A series arc occurring on the DC side of a PV is the preliminary indication of fire provoked from PVs. For DC arc status and fault problems, this paper contributes a DC series arc detection and protection scheme for string-type PVs implemented with a grid-connected inverter. The scheme employs a high frequency signal of the arc as the fault characteristic that is obtained from the filter capacitor in the PV string terminals of the inverter. The detecting algorithm is established according to the sample entropy and the standard deviation of the arc signal. 2-stage protection criteria and a reclosing strategy are proposed to improve reliability, and to satisfy the sample rate of the processor in the inverter. In line with the constitution of the circuit and operating principle of the inverters, a modification strategy is proposed to fulfill arc protection action. A platform is established for PV series arc testing. The proposed method can achieve reliable detection and protection, and the effectiveness of the method is verified for many cases. This work is supported by National Natural Science Foundation of China (No. 51877186) and Science and Technology Project of State Grid Jibei Electric Power Co., Ltd. (No. 5201041800N7).