The capability and versatility of protection hardware platforms has significantly increased over recent years opening opportunities for more centralisation and virtualisation of functions. This has been recognised and preparations for future standards, requirements are currently in preparation as part of CIGRE working groups and current innovation projects.
The proposed solution aims to take the next step in this development by delivering a demonstrator for a centralised substation platform. The solution will consist of Merging Units, process bus network and centralised PAC platform.
The project will include an assessment of current HW capability, SW architectures, development of specifications and requirements for scalable, open, cyber secure transmission substation solution, test methodology and a demonstrator for laboratory-based evaluation
Benefits
As the current TRL level for centralised PAC systems is low, benefits have been estimated based on the experience as part of the recent evolution of fully digital secondary systems. The assumptions for the benefit estimation include the following: The technology development continues, is successful and leads to the availability of centralised PAC systems from 2026 onwards. Should this be the case, a conservative estimate would provide a cost saving over the period of 2026 – 2031 of around £7M (NPV).
Learnings
Outcomes
Year 2022/2023:
- Using a typical network load of 64 IEC61850 SV streams at 60 HZ, the SEAPATH configuration on the computer achieved an average packet processing latency of 200 µs and a maximum of 1300 µs.
- SEAPATH was able to schedule ten real-time applications scheduled every 1 ms each, with a maximum total jitter of 250 µs.
Year 2023/2024:
Achieving Virtualised Protection using SEAPATH as of our studies and investigations. The prototype deployed in the lab demonstrates this. The prototype included a fully functioning deployment of the SEAPATH architecture with 4 merging units connected to the process bus and capability for further digital injection of SMV and Generic Object-Oriented Substation Event (GOOSE).
The prototype has been proven to deliver deterministic tripping for overcurrent protection with a round trip time of 10ms.
Lessons Learnt
Year 2022/2023:
From the tests carried out so far, the following lessons have been learned.
- Optimal SEAPATH configuration is to use KVM/QEMU Virtual Machines (VMs). This provides a high level of network security.
- Real time performance can be achieved through Interrupt Request (IRQ) and application priority optimisation, as well as CPU core assignments.
- Average Packet Processing latencies are 200µs with a maximum of 1250µs.
- Each Virtual Machine was able to schedule one application per CPU Core every 100µs.
- For the network stack, Peripheral Component Interconnect (PCI) passthrough provides the best latency. If more VMs are required than available Network Interface Cards (NIC), then Single Root I/O Virtualization (SR-IOV) technology can be applied to share once physical NIC amongst multiple VMs.
- Border Peer Routing Control Filtering (BPRC) filtering can be used to reduce maximum latencies by half. Normally, all frames including non-sampled value frames are sent from the driver to the subscriber software. However, BPFC filtering is a solution offered by LINUX so that only the relevant sampled values messages are received in the SV Subscriber.
Year 2023/2024:
- Deterministic and dependable operation of an overcurrent protection function has been proven as part of a full analogue secondary injection test via merging units.
- This is the result of extensive optimisation work on the Sample Measured Values (SMV) publisher, the SMV client receiving and analysing the SMV as well as the SMV dispatcher between SMV client and Straton protection function.
- Performance of 10ms from fault inception to MU trip output was validated.
- Deployment of other protection functions has been proven as well as a development kit for the deployment of further protection functions.
- In general, as with many innovation projects some flexibility with regards to the effort and duration for some of the tasks should be accounted for due to the innovative nature of the work.
