Zero row ground row is straight through with the metal casing of the distribution cabinet, and is fixed directly to the metal frame of the distribution cabinet. Above the yellow and green two-color ground wire, or metal flexible tape connected to it. Zero row and ground row is the obvious difference is that the zero row is not directly fixed in the frame of the cabinet, but through the insulated Bakelite mat fixed, it is not directly connected to the cabinet metal casing, it is generally connected to the top of the blue wire (zero)