Can somebody please tell me what is the meaning of 'ladder' type of cable duct as used in power and control cables and 'perforated type' of cable duct as used in instrumentation cable.
Perforated cable tray it is cable tray according to European standard IEC 61537 and ladder cable tray it is according American [USA] standard NEMA VE-1
From definition cable duct is a system of conduit [or ducts] for underground run of cables. There are also rooms buried in place and connected with the duct bank, to allow the cables to be pulled or to provide side outlets of the cables to the location of the equipment. In these rooms cable tray may be installed.