CN112001081B - Lightweight vehicle-mounted traction transformer hotspot factor calculation method - Google Patents
Lightweight vehicle-mounted traction transformer hotspot factor calculation method Download PDFInfo
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- CN112001081B CN112001081B CN202010860353.4A CN202010860353A CN112001081B CN 112001081 B CN112001081 B CN 112001081B CN 202010860353 A CN202010860353 A CN 202010860353A CN 112001081 B CN112001081 B CN 112001081B
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Abstract
The invention discloses a lightweight vehicle-mounted traction transformer hotspot factor calculation method, which comprises the following steps of: the method comprises the steps of establishing an axisymmetric two-dimensional model of the lightweight vehicle-mounted traction transformer, arranging temperature monitoring nodes, calculating thermal resistances of all parts, distributing heating power for winding temperature nodes, solving winding hot point temperature, simultaneously obtaining environment temperature at the moment, calculating and obtaining hot point temperature rise, and respectively bringing the hot point temperature rise under rated load and the hot point temperature rise under different loads into a hot point temperature rise calculation model to calculate and obtain hot point factors. The method can widen and improve the application range and the calculation precision of a two-section type temperature rise calculation formula in IEEE and IEC standards, and provides technical support for temperature rise online monitoring and service life evaluation of the vehicle-mounted traction transformer.
Description
Technical Field
The invention relates to a lightweight vehicle-mounted traction transformer hotspot factor calculation method, and belongs to the field of electrical insulation online detection and fault diagnosis.
Technical Field
The vehicle-mounted traction transformer is a core device of a traction system of a high-speed motor train unit, and the safe and reliable operation of the vehicle-mounted traction transformer is important for the operation development of a high-speed railway. The internal insulation performance of the transformer directly influences the working life of the transformer, and temperature rise is an important influence factor of the deterioration of the insulation performance of the transformer, so that the problem of temperature rise is a long-standing research focus in the field of transformers.
The light-weight vehicle-mounted traction transformer is a brand new design idea, and the light weight of the vehicle-mounted traction transformer is realized. But compared with the traditional oil-immersed vehicle-mounted transformer, the cooling components such as insulating oil, an oil tank, a radiator and the like are reduced, and the temperature rise characteristic of the transformer is different from that of the oil-immersed vehicle-mounted traction transformer. The online monitoring of the internal temperature rise of the oil-immersed transformer can be realized according to a two-section type temperature rise calculation formula in IEEE and IEC standards, but relevant recommended parameters in the formula only aim at the oil-immersed transformer at present. The hot spot factor is a constant in a hot spot temperature rise formula for calculating the lightweight vehicle-mounted traction transformer, and if the hot spot factor suitable for the lightweight vehicle-mounted traction transformer can be quickly and accurately obtained, the application range and the calculation precision of a 'two-section type' temperature rise calculation formula in the standard can be further widened and improved, and technical support is provided for online temperature rise monitoring and service life evaluation of the lightweight vehicle-mounted traction transformer.
Disclosure of Invention
In view of the above technical problems, the invention aims to provide a lightweight vehicle-mounted traction transformer hotspot factor calculation method, which can realize rapid calculation of a lightweight vehicle-mounted traction transformer hotspot factor.
The technical scheme for realizing the invention is as follows:
firstly, establishing an axisymmetric two-dimensional model of a lightweight vehicle-mounted traction transformer
Carrying out primary treatment according to the structural characteristics of the lightweight vehicle-mounted traction transformer: structures with small influence on temperature distribution, such as winding outlet terminals, clamps, stays and the like, are deleted, and a cooling air duct is simplified into an annular pipeline with constant heat flow on the inner wall surface and the outer wall surface simultaneously or independently;
secondly, arrange the temperature monitoring node, the temperature monitoring node includes: the winding temperature nodes, the insulating paper boundary nodes, the epoxy resin boundary nodes and the air temperature nodes are connected through thermal resistance to form a lightweight vehicle-mounted traction transformer thermal network model; the node arrangement method specifically comprises the following steps:
1) 1 winding temperature node is arranged at the center of each turn of the winding conductor, and the winding temperature nodes are aligned in the axial direction and the radial direction according to the winding structure;
2) 4 insulation paper boundary nodes are respectively arranged in the upper, lower, left and right 4 directions of the winding temperature node;
3) 2 epoxy resin boundary nodes are respectively arranged on the upper side and the lower side of the upper insulating paper boundary node and the lower insulating paper boundary node;
4) 1 air temperature node is arranged between 2 epoxy resin boundary nodes on two sides of the cooling air channel;
5) the winding temperature nodes are connected with the insulating paper boundary nodes through insulating paper thermal resistances, the insulating paper boundary nodes are connected with the epoxy resin boundary nodes through epoxy resin thermal resistances, the epoxy resin boundary nodes are connected with the air temperature nodes through convective thermal resistances, and the air temperature nodes are connected through air thermal resistances;
thirdly, calculating the thermal resistance of each part
1) Thermal resistance R of insulating paperpCalculated using the following formula:
in the formula, kpIs the thermal conductivity (W.m) of the insulating paper-1·k-1)，lpIs the thickness (m) of the insulating paper in the direction of heat flow of the thermal resistance of the insulating paper, SpThe contact area (m) of the insulating paper and the copper conductor in the heat flow direction of the thermal resistance of the insulating paper2)；
2) Thermal resistance R of epoxy resineCalculated using the following formula:
in the formula, keIs the thermal conductivity (W.m) of the epoxy resin-1·k-1)，leIs the thickness (m), S, of the epoxy resin in the heat flow direction of the epoxy resin heat resistanceeThe contact area (m) of the epoxy resin and the insulating paper in the heat flow direction of the epoxy resin heat resistance2)；
3) Air thermal resistance RairCalculated using the following formula:
in the formula, mairMass flow (kg.s) of air in cooling duct-1)，Cp_airThe specific heat capacity (J.kg) of air-1·K-1)，LductIs the total length (m) of the cooling air duct, and l is the axial width (m) of the conductor;
4) convective heat resistance RconvCalculated using the following formula:
in the formula, DoIs the outer diameter (m), D of the cooling air ductiIs the inner diameter (m) of the cooling air duct, NuxIs a local Nussel number, kairIs emptyThermal conductivity of gas (W.m)-1·k-1)，SductThe contact area (m) of the epoxy resin outside the temperature node of a single winding and the cooling air duct2)；
The convective thermal resistance RconvIn the formula (2), NuxThe calculation formula of (a) is as follows:
in the formula, n is the number of the winding temperature node, and the rule is as follows: the winding temperature node at the inlet of the innermost cooling air duct is numbered as No. 1, and the winding temperature nodes from the inlet of the innermost cooling air duct to the outlet of the outermost cooling air duct are numbered as 2, 3 and 4 … in sequence; x is the distance (m) from the air duct inlet, R is the central line radius (m) of the cooling air duct, Re is the Reynolds number of the cooling air duct, and the Reynolds number is calculated by using the following formula:
wherein ρ is an air density (kg · m)-3) V is the air flow velocity (m · s)-1) μ is aerodynamic viscosity (kg · m)-1·s-1)；
Fourthly, distributing heating power for winding temperature nodes
The heating power distributed to the winding temperature node with the number n is calculated according to the following formula:
in the formula, VnConductor volume (m) corresponding to winding temperature node numbered n3)，VGeneral assemblyIs the total volume (m) of the winding3) Q is the load loss (W) obtained by the field test of the transformer;
fifthly, acquiring the temperature rise of the hot spot
According to the lightweight vehicle-mounted traction transformer thermal network model structure from the first step to the fourth step, solving the winding temperature node temperature according to a kirchhoff law column writing node voltage equation to obtain the hottest point temperature, and simultaneously obtaining the ambient temperature of the corresponding time point, wherein the environment temperature is subtracted from the hottest point temperature to obtain the hot point temperature rise;
sixthly, calculating hot spot factors
According to the method for acquiring the hot spot temperature rise in the fifth step, rated load loss is applied, and the hot spot temperature rise delta T under the rated load loss is acquiredn(K) (ii) a Then applying the loss under the rated current of 0.5 time, 0.6 time, 0.7 time, 0.8 time, 0.9 time, 1.1 time, 1.2 time, 1.3 time, 1.4 time and 1.5 time in sequence to obtain the corresponding hot point temperature rise (K) under the loss and respectively marking as delta Ti(i ═ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10); the hotspot factor δ is calculated using the following formula:
in the formula (I), the compound is shown in the specification,
Iifor the temperature rise of the hot spot to be delta TiCorresponding load current (A), InThe rated current (A) is obtained.
The method for calculating the hotspot factor of the lightweight vehicle-mounted traction transformer has the advantages that:
1) the hot spot factor of the light vehicle-mounted traction transformer can be rapidly and accurately calculated, and a way is provided for online monitoring of the hot spot temperature rise of the light vehicle-mounted traction transformer;
2) the application range and the calculation precision of a two-section temperature rise calculation formula in IEEE and IEC standards are widened and improved, and the on-line monitoring result of the hot spot temperature rise of the light-weight vehicle-mounted traction transformer is more reliable.
Drawings
FIG. 1 is a flow chart of a lightweight vehicle-mounted traction transformer hotspot factor calculation method according to the present invention;
FIG. 2 is a schematic diagram of structural parameters of a lightweight vehicle-mounted traction transformer to be analyzed;
FIG. 3 is an axisymmetric two-dimensional model of a lightweight on-board traction transformer to be analyzed;
FIG. 4 is a schematic view of a temperature monitoring node arrangement local to a lightweight on-board traction transformer;
Detailed Description
The invention is further described with reference to the accompanying drawings and the specific implementation procedures. It should be emphasized that the embodiments described herein are merely illustrative of the invention and do not limit the scope of the inventive concept and its claims.
Firstly, establishing an axisymmetric two-dimensional model of a lightweight vehicle-mounted traction transformer
The method comprises the following steps of obtaining structural parameters (see figure 2) of a certain lightweight vehicle-mounted traction transformer to be analyzed, carrying out two-layer winding and 168 turns of conductor, and carrying out primary treatment according to the characteristics: deleting structures with small influence on temperature distribution, such as winding outlet terminals, clamps, stays and the like, simplifying a cooling air duct into an annular pipeline with inner and outer wall surfaces having constant heat flow simultaneously or independently, and finally establishing a corresponding axisymmetric two-dimensional model (see fig. 3);
secondly, arrange the temperature monitoring node, the temperature monitoring node includes: the winding temperature nodes, the insulating paper boundary nodes, the epoxy resin boundary nodes and the air temperature nodes are connected through thermal resistance to form a lightweight vehicle-mounted traction transformer thermal network model; the node arrangement method is specifically as follows (see fig. 4):
1) 1 winding temperature node is arranged at the center of each turn of the winding conductor, and the winding temperature nodes are aligned in the axial direction and the radial direction according to the winding structure;
2) 4 insulation paper boundary nodes are respectively arranged in the upper, lower, left and right 4 directions of the winding temperature node;
3) 2 epoxy resin boundary nodes are respectively arranged on the upper side and the lower side of the upper insulating paper boundary node and the lower insulating paper boundary node;
4) 1 air temperature node is arranged between 2 epoxy resin boundary nodes on two sides of the cooling air channel;
5) the winding temperature nodes are connected with the insulating paper boundary nodes through insulating paper thermal resistances, the insulating paper boundary nodes are connected with the epoxy resin boundary nodes through epoxy resin thermal resistances, the epoxy resin boundary nodes are connected with the air temperature nodes through convective thermal resistances, and the air temperature nodes are connected through air thermal resistances;
thirdly, calculating the thermal resistance of each part
1) Thermal resistance R of insulating paperpCalculated using the following formula:
in the formula, kpIs the thermal conductivity (W.m) of the insulating paper-1·k-1)，lpIs the thickness (m) of the insulating paper in the direction of heat flow of the thermal resistance of the insulating paper, SpThe contact area (m) of the insulating paper and the copper conductor in the heat flow direction of the thermal resistance of the insulating paper2)；
2) Thermal resistance R of epoxy resineCalculated using the following formula:
in the formula, keIs the thermal conductivity (W.m) of the epoxy resin-1·k-1)，leIs the thickness (m), S, of the epoxy resin in the heat flow direction of the epoxy resin heat resistanceeThe contact area (m) of the epoxy resin and the insulating paper in the heat flow direction of the epoxy resin heat resistance2)；
3) Air thermal resistance RairCalculated using the following formula:
in the formula, mairMass flow (kg.s) of air in cooling duct-1)，Cp_airThe specific heat capacity (J.kg) of air-1·K-1)，LductFor cooling air ductsL is the axial width (m) of the conductor;
4) convective heat resistance RconvCalculated using the following formula:
in the formula, DoIs the outer diameter (m), D of the cooling air ductiIs the inner diameter (m) of the cooling air duct, NuxIs a local Nussel number, kairIs the thermal conductivity (W.m) of air-1·k-1)，SductThe contact area (m) of the epoxy resin outside the temperature node of a single winding and the cooling air duct2)；
The convective thermal resistance RconvIn the formula (2), NuxThe calculation formula of (a) is as follows:
in the formula, n is the number of the winding temperature node, and the rule is as follows: the winding temperature node at the inlet of the innermost cooling air duct is numbered as No. 1, and the winding temperature nodes from the inlet of the innermost cooling air duct to the outlet of the outermost cooling air duct are numbered as 2, 3 and 4 … in sequence; x is the distance (m) of air leaving the inlet of the cooling air duct, R is the radius (m) of the central line of the cooling air duct, Re is the Reynolds number of the cooling air duct, and the Reynolds number is calculated by using the following formula:
wherein ρ is an air density (kg · m)-3) V is the air flow velocity (m · s)-1) μ is aerodynamic viscosity (kg · m)-1·s-1)；
Fourthly, distributing heating power for winding temperature nodes
The heating power distributed to the winding temperature node with the number n is calculated according to the following formula:
in the formula, VnConductor volume (m) corresponding to winding temperature node numbered n3)，VGeneral assemblyIs the total volume (m) of the winding3) Q is the load loss (W) obtained by the field test of the transformer;
fifthly, acquiring the temperature rise of the hot spot
According to the lightweight vehicle-mounted traction transformer thermal network model structure from the first step to the fourth step, writing a node voltage equation according to kirchhoff's law, solving the winding temperature node temperature by using MATLAB programming to obtain the hottest point temperature, and simultaneously obtaining the ambient temperature of the corresponding time point, wherein the hot point temperature rise is obtained by subtracting the ambient temperature from the hottest point temperature;
sixthly, calculating hot spot factors
According to the method for acquiring the hot spot temperature rise in the fifth step, rated load loss is applied, and the hot spot temperature rise delta T under the rated load is acquiredn76.5K; then applying the loss under the rated current of 0.5 time, 0.6 time, 0.7 time, 0.8 time, 0.9 time, 1.1 time, 1.2 time, 1.3 time, 1.4 time and 1.5 time in sequence to obtain the hot spot temperature rise delta T under the lossi(i ═ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10) at 20.1K, 28.5K, 38.6K, 49.7K, 62.4K, 92.5K, 109.3K, 127.9K, 148.2K, 169.7K, respectively, the hotspot factor δ was calculated by substituting the above data into the following equation:
in the formula (I), the compound is shown in the specification,
Iifor the temperature rise of the hot spot to be delta TiCorresponding load current (A), InThe rated current (A) is obtained.
The hotspot factor δ was calculated to be 0.515.
Claims (1)
1. A lightweight vehicle-mounted traction transformer hotspot factor calculation method is characterized by comprising the following steps:
firstly, establishing an axisymmetric two-dimensional model of a lightweight vehicle-mounted traction transformer
Carrying out primary treatment according to the structural characteristics of the lightweight vehicle-mounted traction transformer: the winding outlet terminal, the clamping piece and the stay structure are deleted, and the cooling air duct is simplified into an annular pipeline with the inner wall surface and the outer wall surface having constant heat flow simultaneously or independently;
secondly, arrange the temperature monitoring node, the temperature monitoring node includes: the winding temperature nodes, the insulating paper boundary nodes, the epoxy resin boundary nodes and the air temperature nodes are connected through thermal resistance to form a lightweight vehicle-mounted traction transformer thermal network model; the node arrangement method specifically comprises the following steps:
1) 1 winding temperature node is arranged at the center of each turn of the winding conductor, and the winding temperature nodes are aligned in the axial direction and the radial direction according to the winding structure;
2) 4 insulation paper boundary nodes are respectively arranged in the upper, lower, left and right 4 directions of the winding temperature node;
3) 2 epoxy resin boundary nodes are respectively arranged on the upper side and the lower side of the upper insulating paper boundary node and the lower insulating paper boundary node;
4) 1 air temperature node is arranged between 2 epoxy resin boundary nodes on two sides of the cooling air channel;
5) the winding temperature nodes are connected with the insulating paper boundary nodes through insulating paper thermal resistances, the insulating paper boundary nodes are connected with the epoxy resin boundary nodes through epoxy resin thermal resistances, the epoxy resin boundary nodes are connected with the air temperature nodes through convective thermal resistances, and the air temperature nodes are connected through air thermal resistances;
thirdly, calculating the thermal resistance of each part
1) Thermal resistance R of insulating paperpCalculated using the following formula:
in the formula, kpIs the thermal conductivity of the insulating paper, and has a unit of W.m-1·K-1，lpThe thickness of the insulating paper in the direction of heat flow of the thermal resistance of the insulating paper is given in m, SpThe contact area of the insulating paper and the copper conductor in the heat flow direction of the thermal resistance of the insulating paper is m2；
2) Thermal resistance R of epoxy resineCalculated using the following formula:
in the formula, keIs the thermal conductivity of the epoxy resin and has the unit of W.m-1·K-1，leIs the thickness of the epoxy resin in the heat flow direction of the epoxy resin thermal resistance and has a unit of m, SeThe contact area of the epoxy resin and the insulating paper in the heat flow direction of the epoxy resin heat resistance is m2；
3) Air thermal resistance RairCalculated using the following formula:
in the formula, mairIs the mass flow of air in the cooling air duct, and has the unit of kg.s-1，Cp_airIs the specific heat capacity of air, and has a unit of J.kg-1·K-1，LductThe unit is m for the total length of the cooling air duct, and l is the axial width of the conductor and the unit is m;
4) convective heat resistance RconvCalculated using the following formula:
in the formula, DoIs the outer diameter of the cooling air duct, and has the unit of m and DiIs the inner diameter of the cooling air duct, and the unit is m, NuxIs a local Nussel number，kairIs the thermal conductivity of air, and has the unit of W.m-1·K-1，SductThe contact area of the epoxy resin outside the temperature node of a single winding and the cooling air duct is m2；
The convective thermal resistance RconvIn the formula (2), NuxThe calculation formula of (a) is as follows:
in the formula, n is the number of the winding temperature node, and the rule is as follows: the winding temperature node at the inlet of the innermost cooling air duct is numbered as No. 1, and the winding temperature nodes from the inlet of the innermost cooling air duct to the outlet of the outermost cooling air duct are numbered as 2, 3 and 4 … in sequence; x is the distance from the air duct inlet, and the unit is m, R is the center line radius of the cooling air duct, the unit is m, and Re is the Reynolds number of the cooling air duct, and the following formula is used for calculating:
where ρ is the air density in kg · m-3V is the air flow rate in m.s-1Mu is aerodynamic viscosity in kg.m-1·s-1；
Fourthly, distributing heating power for winding temperature nodes
The heating power distributed to the winding temperature node with the number n is calculated according to the following formula:
in the formula, VnConductor volume corresponding to winding temperature node numbered n in m3，VGeneral assemblyIs the total volume of the winding, in m3Q is the load loss obtained by the field test of the transformer, and the unit is W;
fifthly, acquiring the temperature rise of the hot spot
According to the lightweight vehicle-mounted traction transformer thermal network model structure from the first step to the fourth step, solving the winding temperature node temperature according to a kirchhoff law column writing node voltage equation to obtain the hottest point temperature, and simultaneously obtaining the ambient temperature of the corresponding time point, wherein the environment temperature is subtracted from the hottest point temperature to obtain the hot point temperature rise;
sixthly, calculating hot spot factors
According to the method for acquiring the hot spot temperature rise in the fifth step, rated load loss is applied, and the hot spot temperature rise delta T under the rated load loss is acquirednIn units of K; then, the loss under the rated current of 0.5 times, 0.6 times, 0.7 times, 0.8 times, 0.9 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times and 1.5 times is applied in sequence to obtain the corresponding hot spot temperature rise under the loss, the unit is K, and the temperature rise is respectively marked as delta Ti1, 2, 3, 4, 5, 6, 7, 8, 9, 10; the hotspot factor δ is calculated using the following formula:
in the formula (I), the compound is shown in the specification,
Iifor the temperature rise of the hot spot to be delta TiThe unit of the corresponding load current is A, InIs the rated current, and has the unit of A.
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| CN109255192A (en) * | 2018-09-21 | 2019-01-22 | 国网电力科学研究院武汉南瑞有限责任公司 | A kind of emulated computation method of Transformer Winding Temperature Rise characteristic |
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