Transformer winding hot-spot temperature calculation method and system, electronic equipment and medium

Abstract

The invention discloses a transformer winding hot-spot temperature calculation method and system, electronic equipment and a medium, and relates to the technical field of transformers. According to the method, after a hot-spot temperature calculation model meeting the IEC 354 standard is obtained to serve as an initial hot-spot temperature calculation model, the initial hot-spot temperature calculation model is corrected based on the influence of the load rate on the hot-spot temperature of the transformer winding, and a ready hot-spot temperature calculation model is obtained; and then correcting the hot-spot temperature calculation preparation model based on the influence of power flow switching on the hot-spot temperature of the transformer winding to obtain a hot-spot temperature calculation model, and finally determining the hot-spot temperature of the transformer winding based on the hot-spot temperature calculation model. Therefore, the problems that in the prior art, the hot-spot temperature of the transformer winding is monitored through an optical fiber temperature measurement technology, accuracy is not high, and arrangement is complex are solved, hot-spot temperature prediction accuracy is improved, the service life of the transformer is effectively prolonged, and operation safety of the transformer is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of transformers, and more particularly, to a method, a system, an electronic device, and a medium for calculating the hot-spot temperature of a transformer winding. Background Art

[0002] With the large-scale grid connection of new energy, its inherent randomness and volatility characteristics lead to frequent overload pressures on grid facilities. Coupled with the power electronic devices commonly equipped in new energy systems, the harmonic distortion degree of grid-connected current is further aggravated. In addition, new energy power stations are often built in remote areas, and harsh natural conditions are prone to trigger short-circuit faults. To sum up, the access of new energy may not only cause the reversal of the traditional grid power flow, that is, the step-down substation assumes the role of the step-up substation, but also introduce a large number of load-side harmonics, changing the characteristics of the fault short-circuit current. These all pose severe challenges to the safe and stable operation of the power grid and accelerate the loss of power equipment, especially transformers.

[0003] The service life of a transformer is closely related to the operating temperature of its oil-paper insulation material. However, the internal structure of the transformer is complex, and the temperature distribution is not uniform. Among them, the hot-spot area near the top of the winding, due to the significantly higher aging rate than other parts, becomes the key factor determining the overall life. Therefore, accurately monitoring and mastering the hot-spot temperature of the winding is crucial for achieving accurate life assessment and prediction. However, although the optical fiber temperature measurement technology has made some progress, due to the problems of its life and reliability not being completely solved, the current technology still faces challenges in dealing with the complexity and accuracy requirements of transformer winding hot-spot temperature monitoring. Especially when considering the comprehensive influence of thermal life and load capacity, there is an urgent need to develop a more precise and forward-looking calculation method to meet the high standards of the modern power system for the efficient, safe, and long-term operation of transformers. Summary of the Invention

[0004] The purpose of the present invention is to provide a method, a system, an electronic device, and a medium for calculating the hot-spot temperature of a transformer winding to solve the problems of low accuracy and complex layout faced by the prior art in monitoring the hot-spot temperature of a transformer winding through optical fiber temperature measurement technology.

[0005] In a first aspect, the present invention provides a method for calculating the hot-spot temperature of a transformer winding, including:

[0006] Obtaining an initial model for calculating the hot-spot temperature, where the initial model for calculating the hot-spot temperature is a hot-spot temperature calculation model that conforms to the IEC 354 standard;

[0007] Based on the influence of the load factor on the hot-spot temperature of the transformer winding, modifying the initial model for calculating the hot-spot temperature to obtain a preliminary model for calculating the hot-spot temperature;

[0008] Based on the influence of power flow switching on the hot spot temperature of the transformer winding, the preliminary model for calculating the hot spot temperature is corrected to obtain a model for calculating the hot spot temperature;

[0009] Based on the model for calculating the hot spot temperature, the hot spot temperature of the transformer winding is determined.

[0010] In a preferred embodiment, the initial model for calculating the hot spot temperature is a model that conforms to the aging mechanism of the insulation of a power transformer under power flow switching conditions.

[0011] In a preferred embodiment, the aging mechanism is the reaction rate of a chemical reaction described by a first preset formula;

[0012] Wherein, the first preset formula is:

[0013]

[0014] Wherein, v represents the reaction rate of the chemical reaction, v0 and k are constants, W a represents the activation energy of the chemical reaction, and T represents the absolute temperature.

[0015] In a preferred embodiment, the initial model for calculating the hot spot temperature is a model established based on the heat generation mechanism of the iron core and winding of a power transformer.

[0016] In a preferred embodiment, the heat generation mechanism is the loss of the power transformer described by a second preset formula;

[0017] Wherein, the second preset formula is:

[0018]

[0019] Wherein, P T represents the total loss; P NL represents the no-load loss; P LL represents the load loss; P SL represents the additional loss; represents the hysteresis loss in the iron core; represents the eddy current loss in the iron core; Bm represents the maximum value of the magnetic flux density; P R represents the winding resistance loss; P EC represents the eddy current loss in the winding; P OSL represents the stray loss.

[0020] In a preferred embodiment, the correction of the initial model for calculating the hot spot temperature of the transformer winding based on the influence of the load rate includes:

[0021] Based on the influence of the load on the hot spot temperature of the transformer winding, a constraint condition is established;

[0022] Modify the initial model for calculating the hot-spot temperature based on the said constraints;

[0023] Among them, the said constraints include:

[0024] The oil temperature within each winding of the power transformer increases linearly from bottom to top;

[0025] The temperature of each said winding increases linearly from low to high, and at the same height, the temperature difference between the temperature of the winding and the oil temperature is a constant value;

[0026] The temperature at the top of each said winding is the highest.

[0027] In a preferred embodiment, the preliminary model for calculating the hot-spot temperature includes:

[0028]

[0029] Among them, θ h represents the hot-spot temperature of the power transformer under any load; represents the real-time ambient temperature at which the power transformer operates; represents the dynamic temperature rise of the top-layer oil relative to the environment within the time interval t; represents the dynamic temperature rise of the winding hot spot relative to the top-layer oil within the time interval t.

[0030] In a preferred embodiment, the dynamic temperature rise of the top-layer oil relative to the environment within the time interval t is represented based on a third preset formula;

[0031] Among them, the third preset formula is:

[0032]

[0033] Among them, and respectively represent the initial temperature rise and the final temperature rise of the top-layer oil relative to the environment within the time interval t; τ to represents the top-layer oil time constant;

[0034] Among them, the top-layer oil time constant is:

[0035]

[0036] Among them, τ to,R represents the top-layer oil time constant under rated load; is the temperature rise of the top-layer oil relative to the environment under rated current within the time interval t; n represents the top-layer oil temperature rise calculation index of the power transformer, and when n = 1, τ to = τ to,R .

[0037] In a preferred embodiment, the dynamic temperature rise of the winding hot spot relative to the top - layer oil within the time interval t is represented based on a fourth preset formula;

[0038] Wherein, the fourth preset formula is:

[0039]

[0040] Wherein, And respectively represent the initial temperature rise and the final - state temperature rise of the winding hot spot relative to the top - layer oil in the time interval t; τ w represents the winding time constant;

[0041] Wherein, the initial temperature rise and the final - state temperature rise of the winding hot spot relative to the top - layer oil in the time interval t are respectively:

[0042]

[0043] Wherein, K t is the load factor of the power transformer within the time interval t; Δθ to,R is the temperature rise of the top - layer oil relative to the environment under the rated current; R is the ratio of the load loss to the no - load loss of the transformer under the rated current; Δθ h,R is the temperature rise of the winding hot spot relative to the top - layer oil under the rated load; m is the winding hot - spot temperature - rise calculation index of the transformer.

[0044] In a preferred embodiment, based on the influence of the power - flow switching on the temperature of the transformer winding hot spot, the preliminary hot - spot temperature calculation model is corrected, including:

[0045] Determine the harmonic current and the exciting voltage under the power - flow switching;

[0046] Determine the additional losses caused to the power transformer under the action of the harmonic current and the exciting voltage;

[0047] Based on the additional losses, determine the influence of the power - flow switching on the temperature of the transformer winding hot spot, so as to correct the preliminary hot - spot temperature calculation model.

[0048] In a preferred embodiment, the additional losses caused to the power transformer under the action of the harmonic current include: winding eddy - current loss, stray loss, and winding resistance loss;

[0049] Wherein, the winding eddy - current loss P EC , the stray loss P OSL and the winding resistance loss P R are respectively:

[0050]

[0051] Among them, P EC-O and P OSL-O respectively represent the winding eddy current loss and stray loss under the action of the fundamental current; P EC-R and P OSL-R respectively represent the winding eddy current loss and stray loss under rated operating conditions; I1 is the fundamental current; I R is the rated current; F HL-EC and F HL-OSL are respectively the winding eddy current harmonic loss factor and stray harmonic loss factor; I h(1) and I h(2) respectively represent the harmonic currents applied to the primary side and secondary side of the power transformer; R h(1) and R h(2) respectively represent the resistances of the primary side and secondary side windings of the transformer under the action of the hth harmonic current; I h(m) and R h(m) respectively represent the exciting current and exciting resistance under the action of the hth harmonic current.

[0052] In a preferred embodiment, the additional losses caused to the power transformer under the action of the excitation voltage include: the no-load loss of the power transformer;

[0053] Among them, the no-load loss P0 of the power transformer is:

[0054]

[0055] u% = u1% + u2% - u1%·u2% ≈ u1% + u2%

[0056] Among them, U N is the rated voltage of the power transformer; G T is the no-load loss coefficient of the power transformer, representing the loss value per unit voltage square; is the voltage drop on the primary side; is the voltage on the primary side; is the current on the primary side; R1 and X 1σ are respectively the resistance and leakage reactance of the primary side; u1% is the percentage voltage loss on the primary side; u2% is the percentage voltage loss on the secondary side; u% is the total percentage loss; R2 and X 2σ are respectively the resistance and leakage reactance of the secondary side; is the voltage on the secondary side; is the current on the secondary side.

[0057] In a preferred embodiment, after determining the hot-spot temperature of the transformer winding based on the hot-spot temperature calculation model, it further includes:

[0058] Determine the relative aging rate of the power transformer based on the hot-spot temperature of the transformer winding;

[0059] Determine the insulation life loss of the power transformer based on the relative aging rate;

[0060] Wherein, the relative aging rate V and the insulation life loss L are determined based on a fifth preset formula and a sixth preset formula respectively;

[0061] The fifth preset formula and the sixth preset formula are respectively:

[0062]

[0063] Wherein, θ h represents the hot-spot temperature of the transformer winding; t represents the time interval; N represents the total number of intervals of the time interval; n represents the ordinal number of the time interval.

[0064] In a second aspect, the present invention provides a system for calculating the hot-spot temperature of a transformer winding, which is used to run the method for calculating the hot-spot temperature of a transformer winding provided in the first aspect of the present invention, and includes:

[0065] An acquisition unit, configured to obtain an initial model for calculating the hot-spot temperature, and the initial model for calculating the hot-spot temperature is a hot-spot temperature calculation model that conforms to the IEC 354 standard;

[0066] A first correction unit, configured to correct the initial model for calculating the hot-spot temperature based on the influence of the load rate on the hot-spot temperature of the transformer winding, so as to obtain a preliminary model for calculating the hot-spot temperature;

[0067] A second correction unit, configured to correct the preliminary model for calculating the hot-spot temperature based on the influence of the power flow switching on the hot-spot temperature of the transformer winding, so as to obtain a model for calculating the hot-spot temperature;

[0068] A temperature determination unit, configured to determine the hot-spot temperature of the transformer winding based on the model for calculating the hot-spot temperature.

[0069] In a third aspect, the present invention provides an electronic device, and the electronic device includes:

[0070] A processor;

[0071] A memory for storing executable instructions of the processor;

[0072] The processor is configured to execute the method for calculating the hot-spot temperature of the transformer winding provided in the first aspect above.

[0073] Fourthly, the present invention provides a computer-readable storage medium storing a computer program, which when executed by a processor, implements the steps of the method provided in the first aspect of the present invention.

[0074] To achieve the above object, the method, system, electronic device and medium for calculating the hot-spot temperature of a transformer winding provided by the present invention first obtain a hot-spot temperature calculation model that conforms to the IEC 354 standard as the initial hot-spot temperature calculation model, and then correct the initial hot-spot temperature calculation model based on the influence of the load rate on the hot-spot temperature of the transformer winding to obtain a preliminary hot-spot temperature calculation model. Then, based on the influence of the power flow switching on the hot-spot temperature of the transformer winding, the preliminary hot-spot temperature calculation model is corrected to obtain a hot-spot temperature calculation model. Finally, based on the hot-spot temperature calculation model, the hot-spot temperature of the transformer winding is determined. The prediction of the hot-spot temperature of the power transformer is realized under the coexisting working conditions of forward power transmission and reverse power transmission of the power transformer, and the accuracy of the hot-spot temperature prediction is improved, thereby effectively extending the service life of the power transformer and ensuring its safe operation. Description of the Drawings

[0075] Figure 1 It is a flowchart of a method for calculating the hot-spot temperature of a transformer winding provided by an embodiment of the present invention.

[0076] Figure 2 It is a diagram showing the internal temperature distribution of a power transformer provided by an embodiment of the present invention.

[0077] Figure 3 It is a diagram showing the no-load loss test results of a power transformer provided by an embodiment of the present invention.

[0078] Figure 4 It is a diagram showing the relationship between the relative loss of insulation life and the load rate under different harmonic distortion rates provided by an embodiment of the present invention.

[0079] Figure 5 It is a structural diagram of a system for calculating the hot-spot temperature of a transformer winding provided by an embodiment of the present invention.

[0080] Figure 6 It is a schematic structural diagram of an electronic device provided by an embodiment of the present invention. Detailed Embodiments

[0081] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0082] The method for calculating the hot-spot temperature of a transformer winding provided by the present invention is executed on an electronic device, which can be a temperature predictor configured on the transformer, or a controller independent of the transformer, or an intelligent terminal device such as a laptop, a personal computer, and a tablet computer that can be connected to the transformer. Of course, in some cases, it can also be a server on the network side.

[0083] As Figure 1 shown, the method for calculating the hot-spot temperature of a transformer winding provided by an embodiment of the present invention mainly includes the following steps:

[0084] 110. Obtain an initial model for calculating the hot-spot temperature.

[0085] Among them, the initial model for calculating the hot-spot temperature is a hot-spot temperature calculation model that conforms to the IEC 354 standard.

[0086] It can be understood that the International Electrotechnical Commission (IEC for short) is the world's earliest established non-governmental international electrotechnical standardization organization and is a Class A consulting organization of the United Nations Economic and Social Council (ECOSOC). It has developed a series of standards and detailed guidelines. Among them, the hot-spot temperature calculation model recommended in the IEC 354 standard is the most basic and most widely used model in engineering practice. In this estimation model, only the load condition of the power transformer and the ambient temperature during its operation need to be obtained to calculate the estimated value of the real-time hot-spot temperature of the transformer winding during actual operation.

[0087] In an optional embodiment, the initial model for calculating the hot-spot temperature in step 110 is a model that conforms to the aging mechanism of the insulation of a power transformer under the condition of power flow switching.

[0088] Furthermore, based on the aging mechanism of the insulation of a power transformer under frequent power flow switching, the chemical reaction rate equation following the Arrhenius equation is as follows:

[0089]

[0090] In formula (1), v represents the chemical reaction rate, ν0 and k are constants, W a represents the activation energy of this chemical reaction, T represents the absolute temperature. Generally, it is considered that the higher the temperature, the faster the thermal degradation rate, the faster the aging rate of the equipment, and the shorter the remaining service life.

[0091] Even further, based on the aging mechanism of the insulation of a power transformer under frequent power flow switching, the relative aging rate and the insulation life loss formula are as follows:

[0092] Relative aging rate:

[0093]

[0094] In Formulas (2) and (3), θ h represents the hot-spot temperature of the transformer winding.

[0095] According to the above Formulas (2) and (3), the relative aging rate values of the insulating material at different hot-spot temperatures can be calculated, and the formula for calculating the insulation life loss according to the relative aging rate formula of the insulation is:

[0096]

[0097] In Formulas (4) and (5), V represents the relative aging rate at time point t; t represents the time interval, and generally the value should be less than (1 / 2)τ ω , where τ ω represents the given winding time constant of the power transformer; N represents the total number of intervals of the time interval; n represents the ordinal number of the time interval.

[0098] In an optional embodiment, the initial model for calculating the hot-spot temperature in step 110 is a model established based on the heat generation mechanism of the iron core and winding of the power transformer.

[0099] Among them, the heat generation mechanism is the loss of the power transformer described by the following Formula (6), which further includes no-load loss and load loss, that is, it is expressed as follows:

[0100]

[0101] In Formula (6), P T represents the total loss (W); P NL represents the no-load loss (W); P LL represents the load loss (W); P SL represents the additional loss (W); represents the hysteresis loss (W) in the iron core; represents the eddy current loss (W) in the iron core; B m represents the maximum value of the magnetic flux density (Wb / m 2 ); P R represents the winding resistance loss (W), which is determined by the load current and the DC resistance of the winding; P EC represents the eddy current loss (W) in the winding; P OSL represents the stray loss (W).

[0102] Specifically, the first half of Formula (6) represents the no-load loss of the power transformer, which is mainly caused by the eddy current loss and hysteresis loss of the iron core. Since the magnetization curve of the iron core has a saturation characteristic, and the manufacturer designs the B of the iron core when designing the power transformer mSet near the saturation region of the magnetization curve, resulting in that when the current in the winding increases, the B of the iron core m basically remains unchanged, and the eddy current loss and hysteresis loss in the iron core do not increase significantly either. Therefore, when the power transformer is operating normally, the heat generated by the no-load loss has a negligible impact on the hot spot temperature rise.

[0103] And the second half of formula (6) represents the load loss of the power transformer, which is mainly caused by the resistance loss P R in the winding conductor, the eddy current loss P EC and the stray loss P OSL . Among them, the heat generated by P R and P EC acts directly on the winding, thereby causing the temperature of the transformer winding to rise, while P OSL does not act on the winding, and it will cause the temperature of the oil inside the transformer to rise. Therefore, when the current in the power transformer winding increases, P R and P EC in the winding will increase, causing the hot spot temperature of the winding to rise. At the same time, P OSL also increases with the increase of the current, causing the temperature of the internal oil to rise. If there are harmonic components in the load current, due to the skin effect, P R will have an additional increase, and at the same time P EC and P OSL will also increase to some extent, so that the hot spot temperature of the winding will have an additional rise on the original basis.

[0104] 120. Based on the influence of the load factor on the hot spot temperature of the transformer winding, the initial model for calculating the hot spot temperature is corrected to obtain a preliminary model for calculating the hot spot temperature.

[0105] In an alternative embodiment, a simplified model of the internal thermal distribution of the power transformer as shown in Figure 2 given in the "Load Guide" is adopted. Based on some simplifications and assumptions made on the internal temperature distribution of the power transformer, the initial model for calculating the hot spot temperature is corrected to obtain a preliminary model for calculating the hot spot temperature.

[0106] That is, it is assumed that the oil temperature in each winding of the power transformer increases linearly from bottom to top; the winding temperature also increases linearly from bottom to top, and the growth rate of the winding temperature is the same as that of the oil temperature, that is, the difference between the winding temperature and the oil temperature at the same height from bottom to top is a constant value. And considering the influence of factors such as stray loss and oil flow, it is assumed that the temperature at the top of the winding (hot spot) is slightly higher, that is, the temperature at the top of each winding is the highest.

[0107] Furthermore, from Figure 2It can be seen that the hot-spot temperature of the power transformer under any load is composed of the ambient temperature, the top-oil temperature rise, and the winding hot-spot temperature rise, that is, the preliminary model for calculating the hot-spot temperature includes:

[0108]

[0109] In formula (7), θ h represents the hot-spot temperature of the power transformer under any load; represents the real-time ambient temperature at which the power transformer operates; represents the dynamic temperature rise of the top oil relative to the environment within the time interval t; represents the dynamic temperature rise of the winding hot spot relative to the top oil within the time interval t.

[0110] Furthermore, the dynamic temperature rise of the top oil relative to the environment within the time interval t is:

[0111]

[0112] In formula (8), and respectively represent the initial temperature rise and the final temperature rise of the top oil relative to the environment within the time interval t; τ to represents the top-oil time constant, which is shown in formula (9) as follows:

[0113]

[0114] where τ to,R represents the top-oil time constant under rated load, and its value can be provided by the transformer manufacturer; is the temperature rise of the top oil relative to the environment under rated current within the time interval t; n represents the calculation index of the top-oil temperature rise of the power transformer, usually taking values between 0.8 and 1, and when n = 1, τ to = τ to,R .

[0115] The dynamic temperature rise of the winding hot spot relative to the top oil within the time interval t can be expressed by the following formula (10):

[0116]

[0117] In formula (10), and respectively represent the initial temperature rise and the final temperature rise of the winding hot spot relative to the top oil within the time interval t; τ w represents the winding time constant, which has nothing to do with the transformer load factor and is only related to the winding material structure of the transformer. Therefore, its value can be provided by the transformer manufacturer.

[0118] Among them, the initial temperature rise and the final temperature rise of the winding hot spot relative to the top-layer oil at the time interval t are respectively:

[0119]

[0120] In formulas (11) and (12), K t is the load factor of the power transformer within the time interval t; Δθ to,R is the temperature rise of the top-layer oil relative to the environment under the rated current; R is the ratio of the load loss to the no-load loss of the transformer under the rated current; Δθ h,R is the temperature rise of the winding hot spot relative to the top-layer oil under the rated load; m is the winding hot spot temperature rise calculation index of the transformer.

[0121] 130. Based on the influence of the power flow switching on the winding hot spot temperature of the transformer, the preliminary model for calculating the hot spot temperature is corrected to obtain the hot spot temperature calculation model.

[0122] Specifically, step 130 is a hot spot temperature calculation model constructed considering the harmonic current and the exciting voltage under frequent power flow switching.

[0123] More specifically, under the action of the harmonic current and the exciting voltage, additional losses will be caused to the power transformer. The additional loss P in the power transformer winding considering the load factor and the harmonic distortion rate SL can be subdivided into the winding eddy current loss P EC and the stray loss P OSL , and the calculations of these two losses are as follows:

[0124]

[0125] In formulas (13) and (14), P EC-O and P OSL-O respectively represent the winding eddy current loss and the stray loss under the action of the fundamental current; P EC-R and P OSL-R respectively represent the winding eddy current loss and the stray loss under the rated operating conditions; I1 is the fundamental current; I R is the rated current; F HL-EC and F HL-OSL are respectively the winding eddy current harmonic loss factor and the stray harmonic loss factor, and their definitions in the IEEE standard are respectively:

[0126]

[0127] In formulas (15) and (16), h is the harmonic current order; h max is the highest harmonic current order; I h is the hth harmonic current.

[0128] Among them, the resistance per unit length r h is calculated by the formula:

[0129]

[0130] In formula (17), ω represents the operating frequency; μ represents the absolute magnetic permeability of the conductor; b represents the radius of the conductor; σ represents the conductivity; δ c represents the skin depth.

[0131] Furthermore, the expression of the winding resistance loss under the action of harmonic current is:

[0132]

[0133] In formula (18), I h(1) and I h(2) respectively represent the harmonic currents applied to the primary side and the secondary side of the transformer, R h(1) and R h(2) respectively represent the resistances of the primary side and the secondary side windings of the transformer under the action of the h-th harmonic current, I h(m) and R h(m) respectively represent the exciting current and the exciting resistance under the action of the h-th harmonic current.

[0134] Even further, according to the ratio of the harmonic resistance value of each order to the fundamental wave resistance value, by analogy with the winding eddy current harmonic loss factor and the stray harmonic loss factor, the winding resistance harmonic loss factor F HL-R is introduced as:

[0135]

[0136] Thus, the calculation of the winding resistance loss under the action of harmonic current becomes:

[0137]

[0138] In formula (20), P R-0 represents the winding resistance loss under the action of the fundamental wave current; P R-R represents the winding eddy current loss under the rated operating conditions.

[0139] Then, the load loss of the transformer under the injection of harmonic current is as follows:

[0140]

[0141] In an optional embodiment, since the no-load loss (iron loss) P0 of the transformer is proportional to the square of the voltage, increasing the operating voltage of the transformer will necessarily lead to an increase in the no-load loss, and the loss is proportional to the square of the voltage. Therefore, there is:

[0142]

[0143] u% = u1% + u2% - u1%·u2% ≈ u1% + u2% (26)

[0144] In the above formula, U N is the rated voltage of the power transformer; G T is the no-load loss coefficient of the power transformer, representing the loss value per unit voltage square; is the voltage drop on the primary side; is the voltage on the primary side; is the current on the primary side; R1 and X 1σ are the resistance and leakage reactance of the primary side respectively; u1% is the percentage voltage loss on the primary side; u2% is the percentage voltage loss on the secondary side; u% is the total percentage loss; R2 and X 2σ are the resistance and leakage reactance of the secondary side respectively; is the voltage on the secondary side; is the current on the secondary side.

[0145] From Figure 3 it can be seen that the no-load loss (iron loss) of the transformer is proportional to the square of the voltage. Increasing the operating voltage of the transformer will inevitably lead to an increase in the no-load loss. Taking a certain three-phase double-winding oil-immersed transformer as an example, the influence of the load factor and the harmonic distortion rate on the insulation life of the power transformer is analyzed. Among them, the specific parameters of this power transformer are shown in Table 1, and the given harmonic current content is shown in Table 2. Substituting the data in Table 1 and Table 2 into the previously established hot-spot temperature calculation model, the Figure 4 result graph of the relative aging rate of the transformer as shown can be obtained.

[0146] Figure 3 The following shows the relationship graph between the no-load loss (iron loss) of the transformer and the primary side voltage. From Figure 3 it can be seen that the no-load loss (iron loss) of the transformer is proportional to the square of the voltage. Increasing the operating voltage of the transformer will inevitably lead to an increase in the no-load loss.

[0147] Taking a certain three-phase double-winding oil-immersed transformer as an example, the influence of the load factor and the harmonic distortion rate on the insulation life of the power transformer is analyzed. Among them, the specific parameters of this power transformer are shown in Table 1, and the given harmonic current content is shown in Table 2. Substituting the data in Table 1 and Table 2 into the previously established hot-spot temperature calculation model, then the Figure 4 result graph of the relative aging rate of the transformer as shown can be obtained.

[0148] Table 1 Transformer parameters

[0149] Model S9-1600 / 35 Rated no-load loss / W 2100 Rated short-circuit loss / W 17550 Cooling method ONAN

[0150] Table 2 Harmonic current content of the transformer

[0151] h 1 S 7 11 13 17 19 <![CDATA[I h / I1(%)]]> 1 8.28 5.06 2.07 1.33 0.69 0.46

[0152] It can be seen from Figure 4 that the relative aging rate of the transformer increases with the increase of the load rate and the harmonic distortion rate, and the load rate has a more serious impact; in the case of heavy load or overload, within the harmonic distortion rate range shown in the figure, the relative aging rate of the reverse power transmission small harmonic is also greater than that of the forward power transmission large harmonic; the relative aging rate of the thermal life of the transformer under reverse light load is less than that of the transformer under forward heavy load; and when the load rate reaches 1.1, there is a significant increase in the insulation life loss. At the same time, when the harmonic distortion rate is relatively high, the rate of increase in insulation life loss is also relatively fast.

[0153] 140. Based on the hot spot temperature calculation model, determine the hot spot temperature of the transformer winding.

[0154] In summary, by considering the reverse of the power grid current and the influence of harmonic introduction under frequent switching of power flow, the present invention proposes a method for calculating the hot spot temperature of a transformer winding applicable to frequent switching of power flow as provided in the above embodiments. Among them, based on the analysis of the aging mechanism of power transformers, the relationship between the insulation life loss of the transformer and the hot spot temperature of the winding is obtained, and then the calculation model of the hot spot temperature of the winding is discussed. On this basis, considering the harmonic pollution problem of the transformer, the load loss of the power transformer under the injection of harmonic current is quantitatively analyzed, and the hot spot temperature calculation method provided by the IEEE standard is improved, and then a calculation model for the hot spot temperature of the transformer winding considering both the load rate and the harmonic distortion rate is established, which improves the accuracy of hot spot temperature prediction, thereby effectively extending the service life of the transformer and ensuring its safe operation.

[0155] Next, the transformer winding hot spot temperature calculation system provided by the embodiments of the present invention will be introduced. The transformer winding hot spot temperature calculation system described below can be considered as a module architecture for implementing the transformer winding hot spot temperature calculation method provided by the embodiments of the present invention; the content described below can be referred to each other with the above content.

[0156] Optionally, referring to Figure 5 , Figure 5 is a structural block diagram of a transformer winding hot spot temperature calculation system provided by an embodiment of the present invention. The system may include:

[0157] An acquisition unit 10, configured to obtain an initial hot spot temperature calculation model, where the initial hot spot temperature calculation model is a hot spot temperature calculation model that conforms to the IEC354 standard;

[0158] A first correction unit 20, configured to correct the initial hot spot temperature calculation model based on the influence of the load rate on the hot spot temperature of the transformer winding to obtain a preliminary hot spot temperature calculation model;

[0159] The second correction unit 30 is configured to correct the preliminary model for calculating the hot-spot temperature of the transformer winding based on the influence of the power flow switching on the hot-spot temperature, so as to obtain the model for calculating the hot-spot temperature;

[0160] The temperature determination unit 40 is configured to determine the hot-spot temperature of the transformer winding based on the model for calculating the hot-spot temperature.

[0161] Optionally, the initial model for calculating the hot-spot temperature is a model that conforms to the aging mechanism of the insulation of the power transformer under the power flow switching condition.

[0162] Optionally, the initial model for calculating the hot-spot temperature is a model established based on the heat generation mechanisms of the iron core and winding of the power transformer.

[0163] Optionally, correcting the initial model for calculating the hot-spot temperature based on the influence of the load rate on the hot-spot temperature of the transformer winding includes:

[0164] Establishing a constraint condition based on the influence of the load on the hot-spot temperature of the transformer winding;

[0165] Correcting the initial model for calculating the hot-spot temperature based on the constraint condition;

[0166] Wherein, the constraint condition includes:

[0167] The oil temperature in each winding of the power transformer increases linearly from bottom to top;

[0168] The temperatures of the windings increase linearly from low to high, and at the same height, the temperature difference between the winding temperature and the oil temperature is a constant value;

[0169] The temperature at the top of each winding is the highest.

[0170] Optionally, correcting the preliminary model for calculating the hot-spot temperature based on the influence of the power flow switching on the hot-spot temperature of the transformer winding includes:

[0171] Determining the harmonic current and the exciting voltage under the power flow switching;

[0172] Determining the additional losses caused to the power transformer under the action of the harmonic current and the exciting voltage;

[0173] Determining the influence of the power flow switching on the hot-spot temperature of the transformer winding based on the additional losses, so as to correct the preliminary model for calculating the hot-spot temperature.

[0174] Optionally, the additional losses caused to the power transformer under the action of the harmonic current include: winding eddy current losses, stray losses, and winding resistance losses.

[0175] Optionally, the additional losses caused to the power transformer under the action of the exciting voltage include: no-load losses of the power transformer.

[0176] Optionally, after determining the hot-spot temperature of the transformer winding based on the hot-spot temperature calculation model, it further includes:

[0177] Determine the relative aging rate of the power transformer based on the hot-spot temperature of the transformer winding;

[0178] Determine the insulation life loss of the power transformer based on the relative aging rate.

[0179] Next, with reference to Figure 6 to describe the electronic device provided by the embodiment of the present application. The electronic device provided by this embodiment may include: at least one processor 100, at least one communication interface 200, at least one memory 300, and at least one communication bus 400;

[0180] In the embodiment of the present invention, the number of the processor 100, the communication interface 200, the memory 300, and the communication bus 400 is at least one, and the processor 100, the communication interface 200, and the memory 300 complete mutual communication through the communication bus 400; Obviously, Figure 6 The communication connection schematic diagram of the shown processor 100, communication interface 200, memory 300, and communication bus 400 is only optional;

[0181] Optionally, the communication interface 200 may be an interface of a communication module, such as an interface of a GSM module; the processor 100 may be a central processing unit CPU, or a specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0182] The memory 300 may include a high-speed RAM memory, and may also include a non-volatile memory, such as at least one disk memory.

[0183] Among them, the processor 100 is specifically configured to execute the application program in the memory to implement the steps of the above-mentioned method for calculating the hot-spot temperature of the transformer winding.

[0184] In addition, the embodiment of the present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the method for calculating the hot-spot temperature of the transformer winding provided by the above-mentioned various methods.

[0185] The above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for calculating the hot-spot temperature of a transformer winding, characterized in that, Including: Obtain an initial model for calculating the hot-spot temperature, where the initial model for calculating the hot-spot temperature is a hot-spot temperature calculation model that complies with IEC 354 standard; Based on the influence of the load rate on the hot-spot temperature of the transformer winding, correct the initial model for calculating the hot-spot temperature to obtain a preliminary model for calculating the hot-spot temperature; Based on the influence of the power flow switching on the hot-spot temperature of the transformer winding, correct the preliminary model for calculating the hot-spot temperature to obtain a model for calculating the hot-spot temperature; Based on the model for calculating the hot-spot temperature, determine the hot-spot temperature of the transformer winding.

2. The method for calculating the hot-spot temperature of a transformer winding according to claim 1, wherein The initial model for calculating the hot-spot temperature is a model that conforms to the aging mechanism of the insulation of the power transformer under the power flow switching condition.

3. The method for calculating the hot spot temperature of a transformer winding according to claim 2, characterized in that, The aging mechanism is the chemical reaction rate described by a first preset formula; Wherein, the first preset formula is: Among them, v represents the reaction rate of a chemical reaction, v0 and k are constants, W a represents the activation energy of the said chemical reaction, and T represents the absolute temperature.

4. The method for calculating the hot-spot temperature of a transformer winding according to claim 1, characterized in that, The initial model for calculating the hot-spot temperature is a model established based on the heat generation mechanism of the iron core and winding of the power transformer.

5. The method for calculating the hot-spot temperature of a transformer winding according to claim 4, characterized in that, The heat generation mechanism is the loss of the power transformer described by a second preset formula; Wherein, the second preset formula is: Among them, P T represents the total loss; P NL represents the no-load loss; P LL represents the load loss; P SL represents the additional loss; represents the hysteresis loss in the iron core; represents the eddy current loss in the iron core; Bm represents the maximum value of the magnetic flux density; P R represents the winding resistance loss; P EC represents the eddy current loss in the winding; P OSL represents the stray loss.

6. The method for calculating the hot spot temperature of a transformer winding according to claim 1, characterized in that, The correction of the initial model for calculating the hot-spot temperature based on the influence of the load rate on the hot-spot temperature of the transformer winding includes: Establish a constraint condition based on the influence of the load on the hot-spot temperature of the transformer winding; Based on the constraint condition, correct the initial model for calculating the hot-spot temperature; Wherein, the constraint condition includes: The oil temperature in each winding of the power transformer increases linearly from bottom to top; The temperature of each winding increases linearly from low to high, and at the same height, the temperature difference between the winding temperature and the oil temperature is a constant value; The temperature at the top of each winding is the highest.

7. The method for calculating the hot-spot temperature of a transformer winding according to claim 6, wherein The preliminary model for calculating the hot-spot temperature includes: Among them, θ h represents the hot spot temperature of the power transformer under any load; represents the real-time ambient temperature at which the power transformer operates; represents the dynamic temperature rise of the top-layer oil relative to the environment within the time interval t; represents the dynamic temperature rise of the winding hot spot relative to the top-layer oil within the time interval t.

8. The method for calculating the hot spot temperature of a transformer winding according to claim 7, characterized in that, Express the dynamic temperature rise of the top-layer oil relative to the environment within the time interval t based on a third preset formula; Wherein, the third preset formula is: wherein, and respectively represent the initial temperature rise and the final temperature rise of the top-layer oil relative to the environment within the time interval t; τ to represents the top-layer oil time constant; Wherein, the top-layer oil time constant is: Among them, τ to,R represents the top oil time constant under rated load; is the temperature rise of the top oil relative to the environment under rated current within the time interval t; n represents the calculation index of the top oil temperature rise of the power transformer, and when n = 1, τ to = τ to,R .

9. The method for calculating the hot spot temperature of a transformer winding according to claim 7, characterized in that, Express the dynamic temperature rise of the winding hot spot relative to the top-layer oil within the time interval t based on a fourth preset formula; Wherein, the fourth preset formula is: Among them, and respectively represent the initial temperature rise and the final temperature rise of the hot spot of the winding relative to the top-layer oil of the time interval t; τ w represents the winding time constant. Wherein, the initial temperature rise and final temperature rise of the winding hot spot relative to the top-layer oil in the time interval t are respectively: Among them, K t is the load rate of the power transformer within the time interval t; R is the ratio of the load loss to the no-load loss of the transformer under the rated current; is the temperature rise of the winding hot spot relative to the top-layer oil under the rated load within the time interval t; m is the winding hot spot temperature rise calculation index of the transformer.

10. The method for calculating the hot spot temperature of a transformer winding according to claim 1, characterized in that The correction of the preliminary model for calculating the hot-spot temperature based on the influence of the power flow switching on the hot-spot temperature of the transformer winding includes: Determine the harmonic current and exciting voltage under the power flow switching; Determine the additional loss caused to the power transformer under the action of the harmonic current and the exciting voltage; Based on the additional loss, determine the influence of the power flow switching on the hot-spot temperature of the transformer winding to correct the preliminary model for calculating the hot-spot temperature.

11. The method for calculating the hot spot temperature of a transformer winding according to claim 10, characterized in that, The additional loss caused to the power transformer under the action of the harmonic current includes: winding eddy current loss, stray loss and winding resistance loss; Among them, the winding eddy current loss \(P\) EC , the stray loss \(P\) OSL and the winding resistance loss \(P\) R are respectively:[[]]END]] Among them, P EC-O and P OSL-O respectively represent the winding eddy current loss and stray loss under the action of the fundamental current; P EC-R and P OSL-R respectively represent the winding eddy current loss and stray loss under rated operating conditions; I1 is the fundamental current; I R is the rated current; F HL-EC and F HL-OSL are the winding eddy current harmonic loss factor and stray harmonic loss factor respectively; I h(1) and I h(2) respectively represent the harmonic currents applied to the primary and secondary sides of the power transformer; R h(1) and R h(2) respectively represent the resistances of the primary and secondary side windings of the transformer under the action of the h - th harmonic current; I h(m) and R h(m) respectively represent the exciting current and exciting resistance under the action of the h - th harmonic current.

12. The method for calculating the hot spot temperature of a transformer winding according to claim 10, wherein The additional loss caused to the power transformer under the action of the exciting voltage includes: no-load loss of the power transformer; Wherein, the no-load loss P0 of the power transformer is: u%=u1%+u2%-u1%·u2%≈u1%+u2% Among them, U N is the rated voltage of the power transformer; G T is the no-load loss coefficient of the power transformer, representing the loss value per unit voltage squared; is the voltage drop on the primary side; is the voltage on the primary side; is the primary side current; R1 and X 1σ are the resistance and leakage reactance of the primary side respectively; u1% is the percentage voltage loss on the primary side; u2% is the percentage voltage loss on the secondary side; u% is the total percentage loss; R2 and X 2σ are the resistance and leakage reactance of the secondary side respectively; is the voltage on the secondary side; is the secondary side current.

13. The method for calculating the hot spot temperature of a transformer winding according to any one of claims 1 to 12, characterized in that, After determining the hot-spot temperature of the transformer winding based on the model for calculating the hot-spot temperature, it further includes: Determine the relative aging rate of the power transformer based on the hot-spot temperature of the transformer winding; Determine the insulation life loss of the power transformer based on the relative aging rate; Wherein, the relative aging rate V and the insulation life loss L are determined based on a fifth preset formula and a sixth preset formula respectively; The fifth preset formula and the sixth preset formula are respectively: Among them, θ h represents the hot spot temperature of the transformer winding; t represents the time interval; N represents the total number of intervals of the time interval; n represents the ordinal number of the time interval.

14. A transformer winding hot-spot temperature calculation system for operating the transformer winding hot-spot temperature calculation method according to any one of claims 1-13, characterized in that, Including: An acquisition unit, configured to obtain an initial hot-spot temperature calculation model, where the initial hot-spot temperature calculation model is a hot-spot temperature calculation model that conforms to the IEC354 standard; A first correction unit, configured to correct the initial hot-spot temperature calculation model based on the influence of the load rate on the hot-spot temperature of the transformer winding, and obtain a preliminary hot-spot temperature calculation model; A second correction unit, configured to correct the preliminary hot-spot temperature calculation model based on the influence of the power flow switching on the hot-spot temperature of the transformer winding, and obtain a hot-spot temperature calculation model; A temperature determination unit, configured to determine the hot-spot temperature of the transformer winding based on the hot-spot temperature calculation model.

15. An electronic device, characterized in that, The electronic device includes: A processor; A memory for storing instructions executable by the processor; The processor is configured to execute the method for calculating the hot-spot temperature of the transformer winding according to any one of claims 1 to 13 above.

16. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, the steps of the method for calculating the hot-spot temperature of the transformer winding according to any one of claims 1 to 13 are implemented.

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