I use a Manta 5000 often (today as a matter of fact). It can do 3 phase tripping quite easily. I've seen others build interface boxes for their Dobles, using latching relays to simulate each breaker TC/CC and 52a/52b. The guy who built it for our local utility brags that it cost $10k to build the box when all was said and done (and he used to work for a recloser controller mfg.)
I find the problem with the Manta 79 Multifunctional Productivity mode, is that one is limited in what and how things can be tested (P-N faults only, or Ph-Ph or 3 Ph). I'm not sure how your protection scheme is operating, but if you are concerned about Neg/Zero sequence elements in an open condition, I think you would have to use the general mode and many states and that would be a lot of programming. It may make your head spin a bit. The Manta Outputs do act as a breaker simulator, so you dont have to think too much about that. I did 7 651R's with the Manta this year and due to the lack of test switches in a typical recloser application, the amount of wiring involved to make a 651R-Viper ST scheme test out properly (without using the 'breaker') was enormous. My test document was tedious as the built in Manta reporting is lacking in some areas.
If you have many 651R's to do and have some kind of NERC requirement, it may very well be worth your while to check out the Omicron when all costs are considered.
