The loco is attatched at Kasara to many trains as it is the starting of ghat section and thus a loco is attatched from behind.This is not to give more power to loco but to assist the coupling or to prevent coupling from breaking as the slope/gradient of ghat is much.These locos are then dettatched at Igatpuri (IGP) and a new loco (maybe WAP series, WAM series, WDM series or WDP series) is attatched.
PS-This maybe a half information.Please ask some senior man in this forum.
Regards