Following Expression in SSRS will convert Second to Hours Minutes Second Format
HH : MM : SS
=Floor(sum(Fields!Second.Value)/ 3600) &":"& Format(DateAdd("s", sum(Fields!Second.Value), "00:00"),"mm:ss")
Following Expression in SSRS will convert Second to Days Hours Minutes Second Format
DD :HH : MM : SS
=Floor(sum(Fields!Second.Value) / 86400) &":"& Format(DateAdd("s", sum(Fields!Second.Value), "00:00:00"), "HH:mm:ss")
Exampe From Report