ABSTRACT

System grounding refers to the electrical connection between the phase conductors and the ground and dictates the manner in which the neutral points of wye-connected transformers and generators or artificially derived neutral systems through delta-wye or zigzag transformers are grounded. In a solidly grounded system, there is no intentional impedance between the system neutral and the ground. A power system is solidly grounded when the generator, power transformer, or grounding transformer neutral is directly connected to the ground. The utility systems at transmission, sub-transmission, and distribution levels are solidly grounded. The main reason for this is that on occurrence of a ground fault, enough ground fault current should be available to selectively trip the faulty circuit. The magnetic fields, surrounding each bus, constrain the arc to jump phase to phase, which results in more slowly evolving phase-to-phase fault, and for a greater period of time, it remains as a phase-to-ground fault.