1. Is a RTU a device or a function?
What exactly is an RTU (Remote Terminal Unit) in this day and age? RTUs started out life as rather humble individuals, merely collecting and collating data for reporting to a master whenever the master was ready for it. These days RTUs seem to be nigh on autonmous beings. And then there are all these nice web enabled RTUs. Is it time to call a halt and lay down definitions for various levels of RTU, say, from dumb RTU right up to self governing fully autonmous rtus, and where do u draw the line before such an RTU turns into a master station? Is the traditional domain of the RTU now seriously under threat from new superior IEDs that seem to be cropping up in ever increasing numbers?
By the letter of the law, an RTU is a Remote TERMINAL Unit, i.e. one which gathers data from local I/O and reports it to a distant master. However, RTUs have become data concentrators, protocol gateways, routers, PLCs, automation application platforms, meters, switch controllers, cap bank controllers, reclosers, and are even beginning toimplement some protection functions. Simultaneously, most IEDs are beginning to take on the basic I/O functions of a traditional RTU. There seems to be no need to define a "next generation RTU". The Utility Communications Architecture (UCA) proposes as part of its Generic Object Model for Substation and Feeder Equipment (GOMSFE) that the various functions within a substation be divided into what it calls "building bricks". The generic I/O functions of a basic RTU are just some of those bricks, as are metering functions, protection functions, etc.
Any set of these functions will soon be able to reside in any device in the substation. As that happens, it will cease to matter what any device is actually called. Some devices may be called IEDs, some RTUs, some PLCs, some Relays, some meters, some computers, etc. because their vendors believe that is the main function of the device.
The important thing will be whether the subset of functions provided by the device meets a market niche, or whether it is flexible enough to fit several niches simultaneously.