China is faced with the large-scale uprating of old underground distribution cables. It is an effective technical measure for short-term ampacity uprating of single-core cable to change solid grounding of metal sheath into special grounding. However

for the huge distribution network cable upgrading project

the existing research lacks the optimization segmentation and comprehensive evaluation method of the special grounding mode. Consequently

we first studied the cable ampacity calculation formula under the special grounding mode

and then analyzed and formulated the standing voltage value of the metal sheath according to the electric shock protection theory. Taking the standing voltage as the constraint

we put forward an optimization segmentation method of the special grounding mode of the cable

and formulated the corresponding engineering technical reference charts. On this basis

by integrating the factors of uprating

reliability

and economy effect

a comprehensive evaluation method of cable special grounding mode was designed. Finally

an actual case of distribution network cable uprating was used to illustrate the engineering application of the proposed method

which was verified by the ATP/EMTP software. The results show that changing the single core cable to special grounding can fully tap the ampacity potential of the laid cable

and the copper core cable in parallel interval arrangement has considerable ampacity increase space. Combination of the optimized segmentation and comprehensive evaluation index of special grounding type can help improve the uprating efficiency and clarify the uprating effect.