Real-Time Networks and Timing Assessment
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This document summarizes the results of research into using real-time Ethernet networks and precision time protocol for process automation applications. Key findings include: 1) The quality of the grandmaster clock and slave clocks directly affects synchronization performance. Transparent clocks are required in switches to mitigate precision time protocol latency. 2) Outbound GOOSE messages and inbound sampled value traffic do not significantly interact or interfere with each other. 3) Most latency is introduced at the first Ethernet switch rather than along the rest of the network path. 4) Protection systems using sampled values can respond nearly as fast as conventional current transformer-based systems, while GOOSE-based protection is about 3 milliseconds faster than relay contact
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Real-Time Networks and Timing Assessment
- 1. © CIGRE Australia AP B5 SEAPAC 2013 Slide Paper Reference Assessment of Real-Time Networks and Timing for Process Bus Applications 147_AU_Ingram 1 Author Organisation Email Presenter David Ingram Queensland University of Technology (QUT) david.ingram@ieee.org Pascal Schaub QGC Pty Ltd pascal.schaub@bg-group.com Duncan Campbell QUT da.campbell@qut.edu.au Richard Taylor QUT rr.taylor@qut.edu.au
- 2. © CIGRE Australia AP B5 SEAPAC 2013 Slide Process Bus Test Bed 2
- 3. © CIGRE Australia AP B5 SEAPAC 2013 Slide Measuring Ethernet Switch Latency3 P0GOOSE,0SV P4GOOSE,0SV P7GOOSE,0SV P0GOOSE,12SV P4GOOSE,12SV P7GOOSE,12SV P0GOOSE,20SV P4GOOSE,20SV P7GOOSE,20SV 363840 Outgoing GOOSE Latency with SV Traffic GOOSELatency(µs) NoGOOSE MU1 NoGOOSE MU20 Pri0GOOSE MU1 Pri4GOOSE MU1 Pri7GOOSE MU1 Pri0GOOSE MU20 Pri4GOOSE MU20 Pri7GOOSE MU20 50150 Effect of Outbound GOOSE on Sampled Values SVLatency(µs)
- 4. © CIGRE Australia AP B5 SEAPAC 2013 Slide Merging Unit Performance4 99.97% Logarithmic y-axis Figures © 2012 IEEE, reproduced with permission from doi:10.1109/TII.2012.2228874
- 5. © CIGRE Australia AP B5 SEAPAC 2013 Slide Measuring PTP Performance5 Sync performance of PTP devices Effect of sampled Value traffic on PTP performance Figures © 2012 IEEE, reproduced with permission from doi:10.1109/TIM.2013.2245188
- 6. © CIGRE Australia AP B5 SEAPAC 2013 Slide PTP Clock Performance 6 Figure © 2012 IEEE, reproduced with permission from doi:10.1109/TIM.2013.2245188
- 7. © CIGRE Australia AP B5 SEAPAC 2013 Slide Grandmaster Drift Without Redundancy With Redundancy 7 0 20 40 60 80 -0.50.00.51.01.5 PTPA Correction Offset(µs) PTPA GPS Drift 0 20 40 60 80 -1.5-1.0-0.50.00.5 Time (s) Offset(µs) PTPB Slave PTPF Slave 0 20 40 60 80 -1.5-1.0-0.50.00.5 PTPC Correction Offset(µs) PTPC GPS Drift 0 20 40 60 80 -0.50.00.51.01.5 Time (s) Offset(µs) PTPB Slave PTPF Slave -1000-5000500 GPS Antenna Failure on Grandmaster PTPA Offset(ns) 17:46:00 17:48:00 17:50:00 17:52:00 17:54:00 17:56:00 Disconnect Reconnect Slave c.f. PTPC PTPB PTPF PTPA c.f. PTPC PTPA Time G'master 17:46:00 17:48:00 17:50:00 17:52:00 17:54:00 17:56:00 CA
- 8. © CIGRE Australia AP B5 SEAPAC 2013 Slide Transparent Clock Assessment8 Background trafficNormal PTP messages sent by grandmaster
- 9. © CIGRE Australia AP B5 SEAPAC 2013 Slide Interaction of Sampled Values & PTP9 40 60 80 100 120 140 0.000.020.04 Effect of Prioritisation – 12x SV MU Offset (ns) Density PTP Priority 2 4 7 40 60 80 100 120 140 0.000.020.040.06 Effect of Prioritisation – 21x SV MU Offset (ns) Density PTP Priority 2 4 7 60 80 100 120 140 160 180 0.000.010.020.030.040.05 Effect of Sampled Value Traffic on PTP Performance Offset (ns) Density SV Traffic none 1x MU 3x MU 6x MU 12x MU 21x MU
- 10. © CIGRE Australia AP B5 SEAPAC 2013 Slide Protection System Performance10 RTDS GOOSE OMICRON SV/GOOSE OMICRON CT/GOOSE RTDS Relay OMICRON SV/Relay OMICRON CT/Relay 101214161820 Three-phase HV Faults ResponseTime(ms) RTDS OMICRON SV OMICRON CT GOOSE Relay 0 12 18 101214161820 Different Multicast Destination Background SV Load (MU Equivalent) ResponseTime(ms) 0 12 16 17 18 101214161820 Same Multicast Destination Background SV Load (MU Equivalent) ResponseTime(ms) Load ~
- 11. © CIGRE Australia AP B5 SEAPAC 2013 Slide • Quality of GM & slave directly affects sync performance • Interactions are a non-issue o Transparent clocks required for PTP o Outbound GOOSE & inbound SV do not interact • Most latency created at first switch • Protection performance o Sampled values similar speed to conventional CTs o GOOSE ~ 3 ms faster than relay contacts • Multivendor process bus works! Conclusions 11
- 12. © CIGRE Australia AP B5 SEAPAC 2013 Slide Acknowledgements • Project support • Equipment support 12