This appears to be a GE/Multilin SR469 Relay. From the manual...
"The PHASE DIFFERENTIAL CT PRIMARY must be entered if the differential feature is to be
used. If two CTs are used per phase in a vectorial summation configuration, the CTs should
be chosen to ensure there is no saturation during motor starting. If however, a core
balance CT is used for the differential protection in each phase, a low CT rating of 50 or 100
A allows for very sensitive differential protection."
I have found that the use of the 87-Differential description for this relay a bit misleading, vs. a traditional 87 relay (GE CFD, which is a percentage differential for a machine application). The SR 469 implementation is more like an inst or short time over current element, or a traditional partial differential application using overcurrent relays.