Version control and patch management of protection and automation systems

In the past it was perfectly reasonable for asset owners to assume that the protection and automation systems installed in a new substation would be left undisturbed for many decades throughout the equipment's useful lifetime, with the possible exception of occasional settings changes. As such it was common practice to commission complete systems as a whole and stipulate that if changes were made to device software or firmware, that complete re-testing and recommissioning was required. With the introduction of digital substations there are many instances where these assumptions may no longer be feasible and a new approach is required. A modern substation device installed today may now need to be upgraded or modified many times throughout its lifetime. Scenarios where this might be required include: when a new relay software version is released to provide additional features and take advantage of technology developments, to improve product reliability by fixing bugs, or to apply patches to cybersecurity vulnerabilities. Such `patch' or `version' management is a well understood problem within the IT domain where updates are often required very frequently, in some cases even on a weekly basis. But applying these same practices to a live substation environment requires special consideration as the risk that would be introduced to the continuous availability of the power system is unacceptably high. There will be some instances where it is necessary to apply new updates to existing equipment, and other instances where it is more appropriate to leave the equipment in question `as-is'. This paper will detail processes for the application of version control and patch management that are applicable to the complete range of secondary substation equipment including but not limited to: protection relays, Ethernet switches, merging units, substation gateways and PC based engineering workstations. Potential technologies that can support these processes will also be discussed.