To illustrate with an example, let us consider your city Ahmedabad itself, a major Jn. Pt for Kalol / Viramgam / Jaipur / Vadodara. The ADI-BRC-BCT is electrified line where rest all lines are diesel. Trains which come from BCT/BRC side and bound for say RJT/GIMB/JP via ADI must change their locos to diesel at ADI. The Electric Locos are detached and Diesel locos are attached. There must be a place for the electric locos to rest so that the maintenance staff can look after them well and make them fit for the next run. Here Trip Shed serves the purpose. There is only Electric Trip Shed at ADI and need for Diesel Trip Shed is eliminated, since ADI has DLS at VTA where diesel locos are taken care of. In case of stations with Electric Loco Sheds, there will be Diesel Trip Sheds and no separate Electric Trip Sheds, since...
more... ELS itself will take care of Electric locos.