No, Dutchrailnut is wrong. During operation the ground relay only protects the high voltage system. When starting, the low voltage and high voltage systems are connected so a low-voltage ground shows up by tripping GR.
It can be a bear to track one down, especially if it's a negative because they are all daisy-chained together. But it's a necessary task. Grounds are not only a no-no to the FRA man, but get the wrong ones and all sorts of things can happen. Years ago a crew climbed off some ALCO Centuries on the D&H at Mechanicville. They failed to center the reverser or open Gen Field. Something went to ground, connected with a ground already there, and the units went to 8th notch and roared up the yard into a cut of cars. The independent brake was no match for wide-open locos.
Results are not always that drastic but an on-the-ball mechanic will take the time to track it down. The lazy or incompetent ones will jump out the GR, which is about like putting a penny in the fuse box!