Performance of the Common Grounding System during ground faults

The paper deals with the performance during ground faults of MV/LV substation grounding systems belonging to a “Common Grounding System” as per CENELEC HD 637 S1–1999 E. A parametric analysis is performed, by means of ATP-EMTP, on a typical 150/20/0.4 kV distribution system, considering the MV neutral ungrounded or resonant-grounded. Results obtained highlight the benefits brought by the Common Grounding System but also fault conditions, such as double-earth-fault on MV line(s) or 1-Phase-to-Ground fault HV side in the HV/MV substation, which can still generate significant touch and step voltages that should not be disregarded in the system grounding design.