SIARA - System Integrity & Restorative Actions

Authors: Priyanka Mohapatra, SP Energy Networks, UK and Hao Guo, Power Networks Demonstration Center, UK

Conclusion and Next Steps

The offsite testing of project SIARA proved that the OTN Systems MPLS-TP communication devices (XT-2210) could carry the R-GOOSE messages generated by GE C30 and N60 protection devices. These R-GOOSE messages were used for remote tripping and analogue signal exchange in a hardware in loop set-up. The R-GOOSE messages generated during the test were of size between 209 bytes and 239 bytes. When there was no other background traffic and no artificial delay, the network propagation latency and asymmetrical latency of R-GOOSE messages going through two XTran nodes was up to 70 µs and 2.5 µs. These values satisfied the requirement of ENA TS 48-6-7 where the propagation latency should not exceed 6 ms and the asymmetrical latency should not be greater than 400 µs. The bandwidth occupied by a single R-GOOSE stream (packet size between 209 bytes and 239 bytes) was about 80 kb/s. Analogue R-GOOSE was configured so that it would be continuously transmitted. Hence, if analogue R-GOOSE were transmitted from both N60_A and N60_B and a power system fault event was applied which could trigger binary R-GOOSE from both N60_A and N60_B, the maximum bandwidth among N60_A, C30 and N60_B would be 320 kb/s. 

The instantaneous over-current (IOC) protection, under-frequency protection and over-frequency protection were used on GE N60. The associated local tripping time (when there was no other background traffic and no artificial delay) were:

  • Local IOC protection for fault: about 22.65 ms
  • Local under-frequency protection for under-frequency disturbance: either 92.7 ms or 112.8 ms
  • Local over-frequency protection for over-frequency disturbance: either 97.8 ms or 117.8 ms

The analogue R-GOOSE from N60 could only update the value of analogue quantities every 0.1 s, which might not be suitable for protection scheme requiring instantaneous measurement. The tests provided valuable insight regarding bandwidth, time synchronization requirements, latency, and different protection schemes overall operational times using R-GOOSE over wide area network.
There were some limitations to the offline testing that did not take into account the cyber security requirement on the wide area network and this test needs to be performed with appropriate encryption on the network. This may or may not have implications on the latency and the overall operational times of the R-GOOSE based WPAC schemes provided adequate bandwidth requirements are considered during the deployment.

The offline testing has proved SPEN enough confidence to trial R-GOOSE based WPAC schemes on the SPT network. There are 2 proposals currently being considered for the first trial of R-GOOSE. The first step will be to deploy the offline arrangement at 3 nodes of the network and repeat the tests over the SP Transmission wide area network. Potential future deployment of the technology is on projects where multi-site communication and control is a key requirement, one such project that is currently being developed by SPEN is the Generator Export Management System (GEMS). GEMS aims to monitor and manage generation output across south west Scotland according to a System Operator led commercial constraint market by maximizing the utilization of available transmission capacity, whilst ensuring security of supply is maintained. The GEMS project is currently considering R-GOOSE as the main communication protocol, providing means for fast, reliable and secure data exchange over a dual redundant ring wide area network architecture. The final decision regarding use of R-GOOSE in the GEMS project will be dependent on a cost benefit analysis and a detailed risk assessment considering the time scales for deployment, cyber-security, the availability of suitable IEDs and communication network infrastructure.

SIARA through its offsite testing has already alleviated some of the risks and concerns and we remain positive regarding the roll-out of this technology on our network.
Our offsite testing experience shows that IEC61850-90-5 based R-GOOSE is a viable technology for future system integrity and restorative action schemes. The protection IEDs and testing tools supplier base compatible with R-GOOSE currently is limited and this could potentially affect roll-out of this technology on a wider scale. There are significant benefits of using R-GOOSE over WAN in terms of reduced number of IEDs used for protocol conversions and cyber security provided the right level of encryption is applied.
There is a huge potential for application of R-GOOSE in future utility WPAC schemes provided the right level of reliability, availability and security can be ensured over the wide area network.

BeijingSifang June 2016