Evaluation method for circumferential heat dissipation uniformity degree of dry-type traction transformer winding

Abstract

The invention discloses a method for evaluating the circumferential heat dissipation uniformity of a dry-type traction transformer winding. Comprising the following steps: establishing a dry-type traction transformer winding circumferential heat dissipation uniformity degree test platform, obtaining air duct inlet air speed and air duct outlet temperature data at a low air speed, obtaining air duct inlet air speed and air duct outlet temperature data at a high air speed, calculating a circumferential heat dissipation uniformity coefficient at the low air speed, and calculating the circumferential heat dissipation uniformity degree of the dry-type traction transformer winding. And calculating a circumferential heat dissipation uniformity coefficient at a high wind speed, calculating a winding circumferential heat dissipation uniformity degree evaluation coefficient, and evaluating the circumferential heat dissipation uniformity degree of the dry traction transformer winding. The method has the beneficial effects that the heat dissipation capability and the temperature distribution difference of the dry-type traction transformer winding in the circumferential direction are effectively evaluated, and a new method is provided for rationality judgment of a design scheme of a cylindrical winding cooled by train running air; therefore, technical support is provided for optimization design of a winding heat dissipation structure, improvement of cooling performance and improvement of the space structure utilization rate.

Description

Technical Field

[0001] The invention relates to the field of online detection and fault diagnosis of electrical insulation, and in particular to a method for evaluating the uniformity of circumferential heat dissipation of a dry-type traction transformer winding. Background Art

[0002] The traction transformer is a key device in the electric traction system of the EMU, which is used to convert the high-voltage electric energy of the contact network into low-voltage electric energy that can be used by the traction converter. The traditional EMU traction transformer is an oil-immersed transformer with the disadvantage of being heavy. In recent years, as the EMU is developing towards a higher speed level of 400km / h, the lightweight of on-board electrical equipment has attracted widespread attention from researchers. The dry-type traction transformer completely removes the components with a relatively large weight, such as the insulating oil, oil tank, and radiator, in the traditional EMU traction transformer. By introducing the running wind generated by the EMU into the traction transformer air duct for direct cooling, a significant weight reduction of on-board electrical equipment is achieved. Heat dissipation design is the focus of transformer design work, because temperature is the primary factor affecting insulation aging and degradation. Improper heat dissipation design will cause the internal insulation to age rapidly or even be damaged, which will lead to serious accidents, threatening the personal safety of passengers and causing extremely bad social impacts. The heat dissipation of traditional oil-immersed traction transformers relies on the convection heat transfer of insulating oil in the oil channel. Driven by the oil pump, the insulating oil flows evenly through the surface of the winding through the diverter device at the clamp, so that the winding can obtain uniform and stable cooling performance, and the overall temperature is relatively uniform. However, for dry-type traction transformers that use running air for direct cooling, the flow stability of the cooling airflow before entering the air duct is poor and the randomness is high. It is difficult to evenly distribute it to each independent air duct in the circumferential direction, which puts forward higher requirements on the size design of the winding and the air duct. The uneven airflow distribution caused by poor design will aggravate the unevenness of the winding temperature distribution, and it is easy to develop local severe overheating areas that endanger the safe operation of the dry-type traction transformer. Therefore, before the dry-type traction transformer is put into operation, it is necessary to carry out a test on the uniformity of the circumferential heat dissipation of the winding to determine whether the heat dissipation design is reasonable. At present, there is no means to evaluate the heat dissipation design of dry-type traction transformers in EMUs. It is necessary to propose a test method for the uniformity of circumferential heat dissipation of dry-type traction transformer windings, and to propose evaluation indicators that can be used to evaluate the heat dissipation capacity of the windings in the circumferential direction and the difference in temperature distribution, so as to minimize the consumption of manpower and material resources during the test process, and help to reduce the weight of on-board electrical equipment of high-speed EMUs and their safe operation. Summary of the invention

[0003] In view of the above technical problems, the purpose of the present invention is to propose a method for evaluating the uniformity of circumferential heat dissipation of dry-type traction transformer windings, which can effectively evaluate the heat dissipation capacity and temperature distribution differences of dry-type traction transformer windings in the circumferential direction.

[0004] The technical solution for achieving the purpose of the present invention is as follows:

[0005] The first step is to establish a test platform for the uniformity of circumferential heat dissipation of dry-type traction transformer windings

[0006] The circumferential heat dissipation uniformity test platform of the dry-type traction transformer winding comprises: a large diameter cylindrical winding (1), a small diameter cylindrical winding (2), a stay (3), a winding support (4), a large diameter cylindrical winding lead-out terminal 1 (5), a large diameter cylindrical winding lead-out terminal 2 (6), a small diameter cylindrical winding lead-out terminal 1 (7), a small diameter cylindrical winding lead-out terminal 2 (8), a short-circuit wire (9), an adjustable DC power supply (10), an air duct inlet air velocity sensor (11), an air duct outlet air temperature sensor (12), a data acquisition terminal (13), a variable frequency axial flow fan (14), and a fan outlet wind velocity sensor (15);

[0007] The large diameter cylindrical winding (1) is located at the outermost side of the test device, and the small diameter cylindrical winding (2) is coaxially mounted inside the large diameter cylindrical winding (1). A support bar (3) is inserted between the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) to stably fix the small diameter cylindrical winding (2) inside the large diameter cylindrical winding (1), and to form a plurality of winding air ducts that are located between the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) and are independent of each other, wherein the air duct opening facing the variable frequency axial flow fan (14) is the air duct inlet, and the air duct opening at the other end is the air duct outlet; each air duct inlet is equipped with an air duct inlet air velocity sensor A sensor (11) is provided at each air duct outlet, and an air duct outlet air temperature sensor (12) is installed at each air duct outlet. All air duct inlet air velocity sensors (11) and air duct outlet air temperature sensors (12) are connected to a data acquisition terminal (13) for collecting air velocity at all air duct inlets and air temperature at all air duct outlets. The large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) are both formed by winding conductors wound in a single turn and in a single direction. The two ends of the winding conductor of the large diameter cylindrical winding (1) are respectively led to large diameter cylindrical winding lead-out terminals 1 (5) and large diameter cylindrical winding lead-out terminals 2 (6), and the winding conductor of the small diameter cylindrical winding (2) is respectively led to a large diameter cylindrical winding lead-out terminal 1 (5) and a large diameter cylindrical winding lead-out terminal 2 (6). A small diameter cylindrical winding lead-out terminal 1 (7) and a small diameter cylindrical winding lead-out terminal 2 (8) are respectively led out from both ends of the body; the adjustable DC power supply (10) is used to make the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) generate heat under the action of DC current to simulate the winding copper loss during the operation of the dry traction transformer; the large diameter cylindrical winding lead-out terminal 1 (5) is connected to the negative output of the adjustable DC power supply (10), the small diameter cylindrical winding lead-out terminal 1 (7) is connected to the positive output of the adjustable DC power supply (10), and the large diameter cylindrical winding lead-out terminal 2 (6) and the small diameter cylindrical winding lead-out terminal 2 (8) are connected via a short-circuit wire (9) , so that the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) form a series relationship; a winding bracket (4) is provided below the large diameter cylindrical winding (1) to support the test platform winding part formed by the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2), and the length of the winding part is L, in meters; the center height of the fan blade of the variable frequency axial flow fan (14) is consistent with the center height of the test platform winding part, and is used to provide a variable speed airflow required for cooling the dry traction transformer; a fan outlet wind speed sensor (15) is provided at the outlet of the variable frequency axial flow fan, and is connected to the data acquisition terminal (13) to monitor the wind speed at the fan outlet;

[0008] Step 2: Obtain the duct inlet wind speed and duct outlet temperature data at low wind speed

[0009] Start the variable frequency axial flow fan (14), and set the fan outlet wind speed to v according to the wind speed monitoring data of the fan outlet wind speed sensor (15). low , v low ∈(1,5], the unit is m / s; start the adjustable DC power supply (10), and apply the rated loss value of the winding to the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) at the same time, which is recorded as P loss , with the unit of W; the number of the braces (3) is recorded as N, the number of the air ducts, the number of the air duct inlets and the number of the air duct outlets formed thereby are all N, the number of the air velocity sensors (11) at the air duct inlet and the number of the air temperature sensors (12) at the air duct outlet are also N; the N wind speed data monitored by the air velocity sensors (11) at all the air duct inlets are obtained through the data acquisition terminal (13), recorded as v in-low-n , where n is 1, 2, 3, ..., N; when the fluctuation degree of the monitored temperature data of all the air duct outlet air temperature sensors (12) is less than 1°C / h, N temperature data are obtained through the data acquisition terminal (13), which is recorded as T out-low-n , where n is 1, 2, 3, …, N;

[0010] Step 3: Obtain the duct inlet wind speed and duct outlet temperature data at high wind speed

[0011] The output of the adjustable DC power supply (10) is kept unchanged, so that the applied value of the winding loss is the same as that in the second step. On this basis, the speed of the variable frequency axial flow fan (14) is increased, and the fan outlet wind speed is increased to v according to the wind speed monitoring data of the fan outlet wind speed sensor (15). high , v high ∈(5,10], the unit is m / s; the N wind speed data monitored by the air speed sensors (11) at the inlet of all air ducts are obtained through the data acquisition terminal (13), which is recorded as v in-high-n , where n is 1, 2, 3, ..., N; when the fluctuation degree of the monitored temperature data of all the air duct outlet air temperature sensors (12) is less than 1°C / h, N temperature data are obtained through the data acquisition terminal (13), which is recorded as T out-high-n , where n is 1, 2, 3, …, N;

[0012] Step 4: Calculate the circumferential heat dissipation uniformity coefficient C at low wind speed L

[0013]

[0014] Step 5: Calculate the circumferential heat dissipation uniformity coefficient C under high wind speed H

[0015]

[0016] Step 6: Calculate the evaluation coefficient S of the circumferential heat dissipation uniformity of the winding

[0017] S=(C L +C H ) 2 / 3

[0018] Step 7: Evaluate the uniformity of circumferential heat dissipation of dry-type traction transformer windings

[0019] If S<5, the circumferential heat dissipation uniformity of the dry-type traction transformer winding is good, and the design scheme can meet the engineering requirements; if S≥5, the circumferential heat dissipation uniformity of the dry-type traction transformer winding is poor, and the design scheme has a greater risk of overheating and needs further improvement.

[0020] The beneficial effect of the present invention is that a method for evaluating the uniformity of circumferential heat dissipation of a dry-type traction transformer winding has the following advantages:

[0021] 1) The present invention proposes for the first time an evaluation index for the circumferential heat dissipation uniformity of the winding, which takes into account the cooling effects of high-speed and low-speed wind speeds, and uses the wind speed at the air duct inlet as the entry point. This can effectively evaluate the heat dissipation capacity and temperature distribution differences of the dry-type traction transformer winding in the circumferential direction, and provide a new method for judging the rationality of the design scheme of the cylindrical winding cooled by the running wind of the train, thereby providing technical support for the optimal design of the winding heat dissipation structure, the improvement of cooling performance and the improvement of the space structure utilization rate;

[0022] 2) Compared with the blindness and repetitiveness of traditional transformer winding thermal performance tests, the method proposed in the present invention can effectively improve the work efficiency in the transformer winding structure design stage and reduce the consumption of manpower and material resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention relates to a flow chart of a method for evaluating the uniformity of circumferential heat dissipation of a dry-type traction transformer winding;

[0024] Figure 2 The invention discloses a structural schematic diagram of a dry-type traction transformer winding circumferential heat dissipation uniformity test platform. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and specific implementation processes. It should be emphasized that the specific implementation cases described herein are only used to explain the present invention and do not limit the scope of the present invention and its claims.

[0026] The first step is to establish a test platform for the uniformity of circumferential heat dissipation of dry-type traction transformer windings

[0027] The circumferential heat dissipation uniformity test platform of the dry-type traction transformer winding comprises: a large diameter cylindrical winding (1), a small diameter cylindrical winding (2), a stay (3), a winding support (4), a large diameter cylindrical winding lead-out terminal 1 (5), a large diameter cylindrical winding lead-out terminal 2 (6), a small diameter cylindrical winding lead-out terminal 1 (7), a small diameter cylindrical winding lead-out terminal 2 (8), a short-circuit wire (9), an adjustable DC power supply (10), an air duct inlet air velocity sensor (11), an air duct outlet air temperature sensor (12), a data acquisition terminal (13), a variable frequency axial flow fan (14), and a fan outlet wind velocity sensor (15);

[0028] The large diameter cylindrical winding (1) is located at the outermost side of the test device, and the small diameter cylindrical winding (2) is coaxially mounted inside the large diameter cylindrical winding (1), and the central axes of the two coincide in the vertical direction and are aligned at both ends; a support bar (3) is inserted between the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) to stably fix the small diameter cylindrical winding (2) inside the large diameter cylindrical winding (1), and to form a plurality of winding air ducts that are located between the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) and are independent of each other, wherein the air duct opening facing the variable frequency axial flow fan (14) is the air duct inlet, and the air duct opening at the other end is the air duct outlet; each air duct inlet is installed There is an air velocity sensor (11) at the inlet of the air duct, and each air duct outlet is equipped with an air temperature sensor (12) at the outlet of the air duct. All the air velocity sensors (11) at the inlet of the air duct and the air temperature sensors (12) at the outlet of the air duct are connected to a data acquisition terminal (13) for collecting the air velocity at all the inlets of the air duct and the air temperature at all the outlets of the air duct. The large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) are both formed by winding conductors wound in a single turn and in a single direction. The two ends of the winding conductor of the large diameter cylindrical winding (1) are respectively led out to the large diameter cylindrical winding lead-out terminal 1 (5) and the large diameter cylindrical winding lead-out terminal 2 (6), and the small diameter cylindrical winding is led out to the lead-out terminal 1 (5) and the lead-out terminal 2 (6) of the small diameter cylindrical winding. The winding conductor of the group (2) is led out to a small diameter cylindrical winding lead-out terminal 1 (7) and a small diameter cylindrical winding lead-out terminal 2 (8) at both ends; the adjustable DC power supply (10) is used to make the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) generate heat under the action of DC current to simulate the winding copper loss during the operation of the dry traction transformer; the large diameter cylindrical winding lead-out terminal 1 (5) is connected to the negative output of the adjustable DC power supply (10), the small diameter cylindrical winding lead-out terminal 1 (7) is connected to the positive output of the adjustable DC power supply (10), and the large diameter cylindrical winding lead-out terminal 2 (6) and the small diameter cylindrical winding lead-out terminal 2 (8) are connected via a short-circuit wire (9) The large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) are connected to form a series relationship; a winding bracket (4) is arranged below the large diameter cylindrical winding (1) to support the test platform winding part formed by the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2), and the length of the winding part is L, L=0.90m; the center height of the fan blade of the variable frequency axial flow fan (14) is consistent with the center height of the test platform winding part, and is used to provide a variable speed airflow required for cooling the dry traction transformer; a fan outlet wind speed sensor (15) is arranged at the outlet of the variable frequency axial flow fan, and is connected to the data acquisition terminal (13) to monitor the wind speed at the fan outlet;

[0029] Step 2: Obtain the duct inlet wind speed and duct outlet temperature data at low wind speed

[0030] Start the variable frequency axial flow fan (14), and set the fan outlet wind speed to v according to the wind speed monitoring data of the fan outlet wind speed sensor (15). low =3m / s; start the adjustable DC power supply (10) and apply the rated loss value P of the winding to the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) at the same time. loss =374W; the number of the struts (3) is N=8, and the number of the air ducts, the number of the air duct inlets and the number of the air duct outlets are all 8, and the number of the air duct inlet air speed sensors (11) and the air duct outlet air temperature sensors (12) are also 8; the 8 wind speed data monitored by the air duct inlet air speed sensors (11) are obtained through the data acquisition terminal (13), which are v in-low-1 =1.85m / s, v in-low-2 =2.12m / s, v in-low-3 =2.49m / s, v in-low-4 =3.00m / s, v in-low-5 =2.31m / s, v in-low-6 =2.08m / s, v in-low-7 =1.97m / s, v in-low-8 =1.90m / s; when the fluctuation degree of the monitored temperature data of all duct outlet air temperature sensors (12) is less than 1°C / h, 8 temperature data are obtained through the data acquisition terminal (13), which are T out-low-1 =24.48℃、T out-low-2 =24.16℃、T out-low-3 =23.72℃、T out-low-4 =23.18℃、T out-low-5 =24.58℃、T out-low-6 =24.33℃、T out-low-7 =24.25℃、T out-low-8 =24.19℃;

[0031] Step 3: Obtain the duct inlet wind speed and duct outlet temperature data at high wind speed

[0032] Maintain the output P of the adjustable DC power supply (10) loss =374W unchanged, so that the applied value of the winding loss is the same as that in the second step, on this basis, the speed of the variable frequency axial flow fan (14) is increased, and the fan outlet wind speed is increased to v according to the wind speed monitoring data of the fan outlet wind speed sensor (15). high =7m / s; 8 wind speed data monitored by the air speed sensors (11) at all air duct inlets are obtained through the data acquisition terminal (13), which are v in-high-1 =6.01m / s,v in-high-2 =6.35m / s, v in-high-3=6.42m / s, v in-high-4 =6.94m / s,v in-high-5 =7.12m / s, v in-high-6 =7.03m / s, v in-high-7 =6.88m / s, v in-high-8 =6.34m / s; when the fluctuation degree of the monitored temperature data of all the air duct outlet air temperature sensors (12) is less than 1°C / h, 8 temperature data are obtained through the data acquisition terminal (13), which are T out-high-1 =16.33℃、T out-high-2 =16.62℃、T out-high-3 =17.34℃、T out-high-4 =17.15℃、T out-high-5 =17.73℃、T out-high-6 =17.67℃、T out-high-7 =17.42℃、T out-high-8 =17.55℃;

[0033] Step 4: Calculate the circumferential heat dissipation uniformity coefficient C at low wind speed L

[0034] Substitute the structural parameter L in the first step and the data obtained in the second and third steps into the following formula to calculate the circumferential heat dissipation uniformity coefficient C at low wind speed. L , and get C L =3.26;

[0035]

[0036] Step 5: Calculate the circumferential heat dissipation uniformity coefficient C under high wind speed H

[0037] Substitute the data obtained in the third step into the following formula to calculate the circumferential heat dissipation uniformity coefficient C under high wind speed H , and get C H =2.85;

[0038]

[0039] Step 6: Calculate the evaluation coefficient S of the circumferential heat dissipation uniformity of the winding

[0040] Substituting the coefficients calculated in steps 4 and 5 into the following formula, we get S = 3.34;

[0041] S=(C L +C H ) 2 / 3

[0042] Step 7: Evaluate the uniformity of circumferential heat dissipation of dry-type traction transformer windings

[0043] If S<5, the circumferential heat dissipation uniformity of the dry-type traction transformer winding is good, and the design scheme can meet the engineering requirements; if S≥5, the circumferential heat dissipation uniformity of the dry-type traction transformer winding is poor, and the design scheme has a greater risk of overheating and needs further improvement.

Claims

1. A method for evaluating the uniformity of circumferential heat dissipation of a dry-type traction transformer winding, characterized in that: The following steps are involved: The first step is to establish a test platform for the uniformity of circumferential heat dissipation of dry-type traction transformer windings The circumferential heat dissipation uniformity test platform of the dry-type traction transformer winding comprises: a large diameter cylindrical winding (1), a small diameter cylindrical winding (2), a stay (3), a winding support (4), a large diameter cylindrical winding lead-out terminal 1 (5), a large diameter cylindrical winding lead-out terminal 2 (6), a small diameter cylindrical winding lead-out terminal 1 (7), a small diameter cylindrical winding lead-out terminal 2 (8), a short-circuit wire (9), an adjustable DC power supply (10), an air duct inlet air velocity sensor (11), an air duct outlet air temperature sensor (12), a data acquisition terminal (13), a variable frequency axial flow fan (14), and a fan outlet wind velocity sensor (15); The large diameter cylindrical winding (1) is located at the outermost side of the test device, and the small diameter cylindrical winding (2) is coaxially mounted inside the large diameter cylindrical winding (1). A support bar (3) is inserted between the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) to stably fix the small diameter cylindrical winding (2) inside the large diameter cylindrical winding (1), and to form a plurality of winding air ducts that are located between the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) and are independent of each other, wherein the air duct opening facing the variable frequency axial flow fan (14) is the air duct inlet, and the air duct opening at the other end is the air duct outlet; each air duct inlet is equipped with an air duct inlet air velocity sensor A sensor (11) is provided at each air duct outlet, and an air duct outlet air temperature sensor (12) is installed at each air duct outlet. All air duct inlet air velocity sensors (11) and air duct outlet air temperature sensors (12) are connected to a data acquisition terminal (13) for collecting air velocity at all air duct inlets and air temperature at all air duct outlets. The large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) are both formed by winding conductors wound in a single turn and in a single direction. The two ends of the winding conductor of the large diameter cylindrical winding (1) are respectively led to large diameter cylindrical winding lead-out terminals 1 (5) and large diameter cylindrical winding lead-out terminals 2 (6), and the winding conductor of the small diameter cylindrical winding (2) is respectively led to a large diameter cylindrical winding lead-out terminal 1 (5) and a large diameter cylindrical winding lead-out terminal 2 (6). A small diameter cylindrical winding lead-out terminal 1 (7) and a small diameter cylindrical winding lead-out terminal 2 (8) are respectively led out from both ends of the body; the adjustable DC power supply (10) is used to make the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) generate heat under the action of DC current to simulate the winding copper loss during the operation of the dry traction transformer; the large diameter cylindrical winding lead-out terminal 1 (5) is connected to the negative output of the adjustable DC power supply (10), the small diameter cylindrical winding lead-out terminal 1 (7) is connected to the positive output of the adjustable DC power supply (10), and the large diameter cylindrical winding lead-out terminal 2 (6) and the small diameter cylindrical winding lead-out terminal 2 (8) are connected via a short-circuit wire (9) , so that the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) form a series relationship; a winding bracket (4) is provided below the large diameter cylindrical winding (1) to support the test platform winding part formed by the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2), and the length of the winding part is L, in meters; the center height of the fan blade of the variable frequency axial flow fan (14) is consistent with the center height of the test platform winding part, and is used to provide a variable speed airflow required for cooling the dry traction transformer; a fan outlet wind speed sensor (15) is provided at the outlet of the variable frequency axial flow fan, and is connected to the data acquisition terminal (13) to monitor the wind speed at the fan outlet; Step 2: Obtain the duct inlet wind speed and duct outlet temperature data at low wind speed Start the variable frequency axial flow fan (14), and set the fan outlet wind speed to v according to the wind speed monitoring data of the fan outlet wind speed sensor (15). low , v low ∈(1,5], the unit is m / s; start the adjustable DC power supply (10), and apply the rated loss value of the winding to the large diameter cylindrical winding (1) and the small diameter cylindrical winding (2) at the same time, which is recorded as P loss , with the unit of W; the number of the braces (3) is recorded as N, the number of the air ducts, the number of the air duct inlets and the number of the air duct outlets formed thereby are all N, the number of the air velocity sensors (11) at the air duct inlet and the number of the air temperature sensors (12) at the air duct outlet are also N; the N wind speed data monitored by the air velocity sensors (11) at all the air duct inlets are obtained through the data acquisition terminal (13), recorded as v in-low-n , where n is 1, 2, 3, ..., N; when the fluctuation degree of the monitored temperature data of all the air duct outlet air temperature sensors (12) is less than 1°C / h, N temperature data are obtained through the data acquisition terminal (13), which is recorded as T out-low-n , where n is 1, 2, 3, …, N; Step 3: Obtain the duct inlet wind speed and duct outlet temperature data at high wind speed The output of the adjustable DC power supply (10) is kept unchanged, so that the applied value of the winding loss is the same as that in the second step. On this basis, the speed of the variable frequency axial flow fan (14) is increased, and the fan outlet wind speed is increased to v according to the wind speed monitoring data of the fan outlet wind speed sensor (15). high , v high ∈(5,10], the unit is m / s; the N wind speed data monitored by the air speed sensors (11) at the inlet of all air ducts are obtained through the data acquisition terminal (13), which is recorded as v in-high-n , where n is 1, 2, 3, ..., N; when the fluctuation degree of the monitored temperature data of all the air duct outlet air temperature sensors (12) is less than 1°C / h, N temperature data are obtained through the data acquisition terminal (13), which is recorded as T out-high-n , where n is 1, 2, 3, …, N; Step 4: Calculate the circumferential heat dissipation uniformity coefficient C at low wind speed L Step 5: Calculate the circumferential heat dissipation uniformity coefficient C under high wind speed H Step 6: Calculate the evaluation coefficient S of the circumferential heat dissipation uniformity of the winding S=(C L +C H ) 2 / 3 Step 7: Evaluate the uniformity of circumferential heat dissipation of dry-type traction transformer windings If S<5, the circumferential heat dissipation uniformity of the dry-type traction transformer winding is good, and the design scheme can meet the engineering requirements; if S≥5, the circumferential heat dissipation uniformity of the dry-type traction transformer winding is poor, and the design scheme has a greater risk of overheating and needs further improvement.

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