The hot spot temperature of a transformer is one of the critical indicators reflecting its operating status.Accurate and fast calculation of hot spot temperature is significant for the online monitoring of transformer...The hot spot temperature of a transformer is one of the critical indicators reflecting its operating status.Accurate and fast calculation of hot spot temperature is significant for the online monitoring of transformers.Considering the low computational efficiency of the transformer’s numerical full model(FM),this paper presents a model simplification method based on the equivalent thermal parameters of windings to expedite hot spot temperature computation.Initially,the representative volume element(RVE)reflecting the periodic structure of windings is selected to formulate a reduced model(RM)for the transformer.Subsequently,to achieve equivalence between the RM and the FM,the equivalent thermal parameters of the RVE are calculated,containing the equivalent thermal conductivity(ETC),the equivalent density(ED),and the equivalent specific heat capacity(ESHC).Finally,the validity of the RM is verified by the temperature rise test.The results show that,compared with the tested data,the maximum error of the hot spot temperature calculated by the RM is 2.56 K,demonstrating the accuracy of the hot spot temperature calculation by the RM.Compared with the FM,the computing time of the proposed RM is reduced to 1/189,which significantly improves the computational efficiency.展开更多
C_(5)F_(10)O/CO_(2)gas mixture is one of the most promising alternatives to SF_(6)as an insulating gas in high-voltage switchgear.As a key performance index in product design,the temperature rise characteristics are r...C_(5)F_(10)O/CO_(2)gas mixture is one of the most promising alternatives to SF_(6)as an insulating gas in high-voltage switchgear.As a key performance index in product design,the temperature rise characteristics are rarely reported.In this paper,the thermodynamic parameters of C_(5)F_(10)O/CO_(2)gas mixture were calculated first.Then,the calculation model of transient temperature rise was constructed for a 252 kV/3150 A bus,and a temperature rise experimental platform was built to verify the reliability of the proposed calculation model.On this basis,the influence of different factors such as load current,charging pressure,mixing ratio,and structure size on the temperature rise of the bus was further analysed,and it is found that increasing the charging pressure and the mixing ratio of C5F10O could effectively reduce the bus temperature rise but it still could not reach the level of SF_(6).The main structure size that affects the temperature rise of the bus is the outer diameter of the conductor,which increases by 10.2%,and the temperature rise is the same as that of the original SF_(6)bus.Finally,a high-precision bus temperature rise surrogate model,which combined with the Latin hypercube model,the coefficient of prognosis,and the Kriging fitting method was established to facilitate the structural design.展开更多
The thermodynamic stabilities, electronic structures, and mechanical properties of the Pd-based superalloys are studied by first principles calculations. In this work, we discuss the effect of Pd-based superalloys mad...The thermodynamic stabilities, electronic structures, and mechanical properties of the Pd-based superalloys are studied by first principles calculations. In this work, we discuss the effect of Pd-based superalloys made from Al, Si, Sc, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, Mo, Tc, Hf, Ta, W, Re, Os, Ir and Pt, and we also calculate a face centered cubic （fcc） structure 222 superalloy including 31 Pd atoms and one alloying element TM （Pd31TM）. The mixing energies of these Pd-Based superalloys are negative, indicating that all Pd-based superalloys are thermodynamically stable. The Pd31Mn has the lowest mixing energy with a value of-0.97 eV/atom. The electronic structures of the Pd-based superalloys are also studied, the densities of states, elastic constants and moduli of the mechanical properties of the Pd-based superalloys are determined by the stress-strain method and Voigt-Reuss-Hill approximation. It is found that Pd31TM is mechanically stable, and Pd31Tc has the largest C11, with a value 279.7 GPa. The Pd31Cr has the highest bulk modulus with a value of 299.8 GPa. The Pd31Fe has the largest shear modulus and Youngs modulus with the values of 73.8 GPa and 195.2 GPa, respectively. By using the anisotropic index, the anisotropic mechanical properties of the Pd31TM are discussed, and three-dimensional （3D） surface contours and the planar projections on （001） and （110） planes are also investigated by the Young modulus.展开更多
基金supported by Hubei Technology Innovation Center for Smart Hydropower(SDCXZX-JJ-2023-03).
文摘The hot spot temperature of a transformer is one of the critical indicators reflecting its operating status.Accurate and fast calculation of hot spot temperature is significant for the online monitoring of transformers.Considering the low computational efficiency of the transformer’s numerical full model(FM),this paper presents a model simplification method based on the equivalent thermal parameters of windings to expedite hot spot temperature computation.Initially,the representative volume element(RVE)reflecting the periodic structure of windings is selected to formulate a reduced model(RM)for the transformer.Subsequently,to achieve equivalence between the RM and the FM,the equivalent thermal parameters of the RVE are calculated,containing the equivalent thermal conductivity(ETC),the equivalent density(ED),and the equivalent specific heat capacity(ESHC).Finally,the validity of the RM is verified by the temperature rise test.The results show that,compared with the tested data,the maximum error of the hot spot temperature calculated by the RM is 2.56 K,demonstrating the accuracy of the hot spot temperature calculation by the RM.Compared with the FM,the computing time of the proposed RM is reduced to 1/189,which significantly improves the computational efficiency.
基金Sichuan Science and Technology Program,Grant/Award Number:2023NSFSC0297。
文摘C_(5)F_(10)O/CO_(2)gas mixture is one of the most promising alternatives to SF_(6)as an insulating gas in high-voltage switchgear.As a key performance index in product design,the temperature rise characteristics are rarely reported.In this paper,the thermodynamic parameters of C_(5)F_(10)O/CO_(2)gas mixture were calculated first.Then,the calculation model of transient temperature rise was constructed for a 252 kV/3150 A bus,and a temperature rise experimental platform was built to verify the reliability of the proposed calculation model.On this basis,the influence of different factors such as load current,charging pressure,mixing ratio,and structure size on the temperature rise of the bus was further analysed,and it is found that increasing the charging pressure and the mixing ratio of C5F10O could effectively reduce the bus temperature rise but it still could not reach the level of SF_(6).The main structure size that affects the temperature rise of the bus is the outer diameter of the conductor,which increases by 10.2%,and the temperature rise is the same as that of the original SF_(6)bus.Finally,a high-precision bus temperature rise surrogate model,which combined with the Latin hypercube model,the coefficient of prognosis,and the Kriging fitting method was established to facilitate the structural design.
基金Project supported by the Young-Talent Support Programs of Kunming University of Science and Technology,China(Grant No.11504146)the National Natural Science Foundation of China(Grant No.51762028)
文摘The thermodynamic stabilities, electronic structures, and mechanical properties of the Pd-based superalloys are studied by first principles calculations. In this work, we discuss the effect of Pd-based superalloys made from Al, Si, Sc, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, Mo, Tc, Hf, Ta, W, Re, Os, Ir and Pt, and we also calculate a face centered cubic （fcc） structure 222 superalloy including 31 Pd atoms and one alloying element TM （Pd31TM）. The mixing energies of these Pd-Based superalloys are negative, indicating that all Pd-based superalloys are thermodynamically stable. The Pd31Mn has the lowest mixing energy with a value of-0.97 eV/atom. The electronic structures of the Pd-based superalloys are also studied, the densities of states, elastic constants and moduli of the mechanical properties of the Pd-based superalloys are determined by the stress-strain method and Voigt-Reuss-Hill approximation. It is found that Pd31TM is mechanically stable, and Pd31Tc has the largest C11, with a value 279.7 GPa. The Pd31Cr has the highest bulk modulus with a value of 299.8 GPa. The Pd31Fe has the largest shear modulus and Youngs modulus with the values of 73.8 GPa and 195.2 GPa, respectively. By using the anisotropic index, the anisotropic mechanical properties of the Pd31TM are discussed, and three-dimensional （3D） surface contours and the planar projections on （001） and （110） planes are also investigated by the Young modulus.
