he utility model discloses a zero sequence voltage secondary loop capable of realizing automatic on-off response. The zero sequence voltage secondary loop capable of realizing automatic on-off response is provided with a positive bus secondary loop and a secondary bus secondary loop and is further provided with a zero sequence voltage secondary loop, a positive bus voltage variation knife switch auxiliary contact and a secondary bus voltage variation knife switch auxiliary contact are respectively arranged between an open delta winding in the zero sequence voltage secondary loop and a zero sequence voltage small bus, and air switches are respectively arranged between the zero sequence voltage small bus, and the positive bus voltage variation knife switch auxiliary contact and the secondary bus voltage variation knife switch auxiliary contact. By utilizing a technical scheme above, when the zero sequence voltage secondary loop is in fault, a voltage transformer can not be burned out, skipping of the air switches can be discovered timely, so correct motion of a protective device is guaranteed.