The fault characteristics of half-wavelength transmission line with long transmission distance are significantly different from those of conventional ones. To meet the challenge

a practical protection scheme of half-wavelength transmission line is designed based on the principle of half-wavelength protection such as free wave energy protection

synchronous differential impedance protection

false synchronous differential impedance protection

etc. The proposed scheme forms a system that the single terminal protection clears the near-terminal fault with high speed operation and the remote two-terminal protection achieve rapid fault clearing for whole lines. Since the half-wavelength transmission line protection algorithm has the disadvantages of complex

large amount of calculation

high sampling rate and long channel delay

several key technologies are proposed such as hardware architecture based on CPU and double-DSP

split core processing and split dispatching cycle processing of protection logic and rollback mechanism of false synchronous differential impedance protection sampled data. The complete protection implementation scheme of half-wavelength transmission line protection is formed. At last

the real time digital simulation(RTDS)test and dynamic simulations prove that the protective action and performance index meet all the safety operation requirements of half-wavelength transmission line.