The petal-shaped distribution network has high power supply reliability. However

the closed-loop operation mode and the access of inverter-interfaced distributed generators (IIDGs) bring great challenges to the protection schemes. The current amplitude differential protection is an effective means to solve this problem

but the existing criterions rarely consider both sensitivity to high-resistance faults and low requirements for data synchronization. Therefore

the general variation laws of the amplitude difference between the current steady-state components at both terminals and the phase differences between current fault components at both terminals are revealed. For external faults

the steady-state-component current amplitude difference is around zero and the fault-component current phase difference is around 180°. For internal faults

either the amplitude difference is large or the phase difference is small. Accordingly

a current differential protection scheme based on the pre-fault and post-fault steady-state current is proposed. The amplitude and phase of current at both terminals of the protected line are required in the proposed scheme

which has low requirements for data synchronization. The simulation results show that the proposed protection scheme is not affected by the fault type

position

resistance and capacity of the IIDGs. It can also be applied to radial distribution networks with IIDGs.