Analysis of winding temperature field under dynamic variable load of oil-immersed transformer

Abstract

The research on the temperature field of the transformer winding under dynamic variable load is of great significance for ensuring the safe operation of power systems. This paper takes an SSP-360000/500 transformer as the research object, establishes a 2-D simulation model, and uses the finite volume method to analyze the high voltage winding and low voltage winding temperature distribution of the transformer under dynamic variable load. The simulation calculation results have been fully verified by the experimental data to make the successful prediction of the overall temperature and hot spot temperature position of forced oil circulation transformers with a guided structure. The results show that the most significant temperature raise occurs at the secondary end of the winding. In the case of dynamic variable load. The temperature raise of the winding becomes larger as the load increases, but before the rated load is in the stable temperature rise range, it can run safely for a long time. However, during overload operation, the average temperature raise of the high voltage winding may exceed its limit, the insulation material is damaged.

High proportion and large value harmonic current influence on the magnetic field, loss and temperature distribution for ultrahigh voltage converter transformer

“…The actual current of the converter transformer is regarded as the non-sinusoidal periodic current operating under the superposition of fundamental wave and harmonics, and the losses under different load rates and harmonic currents can be directly calculated by the superposition principle. The derivation process is shown in Equation (20), where W represents the total loss of the winding, V represents the volume, t represents time, T represents a sinusoidal period of 2π, p represents the loss density of the winding, J represents the current density, and J 0 , J 1 , J 2 , etc. represent the DC, fundamental, and harmonic current densities, respectively.…”

“…I rated is the current at the rated load rate. The winding losses under the combined influence of load rate and harmonic current can be calculated by combining Equations (14)(15)(16)(17) and (20)(21). The calculation results of the winding losses in several cases are shown in Table 4.…”

“…Xu Dapeng et al. considered the influence of standby cooler on transformer temperature [20]. Li Huan et al.…”

“…In addition to harmonic currents, other key factors can also affect the temperature of the converter transformer. Xu Dapeng et al considered the influence of standby cooler on transformer temperature [20]. Li Huan et al compared IEC, Susa, Swift and other methods to study the influence of load rate on the winding temperature of transformer and conducted experimental verification [21].…”

Thermal Analysis and Structure Optimization of a Dry-type Transformer with Ceramic Insulated Windings for Offshore Platform

“…Michal et al [25] used the advanced EMAG-CFD-CFD coupling model to analyze the thermal analysis of 8.5MVA power transformer cooled by oil in ONAN mode, and used electromagnetic (EMAG) and fluid dynamics (CFD) models to study the temperature field of the transformer in detail. Xu et al [26] used the finite volume method to simulate the two-dimensional model of the transformer under dynamic variable load, analyzed the temperature distribution of high-voltage and low-voltage windings, and pointed out that this transformer can operate under 1.2 times overload conditions. Duan [27] proposed an equivalent method of radiation-convection heat transfer at transformer boundary based on heat transfer theory, which solves the problem that the boundary is difficult to set accurately in the calculation of transformer temperature field.…”