Analysis of the Relationship Between Digital Network Load and Response Time for the Protection System in Industrial Power Stations

This paper analyses the parameterisation of protective relays in industrial power distribution stations, focusing on the quantitative relationship between network load and protection system response time. Laboratory simulations using a dedicated automation cabinet and varying network configurations (six streams at 80 samples/cycle and two to four streams at 256 samples/cycle) revealed a clear correlation: higher network loads lead to longer trip times. Under maximum load (four streams, 256 samples/cycle), response times reached up to 63.75 ms. These delays stemmed from network congestion rather than relay instability. The extended clearing times increased the short-circuit energy (I2t) by approximately 35% on average and over 55% in critical scenarios, requiring upsizing of PVC-insulated conductors from 16 mm2 to 25 mm2 to maintain short-circuit withstand capacity. The findings demonstrate the practical impact of network-induced delays on protection performance, thermal stress, and cable sizing, providing a basis for optimising relay settings and system configuration in modern digital power distribution networks.