Distribution transformer split-phase anti-impact load early warning method and device

Abstract

The invention discloses a distribution transformer split-phase anti-impact load early warning method and device, and belongs to the technical field of power distribution networks, and the method comprises the steps: obtaining a plurality of pieces of historical transformer data, respectively calculating the steady-state hot-spot temperature of each phase winding corresponding to each piece of historical transformer data, and constructing a temperature change curve corresponding to each phase winding; obtaining the operating age limit, the water content of insulation paper, the real-time current load coefficient of each phase and the real-time impact load duration of the to-be-detected transformer, calculating the bubble initial early warning temperature value of the to-be-detected transformer, and determining a tolerance time matrix corresponding to each phase winding in combination with each temperature change curve; and based on the real-time current load coefficient of each phase and the real-time impact load duration, obtaining the predicted maximum allowable tolerance time of each phase winding in the tolerance time matrix corresponding to each phase winding, and carrying out tolerance early warning on the to-be-detected transformer. Therefore, by implementing the method, the problem of low accuracy of anti-impact load prediction of the distribution transformer in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution networks, and in particular to a method and device for early warning of phase-splitting anti-impact load of a distribution transformer. Background Art

[0002] The shock load resistance of a distribution transformer refers to its ability to withstand short-term, drastically changing abnormal loads (i.e., shock loads) during operation without sustaining damage or significantly degrading performance. This capability is a key indicator of transformer reliability and adaptability to complex power grid environments, and is particularly crucial in industrial power distribution, rural power grids, or scenarios involving shock loads. Shock loads can cause stress on the transformer from three dimensions: electromagnetic shock, insulation shock, and thermal shock. When a distribution transformer is subjected to shock loads during normal operation, the winding temperature rises rapidly, accelerating the aging of the transformer's oil-paper insulation.

[0003] Current research on transformer shock load resistance primarily uses the differential equation method recommended by the IEC. This method treats the three-phase windings as a single equivalent, divides them into different levels using the average load factor, and specifies an allowable operating time based on this. Therefore, the differential equation method recommended by the IEC is only applicable to shock load operation under three-phase balanced conditions. For distribution transformers with varying three-phase load variations, a single load factor level and allowable operating time are insufficient to accurately characterize the distribution transformer's dynamic shock load resistance. Summary of the Invention

[0004] The present invention provides a distribution transformer phase anti-impact load early warning method and device, which can solve the problem of low accuracy in distribution transformer anti-impact load prediction in the prior art.

[0005] In order to solve the above technical problems, the present invention provides a distribution transformer phase anti-impact load early warning method, comprising:

[0006] Acquire a plurality of historical transformer data; wherein the historical transformer data includes each phase current load factor, impact load duration, transformer structural parameters and operating condition data;

[0007] Based on each of the historical transformer data, respectively calculating the steady-state hot spot temperature of each phase winding corresponding to each of the historical transformer data;

[0008] Based on the steady-state hot spot temperature of each phase winding corresponding to each of the historical transformer data, constructing a temperature change curve corresponding to each phase winding;

[0009] Obtain the operating age of the transformer under test, moisture content of the insulation paper, real-time current load factor of each phase, and real-time impact load duration;

[0010] Calculating a bubble initial warning temperature value of the transformer to be tested based on the operating years and the moisture content of the insulating paper;

[0011] Determine a tolerance time matrix corresponding to each phase winding based on the bubble start warning temperature value and each temperature change curve; wherein the elements of the tolerance time matrix include current load factor, impact load duration and maximum allowable tolerance time;

[0012] Based on the real-time current load factor of each phase and the real-time impact load duration, obtaining the predicted maximum allowable withstand time of each phase winding in the withstand time matrix corresponding to each phase winding;

[0013] According to the predicted maximum allowable tolerance time of each phase winding, a tolerance warning is issued for the transformer to be tested.

[0014] As a preferred solution, the step of calculating the steady-state hotspot temperature of each phase winding corresponding to each historical transformer data based on each historical transformer data includes:

[0015] For each historical transformer data, loss data is calculated based on the current load factor of each phase, the transformer structural parameters, and the operating condition data; wherein the loss data includes each phase winding loss, no-load loss, and tank loss;

[0016] Calculating thermal capacity data based on the transformer structural parameters; wherein the thermal capacity data includes the thermal capacity of each phase winding, the thermal capacity of the iron core, the thermal capacity of the oil tank, and the thermal capacity of the transformer oil;

[0017] Calculating thermal resistance data based on the transformer structural parameters and the operating condition data; wherein the thermal resistance data includes the convection heat transfer resistance between each phase winding and the transformer oil, the convection heat transfer resistance between the iron core and the transformer oil, the convection heat transfer resistance between the oil tank wall and the transformer oil, the convection heat transfer resistance between the oil tank wall and the external air, and the temperature coupling thermal resistance between the windings;

[0018] The steady-state hot spot temperature of each phase winding is calculated based on the impact load duration, the loss data, the heat capacity data, and the thermal resistance data.

[0019] As a preferred solution, the calculation of loss data based on the current load factor of each phase, the transformer structural parameters and the operating condition data includes:

[0020] The rated load loss is obtained from the transformer structural parameters, and the loss of each phase winding is calculated using the following formula:

[0021] P iwdn =k i 2 P cu0 i∈{1,2,3}

[0022] Where, P iwdn is the i-th phase winding loss; k i is the current load factor of phase i; P cu0 is the rated load loss;

[0023] Obtaining no-load test data from the transformer structural parameters, and determining no-load loss from loss data in the no-load test data;

[0024] The transformer box surface area is obtained from the transformer structural parameters, the solar radiation angle is obtained from the operating condition data, and the oil tank loss is calculated using the following formula:

[0025] P tank =313.9587A F (sinγ) 1.15

[0026] Where, P tank A is the fuel tank loss; F is the surface area of ​​the transformer box; γ is the solar radiation angle.

[0027] As a preferred solution, the calculation of thermal capacity data according to the transformer structural parameters includes:

[0028] Obtaining the total mass of the transformer coil, the mass of the iron core, the mass of the oil tank, the mass of the transformer oil, and the mass of the metal parts of the transformer other than the transformer coil, the iron core, and the oil tank from the transformer structural parameters;

[0029] Based on the total mass of the transformer coil, the mass of the iron core, the mass of the oil tank, the mass of the transformer oil, and the mass of the metal components of the transformer excluding the transformer coil, the iron core, and the oil tank, the following formulas are used to calculate the heat capacity of each phase winding, the heat capacity of the iron core, the heat capacity of the oil tank, and the heat capacity of the transformer oil:

[0030]

[0031] Where C 1wdn is the heat capacity of the first phase winding; C 2wdn is the heat capacity of the second phase winding; C 3wdn is the third phase winding heat capacity; m wdn is the total mass of the transformer coil; C fe is the heat capacity of the iron core; m fe is the core mass; C tank is the heat capacity of the fuel tank; m tank is the mass of the fuel tank; C oil is the heat capacity of transformer oil; m mp is the mass of metal parts in the transformer except transformer coil, iron core and oil tank; m oiFor transformer oil quality.

[0032] As a preferred solution, the calculation of thermal resistance data based on the transformer structural parameters and the operating condition data includes:

[0033] Obtaining transformer size data, insulating oil density, insulating oil thermal conductivity, insulating oil specific heat capacity, and insulating oil viscosity coefficient from the transformer structural parameters;

[0034] Acquiring instantaneous oil temperature data, instantaneous iron wire temperature data, instantaneous oil tank temperature data and instantaneous winding temperature of each phase from the operating condition data;

[0035] Based on the transformer size data, the insulating oil density, the thermal conductivity of the insulating oil, the specific heat capacity of the insulating oil, the viscosity coefficient of the insulating oil, the instantaneous oil temperature data, the instantaneous iron wire temperature data, the instantaneous oil tank temperature data, and the instantaneous temperature of each phase winding, the following formulas are used to calculate the convection heat transfer resistance between each phase winding and the transformer oil, the convection heat transfer resistance between the iron core and the transformer oil, the convection heat transfer resistance between the oil tank wall and the transformer oil, the convection heat transfer resistance between the oil tank wall and the outside air, and the temperature coupling thermal resistance between the windings:

[0036]

[0037] Where R 1wnd-oil (t) is the convection heat transfer resistance between the first phase winding and the transformer oil at time t; R 2wdn-oil (t) is the convection heat transfer resistance between the second phase winding and the transformer oil at time t; R 3wdn-oil (t) is the convection heat transfer resistance between the third-phase winding and the transformer oil at time t; R fe-oil (t) is the convection heat transfer resistance between the iron core and the transformer oil at time t; R tank-oil (t) is the convection heat transfer resistance between the tank wall and the transformer oil at time t; R tank-amb (t) is the convection heat transfer resistance between the tank wall and the external air at time t; R 1-2 (t) is the temperature coupling thermal resistance between the first phase winding and the second phase winding at time t; R 2-3 (t) is the temperature coupling thermal resistance between the second-phase winding and the third-phase winding at time t; L1 is the winding coil height; L2 is the core height; L3 is the oil tank height; L4 is the oil channel thickness between the two-phase windings; ρoil is the insulating oil density; λ oil is the thermal conductivity of the insulating oil; c oil is the specific heat capacity of insulating oil; μ oilis the viscosity coefficient of the insulating oil; l1 is the axial length of the winding; l2 is the radial length of the winding; l3 is the axial length of the iron core; l4 is the radial length of the iron core; l5 is the axial length of the inner wall of the oil tank; l6 is the radial length of the inner wall of the oil tank; l7 is the axial length of the oil tank shell; l8 is the radial length of the oil tank shell; θ 1wdn (t) is the instantaneous temperature of the first phase winding at time t; θ 2wdn (t) is the instantaneous temperature of the second phase winding at time t; θ 3wdn (t) is the instantaneous temperature of the third-phase winding at time t; θ oil (t) is the instantaneous oil temperature at time t; θ fe (t) is the instantaneous temperature of the iron wire at time t; θ tank (t) is the instantaneous tank temperature at time t.

[0038] As a preferred solution, the fourth-order Runge-Kutta method is used to solve the following differential equation to obtain the steady-state hot spot temperature of each phase winding:

[0039]

[0040] Where, P 1wdn is the first phase winding loss; P 2wdn is the second phase winding loss; P 3wdn is the third phase winding loss; P fe is the no-load loss; P tank is the fuel tank loss; C 1wdn is the heat capacity of the first phase winding; C 2wdn is the heat capacity of the second phase winding; C 3wdn is the heat capacity of the third phase winding; C fe is the heat capacity of the core; C tank is the heat capacity of the fuel tank; C oil is the heat capacity of transformer oil; R 1wnd-oil is the convection heat transfer resistance between the first phase winding and the transformer oil; R 2wdn-oil is the convection heat transfer resistance between the second phase winding and transformer oil; R 3wdn-oil is the convection heat transfer resistance between the third phase winding and transformer oil; R fe-oil is the convection heat transfer resistance between the iron core and the transformer oil; R tank-oil is the convection heat transfer resistance between the tank wall and the transformer oil; R tank-amb is the convection heat transfer resistance between the tank wall and the external air; R 1-2 is the temperature coupling thermal resistance between the first phase winding and the second phase winding; R 2-3 is the temperature coupling thermal resistance between the second phase winding and the third phase winding; θ 1wdn is the steady-state hotspot temperature of the first phase winding; θ 2wdn is the steady-state hotspot temperature of the second-phase winding; θ 3wdn is the steady-state hotspot temperature of the third-phase winding; θoil is the steady-state hotspot temperature of transformer oil; θ fe is the steady-state hot spot temperature of the wire; θ tank is the steady-state hot spot temperature of the tank.

[0041] As a preferred solution, the step of calculating the bubble initial warning temperature value of the transformer to be tested based on the operating years and the moisture content of the insulating paper includes:

[0042] Get the preset safety factor and atmospheric pressure values;

[0043] Calculating a transformer safety factor of the transformer to be tested based on the operating years and the preset safety factor;

[0044] Calculating a preliminary bubble initiation warning temperature value of the transformer to be tested based on the moisture content of the insulating paper and the atmospheric pressure value;

[0045] The preliminary bubble initiation warning temperature value is corrected based on the transformer safety factor to form a bubble initiation warning temperature value of the transformer to be tested.

[0046] As a preferred solution, the step of calculating the transformer safety factor of the transformer to be tested based on the operating years and the preset safety factor includes:

[0047] K safe =1-α×n

[0048] Where: K safe is the transformer safety factor; α is the preset safety factor; n is the operating years;

[0049] The calculating, based on the moisture content of the insulating paper and the atmospheric pressure value, a preliminary bubble initiation warning temperature value of the transformer to be tested includes:

[0050]

[0051] Where, T bubble is the initial bubble warning temperature value; W is the moisture content of the insulation paper; P is the atmospheric pressure value;

[0052] The step of correcting the preliminary bubble initial warning temperature value based on the transformer safety factor to form the bubble initial warning temperature value of the transformer to be tested includes:

[0053] T limit =K safe ×T bubble

[0054] Where, T limit is the bubble initial warning temperature value; K safe is the transformer safety factor; T bubbleIt is the preliminary bubble starting warning temperature value.

[0055] As a preferred solution, the method of providing a tolerance warning for the transformer to be tested based on the predicted maximum allowable tolerance time of each phase winding includes:

[0056] Obtain a first warning time threshold and a second warning time threshold;

[0057] respectively comparing the predicted maximum allowable tolerance time corresponding to each phase winding with the first warning time threshold and the second warning time threshold;

[0058] If the predicted maximum allowable tolerance time of a phase winding is less than the first warning time threshold, a danger warning is issued for the transformer to be tested;

[0059] If the predicted maximum allowable tolerance time of each phase winding is greater than or equal to the first warning time threshold, and the predicted maximum allowable tolerance time of one phase winding is less than the second warning time threshold, the transformer under test issues a relatively dangerous warning;

[0060] If the predicted maximum allowable tolerance time of each phase winding is greater than or equal to the second warning time threshold, no tolerance warning is performed on the transformer to be tested.

[0061] Accordingly, the present invention provides a distribution transformer phase impact load warning device, comprising: a historical data acquisition module, a steady-state temperature data calculation module, a curve construction module, a real-time data acquisition module, a warning value calculation module, a matching module, a prediction module and a warning module;

[0062] The historical data acquisition module is used to acquire a number of historical transformer data; wherein the historical transformer data includes each phase current load factor, impact load duration, transformer structural parameters and operating condition data;

[0063] The steady-state temperature data calculation module is used to calculate the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data based on each historical transformer data;

[0064] The curve construction module is used to construct a temperature change curve corresponding to each phase winding based on the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data;

[0065] The real-time data acquisition module is used to obtain the operating age of the transformer to be tested, the moisture content of the insulation paper, the real-time current load factor of each phase and the real-time impact load duration;

[0066] The warning value calculation module is used to calculate the bubble starting warning temperature value of the transformer to be tested based on the operating years and the moisture content of the insulating paper;

[0067] The matching module is used to determine the tolerance time matrix corresponding to each phase winding based on the bubble start warning temperature value and each temperature change curve; wherein the elements of the tolerance time matrix include the current load factor, the impact load duration and the maximum allowable tolerance time;

[0068] The prediction module is configured to obtain a predicted maximum allowable withstand time of each phase winding from a withstand time matrix corresponding to each phase winding based on the real-time current load factor of each phase and the real-time impact load duration;

[0069] The early warning module is used to provide a tolerance early warning for the transformer to be tested according to the predicted maximum allowable tolerance time of each phase winding.

[0070] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0071] The present invention provides a phase-by-phase anti-impact load warning method for distribution transformers. The method obtains a plurality of historical transformer data including the current load factor of each phase, the duration of the impact load, transformer structural parameters, and operating condition data; based on each historical transformer data, the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data is calculated; based on the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data, a temperature change curve corresponding to each phase winding is constructed. The temperature change curve is constructed based on historical transformer data with different load factor levels, which can characterize the anti-impact load capability of distribution transformers with different three-phase load changes. The operating age, insulation paper moisture content, real-time current load factor of each phase, and real-time impact load duration of the transformer to be tested are obtained; based on the operating age and insulation paper moisture content, the bubble start warning temperature value of the transformer to be tested is calculated; based on the bubble start warning temperature value and each temperature change curve, the tolerance time matrix corresponding to each phase winding is determined; based on the real-time current load factor of each phase and the real-time impact load duration, the predicted maximum allowable tolerance time of each phase winding is obtained from the tolerance time matrix corresponding to each phase winding; and based on the predicted maximum allowable tolerance time of each phase winding, a tolerance warning is issued for the transformer to be tested. The tolerance warning is carried out separately for each phase winding of the transformer to be tested, realizing the phase-by-phase impact load warning, thereby effectively improving the prediction accuracy of the distribution transformer's impact load. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0073] Figure 1A flow chart of an embodiment of the method for early warning of phase-splitting anti-impact load of a distribution transformer provided by the present invention;

[0074] Figure 2 A schematic structural diagram of an embodiment of a three-phase thermal circuit model of a distribution transformer provided by the present invention;

[0075] Figure 3 This is a structural schematic diagram of an embodiment of the phase-split anti-impact load early warning device for distribution transformers provided by the present invention. DETAILED DESCRIPTION

[0076] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions in this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0077] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0078] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0079] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0080] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0081] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0082] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0083] Example 1

[0084] See also Figure 1 To solve the problem of low accuracy in predicting the impact load of distribution transformers in the prior art, an embodiment of the present invention provides a phase-by-phase impact load early warning method for distribution transformers. The method includes steps 101 to 108, each of which is specifically as follows:

[0085] Step 101: Acquire a number of historical transformer data; wherein the historical transformer data includes current load factor of each phase, impulse load duration, transformer structural parameters and operating condition data.

[0086] In actual operation, the three-phase load of distribution transformers may be unbalanced, and the three-phase load factors of distribution transformers may also vary. However, the current method for studying the impact load resistance of transformers often uses a single load factor level and allowable operating time, making it difficult to accurately characterize the dynamic impact load resistance of different distribution transformers.

[0087] In this embodiment of the present invention, by acquiring historical transformer operation and maintenance data, the actual three-phase imbalance of the transformer can be collected. Therefore, by collecting historical transformer data including the current load factor of each phase, the duration of the surge load, transformer structural parameters, and operating condition data, subsequent phase-by-phase surge load warning analysis of distribution transformers can be effectively improved.

[0088] In this embodiment of the present invention, the phase current load factor in historical transformer data refers to the ratio of the actual load current of each phase winding to the rated current of that phase winding. The impact load duration refers to the time from the transformer receiving the impact load to the current moment. A transformer comprises equipment and materials such as three-phase windings, an iron core, an oil tank, and transformer oil. Transformer structural parameters include mass data, dimensions, density data, and thermal conductivity data for each device or material within the transformer. Operating condition data in historical transformer data includes current oil temperature data, iron wire temperature data, oil tank temperature data, and each phase winding temperature.

[0089] Step 102: Based on each of the historical transformer data, respectively calculate the steady-state hot spot temperature of each phase winding corresponding to each of the historical transformer data.

[0090] In this embodiment of the present invention, after acquiring historical transformer data, each historical transformer data set is analyzed to determine the steady-state hotspot temperature of each phase winding corresponding to that historical transformer data set. The steady-state hotspot temperature of each phase winding refers to the highest temperature point within each phase winding of the transformer, resulting from heat loss during stable operation. This parameter can be used to assess the insulation lifespan, safe operation capability, and reliability of the equipment.

[0091] As a preferred solution of this embodiment, based on each of the historical transformer data, respectively calculating the steady-state hot spot temperature of each phase winding corresponding to each of the historical transformer data includes:

[0092] For each historical transformer data, loss data is calculated based on the current load factor of each phase, the transformer structural parameters, and the operating condition data; wherein the loss data includes each phase winding loss, no-load loss, and tank loss;

[0093] Calculating thermal capacity data based on the transformer structural parameters; wherein the thermal capacity data includes the thermal capacity of each phase winding, the thermal capacity of the iron core, the thermal capacity of the oil tank, and the thermal capacity of the transformer oil;

[0094] Calculating thermal resistance data based on the transformer structural parameters and the operating condition data; wherein the thermal resistance data includes the convection heat transfer resistance between each phase winding and the transformer oil, the convection heat transfer resistance between the iron core and the transformer oil, the convection heat transfer resistance between the oil tank wall and the transformer oil, the convection heat transfer resistance between the oil tank wall and the external air, and the temperature coupling thermal resistance between the windings;

[0095] The steady-state hot spot temperature of each phase winding is calculated based on the impact load duration, the loss data, the heat capacity data, and the thermal resistance data.

[0096] In an embodiment of the present invention, a method for obtaining the steady-state hotspot temperature of each phase winding by analyzing historical transformer data is specifically as follows: first, based on the current load factor of each phase, the transformer structural parameters and the operating condition data in the historical transformer data, the winding loss, no-load loss and oil tank loss of each phase are calculated respectively to form loss data; then, based on the transformer structural parameters in the historical transformer data, the thermal capacity of each phase winding, the thermal capacity of the iron core, the thermal capacity of the oil tank and the thermal capacity of the transformer oil are calculated respectively to form thermal capacity data; then, based on the transformer structural parameters and the operating condition data in the historical transformer data, the convection heat transfer thermal resistance between each device in the transformer and the temperature coupling thermal resistance between each phase winding are calculated respectively to form thermal resistance data; finally, the calculated loss data, thermal capacity data and thermal resistance data, as well as the impact load duration in the historical transformer data, are combined to calculate the steady-state hotspot temperature of each phase winding through a differential equation.

[0097] As a preferred solution of this embodiment, the loss data is calculated according to the current load factor of each phase, the structural parameters of the transformer and the operating condition data, including:

[0098] The rated load loss is obtained from the transformer structural parameters, and the loss of each phase winding is calculated using the following formula:

[0099] P iwdn =k i 2 P cu0 i∈{1,2,3}

[0100] Where, P iwdn is the i-th phase winding loss; k i is the current load factor of phase i; P cu0 is the rated load loss, obtained from factory test data;

[0101] Obtaining no-load test data from the transformer structural parameters, and determining no-load loss from loss data in the no-load test data;

[0102] The transformer box surface area is obtained from the transformer structural parameters, the solar radiation angle is obtained from the operating condition data, and the oil tank loss is calculated using the following formula:

[0103] P tank =313.9587A F (sinγ) 1.15

[0104] Where, P tank A is the fuel tank loss; F is the surface area of ​​the transformer box; γ is the solar radiation angle.

[0105] In an embodiment of the present invention, the loss data includes each phase winding loss, no-load loss, and tank loss. Each phase winding loss can be calculated based on the current load factor of each phase and the rated load loss. Among them, the current load factor of each phase can be calculated based on the actual load current of each phase winding and the rated current of the phase winding. Generally, the rated current of each phase winding of the same transformer is the same. As an example, the current load factor of each phase can be calculated using the following formula:

[0106]

[0107] Where k i is the current load factor of the i-th phase; I i is the actual load current of phase i; I r is the rated current of the transformer.

[0108] The no-load loss is the loss data of the transformer during the no-load factory test. Therefore, the no-load test data at the factory can be obtained from the transformer structural parameters, and the loss data therein can be used as the no-load loss.

[0109] The tank loss is equivalent to the heat absorbed by the transformer from solar radiation. Therefore, after obtaining the transformer tank surface area from the transformer structural parameters and the solar radiation angle from the operating condition data, the tank loss can be calculated using the above formula based on the tank surface area and the solar radiation angle.

[0110] As a preferred solution of this embodiment, calculating the thermal capacity data according to the transformer structural parameters includes:

[0111] Obtaining the total mass of the transformer coil, the mass of the iron core, the mass of the oil tank, the mass of the transformer oil, and the mass of the metal parts of the transformer other than the transformer coil, the iron core, and the oil tank from the transformer structural parameters;

[0112] Based on the total mass of the transformer coil, the mass of the iron core, the mass of the oil tank, the mass of the transformer oil, and the mass of the metal components of the transformer excluding the transformer coil, the iron core, and the oil tank, the following formulas are used to calculate the heat capacity of each phase winding, the heat capacity of the iron core, the heat capacity of the oil tank, and the heat capacity of the transformer oil:

[0113]

[0114] Where C 1wdn is the heat capacity of the first phase winding; C 2wdn is the heat capacity of the second phase winding; C 3wdn is the third phase winding heat capacity; m wdn is the total mass of the transformer coil; C fe is the heat capacity of the iron core; m fe is the core mass; C tank is the heat capacity of the fuel tank; mtank is the mass of the fuel tank; C oil is the heat capacity of transformer oil; m mp is the mass of metal parts in the transformer except transformer coil, iron core and oil tank; m oi For transformer oil quality.

[0115] In the embodiments of the present invention, thermal capacity reflects an object's ability to store heat and can quantify transient thermal responses. Therefore, thermal capacity can be used as an inherent property parameter to characterize a transformer's ability to withstand shock loads. Thermal capacity is related to the mass data of the equipment. Therefore, by obtaining the mass of each device within the transformer from the transformer's structural parameters, the thermal capacity data of each device can be calculated using the aforementioned formula.

[0116] As a preferred solution of this embodiment, calculating the thermal resistance data according to the transformer structural parameters and the operating condition data includes:

[0117] Obtaining transformer size data, insulating oil density, insulating oil thermal conductivity, insulating oil specific heat capacity, and insulating oil viscosity coefficient from the transformer structural parameters;

[0118] Acquiring instantaneous oil temperature data, instantaneous iron wire temperature data, instantaneous oil tank temperature data and instantaneous winding temperature of each phase from the operating condition data;

[0119] Based on the transformer size data, the insulating oil density, the thermal conductivity of the insulating oil, the specific heat capacity of the insulating oil, the viscosity coefficient of the insulating oil, the instantaneous oil temperature data, the instantaneous iron wire temperature data, the instantaneous oil tank temperature data, and the instantaneous temperature of each phase winding, the following formulas are used to calculate the convection heat transfer resistance between each phase winding and the transformer oil, the convection heat transfer resistance between the iron core and the transformer oil, the convection heat transfer resistance between the oil tank wall and the transformer oil, the convection heat transfer resistance between the oil tank wall and the outside air, and the temperature coupling thermal resistance between the windings:

[0120]

[0121] Where R 1wnd-oil (t) is the convection heat transfer resistance between the first phase winding and the transformer oil at time t; R 2wdn-oil (t) is the convection heat transfer resistance between the second phase winding and the transformer oil at time t; R 3wdn-oil (t) is the convection heat transfer resistance between the third-phase winding and the transformer oil at time t; R fe-oil (t) is the convection heat transfer resistance between the iron core and the transformer oil at time t; R tank-oil (t) is the convection heat transfer resistance between the tank wall and the transformer oil at time t; R tank-amb (t) is the convection heat transfer resistance between the tank wall and the external air at time t; R 1-2(t) is the temperature coupling thermal resistance between the first phase winding and the second phase winding at time t; R 2-3 (t) is the temperature coupling thermal resistance between the second-phase winding and the third-phase winding at time t; L1 is the winding coil height; L2 is the core height; L3 is the oil tank height; L4 is the oil channel thickness between the two-phase windings; ρoil is the insulating oil density; λ oil is the thermal conductivity of the insulating oil; c oil is the specific heat capacity of insulating oil; μ oil is the viscosity coefficient of the insulating oil; l1 is the axial length of the winding; l2 is the radial length of the winding; l3 is the axial length of the iron core; l4 is the radial length of the iron core; l5 is the axial length of the inner wall of the oil tank; l6 is the radial length of the inner wall of the oil tank; l7 is the axial length of the oil tank shell; l8 is the radial length of the oil tank shell; θ 1wdn (t) is the instantaneous temperature of the first phase winding at time t; θ 2wdn (t) is the instantaneous temperature of the second phase winding at time t; θ 3wdn (t) is the instantaneous temperature of the third-phase winding at time t; θ oil (t) is the instantaneous oil temperature at time t; θ fe (t) is the instantaneous temperature of the iron wire at time t; θ tank (t) is the instantaneous tank temperature at time t.

[0122] In this embodiment of the present invention, the convection heat transfer resistance of each device within the transformer and the temperature coupling resistance between each phase winding serve as a bridge between the electrical load and the thermophysical process. Essentially, this simplifies the complex fluid heat transfer process into quantifiable parameters through heat transfer similarity theory. Calculating this thermal resistance data allows for precise definition of the magnitude and duration limits of shock loads, providing a foundation for assessing the transformer's ability to withstand shock loads.

[0123] In an embodiment of the present invention, the calculation of the convection heat transfer thermal resistance inside the transformer needs to be based on fluid mechanics and heat transfer theory, combined with analysis of the transformer structural parameters. Therefore, the transformer size data and the inherent property parameters of the insulating varnish are obtained from the transformer structural parameters, and combined with the above formula, the convection heat transfer thermal resistance of each device in the transformer and the temperature coupling thermal resistance between each phase winding can be calculated. Among them, the transformer size data includes the characteristic size data of each device in the transformer and the length data of each device. The characteristic size data of each device in the transformer includes the winding coil height, the core height, the oil tank height, and the oil channel thickness between the two-phase windings. The length data of each device includes the axial length and radial length of each device. The inherent property parameters of the insulating varnish include density, thermal conductivity, specific heat capacity, viscosity coefficient, etc.

[0124] As a preferred solution of this embodiment, calculating the steady-state hotspot temperature of each phase winding based on the impact load duration, the loss data, the heat capacity data, and the thermal resistance data includes:

[0125] The fourth-order Runge-Kutta method is used to solve the following differential equation to obtain the steady-state hot spot temperature of each phase winding:

[0126]

[0127] Where, P 1wdn is the first phase winding loss; P 2wdn is the second phase winding loss; P 3wdn is the third-phase winding loss; P fe is the no-load loss; P tank is the fuel tank loss; C 1wdn is the heat capacity of the first phase winding; C 2wdn is the heat capacity of the second phase winding; C 3wdn is the heat capacity of the third phase winding; C fe is the heat capacity of the core; C tank is the heat capacity of the fuel tank; C oil is the heat capacity of transformer oil; R 1wnd-oil is the convection heat transfer resistance between the first phase winding and the transformer oil; R 2wdn-oil is the convection heat transfer resistance between the second phase winding and transformer oil; R 3wdn-oil is the convection heat transfer resistance between the third phase winding and transformer oil; R fe-oil is the convection heat transfer resistance between the iron core and the transformer oil; R tank-oil is the convection heat transfer resistance between the tank wall and the transformer oil; R tank-amb is the convection heat transfer resistance between the tank wall and the external air; R 1-2 is the temperature coupling thermal resistance between the first phase winding and the second phase winding; R 2-3 is the temperature coupling thermal resistance between the second phase winding and the third phase winding; θ 1wdn is the steady-state hotspot temperature of the first phase winding; θ 2wdn is the steady-state hotspot temperature of the second-phase winding; θ 3wdn is the steady-state hotspot temperature of the third-phase winding; θ oil is the steady-state hotspot temperature of transformer oil; θ fe is the steady-state hot spot temperature of the wire; θ tank is the steady-state hot spot temperature of the tank.

[0128] In the embodiment of the present invention, the heat source of the distribution transformer is essentially the conversion of electromagnetic loss into heat energy. Since the loss power is strictly equal to the heat generation power, the loss data can be used to directly quantify the heat source intensity and evaluate the impact load resistance of the distribution transformer. Figure 2, which is a schematic diagram of an embodiment of a three-phase thermal circuit model for a distribution transformer provided by the present invention. Based on this three-phase thermal circuit model for a distribution transformer, the aforementioned differential equation can be constructed. By obtaining loss data, thermal capacity data, and thermal resistance data calculated based on historical transformer data and combining them with the duration of the impact load, the constructed differential equation can be solved to obtain the steady-state hotspot temperature of each phase winding.

[0129] Step 103: constructing a temperature change curve corresponding to each phase winding based on the steady-state hot spot temperature of each phase winding corresponding to each of the historical transformer data.

[0130] In an embodiment of the present invention, by solving the aforementioned differential equation, the steady-state hotspot temperature of each phase winding corresponding to each historical transformer data set can be obtained. Since each historical transformer data set records the current load factor and impact load duration of each phase, a mapping relationship between the current load factor of each phase, the impact load duration, and the steady-state hotspot temperature of each phase winding is constructed for each historical transformer data set, which can be stored in the form of an array. Based on the mapping relationship between the current load factor of each phase, the impact load duration, and the steady-state hotspot temperature of each phase winding, a temperature change curve corresponding to each phase winding can be constructed using multiple historical transformer data sets.

[0131] Step 104: Obtain the operating age, insulation paper moisture content, real-time phase current load factor, and real-time impact load duration of the transformer to be tested.

[0132] In this embodiment of the present invention, when performing phase-by-phase surge load warning for a transformer, the system first collects real-time data on the transformer's operating age, insulation paper moisture content, current load factor for each phase, and surge load duration. The operating age and insulation paper moisture content of the transformer determine the transformer's dynamic warning threshold; the real-time current load factor for each phase and surge load duration are used to analyze the transformer's current surge load resistance.

[0133] Step 105: Calculate the bubble initial warning temperature value of the transformer to be tested based on the operating years and the moisture content of the insulation paper.

[0134] In an embodiment of the present invention, bubbles form in the transformer oil when the transformer reaches its hottest point. Therefore, a bubble initiation warning temperature is set. When the winding temperature of the transformer under test reaches this value, an early warning is issued, effectively improving transformer operational safety. The dynamic bubble initiation warning temperature value for the transformer under test can be calculated based on the operating age of the transformer under test and the moisture content of the insulation paper. Setting a dynamic threshold effectively improves early warning accuracy.

[0135] As a preferred solution of this embodiment, the bubble initial warning temperature value of the transformer to be tested is calculated based on the operating years and the moisture content of the insulating paper, including:

[0136] Get the preset safety factor and atmospheric pressure values;

[0137] Calculating a transformer safety factor of the transformer to be tested based on the operating years and the preset safety factor;

[0138] Calculating a preliminary bubble initiation warning temperature value of the transformer to be tested based on the moisture content of the insulating paper and the atmospheric pressure value;

[0139] The preliminary bubble initiation warning temperature value is corrected based on the transformer safety factor to form a bubble initiation warning temperature value of the transformer to be tested.

[0140] As a preferred solution of this embodiment, calculating the transformer safety factor of the transformer to be tested based on the operating years and the preset safety factor includes:

[0141] K safe =1-α×n

[0142] Where: K safe is the transformer safety factor; α is the preset safety factor; n is the operating years;

[0143] The calculating, based on the moisture content of the insulating paper and the atmospheric pressure value, a preliminary bubble initiation warning temperature value of the transformer to be tested includes:

[0144]

[0145] Where, T bubble is the initial bubble warning temperature value; W is the moisture content of the insulation paper; P is the atmospheric pressure value;

[0146] The step of correcting the preliminary bubble initial warning temperature value based on the transformer safety factor to form the bubble initial warning temperature value of the transformer to be tested includes:

[0147] T limit =K safe ×T bubble

[0148] Where, T limit is the bubble initial warning temperature value; K safe is the transformer safety factor; T bubble It is the preliminary bubble starting warning temperature value.

[0149] In an embodiment of the present invention, the bubble initiation warning temperature value can be composed of two parts: one part is a preliminary bubble initiation warning temperature value calculated based on the moisture content of the insulation paper of the transformer to be tested, and the other part is a transformer safety factor calculated based on the operating life of the transformer to be tested. The transformer safety factor is used to correct the preliminary bubble initiation warning temperature value. Specifically, because atmospheric pressure affects the transformer's ability to withstand shock loads, when calculating the preliminary bubble initiation warning temperature value, not only the moisture content of the insulation paper is required, but also real-time atmospheric pressure data is required. On the other hand, because the transformer's ability to withstand shock loads gradually decreases with operating life, after pre-setting the safety factor, it is also necessary to adjust the transformer safety factor based on the operating life of the transformer to be tested. Based on the preliminary bubble initiation warning temperature value and the transformer safety factor obtained through the above analysis and calculation, a more appropriate bubble initiation warning temperature value can be dynamically obtained, thereby improving the transformer warning effect.

[0150] Step 106: Based on the bubble initial warning temperature value and each of the temperature change curves, determine the tolerance time matrix corresponding to each phase winding; wherein the elements of the tolerance time matrix include current load factor, impact load duration and maximum allowable tolerance time.

[0151] In an embodiment of the present invention, after calculating the bubble start warning temperature value corresponding to the transformer to be tested, combined with the temperature change curve constructed based on historical transformer data, the tolerance time matrix corresponding to each phase winding of the transformer can be obtained. Specifically, each point on the temperature change curve corresponds to a current load factor, a time value, and a temperature value. Therefore, based on the bubble start warning temperature value corresponding to the transformer to be tested, the corresponding current load factor and time value can be determined on the temperature change curve, and the time value is determined as the warning time. The maximum allowable tolerance time can be obtained by subtracting the impact load duration from the warning time. Therefore, based on the bubble start warning temperature value of the transformer to be tested and each temperature change curve, a tolerance time matrix containing the elements current load factor, impact load duration, and maximum allowable tolerance time can be formed.

[0152] Step 107: Based on the real-time current load factor of each phase and the real-time impact load duration, obtain the predicted maximum allowable withstand time of each phase winding from the withstand time matrix corresponding to each phase winding.

[0153] In this embodiment of the present invention, the real-time current load factor and impact load duration of each phase of the transformer under test are collected and compared with the withstand time matrix to obtain the predicted maximum allowable withstand time for each phase winding of the transformer under test. Subsequent early warning analysis can be performed based on this predicted maximum allowable withstand time.

[0154] Step 108: Performing a tolerance warning on the transformer to be tested according to the predicted maximum allowable tolerance time of each phase winding.

[0155] As a preferred solution of this embodiment, a tolerance warning is performed on the transformer to be tested according to the predicted maximum allowable tolerance time of each phase winding, including:

[0156] Obtain a first warning time threshold and a second warning time threshold;

[0157] respectively comparing the predicted maximum allowable tolerance time corresponding to each phase winding with the first warning time threshold and the second warning time threshold;

[0158] If the predicted maximum allowable tolerance time of a phase winding is less than the first warning time threshold, a danger warning is issued for the transformer to be tested;

[0159] If the predicted maximum allowable tolerance time of each phase winding is greater than or equal to the first warning time threshold, and the predicted maximum allowable tolerance time of one phase winding is less than the second warning time threshold, the transformer under test issues a relatively dangerous warning;

[0160] If the predicted maximum allowable tolerance time of each phase winding is greater than or equal to the second warning time threshold, no tolerance warning is performed on the transformer to be tested.

[0161] In an embodiment of the present invention, by setting a first warning time threshold and a second warning time threshold, three different risk levels can be divided. After the predicted maximum allowable tolerance time corresponding to each phase winding is obtained by matching, it is compared with the first warning time threshold and the second warning time threshold respectively. In the three-phase winding, if the predicted maximum allowable tolerance time of one phase winding is less than the first warning time threshold, the risk level of the transformer to be tested is determined to be the first level, and a dangerous warning is required. The corresponding warning prompt light can be set to red. In the three-phase winding, if the predicted maximum allowable tolerance time of the three-phase winding is greater than or equal to the first warning time threshold, and the predicted maximum allowable tolerance time of one phase winding is less than the second warning time threshold, the risk level of the transformer to be tested is determined to be the second level, and a relatively dangerous warning is required. The warning prompt light can be set to yellow. If the predicted maximum allowable tolerance time of each phase winding is greater than or equal to the second warning time threshold, there is no need to perform a tolerance warning on the transformer to be tested, and the warning prompt light can be green.

[0162] The implementation of the above embodiment has the following effects:

[0163] The present invention provides a phase-by-phase anti-impact load warning method for distribution transformers. The method obtains a plurality of historical transformer data including the current load factor of each phase, the duration of the impact load, transformer structural parameters, and operating condition data; based on each historical transformer data, the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data is calculated; based on the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data, a temperature change curve corresponding to each phase winding is constructed. The temperature change curve is constructed based on historical transformer data with different load factor levels, which can characterize the anti-impact load capability of distribution transformers with different three-phase load changes. The operating age, insulation paper moisture content, real-time current load factor of each phase, and real-time impact load duration of the transformer to be tested are obtained; based on the operating age and insulation paper moisture content, the bubble start warning temperature value of the transformer to be tested is calculated; based on the bubble start warning temperature value and each temperature change curve, the tolerance time matrix corresponding to each phase winding is determined; based on the real-time current load factor of each phase and the real-time impact load duration, the predicted maximum allowable tolerance time of each phase winding is obtained from the tolerance time matrix corresponding to each phase winding; and based on the predicted maximum allowable tolerance time of each phase winding, a tolerance warning is issued for the transformer to be tested. The tolerance warning is carried out separately for each phase winding of the transformer to be tested, realizing the phase-by-phase impact load warning, thereby effectively improving the prediction accuracy of the distribution transformer's impact load.

[0164] like Figure 3 As shown, based on the above method embodiment, a corresponding device embodiment is provided;

[0165] An embodiment of the present invention provides a distribution transformer phase impact load warning device, comprising: a historical data acquisition module, a steady-state temperature data calculation module, a curve construction module, a real-time data acquisition module, a warning value calculation module, a matching module, a prediction module, and a warning module;

[0166] The historical data acquisition module is used to acquire a number of historical transformer data; wherein the historical transformer data includes each phase current load factor, impact load duration, transformer structural parameters and operating condition data;

[0167] The steady-state temperature data calculation module is used to calculate the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data based on each historical transformer data;

[0168] The curve construction module is used to construct a temperature change curve corresponding to each phase winding based on the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data;

[0169] The real-time data acquisition module is used to obtain the operating age of the transformer to be tested, the moisture content of the insulation paper, the real-time current load factor of each phase and the real-time impact load duration;

[0170] The warning value calculation module is used to calculate the bubble starting warning temperature value of the transformer to be tested based on the operating years and the moisture content of the insulating paper;

[0171] The matching module is used to determine the tolerance time matrix corresponding to each phase winding based on the bubble start warning temperature value and each temperature change curve; wherein the elements of the tolerance time matrix include the current load factor, the impact load duration and the maximum allowable tolerance time;

[0172] The prediction module is configured to obtain a predicted maximum allowable withstand time of each phase winding from a withstand time matrix corresponding to each phase winding based on the real-time current load factor of each phase and the real-time impact load duration;

[0173] The early warning module is used to provide a tolerance early warning for the transformer to be tested according to the predicted maximum allowable tolerance time of each phase winding.

[0174] It can be understood that the above-mentioned device embodiment corresponds to the method embodiment of the present invention, which can implement the distribution transformer phase anti-impact load warning method provided by any of the above-mentioned method embodiments of the present invention.

[0175] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. Furthermore, in the drawings of the device embodiments provided by the present invention, the connection relationship between modules indicates that they have a communication connection, which may be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement the present invention without inventive effort.

[0176] The specific embodiments described above further illustrate the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A distribution transformer phase impact load warning method, characterized in that: include: Acquire a plurality of historical transformer data; wherein the historical transformer data includes each phase current load factor, impact load duration, transformer structural parameters and operating condition data; Based on each of the historical transformer data, respectively calculating the steady-state hot spot temperature of each phase winding corresponding to each of the historical transformer data; Based on the steady-state hot spot temperature of each phase winding corresponding to each of the historical transformer data, constructing a temperature change curve corresponding to each phase winding; Obtain the operating age of the transformer under test, moisture content of the insulation paper, real-time current load factor of each phase, and real-time impact load duration; Calculating a bubble initial warning temperature value of the transformer to be tested based on the operating years and the moisture content of the insulating paper; Determine a tolerance time matrix corresponding to each phase winding based on the bubble start warning temperature value and each temperature change curve; wherein the elements of the tolerance time matrix include current load factor, impact load duration and maximum allowable tolerance time; Based on the real-time current load factor of each phase and the real-time impact load duration, obtaining the predicted maximum allowable withstand time of each phase winding in the withstand time matrix corresponding to each phase winding; According to the predicted maximum allowable tolerance time of each phase winding, a tolerance warning is issued for the transformer to be tested.

2. The distribution transformer phase-splitting anti-impact load early warning method according to claim 1 is characterized in that: The step of calculating the steady-state hotspot temperature of each phase winding corresponding to each historical transformer data based on each historical transformer data includes: For each historical transformer data, loss data is calculated based on the current load factor of each phase, the transformer structural parameters, and the operating condition data; wherein the loss data includes each phase winding loss, no-load loss, and tank loss; Calculating thermal capacity data based on the transformer structural parameters; wherein the thermal capacity data includes the thermal capacity of each phase winding, the thermal capacity of the iron core, the thermal capacity of the oil tank, and the thermal capacity of the transformer oil; Calculating thermal resistance data based on the transformer structural parameters and the operating condition data; wherein the thermal resistance data includes the convection heat transfer resistance between each phase winding and the transformer oil, the convection heat transfer resistance between the iron core and the transformer oil, the convection heat transfer resistance between the oil tank wall and the transformer oil, the convection heat transfer resistance between the oil tank wall and the external air, and the temperature coupling thermal resistance between the windings; The steady-state hot spot temperature of each phase winding is calculated based on the impact load duration, the loss data, the heat capacity data, and the thermal resistance data.

3. The distribution transformer phase-splitting anti-impact load early warning method according to claim 2, characterized in that: The calculating of loss data according to the current load factor of each phase, the structural parameters of the transformer and the operating condition data includes: The rated load loss is obtained from the transformer structural parameters, and the loss of each phase winding is calculated using the following formula: P iwdn =k i 2 P cu0 i∈{1,2,3} Where, P iwdn is the i-th phase winding loss; k i is the current load factor of phase i; P cu0 is the rated load loss; Obtaining no-load test data from the transformer structural parameters, and determining no-load loss from loss data in the no-load test data; The transformer box surface area is obtained from the transformer structural parameters, the solar radiation angle is obtained from the operating condition data, and the oil tank loss is calculated using the following formula: P tank =313.9587A F (sinγ) 1.15 Where, P tank A is the fuel tank loss; F is the surface area of ​​the transformer box; γ is the solar radiation angle.

4. The distribution transformer phase-splitting anti-impact load early warning method according to claim 3 is characterized in that: Calculating thermal capacity data according to the transformer structural parameters includes: Obtaining the total mass of the transformer coil, the mass of the iron core, the mass of the oil tank, the mass of the transformer oil, and the mass of the metal parts of the transformer other than the transformer coil, the iron core, and the oil tank from the transformer structural parameters; Based on the total mass of the transformer coil, the mass of the iron core, the mass of the oil tank, the mass of the transformer oil, and the mass of the metal components of the transformer excluding the transformer coil, the iron core, and the oil tank, the following formulas are used to calculate the heat capacity of each phase winding, the heat capacity of the iron core, the heat capacity of the oil tank, and the heat capacity of the transformer oil: Where C 1wdn is the heat capacity of the first phase winding; C 2wdn is the heat capacity of the second phase winding; C 3wdn is the third phase winding heat capacity; m wdn is the total mass of the transformer coil; C fe is the heat capacity of the iron core; m fe is the core mass; C tank is the heat capacity of the fuel tank; m tank is the mass of the fuel tank; C oil is the heat capacity of transformer oil; m mp is the mass of metal parts in the transformer except transformer coil, iron core and oil tank; m oi For transformer oil quality.

5. The distribution transformer phase-splitting anti-impact load early warning method according to claim 4 is characterized in that: The calculating of thermal resistance data according to the transformer structural parameters and the operating condition data includes: Obtaining transformer size data, insulating oil density, insulating oil thermal conductivity, insulating oil specific heat capacity, and insulating oil viscosity coefficient from the transformer structural parameters; Acquiring instantaneous oil temperature data, instantaneous iron wire temperature data, instantaneous oil tank temperature data and instantaneous winding temperature of each phase from the operating condition data; Based on the transformer size data, the insulating oil density, the thermal conductivity of the insulating oil, the specific heat capacity of the insulating oil, the viscosity coefficient of the insulating oil, the instantaneous oil temperature data, the instantaneous iron wire temperature data, the instantaneous oil tank temperature data, and the instantaneous temperature of each phase winding, the following formulas are used to calculate the convection heat transfer resistance between each phase winding and the transformer oil, the convection heat transfer resistance between the iron core and the transformer oil, the convection heat transfer resistance between the oil tank wall and the transformer oil, the convection heat transfer resistance between the oil tank wall and the outside air, and the temperature coupling thermal resistance between the windings: Where R 1wnd-oil (t) is the convection heat transfer resistance between the first phase winding and the transformer oil at time t; R 2wdn-oil (t) is the convection heat transfer resistance between the second phase winding and the transformer oil at time t; R 3wdn-oil (t) is the convection heat transfer resistance between the third-phase winding and the transformer oil at time t; R fe-oil (t) is the convection heat transfer resistance between the iron core and the transformer oil at time t; R tank-oil (t) is the convection heat transfer resistance between the tank wall and the transformer oil at time t; R tank-amb (t) is the convection heat transfer resistance between the tank wall and the external air at time t; R 1-2 (t) is the temperature coupling thermal resistance between the first phase winding and the second phase winding at time t; R 2-3 (t) is the temperature coupling thermal resistance between the second-phase winding and the third-phase winding at time t; L1 is the height of the winding coil; L2 is the height of the iron core; L3 is the height of the oil tank; L4 is the thickness of the oil channel between the two-phase windings; ρ oil is the density of insulating oil; oil is the thermal conductivity of insulating oil; c oil is the specific heat capacity of insulating oil; μ oil is the viscosity coefficient of the insulating oil; l1 is the axial length of the winding; l2 is the radial length of the winding; l3 is the axial length of the iron core; l4 is the radial length of the iron core; l5 is the axial length of the inner wall of the oil tank; l6 is the radial length of the inner wall of the oil tank; l7 is the axial length of the oil tank shell; l8 is the radial length of the oil tank shell; θ 1wdn (t) is the instantaneous temperature of the first phase winding at time t; θ 2wdn (t) is the instantaneous temperature of the second phase winding at time t; θ 3wdn (t) is the instantaneous temperature of the third-phase winding at time t; θ oil (t) is the instantaneous oil temperature at time t; θ fe (t) is the instantaneous temperature of the iron wire at time t; θ tank (t) is the instantaneous tank temperature at time t.

6. The distribution transformer phase-splitting anti-impact load early warning method according to claim 5, characterized in that: The calculating the steady-state hot spot temperature of each phase winding based on the impact load duration, the loss data, the heat capacity data, and the thermal resistance data includes: The fourth-order Runge-Kutta method is used to solve the following differential equation to obtain the steady-state hot spot temperature of each phase winding: Where, P 1wdn is the first phase winding loss; P 2wdn is the second phase winding loss; P 3wdn is the third phase winding loss; P fe is the no-load loss; P tank is the fuel tank loss; C 1wdn is the heat capacity of the first phase winding; C 2wdn is the heat capacity of the second phase winding; C 3wdn is the heat capacity of the third phase winding; C fe is the heat capacity of the core; C tank is the heat capacity of the fuel tank; C oil is the heat capacity of transformer oil; R 1wnd-oil is the convection heat transfer resistance between the first phase winding and the transformer oil; R 2wdn-oil is the convection heat transfer resistance between the second phase winding and transformer oil; R 3wdn-oil is the convection heat transfer resistance between the third phase winding and transformer oil; R fe-oil is the convection heat transfer resistance between the iron core and the transformer oil; R tank-oil is the convection heat transfer resistance between the tank wall and the transformer oil; R tank-amb is the convection heat transfer resistance between the tank wall and the external air; R 1-2 is the temperature coupling thermal resistance between the first phase winding and the second phase winding; R 2-3 is the temperature coupling thermal resistance between the second phase winding and the third phase winding; θ 1wdn is the steady-state hotspot temperature of the first phase winding; θ 2wdn is the steady-state hotspot temperature of the second-phase winding; θ 3wdn is the steady-state hotspot temperature of the third-phase winding; θ oil is the steady-state hotspot temperature of transformer oil; θ fe is the steady-state hot spot temperature of the wire; θ tank is the steady-state hot spot temperature of the tank.

7. The distribution transformer phase-splitting anti-impact load early warning method according to claim 1, characterized in that: The calculating, based on the operating years and the moisture content of the insulating paper, a bubble initial warning temperature value of the transformer to be tested includes: Get the preset safety factor and atmospheric pressure values; Calculating a transformer safety factor of the transformer to be tested based on the operating years and the preset safety factor; Calculating a preliminary bubble initiation warning temperature value of the transformer to be tested based on the moisture content of the insulating paper and the atmospheric pressure value; The preliminary bubble initiation warning temperature value is corrected based on the transformer safety factor to form a bubble initiation warning temperature value of the transformer to be tested.

8. The distribution transformer phase-splitting anti-impact load early warning method according to claim 7, characterized in that: The step of calculating the transformer safety factor of the transformer to be tested based on the operating years and the preset safety factor includes: K safe =1-α×n Where: K safe is the transformer safety factor; α is the preset safety factor; n is the operating years; The calculating, based on the moisture content of the insulating paper and the atmospheric pressure value, a preliminary bubble initiation warning temperature value of the transformer to be tested includes: Where, T bubble is the initial bubble warning temperature value; W is the moisture content of the insulation paper; P is the atmospheric pressure value; The step of correcting the preliminary bubble initial warning temperature value based on the transformer safety factor to form the bubble initial warning temperature value of the transformer to be tested includes: T limit =K safe ×T bubb THE Where, T limit is the bubble initial warning temperature value; K safe is the transformer safety factor; T bubble It is the preliminary bubble starting warning temperature value.

9. The distribution transformer phase-splitting anti-impact load early warning method according to claim 1, characterized in that: The step of providing a tolerance warning for the transformer to be tested based on the predicted maximum allowable tolerance time of each phase winding includes: Obtain a first warning time threshold and a second warning time threshold; respectively comparing the predicted maximum allowable tolerance time corresponding to each phase winding with the first warning time threshold and the second warning time threshold; If the predicted maximum allowable tolerance time of a phase winding is less than the first warning time threshold, a danger warning is issued for the transformer to be tested; If the predicted maximum allowable tolerance time of each phase winding is greater than or equal to the first warning time threshold, and the predicted maximum allowable tolerance time of one phase winding is less than the second warning time threshold, the transformer under test issues a relatively dangerous warning; If the predicted maximum allowable tolerance time of each phase winding is greater than or equal to the second warning time threshold, no tolerance warning is performed on the transformer to be tested.

10. A distribution transformer phase impact load warning device, characterized in that: include: Historical data acquisition module, steady-state temperature data calculation module, curve construction module, real-time data acquisition module, warning value calculation module, matching module, prediction module and warning module; The historical data acquisition module is used to acquire a number of historical transformer data; wherein the historical transformer data includes each phase current load factor, impact load duration, transformer structural parameters and operating condition data; The steady-state temperature data calculation module is used to calculate the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data based on each historical transformer data; The curve construction module is used to construct a temperature change curve corresponding to each phase winding based on the steady-state hot spot temperature of each phase winding corresponding to each historical transformer data; The real-time data acquisition module is used to obtain the operating age of the transformer to be tested, the moisture content of the insulation paper, the real-time current load factor of each phase and the real-time impact load duration; The warning value calculation module is used to calculate the bubble starting warning temperature value of the transformer to be tested based on the operating years and the moisture content of the insulating paper; The matching module is used to determine the tolerance time matrix corresponding to each phase winding based on the bubble start warning temperature value and each temperature change curve; wherein the elements of the tolerance time matrix include the current load factor, the impact load duration and the maximum allowable tolerance time; The prediction module is configured to obtain a predicted maximum allowable withstand time of each phase winding from a withstand time matrix corresponding to each phase winding based on the real-time current load factor of each phase and the real-time impact load duration; The early warning module is used to provide a tolerance early warning for the transformer to be tested according to the predicted maximum allowable tolerance time of each phase winding.

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