In order to solve the over-limit problem of short-circuit current

Sichuan power grid often adopts the scheme of out-series operation. When the line with series compensation（SC）is in out-series operation

the failure of the extension side line will cause impact damage to the series compensation system. At the same time

the existence of SC capacitor bank may cause the line submersible current and transient recovery voltage to exceed the original level when the line is tripped

resulting in heavy breakdown of the fracture after the line tripping

which will cause system overvoltage reclosing failure

delayed fault removal and even damage to the circuitbreaker. A protection coordination method for out-series operation of line with SC is proposed

that is to install a remote transmission device on the side of line with SC to receive the tripping command of adjacent lines so as to achieve the intertrip between adjacent lines and SC lines

which can suppress the potential supply current and transient recovery voltage caused by residual voltage of capacitor after tripping of adjacent lines

and also ensure that the capacitor bank is not damaged by impact. Field tests show that in case of a single-phase transient fault on the extension side

the SC can be bypassed correctly

and the series compensation can be re-opened after the line is overlapped; when the phase-to-phase fault occurs on the extension side

the SC can be bypassed permanently

which meets the engineering application. The research results can provide a certain reference for protection adaptability of out-series operation of series compensated line.