Protection automation and control using private 5G: Use-case evaluations for fully digital substations

Control Systems (PACS) are designed and operated. As utilities move from traditional copper wiring toward IEC 61850 based digital architectures, interest has grown in whether private 5G networks could complement or, in certain cases, replace fibre-optic communication on the physical layer. The goal of this paper is to explore that potential by evaluating how private 5G performs when applied to two representative and latency critical use-cases: intra-substation overcurrent protection and inter-substation line differential protection.

To investigate this, a full hardware-in-the-loop laboratory environment was established, integrating real PACS Intelligent Electronic Devices (IED), Process Interface Units (PIU), switching equipment, and a private 5G standalone (SA) network. The setup enabled realistic traffic patterns for IEC 61850 Sampled Values (SV) and Generic Object Oriented System Event

(GOOSE) messages. Several 5G radio configurations were tested for both indoor and outdoor cells at different frequency bands, and additional scenarios incorporated Parallel Redundancy

Protocol (PRP) to assess whether redundancy could enhance performance. Measurements were carried out using a network analyser to capture latency characteristics and using a network sniffer to capture high resolution data for more detailed analysis.

The results show that today’s private 5G configurations can reliably transport PACS related traffic, but the end-to-end latency remains above the stringent thresholds required for fast protection functions, particularly for SV streams. While PRP improves consistency in several scenarios and offers useful insight into how redundancy can mitigate wireless variability, average and minimum latencies still exceed the limits needed for protection elements to operate.

In practical tests, SV measurements delivered over 5G were rejected by the IEDs, preventing the protection functions from issuing trips. GOOSE messaging performs more favourably, with some scenarios achieving latency below 100ms. This suggests that even if the most time critical functions remain challenging for 5G today, there may already be opportunities for its use in less latency sensitive PACS applications, such as blocking schemes or supervisory logic on medium-voltage networks.

Overall, the findings indicate that while private 5G shows promising characteristics further advancements are needed before it can reliably support the most demanding protection functions. At the same time, the study highlights several promising directions for future research, including radio network based time synchronization, optimization of redundancy strategies, and the application of 5G to PACS functions with more relaxed timing requirements.