An Equivalent Circuit for the Evaluation of Cross-Country Fault Currents in Medium Voltage (MV) Distribution Networks

A Cross-Country Fault (CCF) is the simultaneous occurrence of a couple of Line-to-Ground Faults (LGFs), affecting different phases of same feeder or of two distinct ones, at different fault locations. CCFs are not uncommon in medium voltage (MV) public distribution networks operated with ungrounded...

Full description

Bibliographic Details
Main Authors: Fabio Massimo Gatta, Alberto Geri, Stefano Lauria, Marco Maccioni
Format: Article
Language:English
Published: MDPI AG 2018-07-01
Series:Energies
Subjects:
Online Access:http://www.mdpi.com/1996-1073/11/8/1929
id doaj-817124af053e4e20afcc36cce7b24478
record_format Article
spelling doaj-817124af053e4e20afcc36cce7b244782020-11-25T01:15:19ZengMDPI AGEnergies1996-10732018-07-01118192910.3390/en11081929en11081929An Equivalent Circuit for the Evaluation of Cross-Country Fault Currents in Medium Voltage (MV) Distribution NetworksFabio Massimo Gatta0Alberto Geri1Stefano Lauria2Marco Maccioni3Department of Astronautics, Electric and Energy Engineering, “Sapienza” University of Rome, Rome 00184, ItalyDepartment of Astronautics, Electric and Energy Engineering, “Sapienza” University of Rome, Rome 00184, ItalyDepartment of Astronautics, Electric and Energy Engineering, “Sapienza” University of Rome, Rome 00184, ItalyDepartment of Astronautics, Electric and Energy Engineering, “Sapienza” University of Rome, Rome 00184, ItalyA Cross-Country Fault (CCF) is the simultaneous occurrence of a couple of Line-to-Ground Faults (LGFs), affecting different phases of same feeder or of two distinct ones, at different fault locations. CCFs are not uncommon in medium voltage (MV) public distribution networks operated with ungrounded or high-impedance neutral: despite the relatively small value of LGF current that is typical of such networks, CCF currents can be comparable to those that are found in Phase-To-Phase Faults, if the affected feeder(s) consists of cables. This occurs because the faulted cables’ sheaths/screens provide a continuous, relatively low-impedance metallic return path to the fault currents. An accurate evaluation is in order, since the resulting current magnitudes can overheat sheaths/screens, endangering cable joints and other plastic sheaths. Such evaluation, however, requires the modeling of the whole MV network in the phase domain, simulating cable screens and their connections to the primary and secondary substation earth electrodes by suitable computer programs, such as ATP (which is the acronym for alternative transient program) or EMTP (the acronym for electromagnetic transient program), with substantial input data being involved. This paper presents a simplified yet accurate circuit model of the faulted MV network, taking into account the CCF currents’ return path (cable sheaths/screens, ground conductors, and earthing resistances of secondary substations). The proposed CCF model can be implemented in a general-purpose simulation program, and it yields accurate fault currents estimates: for a 20 kV network case study, the comparison with accurate ATP simulations evidences mismatches mostly smaller than 2%, and never exceeding 5%.http://www.mdpi.com/1996-1073/11/8/1929cross country faultsimplified circuit modelmixed cable-overhead MV distribution network
collection DOAJ
language English
format Article
sources DOAJ
author Fabio Massimo Gatta
Alberto Geri
Stefano Lauria
Marco Maccioni
spellingShingle Fabio Massimo Gatta
Alberto Geri
Stefano Lauria
Marco Maccioni
An Equivalent Circuit for the Evaluation of Cross-Country Fault Currents in Medium Voltage (MV) Distribution Networks
Energies
cross country fault
simplified circuit model
mixed cable-overhead MV distribution network
author_facet Fabio Massimo Gatta
Alberto Geri
Stefano Lauria
Marco Maccioni
author_sort Fabio Massimo Gatta
title An Equivalent Circuit for the Evaluation of Cross-Country Fault Currents in Medium Voltage (MV) Distribution Networks
title_short An Equivalent Circuit for the Evaluation of Cross-Country Fault Currents in Medium Voltage (MV) Distribution Networks
title_full An Equivalent Circuit for the Evaluation of Cross-Country Fault Currents in Medium Voltage (MV) Distribution Networks
title_fullStr An Equivalent Circuit for the Evaluation of Cross-Country Fault Currents in Medium Voltage (MV) Distribution Networks
title_full_unstemmed An Equivalent Circuit for the Evaluation of Cross-Country Fault Currents in Medium Voltage (MV) Distribution Networks
title_sort equivalent circuit for the evaluation of cross-country fault currents in medium voltage (mv) distribution networks
publisher MDPI AG
series Energies
issn 1996-1073
publishDate 2018-07-01
description A Cross-Country Fault (CCF) is the simultaneous occurrence of a couple of Line-to-Ground Faults (LGFs), affecting different phases of same feeder or of two distinct ones, at different fault locations. CCFs are not uncommon in medium voltage (MV) public distribution networks operated with ungrounded or high-impedance neutral: despite the relatively small value of LGF current that is typical of such networks, CCF currents can be comparable to those that are found in Phase-To-Phase Faults, if the affected feeder(s) consists of cables. This occurs because the faulted cables’ sheaths/screens provide a continuous, relatively low-impedance metallic return path to the fault currents. An accurate evaluation is in order, since the resulting current magnitudes can overheat sheaths/screens, endangering cable joints and other plastic sheaths. Such evaluation, however, requires the modeling of the whole MV network in the phase domain, simulating cable screens and their connections to the primary and secondary substation earth electrodes by suitable computer programs, such as ATP (which is the acronym for alternative transient program) or EMTP (the acronym for electromagnetic transient program), with substantial input data being involved. This paper presents a simplified yet accurate circuit model of the faulted MV network, taking into account the CCF currents’ return path (cable sheaths/screens, ground conductors, and earthing resistances of secondary substations). The proposed CCF model can be implemented in a general-purpose simulation program, and it yields accurate fault currents estimates: for a 20 kV network case study, the comparison with accurate ATP simulations evidences mismatches mostly smaller than 2%, and never exceeding 5%.
topic cross country fault
simplified circuit model
mixed cable-overhead MV distribution network
url http://www.mdpi.com/1996-1073/11/8/1929
work_keys_str_mv AT fabiomassimogatta anequivalentcircuitfortheevaluationofcrosscountryfaultcurrentsinmediumvoltagemvdistributionnetworks
AT albertogeri anequivalentcircuitfortheevaluationofcrosscountryfaultcurrentsinmediumvoltagemvdistributionnetworks
AT stefanolauria anequivalentcircuitfortheevaluationofcrosscountryfaultcurrentsinmediumvoltagemvdistributionnetworks
AT marcomaccioni anequivalentcircuitfortheevaluationofcrosscountryfaultcurrentsinmediumvoltagemvdistributionnetworks
AT fabiomassimogatta equivalentcircuitfortheevaluationofcrosscountryfaultcurrentsinmediumvoltagemvdistributionnetworks
AT albertogeri equivalentcircuitfortheevaluationofcrosscountryfaultcurrentsinmediumvoltagemvdistributionnetworks
AT stefanolauria equivalentcircuitfortheevaluationofcrosscountryfaultcurrentsinmediumvoltagemvdistributionnetworks
AT marcomaccioni equivalentcircuitfortheevaluationofcrosscountryfaultcurrentsinmediumvoltagemvdistributionnetworks
_version_ 1725153973126561792