CN109633392B - Transformer insulation test method and device - Google Patents
Transformer insulation test method and device Download PDFInfo
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- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
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Abstract
The invention discloses a transformer insulation test method and device. Wherein, the method comprises the following steps: determining a temperature correction coefficient according to the maximum electric field intensity of the tested part of the transformer at different testing temperatures; selecting a maximum temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient; and correcting the voltage of the transformer insulation test according to the voltage correction coefficient, and carrying out insulation test. The invention solves the technical problems that the insulation test method of the transformer in the related technology is easy to cause test failure and can not correctly reflect the insulation performance of the transformer.
Description
Technical Field
The invention relates to the field of electric power, in particular to a transformer insulation test method and device.
Background
In the related technology, the transformer needs to be subjected to related tests when leaving a factory, an insulation system of the transformer is made of an insulation material of the transformer, and the insulation system is a basic condition for normal work and operation of the transformer, so that safe and stable operation of the transformer is ensured. During insulation test, under different environmental temperatures and load conditions, the temperature change of an oil paper insulation system in main insulation inside a transformer can cause the change of the dielectric constant and the dielectric strength of transformer oil and paper boards, so that the transformer can meet the insulation test requirement at normal temperature and can not meet the insulation test requirement at high temperature, the insulation test is invalid, and the insulation performance of the transformer cannot be correctly reflected.
In view of the above problems, no effective solution has been proposed.
Disclosure of Invention
The embodiment of the invention provides a transformer insulation testing method and device, which at least solve the technical problems that a transformer insulation testing method in the related technology is easy to cause testing failure and cannot correctly reflect the insulation performance of a transformer.
According to an aspect of an embodiment of the present invention, there is provided a transformer insulation test method, including: determining a temperature correction coefficient according to the maximum electric field intensity of the tested part of the transformer at different testing temperatures; selecting a maximum temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient; and correcting the voltage of the transformer insulation test according to the voltage correction coefficient, and carrying out insulation test.
Optionally, determining the temperature correction coefficient according to the maximum electric field strength of the tested component of the transformer at different testing temperatures includes: determining the applied equivalent voltage of the tested component at normal temperature according to the temperature of the tested component of the transformer during actual operation and the temperature of the tested component at normal temperature; determining the maximum electric field intensity of the tested part of the transformer at different testing temperatures according to the equivalent voltage and the voltage applied at normal temperature; and determining a temperature correction coefficient according to the maximum electric field intensity, wherein the product of the correction coefficient and the voltage is the equivalent voltage.
Optionally, determining the maximum electric field strength of the tested component of the transformer at different testing temperatures according to the equivalent voltage and the voltage applied at the normal temperature includes: determining a first maximum electric field intensity of the tested component at a temperature corresponding to the equivalent voltage according to the equivalent voltage; determining a second maximum electric field intensity of the tested component according to the voltage applied under the normal temperature condition; wherein determining a temperature correction coefficient according to the maximum electric field strength comprises: and determining the temperature correction coefficient according to the ratio of the first maximum electric field intensity to the second maximum electric field intensity.
Optionally, determining, according to the temperature of the measured component of the transformer occurring during actual operation and the temperature of the measured component at normal temperature, that the measured component is at normal temperature, and before the applied equivalent voltage, the method includes: determining the insulation weak point position of the tested part, wherein the insulation weak point position is the electric field concentration position of the tested part at the corresponding temperature; determining a first variation relation of the maximum electric field intensity of the insulation weak point position along with temperature; and executing the step of determining the first maximum electric field intensity and/or the second maximum electric field intensity according to the first variation relation.
Optionally, the step of determining the first maximum electric field strength and/or the second maximum electric field strength according to the first variation relationship includes: determining a comparison position according to the insulation weak point position of the tested part; determining a second variation relation of the maximum electric field intensity of the comparison position along with the temperature; and determining the first maximum electric field intensity and/or the second maximum electric field intensity according to the first variation relation and the second variation relation.
Optionally, determining the insulation weakness position of the tested component includes: simulating the tested part of the transformer based on the effective element analysis to obtain a simulation result; and determining the insulation weak point position of the tested component according to the simulation result.
Optionally, simulating the tested component of the transformer based on the significant element analysis, and obtaining a simulation result includes: establishing a simulation model of the tested component; adding a boundary condition to the simulation model, wherein the boundary condition comprises at least one of: electric field distribution, electric field strength, electric potentials at different positions; adding attributes to the simulation model, wherein the attributes include dielectric constant, resistance, voltage, current; and (5) carrying out simulation to obtain a simulation result.
Optionally, performing simulation, and obtaining a simulation result includes: obtaining potential distribution conditions of different positions of the tested component and electric field intensity distribution conditions of different positions of the tested component through simulation; and determining an electric field distribution curve of the tested part on a fixed path according to the potential distribution condition and the electric field intensity distribution condition, wherein the electric field distribution curve is used for determining the insulation weak point position.
According to another aspect of the embodiments of the present invention, there is also provided a transformer insulation testing apparatus, including: the determining module is used for determining a temperature correction coefficient according to the maximum electric field intensity of the tested part of the transformer at different testing temperatures; the selection module is used for selecting the maximum temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient; and the test module is used for correcting the voltage of the transformer insulation test according to the voltage correction coefficient and testing the voltage.
According to another aspect of the embodiments of the present invention, there is also provided a storage medium, which is characterized by including a stored program, wherein when the program runs, a device in which the storage medium is located is controlled to execute any one of the above methods.
According to another aspect of the embodiments of the present invention, there is further provided a processor, wherein the processor is configured to execute a program, and wherein the program executes to perform the method of any one of the above.
In the embodiment of the invention, the temperature correction coefficient is determined according to the maximum electric field intensity of the tested part of the transformer at different test temperatures; selecting a maximum temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient; the voltage of the transformer insulation test is corrected according to the voltage correction coefficient, insulation test is carried out, the purpose of correcting the test result is achieved by correcting the test voltage, the technical effect of effectively testing the transformer is achieved, and the technical problems that the test failure is easily caused and the insulation performance of the transformer cannot be correctly reflected in the transformer insulation test method in the related technology are solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
FIG. 1 is a flow chart of a method for testing insulation of a transformer according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of temperature variation characteristics of a transformer oil with respect to dielectric constant according to an embodiment of the present invention;
fig. 3 is a schematic diagram of the temperature change characteristic of the relative dielectric constant of oil impregnated paper sheets according to an embodiment of the invention;
FIG. 4 is a schematic illustration of a double layer of oiled paper according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a computational model of a double-layer oiled paper according to an embodiment of the invention;
FIG. 6 is a schematic diagram of a model for calculating the electric field in the middle of the HV-HV winding according to an embodiment of the present invention;
FIG. 7 is a schematic of an electric field profile of a high voltage-medium subcoil along the A-B path according to an embodiment of the present invention;
FIG. 8 is a schematic of an electric field profile of a high voltage-medium subcoil along the C-D path according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of a temperature variation characteristic of a maximum electric field strength of an oil clearance of a transformer according to an embodiment of the present invention;
FIG. 10 is a schematic illustration of a temperature correction coefficient according to an embodiment of the present invention;
fig. 11 is a schematic diagram of a transformer insulation testing device according to an embodiment of the invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
In accordance with an embodiment of the present invention, there is provided a method embodiment of a transformer insulation test method, it is noted that the steps illustrated in the flowchart of the drawings may be performed in a computer system such as a set of computer executable instructions, and that while a logical order is illustrated in the flowchart, in some cases the steps illustrated or described may be performed in an order different than here.
Fig. 1 is a flowchart of a transformer insulation testing method according to an embodiment of the present invention, as shown in fig. 1, the method includes the following steps:
step S102, determining a temperature correction coefficient according to the maximum electric field intensity of the tested part of the transformer at different testing temperatures;
step S104, selecting the maximum temperature correction coefficient from the temperature correction coefficients as a voltage correction coefficient;
and S106, correcting the voltage of the transformer insulation test according to the voltage correction coefficient, and performing insulation test.
Through the steps, determining a temperature correction coefficient according to the maximum electric field intensity of the tested part of the transformer at different testing temperatures; selecting a maximum temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient; the voltage of the transformer insulation test is corrected according to the voltage correction coefficient, insulation test is carried out, the purpose of correcting the test result is achieved by correcting the test voltage, the technical effect of effectively testing the transformer is achieved, and the technical problems that the test failure is easily caused and the insulation performance of the transformer cannot be correctly reflected in the transformer insulation test method in the related technology are solved.
The temperature correction coefficient is that the transformer can cause an oil paper insulation system in main insulation in the transformer under different temperature conditions, and the dielectric constants and dielectric strengths of transformer oil and paper boards change with temperature to a certain extent. Under the condition of low temperature, the maximum electric field intensity in the transformer oil of the oil-paper insulation system is lower than the normal temperature, which is beneficial to improving the electric field distribution of the oil-paper insulation system; under the condition of high temperature, the maximum electric field intensity in the transformer oil of the oil-paper insulation system is higher than the normal temperature, the temperature of the internal oil-paper insulation system can reach +80 ℃ when the transformer actually operates, the design and the factory insulation test of the transformer are both carried out at the normal temperature, if the same voltage is considered to be applied, the maximum electric field intensity in the transformer oil at the high temperature is higher than the normal temperature, the condition that the insulation margin of the transformer meets the requirement at the normal temperature and the insulation margin does not meet the requirement at the high temperature easily occurs, and then the phenomenon that the actual operation state of the transformer cannot be reflected in the factory test examination of the transformer occurs.
The measured component can be an insulation system of a transformer, and the insulation system comprises transformer oil and oil paper.
In this embodiment, the correction of the temperature is achieved by changing the voltage. For example, the actual temperatures that may occur during the actual operation of the transformer are collected and converted into the equivalent voltage U1 applied to the transformer at normal temperature (e.g., 20 ℃), and when the temperature collected by the transformer is normal temperature, the voltage U2 applied to the transformer defines a temperature correction coefficient K, and U1 is K U2. In order to satisfy all temperature corrections, the present embodiment uses the largest position of the temperature correction coefficients as a voltage correction coefficient to correct the voltage of the transformer at different test temperatures, so as to implement temperature correction during the test.
By applying the corrected voltage to the transformer, the condition of inaccuracy caused by temperature is eliminated, and the effectiveness and the accuracy of the test are effectively improved.
Optionally, determining the temperature correction coefficient according to the maximum electric field strength of the tested component of the transformer at different testing temperatures includes: determining the applied equivalent voltage of the tested component at normal temperature according to the temperature of the tested component of the transformer during actual operation and the temperature of the tested component at normal temperature; determining the maximum electric field intensity of the tested part of the transformer at different testing temperatures according to the equivalent voltage and the voltage applied at normal temperature; and determining a temperature correction coefficient according to the maximum electric field intensity, wherein the product of the correction coefficient and the voltage is an equivalent voltage.
When the temperature correction coefficient is determined, since the voltage is a correction target, the temperature correction coefficient is determined by another parameter, and the voltage is corrected by determining the voltage correction coefficient based on the temperature correction coefficient. In this embodiment, the maximum electric field strength is used to determine the temperature correction coefficient, the maximum electric field strength of the insulation system is E1, and the maximum electric field strength of the oiled paper insulation system at any temperature is E2, which includes: k is E2/E1. That is, the applied equivalent voltage of the tested component at normal temperature is determined according to the temperature of the tested component of the transformer during actual operation and the temperature of the tested component at normal temperature; determining the maximum electric field intensity of the tested part of the transformer at different testing temperatures according to the equivalent voltage and the voltage applied at normal temperature; and determining a temperature correction coefficient according to the maximum electric field intensity, wherein the product of the correction coefficient and the voltage is an equivalent voltage.
When the maximum electric field intensity of the tested component of the transformer at different testing temperatures is determined according to the equivalent voltage and the voltage applied at normal temperature, the first maximum electric field intensity of the tested component at the temperature corresponding to the equivalent voltage can be determined according to the equivalent voltage; determining a second maximum electric field intensity of the tested component according to the voltage applied under the normal temperature condition; wherein determining the temperature correction coefficient according to the maximum electric field strength comprises: and determining a temperature correction coefficient according to the ratio of the first maximum electric field intensity to the second maximum electric field intensity.
Optionally, determining the measured component at normal temperature according to the temperature of the measured component of the transformer during actual operation and the temperature of the measured component at normal temperature, where the applied equivalent voltage includes: determining the insulation weak point position of the tested part, wherein the insulation weak point position is the electric field concentration position of the tested part at the corresponding temperature; determining a first variation relation of the maximum electric field intensity of an insulation weak point position along with temperature; the step of determining the first maximum electric field strength and/or the second maximum electric field strength is performed according to the first variation relation.
The insulation weak point position can be a position where an electric field is concentrated, and can also be a position where the electric field intensity is maximum. The temperature change at the position is most obvious, so when the temperature correction coefficient meets the change condition of the position, the change condition of other positions is necessarily met by analyzing and processing the position. In this example, insulation weakness locations were used for analysis and processing. The method can be used for determining a first variation relation of the maximum electric field intensity of an insulation weak point position with temperature; and when the first maximum electric field intensity and/or the second maximum electric field intensity are/is determined subsequently, determining the first maximum electric field intensity and/or the second maximum electric field intensity according to the first variation relation.
Optionally, the step of determining the first maximum electric field strength and/or the second maximum electric field strength according to the first variation relationship includes: determining a comparison position according to the insulation weak point position of the tested part; determining a second variation relation of the maximum electric field intensity of the comparison position along with the temperature; and determining the first maximum electric field intensity and/or the second maximum electric field intensity according to the first variation relation and the second variation relation.
For the insulation weak point position, the embodiment also provides a comparison position which is compared with the junction edge weak point position, and the analysis and the processing of the comparison position enable the correction result to be more accurate, reliable and stable. And by comparing a second variation relation of the maximum electric field strength at the position along with the temperature, when the conditions of the first maximum electric field strength and/or the second maximum electric field strength are/is determined subsequently, the first maximum electric field strength and/or the second maximum electric field strength are/is determined by combining the first variation relation and the second variation relation.
Optionally, determining the insulation weakness position of the tested component includes: simulating the tested part of the transformer based on the effective element analysis to obtain a simulation result; and determining the insulation weak point position of the tested part according to the simulation result.
The insulation weakness location may be a standard location inherent to the insulation system of the transformer, or it may be determined by calculation or simulation. In the embodiment, the position of the insulation weakness is determined in a simulation mode, so that the method is simple and convenient and can be quickly determined.
Optionally, simulating the tested component of the transformer based on the significant element analysis, and obtaining a simulation result includes: establishing a simulation model of the tested component; adding boundary conditions to the simulation model, wherein the boundary conditions include at least one of: electric field distribution, electric field strength, electric potentials at different positions; adding attributes to the simulation model, wherein the attributes comprise dielectric constant, resistance, voltage, and current; and (5) carrying out simulation to obtain a simulation result.
In this embodiment, the electric field distribution may be main insulation electric field distribution under a 1min power frequency withstand voltage test specified by a simulation standard, the potential may be 395kV for a first line cake of the high-voltage winding incoming line, and the voltage distribution may be linear distribution for voltage gradient between line cakes; the potential can also be that the potential of the medium-voltage winding is 0; as the model is used for intercepting the middle part of the high-voltage-medium-voltage winding and mainly researching the electric field distribution characteristic of main insulation between the high-voltage-medium-voltage winding, the upper, lower, left and right boundary surfaces of the model are homogeneous boundary conditions of the second class of electric fields.
The boundary condition refers to a change rule of a variable or its reciprocal on a boundary of a solution area with time and place. The method mainly comprises a first type of boundary condition and gives a numerical value of an unknown function on a boundary; the second type of boundary condition gives the directional derivative of the normal of the unknown function outside the boundary; a third class of boundary conditions gives a linear combination of the function value of the unknown function on the boundary and the directional derivative of the outer normal. For comsol software, there are only a first type of boundary condition and a second type of boundary condition.
Optionally, performing simulation, and obtaining a simulation result includes: obtaining potential distribution conditions of different positions of the tested component and electric field intensity distribution conditions of different positions of the tested component through simulation; and determining an electric field distribution curve of the tested part on a fixed path according to the potential distribution condition and the electric field intensity distribution condition, wherein the electric field distribution curve is used for determining the position of the insulation weak point.
It should be noted that this embodiment also provides an alternative implementation, and details of this implementation are described below.
The power transformer is the core of energy conversion and transmission in power transmission and distribution, is the most important, key and expensive equipment in power transmission and transformation equipment, and the reliability of the operation of the power transformer is directly related to the economic operation and the safety and stability of a power grid. The real-time insulation state evaluation, fault diagnosis and fault prediction of the power transformer are hot spots for the evaluation and research of the transformer running state at home and abroad at present, wherein the insulation state evaluation is particularly taken as a main research direction.
According to the GB/T1094.3 regulations on the insulation test of the power transformer, the 220kV oil-immersed power transformer needs to be subjected to an external construction frequency withstand voltage test, but the test is generally carried out under factory test conditions, the test environment temperature is normal temperature (20-30 ℃), the transformer is in a non-running state, and the internal temperature of the transformer is uniformly distributed and is the same as or similar to the environment temperature.
Under different environmental temperatures and load conditions, the temperature change range of an oil paper insulation system in the main insulation inside the transformer is-20 ℃ to +80 ℃, and the dielectric constants and dielectric strengths of transformer oil and paper boards change with the temperature to a certain extent. At low temperature (the temperature is lower than 20 ℃), the maximum electric field intensity in the transformer oil of the oil-paper insulation system is lower than the normal temperature, and the electric field distribution of the oil-paper insulation system is favorably improved; at high temperature (the temperature is higher than 20 ℃), the maximum electric field intensity in the transformer oil of the oil-paper insulation system is higher than the normal temperature, when the transformer runs actually, the temperature of the internal oil-paper insulation system can reach +80 ℃, the design and the factory insulation test of the transformer are both carried out at normal temperature, if the same voltage is considered to be applied, the maximum electric field intensity in the transformer oil at high temperature is higher than the normal temperature, the condition that the insulation margin of the transformer meets the requirement at normal temperature and the insulation margin does not meet the requirement at high temperature is easy to occur, further, the phenomenon that the actual running state of the transformer cannot be reflected by the factory test examination of the transformer occurs, therefore, the insulation margin design of the main insulation and the equivalence of the factory insulation test when the interior of the transformer is in a high-temperature state in the actual operation process need to be considered, and then the insulation margin design of the transformer and the factory insulation test are correspondingly corrected.
The embodiment mainly compares the difference between the actual operation temperature and the factory environment temperature, determines the change of the insulation characteristic of the transformer under the actual operation condition and the factory condition, and provides a correction suggestion for the existing test parameters or methods. Specifically, in the embodiment, the influence of the temperature on the electric field distribution characteristic of the 220kV transformer oiled paper insulation system is researched by establishing a simulation model of the actual electrode structure of the main insulation of the transformer. The electric field concentration position of the main insulation of the 220kV transformer under the power frequency withstand voltage test voltage is a first oil gap on the outer surface of the medium-voltage winding and a first oil gap wire cake round angle position on the inner surface of the high-voltage winding. Maximum electric field intensity-temperature change characteristic curves of the first oil clearance on the outer surface of the medium-voltage winding and the first oil clearance on the inner surface of the high-voltage winding are drawn, and basic data can be provided for an insulation test correction method of a 220kV power transformer.
The specific flow of the embodiment is as follows:
1. determining the influence of temperature on the electrical parameters of the oiled paper insulation system;
the influence of the temperature on the relative dielectric constant of the oiled paper insulation system is measured, and the relative dielectric constant and the volume resistivity of the new oil and the oil-immersed paperboard of the 220kV transformer, which are obtained by standard procedure treatment, at the temperature range of-20 ℃ to +80 ℃ are measured.
Fig. 2 is a schematic diagram of temperature variation characteristics of the relative dielectric constant of transformer oil according to an embodiment of the present invention, fig. 3 is a schematic diagram of temperature variation characteristics of the relative dielectric constant of oil-impregnated paper board according to an embodiment of the present invention, as shown in fig. 2 and fig. 3, the test results show that: for transformer oil, the relative dielectric constant of the transformer oil almost shows a linear descending trend along with the rise of temperature; for oil-impregnated paper boards, the relative dielectric constant of the oil-impregnated paper boards almost shows a linear rising trend along with the rise of temperature. Because the relative dielectric constants of the transformer oil and the oil-immersed paperboard are approximately in a linear relation with the temperature, the relative dielectric constant data of the transformer oil and the oil-immersed paperboard in a wider temperature range can be obtained through curve fitting.
The influence of temperature on the electric field distribution of a 220kV transformer, oil-paper insulation is a main insulation structure inside the transformer, and in the main insulation of the transformer, the insulation between windings generally adopts an oil-paper barrier composite insulation structure. Fig. 4 is a schematic view of a double-layer oiled paper according to an embodiment of the present invention, and fig. 5 is a schematic view of a calculation model of a double-layer oiled paper according to an embodiment of the present invention, and as shown in fig. 4 and 5, an oil-paper combined insulation system of a transformer is a parallel combination of two dielectrics of transformer oil and impregnated paper. The applied voltage is U, the distance between electrodes is d, and the dielectric constant of oil is epsilon1Conductivity of gamma1Thickness d1(ii) a Dielectric constant of paper is epsilon2Conductivity of gamma2Thickness d2。
For a 220kV power transformer, the main insulation mainly bears lightning impulse overvoltage, operation impulse overvoltage and power frequency voltage during normal work, which are alternating-current voltages. Under alternating voltage, the strength of the electric field in oil and paper is inversely proportional to its dielectric constant. At different temperatures, the dielectric constants of the transformer oil and the impregnated paper are different, and the field intensity distribution inside the oil-paper insulation system changes, which affects the insulation matching of the oil-paper insulation system.
2. Calculating and analyzing numerical values;
the classical checking of the main insulation (namely the oil-paper composite insulation) of the transformer is determined according to a 1-min power frequency withstand voltage test, namely 1-min power frequency test voltage which is equivalent voltage of operation overvoltage or wave-chopping impact test voltage.
A simulation calculation model is established in simulation software, various complex electrode structures and different dielectrics in the transformer can be simulated by the numerical calculation method based on finite element analysis, and compared with other two calculation methods, the method has the advantages of high calculation accuracy, wide application range and the like and is widely applied to engineering practice of electric field calculation.
A numerical analysis software comsol is used for establishing a calculation model of a main insulation electric field in the middle of a high-voltage winding and a medium-voltage winding of a three-phase three-winding oil-immersed power transformer with the model number of SFSZ-180000/220, a certain phase winding of the transformer is selected, and a two-dimensional axisymmetric model comprising a high-voltage winding wire cake, a medium-voltage winding wire cake, an oil passage between the wire cakes and an oil paper composite insulation structure between the high-voltage winding and the medium-voltage winding is established. Fig. 6 is a schematic diagram of a calculation model of the electric field in the middle of the high-voltage and medium-voltage windings according to an embodiment of the invention, and a simulation model is shown in fig. 6. In the figure, the point A, B is respectively positioned at the round corners of the medium-voltage winding wire cake and the high-voltage winding wire cake, and the line segment AB is a radial line segment at the round corner of the wire cake; the C is positioned in the middle of the outer side surface of the medium-voltage winding wire cake, the D point is positioned near the middle of the inner side surface of the high-voltage winding wire cake, and the line segment CD is a radial line segment in the middle of the wire cake.
Wherein, partial parameters and boundary conditions of the model are set as follows: simulating the distribution of a main insulating electric field under a 1-min power frequency withstand voltage test specified by a standard, wherein the potential of a first line cake of an incoming line of the high-voltage winding is 395kV, and the voltage gradient among the line cakes is in linear distribution; the potential of the medium-voltage winding is 0; as the model is used for intercepting the middle part of the high-voltage-medium-voltage winding and mainly researching the electric field distribution characteristic of main insulation between the high-voltage-medium-voltage winding, the upper, lower, left and right boundary surfaces of the model are homogeneous boundary conditions of the second class of electric fields.
According to the simulation software, the simulation calculation of the electric field distribution can be obtainedAs a result, the relative dielectric constants of the oil-impregnated paper sheet and the transformer oil were respectively ε at normal temperature (20 ℃ C.)z＝5.2、εyThe calculation results of the main insulation potential distribution, the equipotential line distribution and the electric field intensity distribution between the high-voltage and medium-voltage windings can be represented by a color cloud chart, an equipotential line chart or a statistical chart. Two paths from the outer surface of the medium-voltage winding to the inner surface of the high-voltage winding are selected, namely line segment AB and line segment CD in fig. 6, fig. 7 is a schematic diagram of an electric field distribution curve of the high-voltage-medium sub-winding on the path a-B according to the embodiment of the invention, fig. 8 is a schematic diagram of an electric field distribution curve of the high-voltage-medium sub-winding on the path C-D according to the embodiment of the invention, and as shown in fig. 7 and fig. 8, the distribution of radial electric fields along the path AB and the path CD is determined according to the calculation results of the main insulation potential distribution, the equipotential line distribution and the electric field intensity distribution among the high-voltage-medium-voltage windings.
The temperature characteristic of the maximum electric field intensity of the oiled paper insulation under the voltage of a 1-min power frequency test is simulated by simulation calculation to simulate the main insulation electric field distribution of a 220kV transformer under the 1-min power frequency withstand test specified by the standard, the potential of a first line cake of the incoming line of a high-voltage winding is 395kV, the voltage gradient between the line cakes is in linear distribution, and the potentials of a medium-voltage winding and a low-voltage winding are zero. And obtaining the maximum electric field intensity temperature change characteristic of the 220kV transformer oil paper insulation system at different temperatures. And (4) performing simulation calculation on the three-phase three-winding oil-immersed power transformer with the model of SFSZ-180000/220.
The electric field distribution of the main insulation in the middle of the high-voltage and medium-voltage winding of the three-phase three-winding oil-immersed power transformer with the model of SFSZ-180000/220 under the power frequency test voltage of 1min is simulated, and the electric field concentration part and the insulation weak point are positioned at a first oil gap on the outer surface of the medium-voltage winding and a first oil gap wire cake round angle on the inner surface of the high-voltage winding. The calculation results of the maximum electric field strength of the first oil clearance on the outer surface of the medium-voltage winding and the maximum electric field strength temperature change characteristics of the first oil clearance on the inner surface of the high-voltage winding are shown in table 1.
TABLE 1 SFSZ-180000/220 calculation result of maximum electric field intensity of transformer
Fig. 9 is a schematic diagram of a temperature variation characteristic of a maximum electric field intensity of an oil clearance of a transformer according to an embodiment of the present invention, as shown in fig. 9, which is a statistical chart of calculation results obtained according to the result table shown in table 1.
The results show that: along with the increase of the temperature, the maximum electric field intensity of the first oil clearance on the outer surface of the medium-voltage winding and the maximum electric field intensity of the first oil clearance on the inner surface of the high-voltage winding almost linearly increase, and the maximum electric field intensities are relatively close to each other. The maximum electric field intensity in the oil-paper composite insulation system between the high-voltage winding and the medium-voltage winding at the temperature lower than +30 ℃ is generated in the first oil gap on the outer surface of the medium-voltage winding, and the maximum electric field intensity in the oil-paper composite insulation system between the high-voltage winding and the medium-voltage winding at the temperature higher than +30 ℃ is generated in the first oil gap on the inner surface of the high-voltage winding.
Under high temperature, the maximum electric field intensity in the main insulation transformer oil of the 220kV transformer is higher than the normal temperature, the insulation margin design of the main insulation when the interior of the transformer is in a high-temperature state in the actual operation process and the equivalence of a factory power frequency voltage withstand test need to be considered, because the allowable electric field intensities of the first oil gap on the outer surface of the medium-voltage winding and the first oil gap on the inner surface of the high-voltage winding are respectively related to the size of the respective oil duct gaps and the turn insulation thickness of the corresponding winding, the insulation margins of the two windings need to be analyzed separately.
3. A 220kV transformer insulation test correction method;
although the power frequency of 1min is an equivalent voltage according to the operation overvoltage or the wave-chopping impact test voltage, the power frequency can only be used for checking the main insulation strength of the transformer, strictly speaking, the main insulation of the transformer is checked under the impact test voltage, and the electric field distribution of the main insulation of the transformer is calculated according to the transient electric field, because under the action of the impact voltage wave, a complex electromagnetic transient process, namely a wave process, is generated inside a transformer winding. During the wave process, oscillation overvoltage is generated among turns, sections, cakes and parts of the winding to the ground, so that potential distribution of all parts of the winding is uneven, a large potential gradient is generated, and at the moment, a longitudinal electric field between the cakes of the winding is large, and the distribution of the electric field of the main insulation is greatly influenced.
Determining a correction method of a 1min power frequency withstand voltage test, and considering the change of the environmental temperature and load of a test area, wherein in the actual operation process of a 220kV power transformer in the area, the temperature change range of an oil paper insulation system in the main insulation of the 220kV power transformer is-20 ℃ to +80 ℃, and the dielectric constants of transformer oil and a paperboard change with the temperature to a certain extent, so that the maximum electric field intensity of the transformer oil and the paperboard changes. Taking the simulation calculation results of the maximum electric field intensity of the first oil clearance on the outer surface of the medium-voltage winding and the maximum electric field intensity of the first oil clearance on the inner surface of the high-voltage winding in fig. 8 under the power frequency test voltage of 1min as an example, under the condition that the applied voltage is not changed, the maximum electric field intensity is reduced when the temperature is reduced and the maximum electric field intensity is increased when the temperature is increased, namely under the action of the alternating voltage, the insulation margin and the electric intensity of the oil-paper composite insulation system are reduced along with the increase of the temperature.
At high temperature (the temperature is higher than 20 ℃), the maximum electric field intensity in the transformer oil of the oil-paper insulation system is higher than the normal temperature, when the transformer runs actually, the temperature of the internal oil-paper insulation system can reach +80 ℃, the design and the factory insulation test of the transformer are both carried out at normal temperature, if the same voltage is considered to be applied, the maximum electric field intensity in the transformer oil at high temperature is higher than the normal temperature, the condition that the insulation margin of the transformer meets the requirement at normal temperature and the insulation margin does not meet the requirement at high temperature is easy to occur, further, the phenomenon that the actual running state of the transformer cannot be reflected by the factory test examination of the transformer occurs, therefore, the insulation margin design of the main insulation and the equivalence of the factory insulation test when the interior of the transformer is in a high-temperature state in the actual operation process need to be considered, and then the insulation margin design of the transformer and the factory insulation test are correspondingly corrected.
In consideration of the difficulty in changing the test temperature at the time of shipment, the voltage applied in the ac withstand voltage test of the transformer is temperature-corrected. The temperature correction calculation method is as follows:
considering the possible internal temperature T of the 220kV oil-immersed power transformer in actual operationxThe equivalent AC test withstand voltage to be applied when converted to normal temperature (20 ℃) is Ux，U0The tolerance voltage of the AC test applied when the internal temperature of the transformer is normal temperature (20 ℃), K is defined as a temperature correction coefficient, and the tolerance voltage comprises: u shapex＝KU0；
At U0Under the action, the maximum electric field intensity of the oil paper insulation system at normal temperature (20 ℃) is E0The maximum electric field intensity of the oil paper insulation system at any temperature is ExThen, there are: k ═ Ex/E0；
And taking the maximum K value obtained by calculation within the temperature change range of the oil-paper insulation system during the actual operation of the transformer as the final voltage correction coefficient of the 1min power frequency test.
Calculating a correction coefficient of the voltage of the 1-min power frequency withstand voltage test, and obtaining a temperature correction coefficient K calculation result of the power frequency withstand voltage test according to the maximum electric field intensity of the first oil gap on the outer surface of the medium-voltage winding and the maximum electric field intensity of the first oil gap on the inner surface of the high-voltage winding under the action of the 1-min power frequency test voltage in the table 1 according to the simulation calculation result of the temperature change characteristic of the maximum electric field intensity of the first oil gap on the outer surface of the medium-voltage winding and the maximum electric field intensity of the first oil gap on the inner surface of the high-voltage winding in the table 2 aiming at a three-phase three-winding oil-immersed power transformer with the model number of SFSZ-180000/220.
TABLE 2 SFSZ-180000/220 Transformer temperature correction coefficient
Fig. 10 is a diagram illustrating a temperature correction coefficient according to an embodiment of the present invention, as shown in fig. 10, which is a statistical graph of calculation results obtained from the result table shown in table 2.
The results show that: the temperature correction coefficients obtained by calculation according to the temperature change characteristics of the maximum electric field intensity of the first oil clearance on the outer surface of the medium-voltage winding and the maximum electric field intensity of the first oil clearance on the inner surface of the high-voltage winding under the same applied voltage are almost linearly increased along with the increase of the temperature, but the temperature correction coefficients of the medium-voltage winding and the high-voltage winding are different at different temperature points, and the temperature correction coefficient K of the actual transformer 1min power frequency withstand voltage test can be selected to be larger than the temperature correction coefficient K of the medium-voltage winding and the high-voltage winding for voltage check.
Considering that the internal temperature of the transformer can reach 80 ℃ under the actual operation condition, the test voltage of the 1min power frequency voltage withstand test needs to be improved by 3.6% in the factory voltage withstand test at normal temperature, and considering the calculation error, the test voltage of the 1min power frequency voltage withstand test is recommended to be improved by 4%, so that the main insulation strength of the transformer at different operation temperatures can be accurately tested.
The beneficial effect brought by the technical scheme of the embodiment is that the temperature correction of the test method is carried out aiming at the 1min power frequency withstand voltage test of the 220kV oil-immersed power transformer. And (3) proposing a transformer operation and maintenance suggestion, and further proposing a correction method of a 220kV transformer related insulation performance test when the transformer leaves the factory or is handed over, ensuring the operation stability of the power transformer and the safe and stable operation of the power transmission line, and constructing a clean, efficient, safe and stable energy internet safe driving and protection navigation. The principle of the implementation mode is simple and easy to operate.
The technical key point and the point to be protected of the embodiment are the design idea of the transformer insulation test correction method based on the power frequency test. An algorithm of a transformer insulation test correction method based on a power frequency test.
Fig. 11 is a schematic diagram of a transformer insulation testing apparatus according to an embodiment of the present invention, and as shown in fig. 11, according to another aspect of the embodiment of the present invention, there is also provided a transformer insulation testing apparatus including: a determination module 1102, a selection module 1104, and a test module 1106, which are described in more detail below.
A determining module 1102, configured to determine a temperature correction coefficient according to maximum electric field strengths of tested components of transformers at different test temperatures; a selecting module 1104, connected to the determining module 1102, for selecting a maximum temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient; and the test module 1106 is connected with the selection module 1104 and is used for correcting and testing the voltage of the transformer insulation test according to the voltage correction coefficient.
By the device, the determining module 1102 determines the temperature correction coefficient by adopting the maximum electric field intensity of the tested part of the transformer at different testing temperatures; the selecting module 1104 selects the largest temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient; the test module 1106 corrects the voltage of the transformer insulation test according to the voltage correction coefficient, performs the insulation test, and corrects the test voltage to achieve the purpose of correcting the test result, thereby achieving the technical effect of effectively testing the transformer, and further solving the technical problems that the transformer insulation test method in the related art is easy to cause test failure and cannot correctly reflect the insulation performance of the transformer.
According to another aspect of the embodiments of the present invention, there is also provided a storage medium, which is characterized in that the storage medium includes a stored program, wherein when the program runs, the apparatus on which the storage medium is located is controlled to execute the method of any one of the above.
According to another aspect of the embodiments of the present invention, there is further provided a processor, which is characterized in that the processor is configured to execute a program, wherein the program executes to perform the method of any one of the above.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units may be a logical division, and in actual implementation, there may be another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, units or modules, and may be in an electrical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A transformer insulation test method is characterized by comprising the following steps:
determining a temperature correction coefficient according to the maximum electric field intensity of insulation weak point positions of tested parts of the transformer at different test temperatures, wherein the tested parts of the transformer are an insulation system of the transformer, and the insulation weak point positions are electric field concentration positions of the tested parts at corresponding temperatures;
selecting a maximum temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient;
correcting the voltage of the transformer insulation test according to the voltage correction coefficient, and carrying out insulation test;
wherein the method further comprises:
determining the insulation weakness position of the tested part;
determining a first variation relation of the maximum electric field intensity of the insulation weak point position along with temperature;
and determining the maximum electric field intensity according to the first variation relation.
2. The method of claim 1, wherein determining the temperature correction factor based on maximum electric field strengths of the tested components of the transformer at different test temperatures comprises:
determining the applied equivalent voltage of the tested component at normal temperature according to the temperature of the tested component of the transformer during actual operation and the temperature of the tested component at normal temperature;
determining the maximum electric field intensity of the tested part of the transformer at different testing temperatures according to the equivalent voltage and the voltage applied at normal temperature;
and determining a temperature correction coefficient according to the maximum electric field intensity, wherein the product of the correction coefficient and the voltage is the equivalent voltage.
3. The method of claim 2, wherein determining the maximum electric field strengths of the tested components of the transformer at different test temperatures based on the equivalent voltage and the applied voltage at the normal temperature comprises:
determining a first maximum electric field intensity of the tested component at a temperature corresponding to the equivalent voltage according to the equivalent voltage;
determining a second maximum electric field intensity of the tested component according to the voltage applied under the normal temperature condition;
wherein determining a temperature correction coefficient according to the maximum electric field strength comprises:
and determining the temperature correction coefficient according to the ratio of the first maximum electric field intensity to the second maximum electric field intensity.
4. The method according to claim 3, wherein the step of determining the first maximum electric field strength and/or the second maximum electric field strength according to the first variation relation comprises:
determining a comparison position according to the insulation weak point position of the tested part;
determining a second variation relation of the maximum electric field intensity of the comparison position along with the temperature;
and determining the first maximum electric field intensity and/or the second maximum electric field intensity according to the first variation relation and the second variation relation.
5. The method of claim 3, wherein determining the location of an insulation weakness of the component under test comprises:
simulating the tested part of the transformer based on the effective element analysis to obtain a simulation result;
and determining the insulation weak point position of the tested component according to the simulation result.
6. The method of claim 5, wherein simulating the tested component of the transformer based on the significant element analysis, the deriving a simulation result comprising:
establishing a simulation model of the tested component;
adding a boundary condition to the simulation model, wherein the boundary condition comprises at least one of: electric field distribution, electric field strength, electric potentials at different positions;
adding attributes to the simulation model, wherein the attributes include dielectric constant, resistance, voltage, current;
and (5) carrying out simulation to obtain a simulation result.
7. The method of claim 6, wherein performing a simulation to obtain a simulation result comprises:
obtaining potential distribution conditions of different positions of the tested component and electric field intensity distribution conditions of different positions of the tested component through simulation;
and determining an electric field distribution curve of the tested part on a fixed path according to the potential distribution condition and the electric field intensity distribution condition, wherein the electric field distribution curve is used for determining the insulation weak point position.
8. A transformer insulation test device, characterized by comprising:
the device comprises a determining module, a temperature correcting module and a correcting module, wherein the determining module is used for determining a temperature correcting coefficient according to the maximum electric field intensity of insulation weak points of tested parts of the transformer at different testing temperatures, the tested parts of the transformer are an insulation system of the transformer, and the insulation weak points are electric field concentration positions of the tested parts at corresponding temperatures;
the selection module is used for selecting the maximum temperature correction coefficient from the plurality of temperature correction coefficients as a voltage correction coefficient;
the test module is used for correcting the voltage of the transformer insulation test according to the voltage correction coefficient and testing the voltage;
the device is further used for determining the insulation weak point position of the tested component, determining a first variation relation of the maximum electric field strength of the insulation weak point position along with the temperature, and determining the maximum electric field strength according to the first variation relation.
9. A storage medium, comprising a stored program, wherein the program, when executed, controls an apparatus in which the storage medium is located to perform the method of any one of claims 1 to 7.
10. A processor, characterized in that the processor is configured to run a program, wherein the program when running performs the method of any of claims 1 to 7.
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| CN110618361A (en) * | 2019-10-12 | 2019-12-27 | 国网山东省电力公司莱芜供电公司 | Transformer insulation test correction method and device based on lightning full-wave surge test and readable storage medium |
| CN113311299B (en) * | 2021-05-26 | 2023-05-19 | 广西电网有限责任公司南宁供电局 | CVT insulation defect detection method and device |
| CN113985230B (en) * | 2021-10-29 | 2023-08-15 | 全球能源互联网研究院有限公司 | Breakdown testing device under temperature gradient |
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