Fault characteristics of half-wavelength AC transmission lines are significantly different from those of conventional transmission lines.The existing line protection principle is no longer applicable to half-wavelength AC transmission lines.Researchers have developed new half-wavelength line protection devices

which put forward new requirements on line protection testing technology and environment.We realized a real-time closed-loop test of half-wavelength AC transmission line protection devices based on half-wavelength AC transmission dynamic simulation test platform.Moreover

we analyzed the key testing technology of the half-wavelength line protection different from the traditional line protection test and the construction of the test system.The test content was established and the test results were presented.Through the protection performance testing of half-wavelength line protection device

the algorithm defect of protection malfunction under differential current caused by MOA turning-on was detected and the settlement proposals such as blocking zero-sequence differential protection and increasing the braking coefficient were presented.The results lay a foundation for the practical application of half-wavelength AC transmission.