Plc power quality issues

I am trying to find some information such as case studies done on power quality issues with plc's with and without power conditioners. Possibly information on the internet or books. Can anyone help me out with this?
Thanks

No case studies, but you know just about every AB PLC I get has power supply failure after about 6months. These are all ML1000 's on unconditioned power. We get a lot of dirty stuff coming thru here.

I put a UPS on every PLC that I install...Haven't lost one since I started doing this, and most of them are being feed by gensets.

Try looking at some of the UPS Mfgr's sites.
David