Method for evaluating residual life of power transformer

Abstract

The invention relates to a method for evaluating the residual life of a power transformer, and the method comprises the following steps: S1, calculating the current average hot-spot temperature according to the current statistical hot-spot temperature condition of each winding of the transformer; s2, testing a dielectric loss curve of each winding of the transformer by using a DIRANA dielectric response analyzer; s3, calculating a medium accumulated damage value of the current winding; s4, calculating the current dielectric loss accumulated damage coefficient of the current winding; S5, calculating the aging coefficient of the current winding; S6, calculating the polymerization degree value of the current winding; S7, calculating the residual life of the current winding at the constant aging speed corresponding to the current temperature; and S9, selecting the minimum value in all the residual life as the final residual life of the transformer.

Description

Technical Field

[0001] This invention relates to the field of power transformer technology, and in particular to a method for assessing the remaining life of power transformers. Background Technology

[0002] Large oil-immersed transformers are crucial equipment in power systems, and their operational reliability directly impacts the safe and stable operation of the power system. Accurate assessment of the aging state and remaining life of transformer oil-paper insulation is essential for reducing transformer failure rates and developing effective maintenance strategies. Current technologies largely employ the top-layer oil temperature to determine the winding hotspot temperature, combined with the Arrhenius formula to calculate the transformer aging rate. Then, based on the duration corresponding to a specific hotspot temperature, the equivalent time of transformer life loss within that period is calculated, thus indirectly determining the transformer's remaining life.

[0003] However, current methods for assessing transformer remaining life rely on discrete points for the series of hot spot temperatures and their corresponding durations within a certain operating period. This introduces errors in calculating the equivalent time of transformer life loss during that period, and these errors increase with operating time, affecting subsequent assessments of the transformer's remaining life. Furthermore, current methods for evaluating the top oil temperature and hot spot temperatures represent a collective internal average temperature. Using these temperatures only assesses the remaining life of the overall transformer windings, not the remaining life of windings at specific voltage levels. Since the true remaining life of a transformer should be determined by the winding with the shortest remaining life, this leads to inaccurate assessments of the transformer's remaining life. Summary of the Invention

[0004] This invention provides a method for assessing the remaining life of a power transformer, in order to solve the problems of error and inaccuracy in assessing the remaining life of transformers mentioned in the background art.

[0005] This invention provides a method for assessing the remaining life of a power transformer, comprising the following steps: S1: Calculate the current average hot spot temperature based on the current statistics of the hot spot temperatures of each winding of the transformer; S2: Using the DIRANA dielectric response analyzer to test the dielectric loss of each winding of the transformer. curve; S3: Calculate the cumulative dielectric damage value of the current winding. The cumulative damage value of the medium For dielectric loss The area under the curve in the low-frequency range is used to characterize the aging condition of the transformer winding insulation paper, and its expression is: (1); S4: Considering the dielectric loss when the winding is first put into operation curve low frequency band area , the current winding current tan delta cumulative damage coefficient L is calculated, and the expression is: (2); S5: combined with Arrhenius equation, the aging coefficient of the current winding is calculated : (3) Wherein is the current average hot spot temperature; S6: using cellulose second order kinetics model, the current winding degree of polymerization value is calculated : (4) Wherein is the current transformer operating life, is the initial degree of polymerization value of transformer winding; S7: using cellulose second order kinetics model, the remaining life of the current winding under the constant aging speed corresponding to the current temperature is calculated : (5) Wherein, is the degree of polymerization value corresponding to the end of life of transformer winding; is the remaining life of transformer winding; S8: repeat steps S1-S7, and calculate the remaining life of the remaining winding in turn; S9: select the minimum value of the remaining life of all windings as the final remaining life of the transformer.

[0006] Preferably, the power transformer comprises at least one high voltage winding, medium voltage winding and low voltage winding.

[0007] Preferably, the low frequency range in step S3 is 10 -3 ~10 -1 Hz.

[0008] By adopting the above scheme, the present application has the following advantages and beneficial effects: the traditional evaluation method mainly evaluates the aging condition of the whole system winding of the transformer, thereby evaluating the overall residual life condition, however, the aging conditions of each winding of the transformer are different, and the residual life condition of the transformer should be determined by the winding with the shortest internal residual life, therefore, the traditional method has certain limitations. The present application can consider the actual aging conditions of windings of different voltage grades, accurately evaluate the aggregation degree values of different windings inside the transformer, thereby evaluating the residual life of each winding, and further comparing and determining the residual life of the transformer. The DIRANA medium response analyzer is adopted to test the medium loss curve, and the anti-interference ability is strong, and the medium loss curve data are automatically calculated to the reference temperature inside the analyzer, therefore, the evaluation conclusion is less affected by temperature, and is beneficial to the popularization and application of the method. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a flow chart of the transformer winding residual life evaluation method of the present application; Figure 2 is a medium loss curve low-frequency area S schematic diagram. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0011] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0012] In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and do not connote or imply any relative importance or any priority. Thus, a feature defined with "first", "second", etc. can implicitly or explicitly include one or more of the features. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly specified otherwise.

[0013] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0014] The preferred embodiments of the present application are described in detail below with reference to the accompanying drawings, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the protection scope of the present application is more clearly and definitely defined.

[0015] Referring to the drawings attached to the specification Figure 1 A power transformer residual life evaluation method, comprising the following steps: S1: According to the current statistical transformer winding hot spot temperature, the current average hot spot temperature is calculated; S2: Apply DIRANA medium response analyzer to test the dielectric loss of each winding of the transformer curve; S3: Refer to the drawings attached to the specification Figure 2 , the current winding medium cumulative damage value is calculated , the medium cumulative damage value is the area of the dielectric loss curve in the low frequency range (10 -3 ~10 -1 Hz), which is used to characterize the aging of the transformer winding insulation paper, and the expression is: (1); S4: Combined with the low frequency area of the dielectric loss curve of the current winding when it is just put into operation , the current dielectric loss cumulative damage coefficient L of the current winding is calculated, and the expression is: (2); S5: Combined with Arrhenius equation, the aging coefficient of the current winding is calculated: (3) wherein is the current average hotspot temperature; S6: using the cellulose second-order kinetic model, the current winding degree of polymerization value is calculated : (4) wherein is the current transformer operating age, is the initial degree of polymerization value of the transformer winding; S7: using the cellulose second-order kinetic model, the current winding residual life corresponding to the constant aging speed at the current temperature is calculated : (5) wherein, is the degree of polymerization value corresponding to the end of the life of the transformer winding; is the residual life of the transformer winding; S8: repeating steps S1-S7, the residual life corresponding to the remaining winding is calculated in turn; S9: selecting the minimum value of the residual life of all windings as the final residual life of the transformer.

[0016] The present application can consider the actual aging condition of windings of different voltage grades, accurately evaluate the degree of polymerization value of different windings in the transformer, thereby evaluate the residual life of each winding, and further compare and determine the residual life of the transformer. The DIRANA medium response analyzer is used to test the medium loss curve in the present application, which has strong anti-interference ability, and the medium loss curve data is automatically calculated to the reference temperature in the analyzer, so that the evaluation conclusion is less affected by temperature, which is conducive to the popularization and application of the method.

[0017] The above examples only illustrate the technical concept and characteristics of the present application, the purpose of which is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for assessing the remaining life of a power transformer, characterized in that, Includes the following steps: S1: Calculate the current average hot spot temperature based on the current statistics of the hot spot temperatures of each winding of the transformer; S2: Using the DIRANA dielectric response analyzer to test the dielectric loss of each winding of the transformer. curve; S3: Calculate the cumulative dielectric damage value of the current winding. The cumulative damage value of the medium For dielectric loss The area under the curve in the low-frequency range is used to characterize the aging condition of the transformer winding insulation paper, and its expression is: （1）； S4: Considering the dielectric loss when the winding is first put into operation Low-frequency area of ​​the curve Calculate the current cumulative dielectric loss damage coefficient L of the current winding, its expression is: （2）； S5: Calculate the aging factor of the current winding using the Arrhenius equation. : （3） in This represents the current average hotspot temperature; S6: Calculate the degree of polymerization of the current winding using a second-order cellulose kinetic model. : （4） in Given the current service life of the transformer, This represents the initial cohesion value of the transformer windings. S7: Using a second-order kinetic model of cellulose, calculate the remaining life of the current winding at a constant aging rate corresponding to the current temperature. : （5） in, This is the degree of cohesion value corresponding to the end of the transformer winding's life; This refers to the remaining lifespan of the transformer windings. S8: Repeat steps S1-S7 to calculate the remaining life of the other windings in turn. S9: Select the minimum value among all remaining winding lifetimes as the final remaining lifetime of the transformer.

2. The method for assessing the remaining life of a power transformer according to claim 1, characterized in that, The power transformer includes at least one high-voltage winding, a medium-voltage winding, and a low-voltage winding.

3. The method for assessing the remaining life of a power transformer according to claim 1, characterized in that, In step S3, the low-frequency range is 10. -3 ~10 -1 Hz.

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