This thesis explores the impacts and behavior of 3-phase distribution transformers when subject to ungrounded single phase open circuit faults. A simple 3-phase system is modeled using MATLAB Simulink and operation under fault conditions are simulated and studied. Simulation results are confirmed via lab experimentation. Finally, a robust detection and protection method using neutral current injection (as proposed in industry literature) is built and demonstrated.
Electric utility operating experience has demonstrated that all too often, loads on 3-phase distribution transformers are not adequately protected against an ungrounded single phase open circuit fault (commonly called “single phasing”). This type of fault is amongst the least understood and hence the least protected against. This is especially true at end of transmission system radial feeds where 3-phase transformers can re-create the opened phase voltage due to a variety of effects including magnetic coupling, voltage loops and loading effects. Operating experience in the nuclear power industry has shown that the results can be catastrophic especially considering the impacts to motor loads. Impacts can result in unavailability of emergency loads, tripping of motor protection circuits or even motor damage and failure.
","abstract_html":"<p>This thesis explores the impacts and behavior of 3-phase distribution transformers when subject to ungrounded single phase open circuit faults. A simple 3-phase system is modeled using MATLAB Simulink and operation under fault conditions are simulated and studied. Simulation results are confirmed via lab experimentation. Finally, a robust detection and protection method using neutral current injection (as proposed in industry literature) is built and demonstrated.</p> <p>Electric utility operating experience has demonstrated that all too often, loads on 3-phase distribution transformers are not adequately protected against an ungrounded single phase open circuit fault (commonly called “single phasing”). This type of fault is amongst the least understood and hence the least protected against. This is especially true at end of transmission system radial feeds where 3-phase transformers can re-create the opened phase voltage due to a variety of effects including magnetic coupling, voltage loops and loading effects. Operating experience in the nuclear power industry has shown that the results can be catastrophic especially considering the impacts to motor loads. Impacts can result in unavailability of emergency loads, tripping of motor protection circuits or even motor damage and failure.</p>","abstract_has_math":false,"creators":["Montoya, Higinio Ariel"],"institution":null,"degree_name":"MS in Electrical Engineering","degree_level":null,"degree_discipline":"Electrical Engineering","degree_department":null,"school":null,"contributors":["Ali Shaban"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-05-01T07:00:00Z","date_published":"2018-05-01T07:00:00Z","updated_at":"2026-07-24T01:31:56Z","subjects":["single phasing","open phase condition","transformer","MATLAB","three phase","Power and Energy"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["10.15368/theses.2018.23"],"render_values":[{"text":"10.15368/theses.2018.23","href":"https://doi.org/10.15368/theses.2018.23","code":true}]}]},"links":{"outbound_url":"https://digitalcommons.calpoly.edu/theses/1869","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Ali Shaban"]},{"key":"dc:creator","label":"Author","values":["Montoya, Higinio Ariel"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2018-05-25T07:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical Engineering"]},{"key":"thesis:degree_name","label":"Degree Name","values":["MS in Electrical Engineering"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["single phasing","open phase condition","transformer","MATLAB","three phase","Power and Energy"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://digitalcommons.calpoly.edu/theses/1869","10.15368/theses.2018.23"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This thesis explores the impacts and behavior of 3-phase distribution transformers when subject to ungrounded single phase open circuit faults. A simple 3-phase system is modeled using MATLAB Simulink and operation under fault conditions are simulated and studied. Simulation results are confirmed via lab experimentation. Finally, a robust detection and protection method using neutral current injection (as proposed in industry literature) is built and demonstrated.
Electric utility operating experience has demonstrated that all too often, loads on 3-phase distribution transformers are not adequately protected against an ungrounded single phase open circuit fault (commonly called “single phasing”). This type of fault is amongst the least understood and hence the least protected against. This is especially true at end of transmission system radial feeds where 3-phase transformers can re-create the opened phase voltage due to a variety of effects including magnetic coupling, voltage loops and loading effects. Operating experience in the nuclear power industry has shown that the results can be catastrophic especially considering the impacts to motor loads. Impacts can result in unavailability of emergency loads, tripping of motor protection circuits or even motor damage and failure.
"]},{"key":"dc:title","label":"Title","values":["Protection Against Ungrounded Single Phase Open Circuit Faults in 3-Phase Distribution Transformers"]}]}],"canonical_facts":{"dc:contributor":["Ali Shaban"],"dc:creator":["Montoya, Higinio Ariel"],"dc:date.available":["2018-05-25T07:00:00Z"],"dc:description.abstract":["This thesis explores the impacts and behavior of 3-phase distribution transformers when subject to ungrounded single phase open circuit faults. A simple 3-phase system is modeled using MATLAB Simulink and operation under fault conditions are simulated and studied. Simulation results are confirmed via lab experimentation. Finally, a robust detection and protection method using neutral current injection (as proposed in industry literature) is built and demonstrated.
Electric utility operating experience has demonstrated that all too often, loads on 3-phase distribution transformers are not adequately protected against an ungrounded single phase open circuit fault (commonly called “single phasing”). This type of fault is amongst the least understood and hence the least protected against. This is especially true at end of transmission system radial feeds where 3-phase transformers can re-create the opened phase voltage due to a variety of effects including magnetic coupling, voltage loops and loading effects. Operating experience in the nuclear power industry has shown that the results can be catastrophic especially considering the impacts to motor loads. Impacts can result in unavailability of emergency loads, tripping of motor protection circuits or even motor damage and failure.
"],"dc:identifier":["https://digitalcommons.calpoly.edu/theses/1869","10.15368/theses.2018.23"],"dc:subject":["single phasing","open phase condition","transformer","MATLAB","three phase","Power and Energy"],"dc:title":["Protection Against Ungrounded Single Phase Open Circuit Faults in 3-Phase Distribution Transformers"],"thesis:degree_discipline":["Electrical Engineering"],"thesis:degree_name":["MS in Electrical Engineering"]},"updated_at":"2026-07-24T01:31:56Z"}