Method for evaluating steady-state deviation degree of outlet air temperature of dry-type traction transformer

Abstract

The invention discloses a method for evaluating the air temperature steady-state deviation degree of an outlet of a dry-type traction transformer. Comprising the following steps: establishing a dry-type traction transformer steady-state outlet air temperature test platform, carrying out a dry-type traction transformer steady-state outlet air temperature test under a rated condition, collecting data, obtaining a model calculation value of the dry-type traction transformer steady-state outlet air temperature, calculating an outlet air temperature steady-state offset coefficient, and calculating a dry-type traction transformer steady-state outlet air temperature model calculation value. And evaluating the air temperature steady-state deviation degree of the outlet of the dry-type traction transformer. The method has the beneficial effects that the outlet air temperature steady-state deviation degree evaluation index and the corresponding test platform which consider multiple parameters such as the head end temperature, the tail end temperature and the average inlet and outlet temperature of the winding at the same time are provided for the first time; according to the method, the accuracy of the dry-type traction transformer outlet air temperature on-line monitoring data is realized, whether the engineering calculation precision can be met or not can be effectively evaluated, and a new technical means is provided for safe operation guarantee and health state management of the dry-type traction transformer and even rail transit rolling stock.

Description

Technical Field

[0001] The present invention relates to the field of online monitoring, fault prediction and health management of electrical insulation of new transformers in rail transit, and in particular to a method for evaluating the steady-state deviation of outlet air temperature of a dry-type traction transformer. Background Art

[0002] Traction transformers, one of the nine core technologies for rail transit rolling stock, serve as the conversion channel between high-voltage and low-voltage power in train traction power. Traditional oil-immersed traction transformers, due to their oil-immersed insulation and oil-cooled heat dissipation, are inherently heavy and cannot meet the demands of trains operating at higher speeds of 450 km / h and above. As a new type of equipment supporting the lightweighting of electric traction systems in rail transit rolling stock, dry-type traction transformers have recently attracted widespread attention from domestic and international rail transit rolling stock manufacturers and researchers.

[0003] Temperature is a key factor influencing the aging rate and remaining service life of electrical equipment insulation. Excessively high temperatures during operation can accelerate aging, deteriorate, or even damage the insulation. To ensure the safe operation of rail transit rolling stock and assist operations and maintenance units in developing condition-based maintenance plans and conducting accurate asset management, it is crucial to employ technical means to monitor the internal temperature of dry-type traction transformers, particularly the hottest point temperature, in real time. Outlet air temperature is a key intermediate parameter between the internal temperature and ambient temperature of dry-type traction transformers. Accurately obtaining this temperature is a prerequisite for real-time monitoring of the hottest point temperature of dry-type traction transformers. Due to the narrow cooling duct outlet, the probe and cable of the temperature sensor pose a risk of blocking the duct outlet, hindering heat dissipation of the dry-type traction transformer. Furthermore, the high air velocity at the duct outlet causes high-frequency vibration of the temperature sensor under the impact of the high-speed airflow, affecting measurement accuracy and potentially damaging the probe and cable. To achieve sensorless outlet air temperature measurement, mathematical modeling is currently commonly used to construct an analytical model. However, if the parameters of the analytical model are not set properly, or if they are poorly adapted to the design parameters of the dry-type traction transformer, the deviation between the calculated and actual values ​​of the outlet air temperature will become increasingly larger as the operating time increases. Therefore, before the dry-type traction transformer is put into operation, an experiment on the steady-state deviation of the outlet air temperature must be carried out to evaluate whether the calculation results of the analytical model can meet the engineering calculation requirements. Currently, there is no method in engineering that can be used to evaluate the steady-state deviation of the outlet air temperature. It is necessary to propose an evaluation method for the steady-state deviation of the outlet air temperature of a dry-type traction transformer. By implementing a series of steps of "test platform-data acquisition-evaluation index", the accuracy of the online monitoring data of the outlet air temperature can be guaranteed, thereby facilitating the safe operation of the dry-type traction transformer. Summary of the Invention

[0004] In response to the above technical problems, the purpose of the present invention is to propose a method for evaluating the steady-state deviation of the outlet air temperature of a dry-type traction transformer, which can achieve an effective evaluation of the accuracy of the online monitoring data of the outlet air temperature of the dry-type traction transformer and whether it can meet the engineering calculation accuracy, and provide corresponding recommendations on whether regular correction is needed.

[0005] The technical solutions for achieving the purpose of the present invention are as follows:

[0006] The first step is to establish a comprehensive test platform for the dynamic and steady-state test of the outlet air temperature of dry-type traction transformers

[0007] The dry-type traction transformer outlet air temperature dynamic and steady-state comprehensive test platform comprises: dry-type traction transformer high-voltage winding (1), dry-type traction transformer low-voltage winding (2), high-voltage winding lead-out terminal 1 (3), high-voltage winding lead-out terminal 2 (4), low-voltage winding lead-out terminal 1 (5), low-voltage winding lead-out terminal 2 (6), dry-type traction transformer core (7), annular air duct between high-voltage winding and low-voltage winding (8), annular air duct between low-voltage winding and core (9), body support (10), high-voltage winding adjustable power supply (11), low-voltage winding adjustable power supply (12), axial flow fan (13), frequency conversion control cabinet (14), control and data acquisition host (15), air duct inlet wind speed sensor (16), air duct inlet temperature sensor (17), air duct outlet temperature sensor (18), high-voltage winding head end temperature sensor (19), low-voltage winding head end temperature sensor (20), high-voltage winding terminal temperature sensor (21), low-voltage winding terminal temperature sensor (22);

[0008] The high-voltage winding (1) of the dry-type traction transformer and the low-voltage winding (2) of the dry-type traction transformer are both cylindrical structures. The two are sheathed together to form the winding part of the test platform. The winding part is sheathed on the dry-type traction transformer core (7) to form the dry-type traction transformer body. The body bracket (10) realizes the horizontal placement of the body. The high-voltage winding (1) of the dry-type traction transformer has a large diameter and is located on the outside. The low-voltage winding (2) of the dry-type traction transformer has a small diameter and is located on the inside. The high-voltage winding (1) of the dry-type traction transformer and the dry-type traction transformer are arranged on the inside. A ring-shaped air duct (8) between the high-voltage winding and the low-voltage winding is formed between the low-voltage winding (2) of the transformer, and a ring-shaped air duct (9) between the low-voltage winding and the iron core is formed between the low-voltage winding (2) of the dry-type traction transformer and the iron core (7) of the dry-type traction transformer; the positive output terminal of the high-voltage winding adjustable power supply (11) is connected to the high-voltage winding lead-out terminal 1 (3), and the negative output terminal of the high-voltage winding adjustable power supply (11) is connected to the high-voltage winding lead-out terminal 2 (4), providing adjustable heating power for the high-voltage winding (1) of the dry-type traction transformer under test. The positive output terminal of the low-voltage winding adjustable power supply (12) is connected to the low-voltage winding lead-out terminal 1 (5), and the negative output terminal of the low-voltage winding adjustable power supply (12) is connected to the low-voltage winding lead-out terminal 2 (6), providing adjustable heating power for the low-voltage winding (2) of the dry-type traction transformer under test; the axial flow fan (13) is used to provide a cooling airflow with a variable flow rate for the dry-type traction transformer, and the centerline height of the fan blade is consistent with the centerline height of the dry-type traction transformer core (7); the axial flow fan (13) is connected to the frequency conversion control cabinet ( 14), the frequency conversion control cabinet (14) is connected to the control and data acquisition host (15), so as to realize program-controlled adjustment of the cooling air flow speed; the wind speed sensor (16) at the air duct inlet is installed at the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, close to one end of the axial flow fan (13), i.e., the inflow end of the cooling air flow. The number of wind speed sensors (16) at the air duct inlet is the same, and is recorded as N. air , N air >3; the wind speed sensors (16) at the air duct inlet are evenly arranged in the circumferential direction of the annular air duct, and all the wind speed sensors (16) at the air duct inlet are connected to the control and data acquisition host (15) for monitoring and recording the inlet wind speed; the air duct inlet temperature sensors (17) are installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, close to one end of the axial flow fan (13), i.e., the inflow end of the cooling air flow. The number of the air duct inlet temperature sensors (17) installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core is the same, and is recorded as N. tin , N tin>3; the air duct inlet temperature sensors (17) are evenly arranged in the circumferential direction of the annular air duct, and all the air duct inlet temperature sensors (17) are connected to the control and data acquisition host (15) for monitoring and recording the inlet air temperature; the air duct outlet temperature sensors (18) are installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, away from one end of the axial flow fan (13), that is, the outflow end of the cooling air flow. The number of air duct outlet temperature sensors (18) installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core is the same, and is recorded as N tout , N tout >3; the air duct outlet temperature sensors (18) are evenly arranged in the circumferential direction of the annular air duct, and all the air duct outlet temperature sensors (18) are connected to the control and data acquisition host (15) for monitoring and recording the outlet air temperature; the area close to the air duct inlet is defined as the winding head end, and the area close to the air duct outlet is defined as the winding end end, and the high-voltage winding head end temperature sensor (19), the low-voltage winding head end temperature sensor (20), the high-voltage winding end temperature sensor (21), and the low-voltage winding end temperature sensor (22) are respectively installed inside the high-voltage winding head end cast insulation, inside the low-voltage winding head end cast insulation, inside the high-voltage winding end cast insulation, and inside the low-voltage winding end cast insulation, and are all connected to the control and data acquisition host (15) for monitoring the temperature of the conductors at both ends of the winding;

[0009] Step 2: Conduct steady-state outlet air temperature test of dry-type traction transformer under rated operating conditions and collect data

[0010] Start the axial flow fan (13), and set the wind speed of the axial flow fan (13) to the rated wind speed through the control and data acquisition host (15) and the frequency conversion control cabinet (14), which is recorded as v rated , in m / s; start the high voltage winding adjustable power supply (11) and apply its rated heating power to the high voltage winding (1) of the dry-type traction transformer, denoted as Q hvrated , in W; start the low-voltage winding adjustable power supply (12) and apply its rated heating power to the low-voltage winding (2) of the dry-type traction transformer, recorded as Q lvrated , in W; the duct inlet wind speed, duct inlet wind temperature, and duct outlet wind temperature obtained by the duct inlet wind speed sensor (16), the duct inlet temperature sensor (17), and the duct outlet temperature sensor (18) are collected and monitored by the control and data acquisition host (15); when the fluctuation degree of all duct outlet temperature sensors (18) is less than 0.1℃ / min, that is, the duct outlet wind temperature can be regarded as reaching a steady state, the duct inlet wind speed obtained by all duct inlet wind speed sensors (16) at this time is recorded and the average value thereof is calculated and recorded as v ave, unit is m / s; record the air temperature at the air duct inlet obtained by all air duct inlet temperature sensors (17) at this time and calculate its average value and record it as T in_ave , the unit is ℃; record the air temperature at the air duct outlet obtained by all air duct outlet temperature sensors (18) at this time and calculate its average value and record it as T out_ave , in °C; record the winding temperatures obtained by the high-voltage winding head end temperature sensor (19), the low-voltage winding head end temperature sensor (20), the high-voltage winding end temperature sensor (21), and the low-voltage winding end temperature sensor (22) at this time and calculate their average value and record it as T w_ave ;

[0011] Step 3: Obtain the model calculated value T of the steady-state outlet air temperature of the dry-type traction transformer out_model_steady

[0012] Solve the following winding temperature-wind temperature coupling relationship model equations to obtain the outlet wind temperature calculation value T out The curve of change over time, and select T out The temperature value when the steady state is reached for the first time, that is, when the rate of change is less than 0.1℃ / min for the first time, is taken as T out_model_steady The value of

[0013]

[0014] Where, T w_ave_m is the calculated value of the winding temperature model, C wnd is the lumped heat capacity of the winding, C air is the lumped heat capacity of air, t is the time variable, R cond is the lumped conduction thermal resistance of the winding, R air is the lumped thermal resistance of air, R conv is the lumped convection thermal resistance;

[0015] Lumped convection thermal resistance R conv Calculated according to the following formula:

[0016]

[0017] Wherein, x is the distance from the air duct entrance; L1, L2, L3 are respectively the length of the high-voltage winding side surface of the annular air duct (8) between the high-voltage winding and the low-voltage winding along the airflow direction, the length of the low-voltage winding side surface of the annular air duct (8) between the high-voltage winding and the low-voltage winding along the airflow direction, and the length of the low-voltage winding side surface of the annular air duct (9) between the low-voltage winding and the iron core along the airflow direction, and the unit is m; S1, S2, S3 are respectively the high-voltage winding side surface area of ​​the annular air duct (8) between the high-voltage winding and the low-voltage winding, the low-voltage winding side surface area of ​​the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the low-voltage winding side surface area of ​​the annular air duct (9) between the low-voltage winding and the iron core, and the unit is m 2 ;D i1 、Di2 、D i3 They are respectively the inner diameter of the annular air duct (8) between the high-voltage winding and the low-voltage winding on the high-voltage winding side, the inner diameter of the annular air duct (8) between the high-voltage winding and the low-voltage winding on the low-voltage winding side, and the inner diameter of the annular air duct (9) between the low-voltage winding and the core on the low-voltage winding side, in meters; D lv-core is the hydraulic diameter of the annular air duct (9) between the low-voltage winding and the core, in m; k air , ρ, μ are the thermal conductivity, density and dynamic viscosity of the air in the duct respectively;

[0018] Step 4: Calculate the outlet air temperature steady-state deviation coefficient I steady

[0019]

[0020] Step 5: Evaluate the steady-state deviation of the outlet air temperature of the dry-type traction transformer

[0021] If 0≤I steady ≤2, the steady-state deviation of the outlet air temperature of the dry-type traction transformer is low, and direct use can meet the engineering calculation requirements without regular calibration; if 2<I steady ≤4, the dry-type traction transformer outlet air temperature steady-state deviation is high and needs to be calibrated regularly; if I steady <0 or 1 steady >4, the steady-state deviation of the outlet air temperature of the dry-type traction transformer cannot meet the engineering calculation requirements.

[0022] The beneficial effect of the present invention is that a method for evaluating the steady-state deviation of the outlet air temperature of a dry-type traction transformer has the following advantages:

[0023] 1) This invention combines experimental and model-calculated values ​​of outlet air temperature. Based on this, it proposes for the first time an outlet air temperature steady-state deviation evaluation index that considers multiple parameters, including winding head-end temperature, terminal temperature, and average inlet and outlet temperatures. This steady-state deviation experiment can be used to evaluate whether the analytical model's calculation results meet engineering calculation requirements before a dry-type traction transformer is put into operation. This ensures the accuracy, validity, and usability of online outlet air temperature monitoring data, thereby contributing to the safe and stable operation of dry-type traction transformers and even rail transit rolling stock.

[0024] 2) Compared with the blindness and uncertainty of traditional transformer thermal model effectiveness evaluation, the method proposed in this invention can effectively improve the efficiency of the effectiveness judgment of the on-construction monitoring data of dry-type traction transformers before commissioning, and reduce the consumption of manpower and material resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is a flow chart of a method for evaluating the steady-state deviation of outlet air temperature of a dry-type traction transformer according to the present invention;

[0026] Figure 2 The present invention is a structural diagram of a comprehensive test platform for the dynamic and steady-state test of the outlet air temperature of a dry-type traction transformer. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and specific implementation processes. It should be emphasized that the specific implementation cases described herein are only used to illustrate the present invention and do not limit the scope of the present invention and its claims.

[0028] The first step is to establish a comprehensive test platform for the dynamic and steady-state test of the outlet air temperature of dry-type traction transformers

[0029] The dry-type traction transformer outlet air temperature dynamic and steady-state comprehensive test platform comprises: dry-type traction transformer high-voltage winding (1), dry-type traction transformer low-voltage winding (2), high-voltage winding lead-out terminal 1 (3), high-voltage winding lead-out terminal 2 (4), low-voltage winding lead-out terminal 1 (5), low-voltage winding lead-out terminal 2 (6), dry-type traction transformer core (7), annular air duct between high-voltage winding and low-voltage winding (8), annular air duct between low-voltage winding and core (9), body support (10), high-voltage winding adjustable power supply (11), low-voltage winding adjustable power supply (12), axial flow fan (13), frequency conversion control cabinet (14), control and data acquisition host (15), air duct inlet wind speed sensor (16), air duct inlet temperature sensor (17), air duct outlet temperature sensor (18), high-voltage winding head end temperature sensor (19), low-voltage winding head end temperature sensor (20), high-voltage winding terminal temperature sensor (21), low-voltage winding terminal temperature sensor (22);

[0030] The high-voltage winding (1) of the dry-type traction transformer and the low-voltage winding (2) of the dry-type traction transformer are both cylindrical structures. The two are sheathed together to form the winding part of the test platform. The winding part is sheathed on the dry-type traction transformer core (7) to form the dry-type traction transformer body. The body bracket (10) realizes the horizontal placement of the body. The high-voltage winding (1) of the dry-type traction transformer has a large diameter and is located on the outside. The low-voltage winding (2) of the dry-type traction transformer has a small diameter and is located on the inside. The high-voltage winding (1) of the dry-type traction transformer and the dry-type traction transformer are arranged on the inside. A ring-shaped air duct (8) between the high-voltage winding and the low-voltage winding is formed between the low-voltage winding (2) of the transformer, and a ring-shaped air duct (9) between the low-voltage winding and the iron core is formed between the low-voltage winding (2) of the dry-type traction transformer and the iron core (7) of the dry-type traction transformer; the positive output terminal of the high-voltage winding adjustable power supply (11) is connected to the high-voltage winding lead-out terminal 1 (3), and the negative output terminal of the high-voltage winding adjustable power supply (11) is connected to the high-voltage winding lead-out terminal 2 (4), providing adjustable heating for the high-voltage winding (1) of the dry-type traction transformer under test. Power; the positive output terminal of the low-voltage winding adjustable power supply (12) is connected to the low-voltage winding lead-out terminal 1 (5), and the negative output terminal of the low-voltage winding adjustable power supply (12) is connected to the low-voltage winding lead-out terminal 2 (6), providing adjustable heating power for the low-voltage winding (2) of the dry-type traction transformer under test; the axial flow fan (13) is used to provide a cooling airflow with a variable flow rate for the dry-type traction transformer, and the centerline height of the fan blade is consistent with the centerline height of the dry-type traction transformer core (7); the axial flow fan (13) and the frequency conversion control cabinet (14) is connected, the frequency conversion control cabinet (14) is connected to the control and data acquisition host (15) to realize the program-controlled adjustment of the cooling air flow speed; the wind speed sensor (16) at the air duct inlet is installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, close to one end of the axial flow fan (13), that is, the inflow end of the cooling air flow, and the number of wind speed sensors (16) at the air duct inlet installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core is the same, both N air =5, satisfying N air >3 requirements; the wind speed sensors (16) at the air duct inlet are evenly arranged in the circumferential direction of the annular air duct, and all the wind speed sensors (16) at the air duct inlet are connected to the control and data acquisition host (15) for monitoring and recording the inlet wind speed; the air duct inlet temperature sensors (17) are installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, close to one end of the axial flow fan (13), i.e., the inflow end of the cooling air flow, and the number of the air duct inlet temperature sensors (17) installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core is the same, both N tin =5, satisfying N tin>3 requirements; the air duct inlet temperature sensors (17) are evenly arranged in the circumferential direction of the annular air duct, and all the air duct inlet temperature sensors (17) are connected to the control and data acquisition host (15) for monitoring and recording the inlet air temperature; the air duct outlet temperature sensors (18) are installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, away from one end of the axial flow fan (13), that is, the outflow end of the cooling air flow, and the number of the air duct outlet temperature sensors (18) installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core is the same, which is N tout =5, satisfying N tout >3 requirements; the air duct outlet temperature sensors (18) are evenly arranged in the circumferential direction of the annular air duct, and all the air duct outlet temperature sensors (18) are connected to the control and data acquisition host (15) for monitoring and recording the outlet air temperature; the area close to the air duct inlet is defined as the winding head end, and the area close to the air duct outlet is defined as the winding end, the high-voltage winding head end temperature sensor (19), the low-voltage winding head end temperature sensor (20), the high-voltage winding end temperature sensor (21), and the low-voltage winding end temperature sensor (22) are respectively installed inside the high-voltage winding head end cast insulation, inside the low-voltage winding head end cast insulation, inside the high-voltage winding end cast insulation, and inside the low-voltage winding end cast insulation, and are all connected to the control and data acquisition host (15) for monitoring the temperature of the conductors at both ends of the winding;

[0031] Step 2: Conduct steady-state outlet air temperature test of dry-type traction transformer under rated operating conditions and collect data

[0032] Start the axial flow fan (13), and set the wind speed of the axial flow fan (13) to the rated wind speed v through the control and data acquisition host (15) and the frequency conversion control cabinet (14). rated =10m / s; start the high voltage winding adjustable power supply (11) and apply its rated heating power Q to the high voltage winding (1) of the dry-type traction transformer hvrated =5000W; start the low voltage winding adjustable power supply (12) and apply its rated heating power Q to the low voltage winding (2) of the dry-type traction transformer lvrated =4500W; the duct inlet wind speed, duct inlet wind temperature, and duct outlet wind temperature obtained by the duct inlet wind speed sensor (16), the duct inlet temperature sensor (17), and the duct outlet temperature sensor (18) are collected and monitored by the control and data acquisition host (15); when the fluctuation degree of all the duct outlet temperature sensors (18) is less than 0.1°C / min, that is, the duct outlet wind temperature can be regarded as reaching a steady state, the duct inlet wind speed obtained by all the duct inlet wind speed sensors (16) at this time is recorded and the average value v is calculated ave=17.35m / s; record the air temperature at the air duct inlet obtained by all air duct inlet temperature sensors (17) at this time and calculate its average value T in_ave =26.03℃; record the air temperature at the air duct outlet obtained by all air duct outlet temperature sensors (18) at this time and calculate its average value T out_ave =28.94℃; record the winding temperatures obtained by the high-voltage winding head end temperature sensor (19), the low-voltage winding head end temperature sensor (20), the high-voltage winding end temperature sensor (21), and the low-voltage winding end temperature sensor (22) at this time and calculate their average value T w_ave =83.57℃;

[0033] Step 3: Obtain the model calculated value T of the steady-state outlet air temperature of the dry-type traction transformer out_model_steady

[0034] Solve the following winding temperature-wind temperature coupling relationship model equations to obtain the outlet wind temperature calculation value T out The curve of change over time, and select T out The temperature value when the steady state is reached for the first time, that is, when the rate of change is less than 0.1℃ / min for the first time, is taken as T out_model_steady The value of

[0035]

[0036] Where, T w_ave_m is the calculated value of the winding temperature model, C wnd is the lumped heat capacity of the winding, C air is the lumped heat capacity of air, R cond is the lumped conduction thermal resistance of the winding, R air is the lumped thermal resistance of air; the above four parameters are the inherent attribute parameters of the dry-type traction transformer, which can be obtained by full-domain computational fluid dynamics fluid-heat transfer coupling simulation of the dry-type traction transformer combined with reference to the transformer factory manual. In this embodiment, C wnd =116234.521J / ℃、C air =4358.574J / ℃、R cond =0.003891℃ / W、R air =0.000495℃ / W; t is the time variable, R conv is the lumped convection thermal resistance;

[0037] Lumped convection thermal resistance R conv Calculated according to the following formula:

[0038]

[0039] Wherein, x is the distance from the air duct entrance; L1, L2, L3 are respectively the length of the high-voltage winding side surface of the annular air duct (8) between the high-voltage winding and the low-voltage winding along the airflow direction, the length of the low-voltage winding side surface of the annular air duct (8) between the high-voltage winding and the low-voltage winding along the airflow direction, and the length of the low-voltage winding side surface of the annular air duct (9) between the low-voltage winding and the iron core along the airflow direction, and the unit is m; in this embodiment, L1=L2=L3=1.3m; S1, S2, S3 are respectively the high-voltage winding side surface area of ​​the annular air duct (8) between the high-voltage winding and the low-voltage winding, the low-voltage winding side surface area of ​​the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the low-voltage winding side surface area of ​​the annular air duct (9) between the low-voltage winding and the iron core, and the unit is m 2 In this embodiment, S1 = 2.04m 2 , S2=1.43m 2 , S3=1.23m 2 ;D i1 、D i2 、D i3 are respectively the inner diameter of the annular air duct (8) between the high-voltage winding and the low-voltage winding on the high-voltage winding side, the inner diameter of the annular air duct (8) between the high-voltage winding and the low-voltage winding on the low-voltage winding side, and the inner diameter of the annular air duct (9) between the low-voltage winding and the iron core on the low-voltage winding side, in meters; in this embodiment, D i1 =0.50m, D i2 =0.35m, D i3 =0.30m; D lv-core is the hydraulic diameter of the annular air duct (9) between the low-voltage winding and the iron core, in meters; in this embodiment, D lv-core =0.20m;k air , ρ, μ are the thermal conductivity, density and dynamic viscosity of the air in the duct respectively; in this embodiment, k air =0.0242W / (m·℃), ρ=1.225kg / m 3 , μ=1.7894×10 -5 kg / (m·s). Substituting the obtained parameters into the above formula, we can get R conv =0.006193℃ / W. Substitute the thermal resistance and heat capacity parameters obtained above into the winding temperature-wind temperature coupling relationship model equation group to obtain T out_model_steady =30.73℃.

[0040] Step 4: Calculate the outlet air temperature steady-state deviation coefficient I steady

[0041] Substitute the temperature test value and calculated value obtained in the previous steps into the following formula to calculate the outlet air temperature steady-state deviation coefficient I steady , get I steady =2.39;

[0042]

[0043] Step 5: Evaluate the steady-state deviation of the outlet air temperature of the dry-type traction transformer

[0044] If 0≤I steady ≤2, the steady-state deviation of the outlet air temperature of the dry-type traction transformer is low, and direct use can meet the engineering calculation requirements without regular calibration; if 2<I steady ≤4, the dry-type traction transformer outlet air temperature steady-state deviation is high and needs to be calibrated regularly; if I steady <0 or 1 steady >4, the outlet wind temperature steady-state deviation of the dry-type traction transformer cannot meet the engineering calculation requirements. steady Calculation results show that the steady-state deviation of the outlet air temperature of the dry-type traction transformer with these structural parameters is high and requires regular correction.

Claims

1. A method for evaluating the steady-state deviation of the outlet air temperature of a dry-type traction transformer, characterized in that: The following steps are involved: The first step is to establish a comprehensive test platform for the dynamic and steady-state test of the outlet air temperature of dry-type traction transformers The dry-type traction transformer outlet air temperature dynamic and steady-state comprehensive test platform comprises: dry-type traction transformer high-voltage winding (1), dry-type traction transformer low-voltage winding (2), high-voltage winding lead-out terminal 1 (3), high-voltage winding lead-out terminal 2 (4), low-voltage winding lead-out terminal 1 (5), low-voltage winding lead-out terminal 2 (6), dry-type traction transformer core (7), annular air duct between high-voltage winding and low-voltage winding (8), annular air duct between low-voltage winding and core (9), body support (10), high-voltage winding adjustable power supply (11), low-voltage winding adjustable power supply (12), axial flow fan (13), frequency conversion control cabinet (14), control and data acquisition host (15), air duct inlet wind speed sensor (16), air duct inlet temperature sensor (17), air duct outlet temperature sensor (18), high-voltage winding head end temperature sensor (19), low-voltage winding head end temperature sensor (20), high-voltage winding terminal temperature sensor (21), low-voltage winding terminal temperature sensor (22); The high-voltage winding (1) of the dry-type traction transformer and the low-voltage winding (2) of the dry-type traction transformer are both cylindrical structures. The two are sheathed together to form the winding part of the test platform. The winding part is sheathed on the dry-type traction transformer core (7) to form the dry-type traction transformer body. The body bracket (10) realizes the horizontal placement of the body. The high-voltage winding (1) of the dry-type traction transformer has a large diameter and is located on the outside. The low-voltage winding (2) of the dry-type traction transformer has a small diameter and is located on the inside. The high-voltage winding (1) of the dry-type traction transformer and the dry-type traction transformer are arranged on the inside. A ring-shaped air duct (8) between the high-voltage winding and the low-voltage winding is formed between the low-voltage winding (2) of the transformer, and a ring-shaped air duct (9) between the low-voltage winding and the iron core is formed between the low-voltage winding (2) of the dry-type traction transformer and the iron core (7) of the dry-type traction transformer; the positive output terminal of the high-voltage winding adjustable power supply (11) is connected to the high-voltage winding lead-out terminal 1 (3), and the negative output terminal of the high-voltage winding adjustable power supply (11) is connected to the high-voltage winding lead-out terminal 2 (4), providing adjustable heating power for the high-voltage winding (1) of the dry-type traction transformer under test. The positive output terminal of the low-voltage winding adjustable power supply (12) is connected to the low-voltage winding lead-out terminal 1 (5), and the negative output terminal of the low-voltage winding adjustable power supply (12) is connected to the low-voltage winding lead-out terminal 2 (6), providing adjustable heating power for the low-voltage winding (2) of the dry-type traction transformer under test; the axial flow fan (13) is used to provide a cooling airflow with a variable flow rate for the dry-type traction transformer, and the centerline height of the fan blade is consistent with the centerline height of the dry-type traction transformer core (7); the axial flow fan (13) is connected to the frequency conversion control cabinet ( 14), the frequency conversion control cabinet (14) is connected to the control and data acquisition host (15), so as to realize program-controlled adjustment of the cooling air flow speed; the wind speed sensor (16) at the air duct inlet is installed at the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, close to one end of the axial flow fan (13), i.e., the inflow end of the cooling air flow. The number of wind speed sensors (16) at the air duct inlet is the same, and is recorded as N. air , N air >3; the wind speed sensors (16) at the air duct inlet are evenly arranged in the circumferential direction of the annular air duct, and all the wind speed sensors (16) at the air duct inlet are connected to the control and data acquisition host (15) for monitoring and recording the inlet wind speed; the air duct inlet temperature sensors (17) are installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, close to one end of the axial flow fan (13), i.e., the inflow end of the cooling air flow. The number of the air duct inlet temperature sensors (17) installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core is the same, and is recorded as N. tin , N tin >3; the air duct inlet temperature sensors (17) are evenly arranged in the circumferential direction of the annular air duct, and all the air duct inlet temperature sensors (17) are connected to the control and data acquisition host (15) for monitoring and recording the inlet air temperature; the air duct outlet temperature sensors (18) are installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core, away from one end of the axial flow fan (13), that is, the outflow end of the cooling air flow. The number of air duct outlet temperature sensors (18) installed in the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the annular air duct (9) between the low-voltage winding and the iron core is the same, and is recorded as N tout , N tout >3; the air duct outlet temperature sensors (18) are evenly arranged in the circumferential direction of the annular air duct, and all the air duct outlet temperature sensors (18) are connected to the control and data acquisition host (15) for monitoring and recording the outlet air temperature; the area close to the air duct inlet is defined as the winding head end, and the area close to the air duct outlet is defined as the winding end end, and the high-voltage winding head end temperature sensor (19), the low-voltage winding head end temperature sensor (20), the high-voltage winding end temperature sensor (21), and the low-voltage winding end temperature sensor (22) are respectively installed inside the high-voltage winding head end cast insulation, inside the low-voltage winding head end cast insulation, inside the high-voltage winding end cast insulation, and inside the low-voltage winding end cast insulation, and are all connected to the control and data acquisition host (15) for monitoring the temperature of the conductors at both ends of the winding; Step 2: Conduct steady-state outlet air temperature test of dry-type traction transformer under rated operating conditions and collect data Start the axial flow fan (13), and set the wind speed of the axial flow fan (13) to the rated wind speed through the control and data acquisition host (15) and the frequency conversion control cabinet (14), which is recorded as v rated , in m / s; start the high voltage winding adjustable power supply (11) and apply its rated heating power to the high voltage winding (1) of the dry-type traction transformer, denoted as Q hvrated , in W; start the low-voltage winding adjustable power supply (12) and apply its rated heating power to the low-voltage winding (2) of the dry-type traction transformer, recorded as Q lvrated , in W; the duct inlet wind speed, duct inlet wind temperature, and duct outlet wind temperature obtained by the duct inlet wind speed sensor (16), the duct inlet temperature sensor (17), and the duct outlet temperature sensor (18) are collected and monitored by the control and data acquisition host (15); when the fluctuation degree of all duct outlet temperature sensors (18) is less than 0.1℃ / min, that is, the duct outlet wind temperature can be regarded as reaching a steady state, the duct inlet wind speed obtained by all duct inlet wind speed sensors (16) at this time is recorded and the average value thereof is calculated and recorded as v ave , unit is m / s; record the air temperature at the air duct inlet obtained by all air duct inlet temperature sensors (17) at this time and calculate its average value and record it as T in_ave , the unit is ℃; record the air temperature at the air duct outlet obtained by all air duct outlet temperature sensors (18) at this time and calculate its average value and record it as T out_ave , in °C; record the winding temperatures obtained by the high-voltage winding head end temperature sensor (19), the low-voltage winding head end temperature sensor (20), the high-voltage winding end temperature sensor (21), and the low-voltage winding end temperature sensor (22) at this time and calculate their average value and record it as T w_ave , unit is ℃; Step 3: Obtain the model calculated value T of the steady-state outlet air temperature of the dry-type traction transformer out_model_steady Solve the following winding temperature-wind temperature coupling relationship model equations to obtain the outlet wind temperature calculation value T out The curve of change over time, and select T out The temperature value when the steady state is reached for the first time, that is, when the rate of change is less than 0.1℃ / min for the first time, is taken as T out_model_steady The value of is in °C; Where, T w_ave_m is the calculated value of the winding temperature model, C wnd is the lumped heat capacity of the winding, C air is the lumped heat capacity of air, t is the time variable, R cond is the lumped conduction thermal resistance of the winding, R air is the lumped thermal resistance of air, R conv is the lumped convection thermal resistance; Lumped convection thermal resistance R conv Calculated according to the following formula: Wherein, x is the distance from the air duct entrance; L1, L2, L3 are respectively the length of the high-voltage winding side surface of the annular air duct (8) between the high-voltage winding and the low-voltage winding along the airflow direction, the length of the low-voltage winding side surface of the annular air duct (8) between the high-voltage winding and the low-voltage winding along the airflow direction, and the length of the low-voltage winding side surface of the annular air duct (9) between the low-voltage winding and the iron core along the airflow direction, and the unit is m; S1, S2, S3 are respectively the high-voltage winding side surface area of ​​the annular air duct (8) between the high-voltage winding and the low-voltage winding, the low-voltage winding side surface area of ​​the annular air duct (8) between the high-voltage winding and the low-voltage winding, and the low-voltage winding side surface area of ​​the annular air duct (9) between the low-voltage winding and the iron core, and the unit is m 2 ;D i1 、D i2 、D i3 They are respectively the inner diameter of the annular air duct (8) between the high-voltage winding and the low-voltage winding on the high-voltage winding side, the inner diameter of the annular air duct (8) between the high-voltage winding and the low-voltage winding on the low-voltage winding side, and the inner diameter of the annular air duct (9) between the low-voltage winding and the core on the low-voltage winding side, in meters; D lv-core is the hydraulic diameter of the annular air duct (9) between the low-voltage winding and the core, in m; k air , ρ, μ are the thermal conductivity, density and dynamic viscosity of the air in the duct respectively; Step 4: Calculate the outlet air temperature steady-state deviation coefficient I steady Step 5: Evaluate the steady-state deviation of the outlet air temperature of the dry-type traction transformer If 0≤I steady ≤2, the steady-state deviation of the outlet air temperature of the dry-type traction transformer is low, and direct use can meet the engineering calculation requirements without regular calibration; if 2<I steady ≤4, the dry-type traction transformer outlet air temperature steady-state deviation is high and needs to be calibrated regularly; if I steady <0 or I steady >4, the steady-state deviation of the outlet air temperature of the dry-type traction transformer cannot meet the engineering calculation requirements.

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