Solveig Ward

IEEE PSRC Report on Performance of Relaying During Wide-Area Stressed Conditions

This paper is a summary of the IEEE Power System Relaying Committee report. It describes the performance of protective relays during wide-area stressed power system conditions. First, the behavior of protection functions during dynamic operating conditions is described. Then, the lessons learned from studying recent wide area disturbances, as well as the operational history of protection performance during stressed system conditions, are analyzed. Finally, methods of implementing protective relay functions to prevent further propagation of system-wide disturbances are presented.

Use of synchrophasor measurements in protective relaying applications

The IEEE PSRC System Protection Subcommittee Working Group C14 has produced a report that describes practical applications of synchrophasors in protection applications. The report begins with the history of synchrophasors and then goes into issues to consider in their application. Some existing applications are described and then future applications that have been considered or are in development are described. The appendix contains applications that use synchrophasor data but are not considered protection applications. This is a summary of the complete report found on the PSRC website (http://www.pes-psrc.org click on Published Reports).

Inside the Cloud - Network Communications Basics for the Relay Engineer

This paper addresses basic communications network technology and explains the differences between Ethernet, TCP/IP, T1 and SONET with respect to relaying applications. It also makes an attempt to clarify how the access method and application protocols influence (or not) the transport method. LAN, VLAN, VPN and WAN/Internet are also explained. Cyber security issues are discussed for the different networks. Ethernet networks are addressed in some detail as they are becoming more commonly accessible in substations and are a tempting alternative for protective relaying due to their simplicity and lower cost. Wireless Ethernet seems to be an especially attractive, low-cost solution. The paper presents test results that compare the performance of TDMolP with Ethernet GOOSE communications according to the IEC 61850 standard. The IEC 61850 standard is based on an Ethernet LAN but was originally intended for within substations communications only. The cloud is a term used to depict a telecommunication network.

Cyber Security Issues for Protective Relays; C1 Working Group Members of Power System Relaying Committee

This report covers issues concerning the security of electronic communication paths to protection relays. It is the goal of this paper to present the reader with some background material and discussions by which they can become more aware of the concerns associated with electronic communications in the power industry.

Network errors and their influence on current differential relaying

While a point-to-point fiber is the preferred communication link for a protective relaying engineer it is not always available. An OPGW (Optical Ground Wire) on the power line itself could provide a dedicated fiber pair for protection, but often the utility communications network does not follow the power system topology. In addition, multiplexing data over that fiber pair optimizes the use of available communications media. The same physical fiber pair that carries a single channel 64 kbps relaying data could be used for up to OC-192 (10 Gbps) or GigaBit Ethernet. To use an available communications network for relaying makes sense from an economical standpoint. However, even with digital communications, the network is not error free. While many links are optical fiber which are immune to electrical interference, most networks incorporate wired links or microwave paths in their design. Attenuation on long fibers, synchronous clock inaccuracies causing frame slips, etc., contributes to the errors. For evaluation, protective relays are subjected to extensive bench or simulator testing with injected currents and voltages it is less common to include the communications link in the test. Typically, the relays have a direct connection of the communications ports back to back. This excludes the vital communications link that is integral to the operation of a current differential relay. The results are thus valid for a direct fiber application but not necessarily so over networked communications. While a relay engineer typically is not directly involved in the design of the utility communications network, the ability to explain how and why critical pilot relaying channel requirements may differ from other data communication needs could go a long way towards obtaining reliable communications services for protective relaying. This paper examines the type of errors that can be expected over a modern digital communications network and what the consequences for current differential relaying may be. It looks at factors influencing protection system availability and how problems could be mitigated by relay design, proper network configuration and circuit conditioning. Actual testing with current differential relays and a BER (bit error rate) generator illustrate the points.

Justifying pilot protection on transmission lines

This paper concerns the justification of the use of pilot protection on transmission lines.

Redundancy considerations for protective relaying systems

The basic concept of redundancy is simple. Instead of relying on a single piece of equipment, there are duplicate or triplicate sets that perform the same function. Consequently, if one piece of equipment fails, the function will still be performed by a redundant device. Redundancy of components plays a major role in elevating the reliability of protection systems. The impact on the power system when a protection device is not functioning when required is much less severe when there is a redundant device that takes over the job. If the redundant devices are of equal performance, there should be no detrimental effect at all on power system operations, and a non-functioning device would just need to be repaired or replaced. While local redundancy is generally applied, it is not the only mitigation that can be used to improve reliability. Remote protection systems may provide adequate protection system reliability in some situations, provided that remote protection can detect faults and provide clearing times that meet performance requirements. Different users have different terminology for referring to the redundant protection systems. They may be called “System 1” and “System 2” or “System A” and “System B” or sometimes “Primary” and “Backup.” This latter terminology, “Primary” and “Backup”, implies, although unintentionally, that one of the two systems serves the main function of protection and the other serves to assist in the case of failure of the first system, analogous to carrying an undersized spare tire in the trunk of a car in case of a flat. In actual practice, the redundant systems are each fully capable, each system is able to detect and clear faults on its own, and each system serves as a backup to the other. Note that this paper is a summary of the full report. The report will be available on www.pes-psrc.org – Published Reports – in May-June of 2010.

IEEE/PES PSRC report on design and testing of selected System Integrity Protection Schemes

This paper is a summary of an IEEE/PES Power System Relaying Committee (PSRC) report [2] on the design and testing of selected System Integrity Protection Schemes (SIPS). The report includes high level general considerations in SIPS design and testing, and the industry practice in design and testing of the following selected SIPS with example implemented schemes: (1) Generator rejection; (2) Load rejection; (3) Adaptive load mitigation; (4) Dynamic braking; and (5) System separation.

Integrating current differential relaying communications into an IP based infrastructure

Current differential relaying is a proven and time tested method for line protection. One of the main benefits is its simplicity. While having been displaced by distance protections for transmission line protection, current differential relays have regained their popularity thanks to increased access to digital communications media. The present design of numerical current differential relays is made for synchronous communications, such as T1/E1 and SONET/SDH. However, there is nothing in the relaying principle that prevents the use of packetized communications (Ethernet), and this paper has presented several alternatives for how this can be realized.

Summary changes in 2013 IEEE/IEC Dual Logo COMTRADE standard

The globally used COMTRADE standard was initially developed by IEEE and later adopted by IEC. The first IEEE version was published in 1991 and was later revised in 1999. The IEC version was adopted in 2001. The 2013 revision of the COMTRADE standard is an IEEE/IEC Dual Logo standard planned for publication during the first quarter of 2013. The main motivations for the current revisions are: 1) to remove restrictions that were only relevant for computing technologies of the 1990s and 2) to satisfy the requirement of universal time information in COMTRADE files. The second need was identified during the 2003 Northeast Blackout analysis to time synchronize data from different substations. The working group has also addressed other issues, including the availability of a single file. Industry users feel very strongly about this need to easily exchange and manage COMTRADE files, and the working groups recommendations address these concerns.