Contemplation of harmonic currents loading on large-scale photovoltaic transformers

A surge in harmonics and distortion in the South Africa's electric power system has come to the fore in the early phases of integrating renewable energy resources to the national electric grid. Having said that, in this day and age a considerable number of harmonic producing apparatus are present. On the basis of their beneficial effects in efficacy and controllability, harmonic producing apparatus are presumed looking ahead to the realization of the 2030 Integrated Resource Plan (IRP 2030) to increase further. The IRP 2030 is aimed at increasing the total renewable energy generation capacity contribution to about 24.7% by year 2030. Further to this is a considerable increase in the amount of harmonics in the electric power network. The mushroomed harmonics and distortion may drive inflated winding stray loss and thereby peculiar temperature rise phenomena. Undue losses have classically been presumed to be varying in direct proportion with the harmonics order and load current.In this paper, the transformer losses that occur when facilitating solar PV farm environment are investigated based on seasonal basis. The study in particular draw attention to the injection of harmonics and distortion using the IEEE Std. C57.110-2018 recommended practice. In the worst-case scenarios for summer and winter the harmonic current measurements were taken to evaluate the guaranteed services losses. The hourly mean harmonic current profile for summer and winter solar irradiation of a solar PV farm are presented to investigate their effects on the operation of the transformer during service. The findings of the investigation is projected to be used as a foundation for the IPP's and manufacturers for operating and designing transformers serving large-scale solar PV farms within acceptable maximum rating in taking into account the availability of solar irradiation on seasonal basis and robust parametric design at tender stage respectively.