Abstract: Economic selection method of choosing medium and low coltage power cable cross-section  according to economic current is described.Through case studies,the authors explain  how to take advantage of economic currents and economic cross-section.Approach  of choosing  the power cable cross-section  is put forward,according to the economic currents,which can save energy and protect the environment.

Key words: energy-saving and environmental protection, energy-saving power supply system, economic selection of power cables, economic current, economic cross-section