Based on the national standard Quality of electric energy supply-Harmonics in public supply network

some concrete problems about the evaluation and limit calculation of harmonic current existed in distribution power system are studied in this paper. Considering the key parameters of the distribution of harmonic current

the impact of the determination of common connection point of single user access network on system impedance are analyzed

several methods of the short circuit capacity calculation of point of common connection point are provided. Based on the practical engineering cases

the connection of background harmonic voltage and harmonic circuit and the harmonic current amplification of nonlinear load are studied. The above contents provide a reference for the limit calculation and assessment of power quality.