I did a relay upgrade at a peaker plant last fall. Primary gen protection was SEL-300G, backup was 700G with touchscreen. All the old analog meters were removed from the panels. The 700G was also the autosynchronizer, which has a dedicated screen showing the sync window. Having the HMI available at eye level from the 700G was extremely valuable during initial startup, dummy syncs and during AVAR tuning. The HMI has a virtual keyboard, so level 1 and level 2 passwords can be entered with ease. Viewing events, SER, etc is much easier with HMI. In certain utility environments, with represented workers, the PC connection can only be made by the relay techs. Not having that dependency is valuable at times.

Yesterday I started a SEL 735 meter installation at a WWTP. I've set the HMI up in conjunction with the soft buttons on the meter to show events based on PQ triggers. Plant staff can now easily access the SER with the push of a button.

The HMI version has the same PW protection as you would with the serial connection, it's just easier to enter the PW. We don't normally use the HMI option, as all of our devices are SCADA connected and once the device is in service, the need is not really there. The cost, for example on a 751A, for example, doubles with the HMI. If you don't have a station HMI or panel meters, it's a nice feature. As far as failure mode, the HMI could crap out and the relay will still work. It's SEL, so you call them for another free HMI faceplate and you are back in business in less than 15 minutes with a part swap.