I am a apprentice and recently we ran 2-2-2 AL wire from a main panel on a grain bin under ground in schedule 80 PVC to a cow barn but we did not run a ground conducter with the current carrying wire. I asked if this was correct and my employer advised. Grounded neutral conductors serving another building from a main building: Sec. 250-32(b)(2). When a common AC grounded service supplies one or more buildings/structures, you must separately ground each panelboard at each building or structure. You must ground the grounded neutral conductor at the panelboard in the second building/structure, and size it based on the rating or setting of automatic overcurrent protection device (OCPD) in the feeder circuit, as specified in Table 250-122. As per Sec. 225-33(a), the disconnecting means for each supply shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, a group of separate enclosures, or in or on a switchboard. If necessary, Sec. 225-32 and 250-32(d) allows you to locate the disconnecting means elsewhere on the premises. I thought this only had to with grounding electrode conducter not the actual ground conducter that ran from the main to the sub panel?