One of the most serious challenges for power industry restructuring is to maintain power system reliability at an acceptable level and to promote the overall economic efficiency of the whole power industry. To this end

transmission investment and expansion is inevitable. In the past decade

much effort has been made to address institutional structures

business models

incentives and regulation to assure appropriate transmission investments be made

and to develop workable assessment and planning methods for the deregulated environment. In this paper

a comprehensive survey is made on the state-of-the-art of several important issues associated with transmission investment and expansion planning in the electricity market environment

including: challenges of transmission investment and planning in the competitive market environment; transmission investment; merchant transmission; transmission rights; business models; transmission regulation; management of transmission investment and expansion; transmission planning methods; international experience.