The paper introduces line break failure and temporary treatment measures of 220 kV overhead transmission line

then gives the reasons for disconnection of wires through performance mechanical and electrical comparison tests of the broken samples such as pull test

current carrier and temperature rising test

electron microscopy test and energy spectrum analysis.Points out that as a long line running years

the wire had existed significant defects of machinery and electricity before the fracture

and then led to wire break under a small load current due to vicious cycle of local heat development and gradual loss of strength.At the end this paper

stresses the need to control load current and infrared temperature measurement to remove security risks of line

and suggests taking out technical transformation project of fault line as soon as possible.