Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349797
Lifeng Yang
This paper presents a new fault localization system that utilizes the relays in the distribution cable networks that are equipped with the cable fault detection function. The cable fault is characterized with a short pulse and is self-clearing, therefore it is difficult to pinpoint the fault location. When a cable fault occurs on the networks, there could be a few relays to recognize the fault, but extra effort based on the network topology may be required to determine the faulty branch. The proposed fault localization system is comprised of three tiers, from bottom up, local, neighborhood and central. The proposed system assumes all the relays communicate through the Generic Object Oriented Substation Events (GOOSE) messages to its master processing unit which can be a protection relay or a separate industrial computer in its highest hierarchy in a tier. The proposed fault location system does not require adding any extra device or modifying any existing topology, and it only needs the necessary logic to the master processing unit. The system can be easily implemented or added onto the existing protection system that is able to receive the GOOSE message and is allowed to expand through some user programmable approach. The system communications among the components involved use the IEC61850 GOOSE Protocol, and it is easily scaled up or down depending on the application needs. The system, in particular, is suitable for the Medium Voltage (MV) power distribution networks in petrochemical, pharmaceutical, university, hospital, airport, data center, and other large manufacturing compounds.
{"title":"Fault location system for radial MV underground distribution cable networks","authors":"Lifeng Yang","doi":"10.1109/CPRE.2018.8349797","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349797","url":null,"abstract":"This paper presents a new fault localization system that utilizes the relays in the distribution cable networks that are equipped with the cable fault detection function. The cable fault is characterized with a short pulse and is self-clearing, therefore it is difficult to pinpoint the fault location. When a cable fault occurs on the networks, there could be a few relays to recognize the fault, but extra effort based on the network topology may be required to determine the faulty branch. The proposed fault localization system is comprised of three tiers, from bottom up, local, neighborhood and central. The proposed system assumes all the relays communicate through the Generic Object Oriented Substation Events (GOOSE) messages to its master processing unit which can be a protection relay or a separate industrial computer in its highest hierarchy in a tier. The proposed fault location system does not require adding any extra device or modifying any existing topology, and it only needs the necessary logic to the master processing unit. The system can be easily implemented or added onto the existing protection system that is able to receive the GOOSE message and is allowed to expand through some user programmable approach. The system communications among the components involved use the IEC61850 GOOSE Protocol, and it is easily scaled up or down depending on the application needs. The system, in particular, is suitable for the Medium Voltage (MV) power distribution networks in petrochemical, pharmaceutical, university, hospital, airport, data center, and other large manufacturing compounds.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116140766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349820
S. Turner
There is an old saying in the industry… “There are bold protection engineers and there are old ones too but there are no old bold ones.” Often emphasis is placed first on economics but in truth safety is always of the utmost importance since we are working in an energized high voltage power system which is a hazardous environment. Being safe is a state of mind and closely following a good set of well-established practices; it is necessary to maintain this state of mind as a constant goal. You must fully understand these practices and be extremely well versed in them.
{"title":"Safety and its importance in protective relaying","authors":"S. Turner","doi":"10.1109/CPRE.2018.8349820","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349820","url":null,"abstract":"There is an old saying in the industry… “There are bold protection engineers and there are old ones too but there are no old bold ones.” Often emphasis is placed first on economics but in truth safety is always of the utmost importance since we are working in an energized high voltage power system which is a hazardous environment. Being safe is a state of mind and closely following a good set of well-established practices; it is necessary to maintain this state of mind as a constant goal. You must fully understand these practices and be extremely well versed in them.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116536635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349809
M. Adamiak, Zhiying Zhang, I. Voloh
Oscillations on the power system represent an exchange of real or reactive power between entities on the grid or quantities induced onto the grid or as the result of a resonance. Due to the electromechanical make-up of the grid, oscillations have existed from the beginning power system time. In the beginning, the primary source of oscillations was machine-to-machine hunting — resulting in what is known today as Inter-Area Oscillations. As the power system has grown and expanded into new realms, the sources and frequencies of oscillations have expanded. This paper identifies a set of ranges of sub-synchronous oscillations, introduces a new measurement technique for these oscillations, and identifies possible mitigation strategies.
{"title":"Multi-range signal oscillation detection — Concepts and applications","authors":"M. Adamiak, Zhiying Zhang, I. Voloh","doi":"10.1109/CPRE.2018.8349809","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349809","url":null,"abstract":"Oscillations on the power system represent an exchange of real or reactive power between entities on the grid or quantities induced onto the grid or as the result of a resonance. Due to the electromechanical make-up of the grid, oscillations have existed from the beginning power system time. In the beginning, the primary source of oscillations was machine-to-machine hunting — resulting in what is known today as Inter-Area Oscillations. As the power system has grown and expanded into new realms, the sources and frequencies of oscillations have expanded. This paper identifies a set of ranges of sub-synchronous oscillations, introduces a new measurement technique for these oscillations, and identifies possible mitigation strategies.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"640 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122951969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349800
Russ Franklin, Hossein Nabi-Bidhendi, M. Thompson, H. Altuve
Applying high-impedance differential schemes with mismatched-ratio current transformers (CTs) is generally discouraged. However, in instances where facilities are being expanded, new circuit breakers and CTs may have different ratings than the existing equipment, making it necessary to modify purchase standards to match the existing equipment. Techniques have been developed to allow this application when necessary. Each of the methods has advantages and drawbacks that must be considered in determining the best solution for the application. One easy solution is to tap a higher-ratio CT at a matching tap. For this solution, general guidance has cautioned that those considering applying a high-impedance scheme across a partial CT secondary winding tap must evaluate the effect of the higher voltage on the insulation of the circuit components connected to the other terminals of the CT. This paper investigates the issue in detail, including results of testing CTs in a high-current test facility, to provide practical guidance to practicing engineers in determining the risks and application considerations.
{"title":"High-impedance differential applications with mismatched CTs","authors":"Russ Franklin, Hossein Nabi-Bidhendi, M. Thompson, H. Altuve","doi":"10.1109/CPRE.2018.8349800","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349800","url":null,"abstract":"Applying high-impedance differential schemes with mismatched-ratio current transformers (CTs) is generally discouraged. However, in instances where facilities are being expanded, new circuit breakers and CTs may have different ratings than the existing equipment, making it necessary to modify purchase standards to match the existing equipment. Techniques have been developed to allow this application when necessary. Each of the methods has advantages and drawbacks that must be considered in determining the best solution for the application. One easy solution is to tap a higher-ratio CT at a matching tap. For this solution, general guidance has cautioned that those considering applying a high-impedance scheme across a partial CT secondary winding tap must evaluate the effect of the higher voltage on the insulation of the circuit components connected to the other terminals of the CT. This paper investigates the issue in detail, including results of testing CTs in a high-current test facility, to provide practical guidance to practicing engineers in determining the risks and application considerations.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132580332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349806
B. Kasztenny, A. Guzman, M. Mynam, Titiksha Joshi
This paper reviews technical, safety, and economical merits of adaptive autoreclosing based on fault location calculated in real time. These applications include preventing reclosing for faults on cable sections of hybrid lines comprising overhead and cable sections, faults located close to large generating stations, faults on line sections crossing densely populated areas or fire-prone terrain, or faults on line sections near airports that receive small airplanes. The paper explains principles of fault locating based on traveling waves and introduces an adaptive autoreclosing control logic to allow or cancel reclosing based on the location of the fault. The paper includes examples that explain and illustrate these principles. The paper also describes several methods of using operational data — internal and external faults as well as switching events — to further improve the fault-locating accuracy of a commissioned fault locator.
{"title":"Locating faults before the breaker opens — Adaptive autoreclosing based on the location of the fault","authors":"B. Kasztenny, A. Guzman, M. Mynam, Titiksha Joshi","doi":"10.1109/CPRE.2018.8349806","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349806","url":null,"abstract":"This paper reviews technical, safety, and economical merits of adaptive autoreclosing based on fault location calculated in real time. These applications include preventing reclosing for faults on cable sections of hybrid lines comprising overhead and cable sections, faults located close to large generating stations, faults on line sections crossing densely populated areas or fire-prone terrain, or faults on line sections near airports that receive small airplanes. The paper explains principles of fault locating based on traveling waves and introduces an adaptive autoreclosing control logic to allow or cancel reclosing based on the location of the fault. The paper includes examples that explain and illustrate these principles. The paper also describes several methods of using operational data — internal and external faults as well as switching events — to further improve the fault-locating accuracy of a commissioned fault locator.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132239362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349802
Terrence Smith, Christopher White
Transformer differential is one of the most often mis-operated protection systems within the power system. When the differential operates, it is often difficult to determine cause because a fault may be buried deep within the transformer. Dissolved Gas Analysis(DGA) can help the trouble-shooter make statements about thermal faults and arcs and faults and help to identify the presence of a legitimate transformer fault. DGA can also help the transformer asset management team make long term statements about the health of the transformer over-time. An on-line DGA system can be added to the transformed to give reliable continuous data about the health of the transformer. Additionally, the on-line DGA can help to trouble-shoot after a transformer fault by giving dissolved gas analysis of the transformer oil. This paper examines a novel technique which uses the electrical fault data from a transformer and the DGA data and incorporates them into a single report to facilitate faster decision making after a transformer fault.
{"title":"Integration of electrical data and transformer gas analysis for full asset monitoring","authors":"Terrence Smith, Christopher White","doi":"10.1109/CPRE.2018.8349802","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349802","url":null,"abstract":"Transformer differential is one of the most often mis-operated protection systems within the power system. When the differential operates, it is often difficult to determine cause because a fault may be buried deep within the transformer. Dissolved Gas Analysis(DGA) can help the trouble-shooter make statements about thermal faults and arcs and faults and help to identify the presence of a legitimate transformer fault. DGA can also help the transformer asset management team make long term statements about the health of the transformer over-time. An on-line DGA system can be added to the transformed to give reliable continuous data about the health of the transformer. Additionally, the on-line DGA can help to trouble-shoot after a transformer fault by giving dissolved gas analysis of the transformer oil. This paper examines a novel technique which uses the electrical fault data from a transformer and the DGA data and incorporates them into a single report to facilitate faster decision making after a transformer fault.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134403325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349825
M. Zapella, L. Oliveira, R. Hunt, Dylan Stewart
Geomagnetically-induced currents (GICs) are produced by a naturally induced geo-electric field during geomagnetic disturbances. An extreme example of this type of occurrence happened in March 1989, during one of the largest geomagnetic disturbances of the twentieth century. Rapid geomagnetic field variation during this storm led to the induction of electric currents in the Earth's crust. These currents caused wide-spread blackouts across the Canadian Hydro-Quebec power grid, resulting in the loss of electric power to more than 6 million people. If a similar storm-induced blackout had occurred in the Northeastern United States, the economic impact could have exceeded $10 billion. On average, 200 days of strong to severe geomagnetic storms that could produce GICs on the surface of the Earth can be expected during a typical 11-year cycle. However, knowing exact levels of induced currents in power grid infrastructure during a geomagnetic event requires knowledge of deep earth conductivities and transmission line design parameters. GICs are also difficult to measure as they are non-cyclical and slowly varying over time and most of the power systems architecture relies on magnetic transformers tuned for sinusoidal signals.
{"title":"Solving old problems with new technology: How to monitor and measure GIC and OPD currents","authors":"M. Zapella, L. Oliveira, R. Hunt, Dylan Stewart","doi":"10.1109/CPRE.2018.8349825","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349825","url":null,"abstract":"Geomagnetically-induced currents (GICs) are produced by a naturally induced geo-electric field during geomagnetic disturbances. An extreme example of this type of occurrence happened in March 1989, during one of the largest geomagnetic disturbances of the twentieth century. Rapid geomagnetic field variation during this storm led to the induction of electric currents in the Earth's crust. These currents caused wide-spread blackouts across the Canadian Hydro-Quebec power grid, resulting in the loss of electric power to more than 6 million people. If a similar storm-induced blackout had occurred in the Northeastern United States, the economic impact could have exceeded $10 billion. On average, 200 days of strong to severe geomagnetic storms that could produce GICs on the surface of the Earth can be expected during a typical 11-year cycle. However, knowing exact levels of induced currents in power grid infrastructure during a geomagnetic event requires knowledge of deep earth conductivities and transmission line design parameters. GICs are also difficult to measure as they are non-cyclical and slowly varying over time and most of the power systems architecture relies on magnetic transformers tuned for sinusoidal signals.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124782878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349807
H. Jouybari-Moghaddam, T. Sidhu, I. Voloh, M. Zadeh
To achieve more reliable grid it is crucial for utilities to expedite the repair process of critical assets, including Shunt Capacitor Banks (SCBs). Exposure to sharp temperature variations, transient over voltages, aging and manufacturing defects can cause internal failures of capacitor elements. A new method using indicating quantity Superimposed Reactance (SR), is presented in this paper to locate capacitor elements failures in Shunt Capacitor Banks. The proposed quantity is estimated using available measurements to the unbalance protection function of SCBs numerical protective relays. The proposed SR adopts calibrating factors for fault location and can provide live report of the number of failed capacitor elements. The proposed method benefits are: Rapid identification of the SCBs failed elements for fuseless and internally fused designs, Determining failure and faulted phase of single-wye connected banks, Ability to detect consecutive failures, even in the same or different phases due to self-tuning, Online reporting of elements failure for proactive maintenance planning. The developed method supports three different grounding arrangements, wye-ungrounded, wye-grounded via a low ratio current transformer, and wye-grounded via a grounding capacitor at the SCB neutral point. Comprehensive simulation and fault-location analysis using PSCAD and MATLAB have verified the proposed algorithm performance. Advantages of the proposed method reports over conventional unbalance relaying alarms are also demonstrated using a relay test results comparison.
{"title":"New method of capacitors failure detection and location in shunt capacitor banks","authors":"H. Jouybari-Moghaddam, T. Sidhu, I. Voloh, M. Zadeh","doi":"10.1109/CPRE.2018.8349807","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349807","url":null,"abstract":"To achieve more reliable grid it is crucial for utilities to expedite the repair process of critical assets, including Shunt Capacitor Banks (SCBs). Exposure to sharp temperature variations, transient over voltages, aging and manufacturing defects can cause internal failures of capacitor elements. A new method using indicating quantity Superimposed Reactance (SR), is presented in this paper to locate capacitor elements failures in Shunt Capacitor Banks. The proposed quantity is estimated using available measurements to the unbalance protection function of SCBs numerical protective relays. The proposed SR adopts calibrating factors for fault location and can provide live report of the number of failed capacitor elements. The proposed method benefits are: Rapid identification of the SCBs failed elements for fuseless and internally fused designs, Determining failure and faulted phase of single-wye connected banks, Ability to detect consecutive failures, even in the same or different phases due to self-tuning, Online reporting of elements failure for proactive maintenance planning. The developed method supports three different grounding arrangements, wye-ungrounded, wye-grounded via a low ratio current transformer, and wye-grounded via a grounding capacitor at the SCB neutral point. Comprehensive simulation and fault-location analysis using PSCAD and MATLAB have verified the proposed algorithm performance. Advantages of the proposed method reports over conventional unbalance relaying alarms are also demonstrated using a relay test results comparison.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124943589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349793
G. Kobet
At the end of a bird-caused fault sequence, the protection scheme for a 13kV dry-type shunt reactor left the reactor energized and carrying load current on two phases, which resulted in a more severe fault when the field operator attempted to clear the shunt reactor using manually operated disconnect switches. The operator was not injured but given his proximity to the fault and arc, the result could have resulted in serious injury or much worse. In order to avoid such situations, this paper evaluates the protection scheme for 13kV dry-type shunt reactors, highlighting deficiencies, compares company practices against one industry guide, and describes planned improvements.
{"title":"Evaluation of 13kV dry-type shunt reactor protection following near-miss","authors":"G. Kobet","doi":"10.1109/CPRE.2018.8349793","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349793","url":null,"abstract":"At the end of a bird-caused fault sequence, the protection scheme for a 13kV dry-type shunt reactor left the reactor energized and carrying load current on two phases, which resulted in a more severe fault when the field operator attempted to clear the shunt reactor using manually operated disconnect switches. The operator was not injured but given his proximity to the fault and arc, the result could have resulted in serious injury or much worse. In order to avoid such situations, this paper evaluates the protection scheme for 13kV dry-type shunt reactors, highlighting deficiencies, compares company practices against one industry guide, and describes planned improvements.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123948375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.1109/CPRE.2018.8349801
Z. Xu, I. Voloh, L. Torelli
Incipient faults first represent a challenge for the detection of such fault by the primary protection. These faults could last few milliseconds only, being intermittent in nature and possibly evolve eventually over time to a complete insulation breakdown, creating a permanent fault. However, these undetected “ghost” faults may have inadvertent impact on the sensitive protection for adjacent protection zones, compromising its security. This paper will focus on the impact of such faults on the sensitive protection, including transformer restricted ground fault (RGF) and sensitive ground fault protection. Incipient faults create DC offset in currents, which may drive CTs into a light saturation. This paper reviews a real field application case where a repetitive intermittent fault on a 22-kV underground cable was undetected for a long period of time, leading to the transformer neutral CT saturation and to the incorrect operation of two transformer RGF schemes in the substation. The gradual process of CT saturation is explained in detail. Referring to the transformer low impedance restricted ground fault, scheme security is accomplished by the specific algorithm with some additional supervisory features. Particular attention is dedicated to improving the security of the RGF scheme and other affected sensitive protections for this type of external incipient faults, without jeopardizing dependability and speed of operation.
{"title":"Impact of incipient faults on sensitive protection","authors":"Z. Xu, I. Voloh, L. Torelli","doi":"10.1109/CPRE.2018.8349801","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349801","url":null,"abstract":"Incipient faults first represent a challenge for the detection of such fault by the primary protection. These faults could last few milliseconds only, being intermittent in nature and possibly evolve eventually over time to a complete insulation breakdown, creating a permanent fault. However, these undetected “ghost” faults may have inadvertent impact on the sensitive protection for adjacent protection zones, compromising its security. This paper will focus on the impact of such faults on the sensitive protection, including transformer restricted ground fault (RGF) and sensitive ground fault protection. Incipient faults create DC offset in currents, which may drive CTs into a light saturation. This paper reviews a real field application case where a repetitive intermittent fault on a 22-kV underground cable was undetected for a long period of time, leading to the transformer neutral CT saturation and to the incorrect operation of two transformer RGF schemes in the substation. The gradual process of CT saturation is explained in detail. Referring to the transformer low impedance restricted ground fault, scheme security is accomplished by the specific algorithm with some additional supervisory features. Particular attention is dedicated to improving the security of the RGF scheme and other affected sensitive protections for this type of external incipient faults, without jeopardizing dependability and speed of operation.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126949662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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