The traditional differential protection based on lumped parameter can not be applied to half wavelength transmission lines due to the spatial and temporal electrical characteristics of half wavelength transmission line.Consequently

we proposed a method of practical differential protection based on wave equation for half wavelength transmission lines.Through the selection of the special data synchronization point

we improved the the speed

reliability and sensitivity of the protection by constructing the restraint current and setting up two-section phase current differential protections and one section zero sequence current differential protection.Based on this principle

a differential protection device was developed.A simulation model of UHV transmission line based on RTDS was established to verify this device.The simulation results indicate that the synchronous data selection

the restraint current

and two-section phase current differential protections and one section zero sequence current differential can improve the speed

reliability and sensitivity of the protection device.