Hmm...there really isn't a ground but there is casing you can buy to protect your ballast. I remember my HID flickered cause there is power going to the bulb, however something with the ground was not complete. Its within the wiring just make sure everything is tight. The older HID wire allowed you to plug it in reversed and it will snap in tight. However it is wrong.

Go to www.suvlights.com and under HID Xenon bulbs and ballast and under D2R type ballast at the bottom there is an aluminum casing you can buy to protect your ballast. There use to be an ABS plastic type casing. You can e-mail and ask them if its still available.