When a single-phase to ground fault (SPGF) occurs near the main power source in an active distribution network

distance protection section II (DPS-II) located at the distributed generator (DG) side operates with a delay. In gap-grounded transformers

this delay can lead to gap breakdown due to neutral-point overvoltage

which adversely affects the operation of DPS-II on the DG side. To address this issue

this paper proposes an improved DPS designed for active distribution networks with gap-grounded transformers. First

the factors influencing the additional impedance are analyzed after gap breakdown. To mitigate the effects of the additional impedance on DPS performance

an improved DPS based on real short-circuit impedances is introduced for active distribution networks. This scheme utilizes the negative-sequence current distribution factor on the DG side to accurately calculate the additional impedance angle

ensuring reliable protection. Simulation results demonstrate that the proposed scheme effectively operates under forward faults across various DG capacities

fault locations

local loads

and fault transition resistances. In addition

it avoids tripping under reverse faults

thereby confirming its reliability and superiority.