Digitalisation of relay protection and implementation of main protections in digital form

This paper presents a Java-based software demonstration of overcurrent, transformer differential, and distance protection. Its contribution is an implementation-oriented treatment of three complementary protection functions, with explicit signal-processing, decision, and timing logic. The transformer differential component builds on the authors’ earlier study; the present scope also includes four-stage overcurrent logic and a comparison of polygonal and circular distance characteristics. The methodology combines a scalar overcurrent example with offline processing of fault records for the other functions. Measurements of the Java implementation yielded approximately 30–70 ms operating time, 5–20 µs processing time per sample, and a JVM memory footprint of approximately 30–80 MB. At the adopted 4 kHz sampling rate, the reported per-sample processing time corresponds to 2–8% of the 250 µs sampling interval. These measurements support computational feasibility under the tested conditions, while qualitative timing variability remains a limitation. The results do not establish a worst-case execution bound, statistical reliability, or compliance with protection-equipment standards.