The paper deals with the temporary overvoltages that build up in radial MV distribution networks following the inception of a 1-phase-to-ground fault. It will be demonstrated that, for extended cable/overhead MV distribution networks with ungrounded neutral, in case of low resistance faults at critical locations along overhead lines, the neutral voltage can reach very large values, significantly higher than 1 p.u. (up to 2.5 p.u.). The attendant temporary overvoltages on healthy phases can be very large, much higher than ?3 p.u. (up to 3.5 p.u.). Fault currents are also affected, reaching twice the value calculated with simplified methods, i.e. neglecting series impedances. Quick yet accurate analytical formulas for the prediction of maximum overvoltages, fault currents and critical fault distances are presented, together with their validation by detailed ATP-EMTP simulations. The results of a study on an existing Italian 15 kV–50 Hz extended mixed cable/overhead distribution network are finally presented and discussed.

Analytical prediction of abnormal temporary overvoltages due to ground faults in MV network / Gatta, Fabio Massimo; Geri, Alberto; Lauria, Stefano; Maccioni, Marco. - In: ELECTRIC POWER SYSTEMS RESEARCH. - ISSN 0378-7796. - STAMPA. - 77:10, August 2007(2007), pp. 1305-1313. [10.1016/j.epsr.2006.09.023]

Analytical prediction of abnormal temporary overvoltages due to ground faults in MV network

GATTA, Fabio Massimo;GERI, Alberto;LAURIA, Stefano;MACCIONI, Marco
2007

Abstract

The paper deals with the temporary overvoltages that build up in radial MV distribution networks following the inception of a 1-phase-to-ground fault. It will be demonstrated that, for extended cable/overhead MV distribution networks with ungrounded neutral, in case of low resistance faults at critical locations along overhead lines, the neutral voltage can reach very large values, significantly higher than 1 p.u. (up to 2.5 p.u.). The attendant temporary overvoltages on healthy phases can be very large, much higher than ?3 p.u. (up to 3.5 p.u.). Fault currents are also affected, reaching twice the value calculated with simplified methods, i.e. neglecting series impedances. Quick yet accurate analytical formulas for the prediction of maximum overvoltages, fault currents and critical fault distances are presented, together with their validation by detailed ATP-EMTP simulations. The results of a study on an existing Italian 15 kV–50 Hz extended mixed cable/overhead distribution network are finally presented and discussed.
Temporary overvoltages; MV radial network; Neutral grounding; 1-Phase-to-ground fault
01 Pubblicazione su rivista::01a Articolo in rivista
Analytical prediction of abnormal temporary overvoltages due to ground faults in MV network / Gatta, Fabio Massimo; Geri, Alberto; Lauria, Stefano; Maccioni, Marco. - In: ELECTRIC POWER SYSTEMS RESEARCH. - ISSN 0378-7796. - STAMPA. - 77:10, August 2007(2007), pp. 1305-1313. [10.1016/j.epsr.2006.09.023]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/235285
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