current transformer expander. The monitoring oil level of the current transformer is determined based on the evaluation result, thereby improving the accuracy of the oil level monitoring of the current transformer and providing highly reliable data support for the judgment of the oil level status of the current transformer, which is of great significance to the reliable and stable operation of the current transformer.

[0086] In one embodiment, the oil level sensor 1 is disposed on top of the expander housing of the current transformer.

[0087] In one embodiment, a groove is provided at the center of the top of the expander cover, and the oil level sensor is embedded in the groove.

[0088] For example, Figure 4 As shown, a groove is provided at the top center of the expander cover 4 of the A-phase current transformer, and the oil level sensor 1 is embedded in the groove.

[0089] In one embodiment, the repeater is disposed on a support column at the lower end of the current transformer.

[0090] Obviously, those skilled in the art will appreciate that the various modules or steps of the present invention described above can be implemented using a general-purpose computing device, and can be centralized on a single computing device or distributed across a network of multiple computing devices. In one embodiment, they can be implemented using program code executable by a computing device, and thus, can be stored in a storage device and executed by the computing device. In some cases, the steps shown or described herein can be performed in a different order than that shown, or can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0091] The above embodiments are merely exemplary embodiments of the present application and are not intended to limit the scope of the present application. The scope of protection of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and scope of protection of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the scope of protection of the present application.

Claims

1. A method for monitoring the oil level of a current transformer, applied to an oil level monitoring device for a current transformer based on an oil level sensor, characterized in that: include: Obtaining an initial height, an axial displacement, and a radial displacement of the expander, and performing calculations based on the initial height and the axial displacement of the expander to obtain an initial oil level of the current transformer; Correcting the oil level of the current transformer based on the radial displacement of the expander and the initial oil level to obtain a corrected oil level of the current transformer; Performing an effectiveness evaluation on the correction oil level of the current transformer, and obtaining a monitoring oil level of the current transformer according to the evaluation result; The performing effectiveness evaluation on the correction oil level of the current transformer and obtaining the monitoring oil level of the current transformer according to the evaluation result includes: calculating the degree of instability of the expander during expansion based on the corrected oil level and the initial oil level of the current transformer; If the instability is less than or equal to a preset instability threshold, the correction oil level of the current transformer is the monitoring oil level of the current transformer; The instability degree of the expander during expansion is obtained using the following method: in, is the instability, q 0 is the initial wave distance, Correction oil level for current transformer, N is the number of expansion sections of the expander; The corrected oil level of the current transformer is obtained using the following method: in, Correction oil level for current transformer, h is the initial oil level of the current transformer, D m is the average diameter of the expander, q 0 is the initial wave distance, α is the stress action coefficient of the expander causing plane instability; A cu is the average cross-sectional area of ​​the expander metal, is the expander circumferential stress coefficient, satisfying the formula ； in, K r1 is the expander circumferential stress coefficient, e y is the radial displacement of the expander, N is the number of expansion sections of the expander, x is the axial displacement of the expander.

2. The oil level monitoring method of a current transformer according to claim 1, characterized in that: The calculating the initial oil level of the current transformer based on the initial height and axial displacement of the expander includes: The sum of the initial height and the axial displacement of the expander is taken as the initial oil level of the current transformer.

3. An oil level monitoring device for a current transformer based on an oil level sensor, characterized in that: include: Oil level sensor: The oil level sensor is used to collect the axial displacement and radial displacement of the expander of the current transformer; a repeater, the repeater being connected to the oil level sensor via radio, and the repeater being used to transmit the axial displacement and radial displacement of the expander collected by the oil level sensor to a controller; The controller is electrically connected to the repeater, and the controller is used to perform operations corresponding to the oil level monitoring method for a current transformer according to any one of claims 1 to 2.

4. The oil level monitoring device for a current transformer according to claim 3, characterized in that: The oil level sensor is arranged on the top of the expander housing of the current transformer.

5. The oil level monitoring device for a current transformer according to claim 4, characterized in that: A groove is provided at the center of the top of the expander cover, and the oil level sensor is embedded in the groove.

6. The oil level monitoring device for a current transformer according to claim 3, characterized in that: The repeater is arranged on a supporting column at the lower end of the current transformer.

Images