Oil level monitoring method and device of current transformer

Abstract

The invention discloses an oil level monitoring method and device for a current transformer, and the method comprises the steps: obtaining the initial height, axial displacement and radial displacement of an expander, carrying out the calculation based on the initial height and axial displacement of the expander, and obtaining the initial oil level of the current transformer; the oil level of the current transformer is corrected based on the radial displacement and the initial oil level of the expander, and the corrected oil level of the current transformer is obtained; and performing effectiveness evaluation on the corrected oil level of the current transformer, and obtaining the monitored oil level of the current transformer according to an evaluation result. Non-ideal axial deformation occurring in the expansion process of the expander of the current transformer is considered, the oil level monitoring value of the current transformer is corrected based on the axial displacement and the radial displacement of the expander, and the monitoring oil level of the current transformer is determined based on the expansion characteristics of the expander of the current transformer. The accuracy of oil level monitoring of the current transformer is improved, and high-reliability data support is provided for 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 a device for monitoring the oil level of a current transformer. Background Art

[0002] Current transformers are mainly 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 aspects. Current transformers need to have good insulation performance during use to prevent current leakage and equipment damage. Current transformers use oil as an insulating medium. The oil isolates the potential between the windings and between the windings and the ground to prevent problems such as electric shock and discharge. In order to maintain the normal operation and insulation performance of the current transformer, the oil level of the current transformer is monitored. Abnormal oil level may indicate that there is an internal fault in the equipment, such as a short circuit or insulation overheating, which needs to be handled in time.

[0003] The existing oil level monitoring methods for current transformers are mainly through manual inspections or remote monitoring using camera videos, but these two methods have many limitations. Manual regular 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, and the oil level changes of the equipment cannot be understood in real time. This may miss important status changes and delay fault discovery and processing; the video monitoring method cannot obtain detailed data and can only provide a general situation 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 of 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] Acquire the initial height, axial displacement and radial displacement of the expander, and calculate based on the initial height and axial displacement of the expander to obtain the initial oil level of the current transformer;

[0008] 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;

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

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

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

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

[0013] Optionally, the instability degree of the expander during expansion 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 corrected oil level of the current transformer is obtained by the following method:

[0017]

[0018] Where h′ is the calibrated 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, and N is the number of expansion nodes 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 by radio, 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 the controller is used to execute operations corresponding to the above-mentioned oil level monitoring method of 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 initial oil level of the current transformer is obtained by collecting the initial height and axial displacement of the expander through an 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. 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, providing highly reliable data support for the determination 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 according to 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 listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Also, the same reference symbols are used throughout the accompanying drawings to indicate the same components. In the accompanying drawings:

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

[0038] Figure 4 The installation position diagram of an oil level sensor of an oil level monitoring device of a current transformer based on 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 cover of A phase current transformer; 5- expander cover of B phase current transformer; 6- expander cover of C phase 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 the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0042] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[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 a current transformer, such as Figure 1 As shown, the method includes:

[0044] 102: Obtaining an initial height, an axial displacement, and a radial displacement of the expander, and performing calculation based on the initial height and the 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, calibrate the oil level of the current transformer to obtain a calibrated 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, since the current transformer is a fully enclosed power equipment, it is impossible to directly measure the liquid level of its insulating oil, and the oil level measured by manual measurement or video is inaccurate. Due to the special structure of the current transformer, the oil level of the current transformer can be monitored by monitoring the height of the expander. The expander of the current transformer is a key component, which is usually placed on the top of the current transformer or in the oil storage cabinet. Its function is to compensate for the volume change of the transformer oil due to temperature change and ensure that the current transformer can operate safely in a fully sealed state. Specifically, the expander uses the expansion and contraction of the corrugated sheet to compensate for the change in oil volume and ensure that the internal pressure of the current transformer remains stable. When the oil temperature inside the current transformer rises, the volume of the oil will increase, and the corrugated sheet will stretch to accommodate more oil; conversely, when the oil temperature drops, the corrugated sheet will shrink, reduce the amount of oil, and thus maintain the balance of internal pressure. In order to protect the structure of the expander, the expander is covered with an expander cover. The expander cover not only protects the expander, prevents impurities from entering, and improves safety, but also facilitates the observation and monitoring of the working status of the expander to ensure the stable operation of the system.

[0048] An oil level sensor with high precision is installed on the top of the expander housing. The axial displacement and radial displacement of the expander are collected through the oil level sensor; the axial displacement is the distance moved along the axis of the expander, and the radial displacement is the distance moved in a direction perpendicular to the axis of the expander. A positive value indicates expansion, and a negative value indicates contraction.

[0049] The initial oil level monitored by the oil level sensor is calculated based on the initial height of the expander and the axial displacement of the expander. The expander will produce expansion deformation. Based on the non-ideal axial deformation characteristics that occur during the expansion of the expander, the oil level of the current transformer is corrected based on the radial displacement of the expander and the initial oil level, and the corrected oil level of the current transformer is obtained. Due to the deformation of the expander, the corrected oil level is not necessarily 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 deformation of the current transformer expander is evaluated. Then, the effectiveness of the monitored corrected oil level is evaluated 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 through the initial height and axial displacement of the expander collected by 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, determines the monitoring oil level of the current transformer based on the evaluation result, 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 expander of the current transformer is at risk of serious 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 expander of the current transformer is not seriously deformed, and the monitored transformer oil level is valid, and the corrected oil level is used as the monitoring oil level of the current transformer.

[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 serious irreversible deformation, the pressure compensation performance drops sharply, the current transformer oil level monitoring method is considered to be failed, and manual inspection is required.

[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 calibrated 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, and N is the number of expansion nodes of the expander.

[0065] Specifically, considering the non-ideal axial deformation that occurs during the expansion 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 causing plane instability; 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.

[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 implementation of the method shown in the figure, the embodiment of the present invention provides an oil level monitoring device of a current transformer based on an oil level sensor, such as Figure 2 As shown, the device comprises:

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

[0078] A repeater 2, the repeater 2 is connected to the oil level sensor 1 by radio, and the 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 of the current transformer.

[0080] Specifically, an oil level sensor is arranged on the top of the expander cover of the current transformer, and the axial displacement and radial displacement of the expander are collected through the oil level sensor. The repeater is installed on the support column at the lower end of the current transformer, and the repeater is wirelessly connected to the oil level sensor. The repeater receives the initial height of the expander, the axial displacement and the radial displacement of the expander monitored by the oil level sensor through a wireless antenna. The repeater is connected to the controller through a data transmission cable, and the repeater transmits the initial height of the expander, the axial displacement and the radial displacement of the expander collected by the oil level sensor to the controller through the data transmission cable. If the data collected by the oil level sensor is directly transmitted to the controller wirelessly, the transmitted signal power will gradually attenuate, and when it attenuates to a certain extent, it will cause signal distortion, thus causing reception errors. The repeater can complete the connection of the physical line, amplify the attenuated signal, keep it the same as the original data, and accurately transmit the initial height of the expander, the axial displacement and the radial displacement of the expander 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 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 cover 4 of the A-phase current transformer, the expander cover 5 of the B-phase current transformer, and the expander cover 6 of the C-phase current transformer. The repeater 2 is installed on the lower end support column 7 of the B-phase current transformer. The repeater 2 receives the axial displacement and radial displacement of the expander monitored by the three high-precision oil level sensors based on the wireless antenna. The repeater 2 is connected to the host computer or controller 3 through the 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 calculates the initial oil level and the correction oil level of each phase current transformer according to the axial displacement and radial displacement of the expander of each phase current transformer, and evaluates the effectiveness of the correction oil level, and obtains the monitoring oil level corresponding to each phase current transformer according to the evaluation result 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 an oil level sensor, and the non-ideal axial deformation occurring during the expansion process of the expander of the current transformer is taken into consideration. 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, providing highly reliable data support for the determination of the oil level status of the current transformer, and having important significance for the reliable and stable operation of the current transformer.

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

[0087] In one embodiment, a groove is provided at the top center of the expander housing, 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 should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices. In one embodiment, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0091] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope 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 protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope 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: Acquire the initial height, axial displacement and radial displacement of the expander, and calculate based on the initial height and axial displacement of the expander to obtain the initial oil level of the current transformer; 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; The effectiveness of the calibrated oil level of the current transformer is evaluated, and the monitored oil level of the current transformer is obtained according to the evaluation result.

2. The oil level monitoring method of a current transformer according to claim 1, characterized in that: The effectiveness evaluation of the corrected oil level of the current transformer and obtaining the monitored oil level of the current transformer according to the evaluation result include: Based on the corrected oil level and the initial oil level of the current transformer, calculating the instability degree of the expander during the expansion process; If the instability is less than or equal to a preset instability threshold, the corrected oil level of the current transformer is the monitored oil level of the current transformer.

3. The oil level monitoring method of a current transformer as claimed in claim 2, characterized in that: The instability degree of the expander during expansion is obtained by the following method: 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.

4. The oil level monitoring method of a current transformer according to claim 1, characterized in that: The corrected oil level of the current transformer is obtained by the following method: Where h′ is the calibrated 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 K r =max(K r1 ,1); Among them, K r1 is the expander circumferential stress coefficient, e y is the radial displacement of the expander, and N is the number of expansion nodes of the expander.

5. 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 comprises: The sum of the initial height and the axial displacement of the expander is taken as the initial oil level of the current transformer.

6. An oil level monitoring device of 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 by radio, 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 5.

7. The oil level monitoring device for a current transformer according to claim 6, characterized in that: The oil level sensor is arranged on the top of the expander housing of the current transformer.

8. The oil level monitoring device for a current transformer according to claim 7, characterized in that: A groove is provided at the top center of the expander cover, and the oil level sensor is embedded in the groove.

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

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