CN110618361A - Transformer insulation test correction method and device based on lightning full-wave surge test and readable storage medium - Google Patents
Transformer insulation test correction method and device based on lightning full-wave surge test and readable storage medium Download PDFInfo
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- CN110618361A CN110618361A CN201910969390.6A CN201910969390A CN110618361A CN 110618361 A CN110618361 A CN 110618361A CN 201910969390 A CN201910969390 A CN 201910969390A CN 110618361 A CN110618361 A CN 110618361A
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references
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Abstract
The invention provides a method, equipment and a readable storage medium for correcting an insulation test of a transformer based on a lightning full-wave impact test, and the method, equipment and readable storage medium correspondingly correct the insulation margin design of the transformer and a delivery insulation test by considering the insulation margin design of main insulation when the interior of the transformer is in a high-temperature state in the actual operation process and the equivalence of the delivery insulation test, so that the temperature correction of the test method is carried out on the lightning full-wave impact voltage-withstand test of a 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.
Description
Technical Field
The invention relates to the technical field of transformers, in particular to a transformer insulation test correction method, equipment and a readable storage medium based on a lightning full-wave surge test
Background
The power transformer is the core of energy conversion and transmission in power transmission and distribution, is the most important, critical and expensive equipment in power transmission and transformation equipment, and the operation reliability 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. The insulation of the power transformer is an insulation system made of transformer insulation materials, which is a basic condition for normal operation and running of the transformer, and an insulation performance test needs to be carried out regularly to ensure safe and stable running of the power transformer.
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 externally applied lightning impulse 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-operation 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; under 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 normal temperature, when the transformer is actually operated, the temperature of the inner oil-paper insulation system can reach +80 ℃, and 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 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 easily occurs, and then the phenomenon that the factory test examination of the transformer cannot reflect the actual operation state of the transformer occurs.
Disclosure of Invention
In order to overcome the defects in the prior art, the insulation margin design and the factory insulation test of the transformer are correspondingly modified in consideration of the equivalence of the insulation margin design and the factory insulation test of the main insulation when the interior of the transformer is in a high-temperature state in the actual operation process, and the method comprises the following steps:
the method comprises the following steps of firstly, acquiring the influence of temperature on electrical parameters of the oiled paper insulation system;
analyzing the numerical value;
2.1 establishing a model;
utilizing a transformer winding middle model to perform numerical calculation of electric field distribution temperature characteristics in an oil paper insulation system between high-voltage windings and medium-voltage windings under the voltage of a lightning full-wave impact test;
2.2, acquiring the temperature characteristic of the maximum electric field intensity of the oil paper insulation under the lightning full-wave impact test voltage;
checking insulation design under the voltage of the lightning full-wave impact test;
3.1 a correction method based on a lightning full-wave impact voltage withstand test;
3.2, calculating a correction coefficient of the voltage of the lightning full-wave impulse withstand voltage test;
and calculating the temperature correction coefficient Kt of the power frequency withstand voltage test by the three-phase three-winding oil-immersed power transformer according to the maximum electric field intensity of the first oil gap on the inner surface of the high-voltage winding.
It should be further noted that the first step further includes:
1.1, acquiring the influence of temperature on the relative dielectric constant of an oil paper insulation system;
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 is obtained through curve fitting;
1.2, acquiring the influence of temperature on the electric field distribution of the 220kV transformer;
under the action of alternating voltage, the electric field intensity in oil and paper is inversely proportional to the dielectric constant thereof; at different temperatures, the dielectric constants of the transformer oil and the impregnated paper are different, and the field intensity distribution in the oil-paper insulation system is changed, so that the insulation matching of the oil-paper insulation system is influenced.
It should be further noted that, step 2.1 in the second step further includes:
some parameters and boundary conditions of the model are set as follows:
firstly, distributing main insulation electric fields under the condition that a lightning full-wave impact test voltage Ut specified by a simulation standard is 950kV, wherein the potential of a first line cake of an incoming line of a high-voltage winding is 950kV, and the voltage gradient among the line cakes is distributed according to 7%;
the potential of the medium-voltage winding is 0;
thirdly, because the model is used for intercepting the middle part of the high-voltage-medium-voltage winding and the distribution characteristic of the main insulation electric field between the high-voltage-medium-voltage winding, the upper, lower, left and right boundary surfaces of the model are the homogeneous boundary conditions of the second class of the electric field;
under the temperature of 20-25 ℃, the relative dielectric constants of the oil-immersed paperboard and the transformer oil are respectively 5.2 for epsilon z and 2.11 for epsilon y, and the electric field intensity distribution and the electric potential distribution of the main insulation between the high-voltage winding and the medium-voltage winding are calculated;
two radial electric field distributions are selected on the path from the outer surface of the medium voltage winding to the inner surface of the high voltage winding.
It should be further noted that 2.2 in step two further includes:
the distribution of a main insulation electric field of a 220kV transformer under a lightning full-wave impact test voltage specified by a simulation standard is calculated through simulation, the potential of a first line cake of an incoming line of a high-voltage winding is 950kV, the maximum voltage gradient between the line cakes is calculated according to 7%, and the potentials of a medium-voltage winding and a low-voltage winding are zero;
acquiring the maximum electric field intensity temperature change characteristic of a 220kV transformer oil paper insulation system at different temperatures; the simulation calculation aims at a three-phase three-winding oil-immersed power transformer with the model of SFSZ-180000/220;
the method comprises the following steps of carrying out simulation calculation on electric field distribution of a main insulation in the middle of a high-voltage winding and a medium-voltage winding of the SFSZ-180000/220-type three-phase three-winding oil-immersed power transformer under the lightning full-wave impact test voltage, wherein the electric field concentration part and the insulation weakness are located at a first oil gap on the outer surface of a medium-voltage winding and a first oil gap wire cake round angle on the inner surface of a high-voltage winding; and calculating 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 temperature change characteristic of the first oil clearance on the inner surface of the high-voltage winding.
It should be further noted that 3.1 in step three further includes:
in the operation process of a 220kV power transformer, the temperature change range of an oil paper insulation system in internal main insulation 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;
in the simulation calculation results of the temperature variation characteristics 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 under the lightning full-wave impact test voltage, under the condition that the applied voltage is not changed, the temperature is reduced to reduce the maximum electric field intensity and is increased when the temperature is increased, and under the action of the lightning impact test voltage, the insulation margin and the electric intensity of the oil-paper composite insulation system are reduced along with the increase of the temperature;
the temperature correction calculation method is as follows:
the internal temperature of 220kV oil-immersed power transformer during operation is Tx, and equivalent thunder full-wave impact test withstand voltage is Utx, and Ut0 is the thunder full-wave test withstand voltage that should apply when the internal temperature of transformer is 20 ℃ to 25 ℃, and definition Kt is the temperature correction coefficient, and has: utx ═ KtUt 0;
under the action of Ut0, the maximum electric field intensity of the oil paper insulation system at 20-25 ℃ is Et0, and the maximum electric field intensity of the oil paper insulation system at any temperature is Etx, then: kt Etx/Et 0;
and taking the maximum Kt value obtained by calculation within the temperature change range of the oil-paper insulation system during the actual operation of the transformer as a final lightning full-wave impact test voltage correction coefficient.
The invention also provides equipment for realizing the method for correcting the insulation test of the transformer based on the lightning full-wave surge test, which comprises the following steps:
the storage is used for storing a computer program and a transformer insulation test correction method based on a lightning full-wave impact test; and the processor is used for executing the computer program and the transformer insulation test correction method based on the lightning full-wave impact test so as to realize the steps of the transformer insulation test correction method based on the lightning full-wave impact test.
The invention also provides a readable storage medium with a transformer insulation test correction method based on the lightning full-wave surge test, wherein the readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the transformer insulation test correction method based on the lightning full-wave surge test.
According to the technical scheme, the invention has the following advantages:
the temperature correction of the test method is carried out aiming at the lightning full-wave impulse 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 a transmission line, and constructing a clean, efficient, safe and stable energy internet safe driving and protection navigation.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings used in the description will be briefly introduced, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without inventive labor.
FIG. 1 is a diagram of temperature variation characteristics of relative dielectric constants of transformer oil and oil-immersed paper boards;
FIG. 2 is a diagram of a calculation model of double-layer oiled paper insulation;
FIG. 3 is a diagram of a calculation model of the electric field in the middle of the high-and medium-voltage winding;
FIG. 4 is a radial electric field distribution graph in the middle of the high-voltage to medium-voltage winding;
FIG. 5 is a temperature variation characteristic diagram of maximum field strength of an oil gap of an SFSZ-180000/220 transformer;
FIG. 6 is a diagram of the temperature correction coefficient of the SFSZ-180000/220 transformer.
Detailed Description
Those of ordinary skill in the art will appreciate that the elements and algorithm steps of the examples described in connection with the embodiments disclosed in the method for modifying a transformer insulation test based on a lightning full-wave surge test may be implemented in electronic hardware, computer software, or combinations thereof, and that the components and steps of the examples have been generally described in terms of their functionality in the foregoing description for clarity of the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the embodiments provided in the method for correcting the insulation test of the transformer based on the lightning full-wave surge test, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of 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, devices or units, and may also be an electric, mechanical or other form of connection.
The invention provides a method for correcting an insulation test of a transformer based on a lightning full-wave impact test.
Specifically, 1, acquiring the influence of temperature on electrical parameters of an oil paper insulation system;
1.1, acquiring the influence of temperature on the relative dielectric constant of an oil paper insulation system;
the relative dielectric constant and the volume resistivity of the new oil and the oil-immersed paperboard of the 220kV transformer obtained by standard procedure treatment in the temperature range of-20 ℃ to +80 ℃ are measured and obtained, as shown in figure 1.
The test result shows 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 the oil-impregnated paper board, the relative dielectric constant of the oil-impregnated paper board almost shows a linear rising trend along with the rise of the 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.
1.2, acquiring the influence of temperature on the electric field distribution of the 220kV transformer;
the 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. The oil-paper combined insulation system of the transformer is a parallel combination of two dielectrics of transformer oil and impregnated paper, and the structural model of the parallel plate electrode is shown in figure 2. The applied voltage is U, the distance between electrodes is d, the dielectric constant of oil is epsilon 1, the conductivity is gamma 1, and the thickness is d 1; the paper has a dielectric constant of ε 2, an electrical conductivity of γ 2, and a thickness of d 2.
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. Analyzing the numerical value;
2.1 model building
The transformer winding middle model shown in fig. 3 is used for carrying out numerical calculation of the electric field distribution temperature characteristic of the oil paper insulation system between the high-voltage winding and the medium-voltage winding under the lightning full-wave surge test voltage, and the part parameters and the boundary conditions of the model are set as follows:
simulating main insulation electric field distribution under a standard specified lightning full-wave impact test voltage (Ut is 950kV), wherein the potential of a first line cake of an incoming line of a high-voltage winding is 950kV, and the voltage gradient among the line cakes is distributed according to 7%;
the potential of the medium-voltage winding is 0;
thirdly, because the model is used for intercepting the middle part of the high-voltage-medium-voltage winding and mainly researching the distribution characteristic of an electric field of main insulation between the high-voltage-medium-voltage winding, the upper, lower, left and right boundary surfaces of the model are the second class homogeneous boundary conditions of the electric field.
At normal temperature, or at 20 to 25 ℃, the relative dielectric constants of the oil-immersed paperboard and the transformer oil are respectively 5.2 for epsilon z and 2.11 for epsilon y, and the main insulation electric field intensity distribution and the potential distribution between the high-voltage winding and the medium-voltage winding are calculated; two paths from the outer surface of the medium voltage winding to the inner surface of the high voltage winding are taken, i.e. the line segment AB and the line segment CD in fig. 3, and the radial electric field distribution along the path AB and the path CD is shown in fig. 4.
2.2 testing the temperature characteristic of the maximum electric field intensity of the oil paper insulation under the voltage by full-wave impact of lightning;
the distribution of the main insulation electric field of the 220kV transformer under the lightning full-wave impact test voltage specified by a simulation standard is calculated through simulation, the potential of a first line cake of the incoming line of the high-voltage winding is 950kV, the maximum voltage gradient between the line cakes is calculated according to 7%, and the potentials of the medium-voltage winding and the low-voltage winding are zero. And obtaining the maximum electric field intensity temperature change characteristic of the oil paper insulation system of the 220kV transformer 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 voltage of a lightning full-wave impact test is simulated and calculated, 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 results of the calculation of the maximum electric field strength of the first oil gap on the outer surface of the middle voltage winding and the maximum electric field strength temperature variation characteristics of the first oil gap on the inner surface of the high voltage winding are shown in table 1 and fig. 5.
TABLE 1 SFSZ-180000/220 calculation result of maximum electric field intensity of transformer
The results show that: under the impact test voltage, the maximum electric field intensity of a first oil gap on the outer surface of the medium-voltage winding and the maximum electric field intensity of a first oil gap on the inner surface of the high-voltage winding are increased along with the increase of the temperature; under the same temperature, the maximum electric field intensity of the first oil gap on the inner surface of the high-voltage winding is obviously higher than that of the first oil gap on the outer surface of the medium-voltage winding, namely, under different temperatures, the maximum electric field intensity of the oil-paper composite insulation system between the high-voltage winding and the medium-voltage winding is positioned in the first oil gap on the inner surface of the high-voltage winding.
3. Insulation design and check under the voltage of the lightning full-wave impact test;
the environmental temperature of the lightning full-wave impact withstand voltage test based on the transformer is normal temperature, and the test voltage is Ut 0-950 kV.
Under the condition that the temperature is above 45 ℃, 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 lightning full-wave impact resistance test need to be considered, because the maximum electric field intensity of the first oil gap on the inner surface of the high-voltage winding is far higher than the maximum electric field intensity of the first oil gap on the outer surface of the medium-voltage winding, when the insulation margin design under the lightning full-wave impact test voltage and the equivalence analysis of the factory lightning full-wave impact resistance test are considered, only the maximum electric field intensity of the first oil gap on the inner surface of the high-voltage winding.
3.1 correction method for lightning full-wave impulse withstand voltage test
In the actual operation process of a 220kV power transformer, the temperature change range of an oil paper insulation system in the internal main insulation of the transformer is-20 ℃ to +80 ℃, and the dielectric constants of transformer oil and a paperboard change with the temperature to cause the maximum electric field intensity to change. Taking the simulation calculation results of the maximum electric field intensity of the first oil gap on the outer surface of the middle-voltage winding and the maximum electric field intensity of the first oil gap on the inner surface of the high-voltage winding in fig. 5 as an example, under the lightning full-wave impact test voltage, under the condition that the applied voltage is not changed, the maximum electric field intensity is reduced when the temperature is reduced and is increased when the temperature is increased on the basis of the normal temperature (20 ℃ to 25 ℃), namely, under the action of the lightning full-wave impact test voltage, the insulation margin and the electric intensity of the oil-paper composite insulation system are reduced along with the increase of the temperature.
Also, in consideration of the difficulty in changing the test temperature at the time of shipment from the factory, we propose to perform temperature correction of the voltage applied in the lightning full-wave surge test of the transformer. The temperature correction calculation method is as follows:
considering that the temperature which may appear inside a 220kV oil-immersed power transformer during actual operation is Tx, the equivalent lightning full-wave impact test withstand voltage which is applied when the temperature is converted to normal temperature (20 ℃ to 25 ℃) is Utx, Ut0 is the lightning full-wave test withstand voltage which is applied when the temperature inside the transformer is normal temperature (20 ℃ to 25 ℃), Kt is defined as a temperature correction coefficient, and the temperature correction coefficient is as follows: utx ═ KtUt 0;
under the action of Ut0, the maximum electric field intensity of the oil paper insulation system at normal temperature (20 ℃ to 25 ℃) is Et0, and the maximum electric field intensity of the oil paper insulation system at any temperature is Etx, then: kt Etx/Et 0;
and taking the maximum Kt value obtained by calculation within the temperature change range of the oil-paper insulation system during the actual operation of the transformer as a final lightning full-wave impact test voltage correction coefficient.
3.2 calculation of correction coefficient of Voltage in full-wave Surge withstand test
For a three-phase three-winding oil-immersed power transformer with the model of SFSZ-180000/220, the results of calculating the temperature correction coefficient Kt for the power frequency withstand voltage test according to the maximum electric field strength and the temperature variation characteristic of the paper oil insulation system between the high-voltage winding and the medium-voltage winding under the action of the voltage of the lightning full-wave surge withstand voltage test in table 2 are obtained as shown in table 2 and fig. 6.
TABLE 2 SFSZ-180000/220 Transformer temperature correction coefficient
The results show that: the temperature correction coefficient obtained by calculating according to the temperature change characteristic of the maximum electric field intensity of the high-voltage-medium-voltage inter-winding oilpaper composite insulation system under the same external impact voltage is almost linearly increased along with the increase of the temperature.
Under the actual operation condition of the transformer, the internal temperature change range is-20 ℃ to +80 ℃, so that in a factory voltage withstand test at normal temperature, the test voltage of a lightning full-wave impact voltage withstand test needs to be improved by 4 percent, and the insulation performance of the transformer under the actual operation condition can be accurately tested.
Based on the method, the invention also provides equipment for realizing the method for correcting the insulation test of the transformer based on the lightning full-wave impact test, which comprises the following steps:
the storage is used for storing a computer program and a transformer insulation test correction method based on a lightning full-wave impact test;
and the processor is used for executing the computer program and the transformer insulation test correction method based on the lightning full-wave impact test so as to realize the steps of the transformer insulation test correction method based on the lightning full-wave impact test.
Based on the method, the invention also provides a readable storage medium with the transformer insulation test correction method based on the lightning full-wave surge test, and the readable storage medium stores a computer program which is executed by a processor to realize the steps of the transformer insulation test correction method based on the lightning full-wave surge test.
The equipment of the transformer insulation test correction method based on the lightning full-wave surge test is the units and algorithm steps of each example described in combination with the embodiments disclosed herein, and can be realized by electronic hardware, computer software or a combination of the two, and in the above description, the components and steps of each example have been generally described in terms of functions in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
Through the above description of the embodiments, those skilled in the art will readily understand that the method and apparatus for correcting the insulation test of the transformer based on the lightning full-wave surge test described herein may be implemented by software, or may be implemented by software in combination with necessary hardware. Therefore, the technical solution according to the disclosed embodiment of the method for correcting the insulation test of the transformer based on the lightning full-wave surge test can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a usb disk, a mobile hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which can be a personal computer, a server, a mobile terminal, or a network device, etc.) to execute the indexing method according to the disclosed embodiment.
As will be appreciated by one skilled in the art, aspects of the transformer insulation test modification method based on the lightning full-wave surge test may be embodied as a system, method, or program product. Accordingly, various aspects of the present disclosure may be embodied in the form of: an entirely hardware embodiment, an entirely software embodiment (including firmware, microcode, etc.) or an embodiment combining hardware and software aspects that may all generally be referred to herein as a "circuit," module "or" system.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. A transformer insulation test correction method based on a lightning full-wave surge test is characterized by comprising the following steps:
the method comprises the following steps of firstly, acquiring the influence of temperature on electrical parameters of the oiled paper insulation system;
analyzing the numerical value;
2.1 establishing a model;
utilizing a transformer winding middle model to perform numerical calculation of electric field distribution temperature characteristics in an oil-paper insulation system between high-voltage windings and medium-voltage windings under the voltage of a lightning full-wave impact test;
2.2, acquiring the temperature characteristic of the maximum electric field intensity of the oil paper insulation under the lightning full-wave impact test voltage;
checking insulation design under the voltage of the lightning full-wave impact test;
3.1 a correction method based on a lightning full-wave impact voltage withstand test;
3.2, calculating a correction coefficient of the voltage of the lightning full-wave impulse withstand voltage test;
and calculating the temperature correction coefficient Kt of the power frequency withstand voltage test by the three-phase three-winding oil-immersed power transformer according to the maximum electric field intensity of the first oil gap on the inner surface of the high-voltage winding.
2. The method of claim 1,
the first step further comprises the following steps:
1.1, acquiring the influence of temperature on the relative dielectric constant of an oil paper insulation system;
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 is obtained through curve fitting;
1.2, acquiring the influence of temperature on the electric field distribution of the 220kV transformer;
under the action of alternating voltage, the electric field intensity in oil and paper is inversely proportional to the dielectric constant thereof; at different temperatures, the dielectric constants of the transformer oil and the impregnated paper are different, and the field intensity distribution in the oil-paper insulation system is changed, so that the insulation matching of the oil-paper insulation system is influenced.
3. The method of claim 1,
step 2.1 in step two further comprises:
some parameters and boundary conditions of the model are set as follows:
firstly, simulating main insulation electric field distribution under the condition that lightning full-wave impact test voltage Ut specified by a standard is 950kV, wherein the potential of a first line cake of an incoming line of a high-voltage winding is 950kV, and the voltage gradient among the line cakes is distributed according to 7%;
the potential of the medium-voltage winding is 0;
thirdly, because the model is used for intercepting the middle part of the high-voltage-medium-voltage winding and the distribution characteristic of the main insulation electric field between the high-voltage-medium-voltage winding, the upper, lower, left and right boundary surfaces of the model are the homogeneous boundary conditions of the second class of the electric field;
under the temperature of 20-25 ℃, the relative dielectric constants of the oil-immersed paperboard and the transformer oil are respectively 5.2 for epsilon z and 2.11 for epsilon y, and the electric field intensity distribution and the electric potential distribution of the main insulation between the high-voltage winding and the medium-voltage winding are calculated;
two radial electric field distributions are selected on the path from the outer surface of the medium voltage winding to the inner surface of the high voltage winding.
4. The method of claim 1,
step 2.2 in step two further comprises:
the distribution of a main insulation electric field of a 220kV transformer under a lightning full-wave impact test voltage specified by a simulation standard is calculated through simulation, the potential of a first line cake of an incoming line of a high-voltage winding is 950kV, the maximum voltage gradient between the line cakes is calculated according to 7%, and the potentials of a medium-voltage winding and a low-voltage winding are zero;
acquiring the maximum electric field intensity temperature variation characteristic of a 220kV transformer oil paper insulation system at different temperatures;
the method comprises the following steps of carrying out simulation calculation on electric field distribution of a main insulation in the middle of a high-voltage winding and a medium-voltage winding of the three-phase three-winding oil-immersed power transformer under the voltage of a lightning full-wave impact test, wherein the concentration part and the insulation weakness of the electric field 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; and calculating 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 temperature change characteristic of the first oil clearance on the inner surface of the high-voltage winding.
5. The method of claim 1,
step three, 3.1, further comprises:
in the operation process of a 220kV power transformer, the temperature change range of an oil paper insulation system in internal main insulation 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;
in the simulation calculation results 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 under the lightning full-wave impact test voltage, under the condition that the applied voltage is not changed, the temperature is reduced by taking 20-25 ℃ as a reference, the maximum electric field intensity is reduced when the temperature is reduced, the maximum electric field intensity is increased when the temperature is increased, and under the action of the lightning impact test voltage, the insulation margin and the electric strength of the oil-paper composite insulation system are reduced along with the increase of the temperature;
the temperature correction calculation method is as follows:
the temperature of the inside when 220kV oil-immersed power transformer operates is Tx, the equivalent lightning full-wave impact test withstand voltage is Utx, Ut0 is the lightning full-wave test withstand voltage that should be applied when the temperature of the inside of the transformer is 20 ℃ to 25 ℃, Kt is defined as a temperature correction coefficient, and the temperature correction coefficient is as follows: utx ═ KtUt 0;
under the action of Ut0, the maximum electric field intensity of the oil paper insulation system at 20-25 ℃ is Et0, and the maximum electric field intensity of the oil paper insulation system at any temperature is Etx, then: kt Etx/Et 0;
and taking the maximum Kt value obtained by calculation within the temperature change range of the oil-paper insulation system during the actual operation of the transformer as a final lightning full-wave impact test voltage correction coefficient.
6. The equipment for realizing the method for correcting the insulation test of the transformer based on the lightning full-wave impact test is characterized by comprising the following steps of:
the storage is used for storing a computer program and a transformer insulation test correction method based on a lightning full-wave impact test;
a processor for executing the computer program and the method for correcting the insulation test of the transformer based on the lightning full-wave surge test to realize the steps of the method for correcting the insulation test of the transformer based on the lightning full-wave surge test as claimed in any one of claims 1 to 5.
7. A readable storage medium having a lightning full-wave surge test based transformer insulation test modification method, wherein the readable storage medium has a computer program stored thereon, the computer program being executed by a processor to implement the steps of the lightning full-wave surge test based transformer insulation test modification method according to any one of claims 1 to 5.
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