The main purpose of this paper is to investigate the major factors that affect the voltage variation on distribution feeders. This research focuses on the degrees of influence of major factors on the node voltage variations along distribution feeders. First, the definitions and related standards of power quality are introduced. Then, the major factors are identified, analyzed and compared, followed by a concise discussion and conclusion. The research results are of value to distribution engineers to improve operation and maintenance, and to design better distribution feeders. (C) 2012 Elsevier B.V. All rights reserved.