Network Migration for Utilities:Teleprotection overPacket                          Teleprotection over Packet Slide 1
Agenda• Power Utility Communications: Networks in Transition• Teleprotection Connectivity and Delay Considerations• Ensuri...
Power Utility Communications                               Teleprotection over Packet Slide 3
Networks in Transition• Power utility networks are mostly self-owned, privately operated• Require SDH/SONET-level reliabil...
Migration Challenges• Control CapEx and avoid over-burdening network  operations and management      Especially where SDH/...
Teleprotection Connectivity                              Teleprotection over Packet Slide 6
What is Teleprotection• Used for power line protection• Protect equipment from severe damages resulting from faulty HV  li...
Teleprotection Communications• Distance Protection: Trips breakers when impedance  measurements vary from those taken unde...
Teleprotection Connectivity• Traditionally, relays communicated (via a separate comm channel or a  multiplexer) over the S...
Teleprotection Connectivity (Cont’)Two options when migrating to packet communications:• Continue using TDM connectivity f...
Teleprotection Communications –Key Performance Criteria (IEC 60834)   Transmission Time   • Between the moment of change o...
Teleprotection CommunicationsPerformance: Latency Budget• Most power line equipment can withstand a  brief shortage/irrupt...
Teleprotection CommunicationsPerformance: Asymmetric Delay• Differential protection requires same channel delay in  transm...
Ensuring TeleprotectionPerformance over Packet                          Teleprotection over Packet Slide 14
Communications Channel Resiliency• Hardware redundancy:     No single point of failure (NSPF) design with redundant, hot-s...
Traffic Management and Quality ofServiceProvide deterministic quality of service and priority for protection signalswith m...
Performance Monitoring and Testing•   A wealth of carrier-grade Ethernet tools to remotely test, monitor and    troublesho...
Teleprotection over PacketUse Case                             Teleprotection over Packet Slide 18
Teleprotection over PacketProof of Concept Program• RAD’s Megaplex-4100 multiservice access platform was successfully  tes...
Teleprotection over PacketTest ResultsRAD’s Teleprotection multiplexers have successfully met requirements:• Up to 5ms del...
Conclusion• Critical Teleprotection applications require special attention in the  move towards Smart Grids and next-gener...
Appendix           Teleprotection over Packet Slide 22
Appendix I:What is Pseudowire Emulation?• The synchronous bit stream is segmented• Headers are added to each segment to fo...
Appendix II:Latency Sources in TeleprotectionTeleprotection Equipment   • Includes the relay’s fault identification, comma...
Thank YouFor YourAttention            www.rad.com             Teleprotection over Packet Slide 25
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Teleprotection over packet f 30 8-11

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Teleprotection signals from protective relays are among the most critical data transmitted across utility networks, as they help manage the power grid load, as well as to protect equipment within the power network from severe damages resulting from faulty HV lines. By enabling load-sharing, grid adjustments and immediate fault clearance, Teleprotection has a decisive role in ensuring uninterrupted power supply and therefore requires special attention with regards to network performance and reliability. Specifically, protection commands must be assured immediate delivery when problems are detected, so that faulty equipment can be disconnected before causing a system-wide damage.

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Teleprotection over packet f 30 8-11

  1. 1. Network Migration for Utilities:Teleprotection overPacket Teleprotection over Packet Slide 1
  2. 2. Agenda• Power Utility Communications: Networks in Transition• Teleprotection Connectivity and Delay Considerations• Ensuring Communications Performance for Teleprotection over Packet• Teleprotection over Packet Use Case• Conclusion• Appendix: Pseudowire Emulation Latency Sources in Teleprotection Teleprotection over Packet Slide 2
  3. 3. Power Utility Communications Teleprotection over Packet Slide 3
  4. 4. Networks in Transition• Power utility networks are mostly self-owned, privately operated• Require SDH/SONET-level reliability for mission-critical communications• Slow migration to IP, but Ethernet transport and IP/Packet-based networks gradually gain traction for higher throughput and lower OpEx Upgrades to Smart Grid foster transformation New applications: Substation automation (IEC 61850), NG-SCADA systems, WASA synchrophasors, IP video surveillance Teleprotection over Packet Slide 4
  5. 5. Migration Challenges• Control CapEx and avoid over-burdening network operations and management Especially where SDH/SONET and PSN co-exist• Ensure smart communications over packet and service assurance for mission critical apps in PSN environment: Low end-to-end delay High availability SDH/SONET-level resiliency Teleprotection, in particular, has stringent communications performance requirements ! Teleprotection over Packet Slide 5
  6. 6. Teleprotection Connectivity Teleprotection over Packet Slide 6
  7. 7. What is Teleprotection• Used for power line protection• Protect equipment from severe damages resulting from faulty HV lines• Common schemes: Distance (impedance) protection Current differential protection Direct Transfer Trip Combination Teleprotection over Packet Slide 7
  8. 8. Teleprotection Communications• Distance Protection: Trips breakers when impedance measurements vary from those taken under normal conditions Traditionally, no communication was required Pilot-aided distance relays use a communication channel to improve fault clearance• Differential Protection: Disconnects faulty line segments if differential current measurements on both ends of the protection zone are higher than a setpoint Requires communication between the end-point relays Teleprotection over Packet Slide 8
  9. 9. Teleprotection Connectivity• Traditionally, relays communicated (via a separate comm channel or a multiplexer) over the SDH/SONET backbone, power line carrier (PLC) or a dedicated fiber optic connection• Communication channel interfaces: X.21, E1/T1, V.35, E&M; modern relays use IEC C37.94 fiber optic Teleprotection over Packet Slide 9
  10. 10. Teleprotection Connectivity (Cont’)Two options when migrating to packet communications:• Continue using TDM connectivity for Teleprotection in parallel to new packet network installations for non-critical substation traffic Hybrid TDM/PSN multiplexers and access nodes save on network equipment costs• Use Ethernet or packet network for Teleprotection, provided it can guarantee required performance Delivery of TDM-based Teleprotection signals over packet requires pseudowire emulation (see appendix I) Teleprotection over Packet Slide 10
  11. 11. Teleprotection Communications –Key Performance Criteria (IEC 60834) Transmission Time • Between the moment of change of state at the transmitter input and the receiver output Dependability • Valid commands in the presence of interference and/or noise, by minimizing the probability of missing command (Pmc) Security • Preventing false tripping due to a noisy environment, by minimizing the probability of unwanted commands (Puc) Other • Bandwidth consumption and resiliency also impact performance Performance criteria pose a challenge over non-deterministicpacket transport and require enhanced, carrier-grade capabilities Teleprotection over Packet Slide 11
  12. 12. Teleprotection CommunicationsPerformance: Latency Budget• Most power line equipment can withstand a brief shortage/irruption Typical requirement for total fault clearance time = 100ms• Actual operation time of protection systems = 70-80% of this period Including fault recognition, command transmission and line breaker switching Large electromechanical switches take up the majority of time• In modern applications, contact transfer is expected in 10ms or less• For latency sources in Teleprotection communications, see Appendix II Teleprotection over Packet Slide 12
  13. 13. Teleprotection CommunicationsPerformance: Asymmetric Delay• Differential protection requires same channel delay in transmit and receive paths Requires special attention in jitter-prone packet networks Typical relays can tolerate discrepancies of up to 250 μs• The main tools available for lowering delay variation: A jitter “buffer” at each end of the line for queuing sent and received packets Traffic management: Ensure highest transmission priority for Teleprotection Standard PSN-specific synchronization technologies maintain stable networks by disciplining the communications elements to a highly accurate clock source Teleprotection over Packet Slide 13
  14. 14. Ensuring TeleprotectionPerformance over Packet Teleprotection over Packet Slide 14
  15. 15. Communications Channel Resiliency• Hardware redundancy: No single point of failure (NSPF) design with redundant, hot-swappable power supplies Redundant control plane and switch fabric cards• Link redundancy: 1+1 protection topology with automatic switchover between links Link aggregation group (LAG) per IEEE 802.3-2005 LACP (link aggregation control protocol) for Ethernet-based services• Path protection: Ethernet Linear protection Switching (G.8031) , AKA “EVC (Ethernet Virtual Connection) protection” Ethernet Ring Protection Switching (G.8032 ERPS) to provide Five Nines (99.999%) availability Teleprotection over Packet Slide 15
  16. 16. Traffic Management and Quality ofServiceProvide deterministic quality of service and priority for protection signalswith multi-level Ethernet traffic management for predictable latency andjitter performance across the service path:• Classification of incoming traffic into flows• Metering and policing to regulate traffic with different bandwidth profiles• Advanced scheduling and queue management to ensure minimal latency and jitter• Shaping to smooth out bursts and avoid buffer overruns in subsequent network elements• Packet editing and marking to signal proper handling instructions for subsequent network elements Teleprotection over Packet Slide 16
  17. 17. Performance Monitoring and Testing• A wealth of carrier-grade Ethernet tools to remotely test, monitor and troubleshoot the communications links operation• Utility network operators anticipate service degradation ahead of time, as well as cut down truck-rolls and on-site technician calls Service On-going Fault Management Turn-up Monitoring & Recovery Connectivity Performance Fault Detection & Verification Monitoring Isolation Diagnostic Fault Propagation & Loopbacks Threshold Reporting Notification Performance Verification Statistics Collection Reporting Resiliency & Repair & Testing Teleprotection over Packet Slide 17
  18. 18. Teleprotection over PacketUse Case Teleprotection over Packet Slide 18
  19. 19. Teleprotection over PacketProof of Concept Program• RAD’s Megaplex-4100 multiservice access platform was successfully tested by a major energy utility• TDM data received from protection units was converted into packets, then transmitted over an MPLS network employing static routing• The line differential protection equipment featured a variety of TDM communications interfaces, including G.703, X.21, RS-232, E&M, C37.94, Native E1• End-to-end communication delay requirement of 8-10ms in a packet network environment experiencing a jitter of 2.5ms Also required symmetrical latency with maximum tolerance of 100-250μs Teleprotection over Packet Slide 19
  20. 20. Teleprotection over PacketTest ResultsRAD’s Teleprotection multiplexers have successfully met requirements:• Up to 5ms delay with quality of service for signal priority via shaping and traffic engineering tools• Clock accuracy was rigorously maintained throughout transmission• High degree of resiliency through various protection schemes, including DS1-level redundancy Teleprotection over Packet Slide 20
  21. 21. Conclusion• Critical Teleprotection applications require special attention in the move towards Smart Grids and next-generation networks• Viable alternatives to existing deployments need to meet exacting performance criteria of minimal transmission time, reliability and security Extremely low, symmetrical delay, robust clock accuracy, QoS assurance, resiliency, and on-going performance monitoring are “must have” elements for any Teleprotection over packet system• Hybrid TDM/Packet solutions allow utility operators the freedom to choose the migration path that best suits their needs and budgetsDownload comprehensive Teleprotection over Packet Solution Paper Teleprotection over Packet Slide 21
  22. 22. Appendix Teleprotection over Packet Slide 22
  23. 23. Appendix I:What is Pseudowire Emulation?• The synchronous bit stream is segmented• Headers are added to each segment to form the Packet• Packets are forwarded to destination over the PSN network• At destination, the original bit stream is reconstructed by removing headers, concatenating frames and regenerating the timing• The most common pseudowire emulation standards are CESoPSN, SAToP, TDMoIP Teleprotection over Packet Slide 23
  24. 24. Appendix II:Latency Sources in TeleprotectionTeleprotection Equipment • Includes the relay’s fault identification, command initiation Delay and decision time Substation Multiplexer • Minimized via optimal design of ICs, DS0 xconnect, and (TDM interface) • High-performance buffering and forwarding technology • 1-5ms, depending on packet size and # of TDM frames/packetPseudowire Encapsulation • Smaller packets increase bandwidth overhead, but reduce and Packetization Delay latency • Each element adds processing and queuing delay PSN Network Elements • Variable delay poses a greater threat and requires advanced traffic management Teleprotection over Packet Slide 24
  25. 25. Thank YouFor YourAttention www.rad.com Teleprotection over Packet Slide 25

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