Evaluating the Latency Impact for Time-Critical Operational Technology Applications of Transitioning IEC-61850 GOOSE Operations to 5G

5th -Generation (5G) cellular networks enable a new approach to applications that require low latency. As part of 5G infrastructure, Ultra Reliable Low Latency Communication (URLLC) was defined to support low-latency services using small payloads. However, many Operational Technology (OT) protocols designed with latency in mind require larger payloads but allow for latencies that exceed URLLC's 1ms capability for their operation. An example of such protocols is IEC-61850 GOOSE, which mandates a maximum latency of 4ms, but often transports larger payloads. In this paper, we evaluate the latency implications of incorporating the GOOSE protocol over 5G connections. We evaluate network performance by measuring two different Intelligent Electronic Devices' contact closure times and compare those to measurements obtained from a standard GOOSE network setup. This analysis shows the impact on network latency and critical application performance, from which we can derive important network parameters to improve performance for private 5G-based OT network implementations.