Considering　the　large　heat　capacity　of　the　surrounding　soil,　the　influence　of　cable　load　on　the　transient　temperature　rise　of　the　soil　can　be　neglected　within　short　periods　of　time.　A　simplified　transient　thermal　circuit　model　based　on　the　monitoring　ambient　temperature　in　the　trench　is　proposed.　The　thermal　resistance　and　thermal　capacity　of　the　model　are　calculated　by　using　the　empirical　formula.　Considering　the　strong　thermal　interaction　between　multiple　loops　of　the　cables,　the　external　thermal　resistance　is　modified　by　the　load　and　air　temperature.　By　comparing　the　result　of　the　calculation　of　the　model　with　that　of　the　finite　element　method,　the　accuracy　of　the　thermal　circuit　model　is　verified.　Based　on　the　method　of　the　transient　thermal　circuit　model,　the　maximum　permissible　current-carrying　can　be　predicted.　©　2019　IEEE.