Alternator Negative Sequence ITI7521
Protection of alternator against negative sequence. 
This relay operates on an inverse time curve with an adjustable constant "K" such that 
K = I2 t
The ITI7521 may be ordered with two different ranges for K:
8-25% for round rotor machines
13-40% for salient pole machines.

ANSI function: 46

A full brochure is available on the homepage for Static relays.