Eric McCollum, Jared Bestebreur, John Town, A. Gould
The Blue Ridge Electric Cooperative has successfully implemented an automated system to collect intelligent electronic device (IED) oscillography reports. They are now participating in a pilot project to develop software that provides analysis of IED oscillography reports together from across their system. During a power system fault, IEDs provide high-accuracy, time-stamped power system measurements in the format of a high-sample-rate oscillography report. Traditionally, these oscillography reports are analyzed in order to understand the specific details of a fault and the IED operation during the fault. Bringing IED oscillography reports together from across a system into one analysis application improves post-fault analysis efficiency and reporting. It also enables the identification of trends over time, leading to improved system reliability. This paper shares the initial results and benefits that Blue Ridge Energy Cooperative has achieved by bringing IED oscillography from across their system together in one application.
{"title":"Correlating protective relay reports for system-wide, post-event analysis","authors":"Eric McCollum, Jared Bestebreur, John Town, A. Gould","doi":"10.1109/REPC.2018.00012","DOIUrl":"https://doi.org/10.1109/REPC.2018.00012","url":null,"abstract":"The Blue Ridge Electric Cooperative has successfully implemented an automated system to collect intelligent electronic device (IED) oscillography reports. They are now participating in a pilot project to develop software that provides analysis of IED oscillography reports together from across their system. During a power system fault, IEDs provide high-accuracy, time-stamped power system measurements in the format of a high-sample-rate oscillography report. Traditionally, these oscillography reports are analyzed in order to understand the specific details of a fault and the IED operation during the fault. Bringing IED oscillography reports together from across a system into one analysis application improves post-fault analysis efficiency and reporting. It also enables the identification of trends over time, leading to improved system reliability. This paper shares the initial results and benefits that Blue Ridge Energy Cooperative has achieved by bringing IED oscillography from across their system together in one application.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114173446","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349774
M. Proctor
Undervoltage protection is commonly used to protect motors from damage during abnormal conditions and to prevent breaker-fed motors from re-accelerating after a restoration of bus voltage. This protection method has the unfortunate consequence of introducing the possibility of a nuisance trip when VT's fail. This paper explores fundamentals of under voltage protection as well as pros and cons of different methods that can be deployed to prevent VT failure from causing costly outages. Case studies will be presented as well as methods which include both monitoring of hardwired VT status contacts and internal relay algorithms.
{"title":"Application of undervoltage protection to critical motors","authors":"M. Proctor","doi":"10.1109/CPRE.2018.8349774","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349774","url":null,"abstract":"Undervoltage protection is commonly used to protect motors from damage during abnormal conditions and to prevent breaker-fed motors from re-accelerating after a restoration of bus voltage. This protection method has the unfortunate consequence of introducing the possibility of a nuisance trip when VT's fail. This paper explores fundamentals of under voltage protection as well as pros and cons of different methods that can be deployed to prevent VT failure from causing costly outages. Case studies will be presented as well as methods which include both monitoring of hardwired VT status contacts and internal relay algorithms.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125442654","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349831
B. Kasztenny, M. Thompson, Douglas I. Taylor
Transformers experience magnetizing inrush that creates an operating current in the transformer differential protection. Early transformer differential relays had to address the limits of analog technology. Analog filter circuits could extract the second-and fourth-harmonic components of the differential current, and these were used as a surrogate measure for determining if the operating current was due to inrush. Today, we can design algorithms that distinguish directly between inrush characteristics and fault current characteristics. By using the new time-domain algorithms, we can improve sensitivity and speed of transformer differential protection. We can also maintain protection security for transformers built using improved core steels.
{"title":"Time-domain elements optimize the security and performance of transformer protection","authors":"B. Kasztenny, M. Thompson, Douglas I. Taylor","doi":"10.1109/CPRE.2018.8349831","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349831","url":null,"abstract":"Transformers experience magnetizing inrush that creates an operating current in the transformer differential protection. Early transformer differential relays had to address the limits of analog technology. Analog filter circuits could extract the second-and fourth-harmonic components of the differential current, and these were used as a surrogate measure for determining if the operating current was due to inrush. Today, we can design algorithms that distinguish directly between inrush characteristics and fault current characteristics. By using the new time-domain algorithms, we can improve sensitivity and speed of transformer differential protection. We can also maintain protection security for transformers built using improved core steels.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126975055","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349768
A. Guzman, B. Kasztenny, Y. Tong, M. Mynam
This paper describes a single-ended traveling-wave-based fault-locating method that works with currents only. Unlike current transformers, coupling-capacitor voltage transformers do not have a frequency bandwidth that is wide enough to allow measuring of voltage traveling waves for this application. The key to a robust single-ended traveling-wave fault-locating method is to correctly identify reflections from the fault point. For this purpose, the method uses additional information, such as the impedance-based fault location and reflections from the remote terminal and external network elements. This paper presents the single-ended traveling-wave-based fault-locating method in detail and explains how to perform fault locating manually using ultra-high-resolution fault records from any recording device. This paper also presents laboratory test results as well as field cases in which line crews found the actual faults.
{"title":"Accurate and economical traveling-wave fault locating without communications","authors":"A. Guzman, B. Kasztenny, Y. Tong, M. Mynam","doi":"10.1109/CPRE.2018.8349768","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349768","url":null,"abstract":"This paper describes a single-ended traveling-wave-based fault-locating method that works with currents only. Unlike current transformers, coupling-capacitor voltage transformers do not have a frequency bandwidth that is wide enough to allow measuring of voltage traveling waves for this application. The key to a robust single-ended traveling-wave fault-locating method is to correctly identify reflections from the fault point. For this purpose, the method uses additional information, such as the impedance-based fault location and reflections from the remote terminal and external network elements. This paper presents the single-ended traveling-wave-based fault-locating method in detail and explains how to perform fault locating manually using ultra-high-resolution fault records from any recording device. This paper also presents laboratory test results as well as field cases in which line crews found the actual faults.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122662951","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349791
E. Schweitzer, B. Kasztenny
We look back at the history of distance protection, explain the first principles, and discuss why our industry settled on designs we know and appreciate today. We look at why, after a century of refinements, a typical distance element still uses heavily filtered voltages and currents and operates on the order of one power cycle. In the second part of the paper, we explain the principles of time-domain distance protection based on incremental quantities, and operating by processing samples of voltages and currents without band-pass filtering to retrieve phasors. We discuss various choices for a time-domain distance element and present test results and field cases of an implementation with operating times of just a few milliseconds. In the third part of the paper, we discuss the feasibility of a distance element based on traveling waves and operating even faster.
{"title":"Distance protection: Why have we started with a circle, does it matter, and what else is out there?","authors":"E. Schweitzer, B. Kasztenny","doi":"10.1109/CPRE.2018.8349791","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349791","url":null,"abstract":"We look back at the history of distance protection, explain the first principles, and discuss why our industry settled on designs we know and appreciate today. We look at why, after a century of refinements, a typical distance element still uses heavily filtered voltages and currents and operates on the order of one power cycle. In the second part of the paper, we explain the principles of time-domain distance protection based on incremental quantities, and operating by processing samples of voltages and currents without band-pass filtering to retrieve phasors. We discuss various choices for a time-domain distance element and present test results and field cases of an implementation with operating times of just a few milliseconds. In the third part of the paper, we discuss the feasibility of a distance element based on traveling waves and operating even faster.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131144544","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349776
K. Iliev, Ahsan Mirza, Lori Marshall, G. Wen, Saman Alaeddini, A. Bidram
Protection engineers often verify relay settings stored in a database. The conventional way to view settings is to open the setting files with software released by the respective manufacturer. Often times, the most commonly used settings are stored in a report for quick access by protection and other departments within the same utility. Depending on the size of the network, creating and updating such reports can be time consuming. This paper proposes a process to automatically create customized reports based on setting files stored in a database. Logics are programmed to read relay settings and intelligently convey tripping information to the relay engineer. The connection to the settings database is facilitated by using an Open Database Connectivity (ODBC) link. Custom queries are utilized to retrieve relay settings by a predefined search pattern. The relay engineer can generate reports based on a specific settings file, relay, position, or substation.
{"title":"Automated analysis & reporting from relay setting database","authors":"K. Iliev, Ahsan Mirza, Lori Marshall, G. Wen, Saman Alaeddini, A. Bidram","doi":"10.1109/CPRE.2018.8349776","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349776","url":null,"abstract":"Protection engineers often verify relay settings stored in a database. The conventional way to view settings is to open the setting files with software released by the respective manufacturer. Often times, the most commonly used settings are stored in a report for quick access by protection and other departments within the same utility. Depending on the size of the network, creating and updating such reports can be time consuming. This paper proposes a process to automatically create customized reports based on setting files stored in a database. Logics are programmed to read relay settings and intelligently convey tripping information to the relay engineer. The connection to the settings database is facilitated by using an Open Database Connectivity (ODBC) link. Custom queries are utilized to retrieve relay settings by a predefined search pattern. The relay engineer can generate reports based on a specific settings file, relay, position, or substation.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124986865","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349788
T. Sukumara, Janne Starck, J. Vellore, E. Kumar, G. Harish
Protection and control relays (also known as IEDs — Intelligent Electronic Devices), play a critical role in substation protection, control and monitoring functionalities. Smart grid deployments need the seamless flow of data between various devices like protection relays, controllers, gateways, smart meters etc. over private and public communication networks. These kind of deployments lead to inherent requirements for secure communication, strong user authentication and authorization to be considered in the design and development of protection and control relays. Securing relay communication is part of the Defense-In-Depth strategy which is essentially a layered security approach. It uses, multiple layers of network security along with secure architecture which is in-line with current and upcoming cyber security standards to protect the power system/substation automation network against intrusion from physical and cyber-borne attacks while connected to public and private networks. Ensuring confidentiality, integrity and authenticity is an integral part of securing data over the network. This can be achieved with strong authentication and usage of cryptographic protocols like “TLS”.
{"title":"Cyber security — Securing the protection and control relay communication in substation","authors":"T. Sukumara, Janne Starck, J. Vellore, E. Kumar, G. Harish","doi":"10.1109/CPRE.2018.8349788","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349788","url":null,"abstract":"Protection and control relays (also known as IEDs — Intelligent Electronic Devices), play a critical role in substation protection, control and monitoring functionalities. Smart grid deployments need the seamless flow of data between various devices like protection relays, controllers, gateways, smart meters etc. over private and public communication networks. These kind of deployments lead to inherent requirements for secure communication, strong user authentication and authorization to be considered in the design and development of protection and control relays. Securing relay communication is part of the Defense-In-Depth strategy which is essentially a layered security approach. It uses, multiple layers of network security along with secure architecture which is in-line with current and upcoming cyber security standards to protect the power system/substation automation network against intrusion from physical and cyber-borne attacks while connected to public and private networks. Ensuring confidentiality, integrity and authenticity is an integral part of securing data over the network. This can be achieved with strong authentication and usage of cryptographic protocols like “TLS”.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116941736","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349779
Ariana Hargrave, M. Thompson, Brad Heilman
Current transformer (CT) saturation, while a fairly common occurrence in protection systems, is not often clearly understood by protective relay engineers. This paper forgoes the usual physics equations to describe how CTs saturate in a simple and intuitive way. We explain the differences between symmetrical and asymmetrical saturation and how remanence accumulates in the core of a CT. We then describe the CT equivalent circuit and how it results in the familiar CT excitation graph. ANSI ratings of CTs are explained, and we show how to analyze the performance of CTs using simple equations and tools. Finally, we explain how CT saturation can affect relay operation and show how to detect CT saturation in protective relay event reports. Real-world event reports are presented where correct relay operation was compromised as a result of incorrect current values from saturated CTs.
{"title":"Beyond the knee point: A practical guide to CT saturation","authors":"Ariana Hargrave, M. Thompson, Brad Heilman","doi":"10.1109/CPRE.2018.8349779","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349779","url":null,"abstract":"Current transformer (CT) saturation, while a fairly common occurrence in protection systems, is not often clearly understood by protective relay engineers. This paper forgoes the usual physics equations to describe how CTs saturate in a simple and intuitive way. We explain the differences between symmetrical and asymmetrical saturation and how remanence accumulates in the core of a CT. We then describe the CT equivalent circuit and how it results in the familiar CT excitation graph. ANSI ratings of CTs are explained, and we show how to analyze the performance of CTs using simple equations and tools. Finally, we explain how CT saturation can affect relay operation and show how to detect CT saturation in protective relay event reports. Real-world event reports are presented where correct relay operation was compromised as a result of incorrect current values from saturated CTs.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133469275","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349782
B. Kasztenny, J. Rostron
This paper explains the asymmetrical short-circuit interrupting current rating for high-voltage circuit breakers. The paper teaches how the decaying dc component in the asymmetrical fault current affects the breaker, and it explains how the X/R ratio and the relay operating time affect the asymmetrical current breaker rating. The paper briefly introduces, and illustrates with field cases, several ultra-high-speed protection principles that can operate in just a few milliseconds. The paper then explains how to derate a breaker for the relay operating time that is shorter than the standard reference value of 0.5 cycle. The paper calculates the “rating loss” due to fast tripping and suggests that applying customary margins when selecting breakers may be sufficient to mitigate the effect of ultra-high-speed relays without the need to replace breakers.
{"title":"Circuit breaker ratings — A primer for protection engineers","authors":"B. Kasztenny, J. Rostron","doi":"10.1109/CPRE.2018.8349782","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349782","url":null,"abstract":"This paper explains the asymmetrical short-circuit interrupting current rating for high-voltage circuit breakers. The paper teaches how the decaying dc component in the asymmetrical fault current affects the breaker, and it explains how the X/R ratio and the relay operating time affect the asymmetrical current breaker rating. The paper briefly introduces, and illustrates with field cases, several ultra-high-speed protection principles that can operate in just a few milliseconds. The paper then explains how to derate a breaker for the relay operating time that is shorter than the standard reference value of 0.5 cycle. The paper calculates the “rating loss” due to fast tripping and suggests that applying customary margins when selecting breakers may be sufficient to mitigate the effect of ultra-high-speed relays without the need to replace breakers.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133409862","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 : 2018-03-26DOI: 10.1109/CPRE.2018.8349775
J. Theron, Troy Wilsey, A. Colonnese, Russell Gagner, S. Rowe
Industrial facilities with co-generation are in critical need of load shedding to prevent collapse of the cogeneration assets. Load shedding should be sub-cycle speed to manage thousands of distributed loads within a facility. This paper describes the capabilities of such a fast load shedding scheme spanning across a wide array of relays provided by various vendors and potentially a large quantity, and a case study system and experience of applying such a system. The fast load shed scheme described in this paper utilizes a proven system and makes it easy to configure larger and more complex load shed schemes. The paper describes the proposed architecture of a centralized fast load shed controller-based scheme interfaced with local generator/feeder/transformer/motor protection relays over IEC 61850 GOOSE. A major challenge of such a large-scale load shed scheme deployment is the configuration of devices, especially the IEC 61850 GOOSE engineering process which may add further complexity. This paper also discusses IEC 61850 GOOSE scheme configuration with high-speed performance requirements. Lessons learned from the case study fast load shed scheme deployment, testing and operations are also discussed.
{"title":"Applying intelligent fast load shed using IEC 61850 GOOSE","authors":"J. Theron, Troy Wilsey, A. Colonnese, Russell Gagner, S. Rowe","doi":"10.1109/CPRE.2018.8349775","DOIUrl":"https://doi.org/10.1109/CPRE.2018.8349775","url":null,"abstract":"Industrial facilities with co-generation are in critical need of load shedding to prevent collapse of the cogeneration assets. Load shedding should be sub-cycle speed to manage thousands of distributed loads within a facility. This paper describes the capabilities of such a fast load shedding scheme spanning across a wide array of relays provided by various vendors and potentially a large quantity, and a case study system and experience of applying such a system. The fast load shed scheme described in this paper utilizes a proven system and makes it easy to configure larger and more complex load shed schemes. The paper describes the proposed architecture of a centralized fast load shed controller-based scheme interfaced with local generator/feeder/transformer/motor protection relays over IEC 61850 GOOSE. A major challenge of such a large-scale load shed scheme deployment is the configuration of devices, especially the IEC 61850 GOOSE engineering process which may add further complexity. This paper also discusses IEC 61850 GOOSE scheme configuration with high-speed performance requirements. Lessons learned from the case study fast load shed scheme deployment, testing and operations are also discussed.","PeriodicalId":285875,"journal":{"name":"2018 71st Annual Conference for Protective Relay Engineers (CPRE)","volume":"175 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121723367","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：