Assessment of voltage harmonics’ impact on the maximum load capacity of the power supply transformer for the LHCD system

To study the influence of the voltage total harmonic distortion (THDV) and its spectrum on the harmonic loss factor ( F HL ) and the maximum allowable load capacity ratio ( I max ( pu )) for the transformer of the LHCD system, we use MATLAB software to model the LHCD system and study the winding loss and maximum allowed load capacity of the LHCD system transformer when the supply voltage source is sinusoidal and non-sinusoidal, respectively. The calculation is carried out by the method of IEEE standard C57.110 and the method of considering the skin effect. The calculation results of both methods clearly show that the THDV value of the supply voltage has a significant effect on the harmonic dissipation factor ( F HL ) and the maximum allowable load capacity ratio ( I max ( pu )) of the transformer. And the calculation method considering the skin effect increases the maximum allowable load capacity ratio of the LHCD system transformer by about 2%. The research results have important reference value for the future retrofit design of LHCD system transformers.