Characteristics of different power systems neutral grounding techniques: facts and fiction

Resonance in Electrical Power Systems of Petrochemical Plants

“…In large systems where we have a high capital investment in equipment or losses which have a significant economic impact, we use the low impedance grounding [Manning, 1964;Shipp & Angelini, 1991]. In this scheme, a resistor is connected, normally a value that allows only a ground fault current of 200 to 800 A, through the neutral grounding system, see Fig. 2.1.1.…”

“…In this scheme, a resistor is connected, normally a value that allows only a ground fault current of 200 to 800 A, through the neutral grounding system, see Fig. 2.1.1. As the grounding impedance is a resistance, any transient overvoltage is quickly damped and the overvoltage does not stay for a long time [Shipp & Angelini, 1991].…”

“…2.2.1. If the system is not solidly grounded, the neutral system remains floating to ground, and remains as function of the load line to neutral and exposed to unbalanced voltages and instability [Shipp & Angelini, 1991]. …”

“…The perception is that the floating systems provide greater continuity on the service. This is based on an argument that the ground fault current is smaller and therefore, the heating produced by the presence of such failure is negligible [Shipp & Angelini, 1991]. That way, the line to ground faults can remain on the system until it's convenient to remove them.…”

“…When this happens, the high current flow causes high voltages across the unfaulted phases. Transient events due to switching or intermittent faults to the ground can produce overvoltages on floating systems [Shipp & Angelini, 1991]. Table 1.…”