Considering the universally decreased insulation resistance of high voltage cable sheath and the possibility of its decreased withstand voltage level, the paper studies whether the protector can act correctly without damage to protect the sheath with decreased insulation under lightning overvoltage, operation overvoltage and short circuit when configuring protectors with low voltage-current characteristics by establishing ATP-EMTP simulation models of single-ended grounding and crossbonding grounding. The results show that reducing the voltage-current characteristics of protector can reduce the residual voltage acting on the outer sheath, and the current flowing through the protector is still below its nominal discharge current; in the case of single-phase short circuit, under the condition of single-end grounding, the protector needs to absorb a large amount of short circuit energy, reducing the voltage-current characteristics will lead to protector explosion; under the condition of crossbonding grounding, whether the protector explode or not depends on the magnitude of short circuit current, while a larger short-circuit current will cause the protector to explode. Finally, suggestions of the protector configuration of the outer sheath with decreased insulation are proposed.