Relay coordination refers to setting protective devices so that the relay closest to the fault operates first, while upstream relays act as backups. Relay coordination is one of the most critical aspects of electrical power system protection. One-line diagrams and detailed network data (lines, transformers, buses). ABB Type SAB Current Transformer CT's transform line current down to a signal level that is acceptable to the relay. This signal level is typically 5A nominal in North America and 1A in IEC countries. Ratios are stated as “X” primary current to 5A i., 600:5 means that 600A of line current. Focusing on directional overcurrent relays, the study examines optimization-based methods for tuning key relay parameters, which include the pickup current and the time multiplier setting, to minimize the total relay operating times and ensure reliable protection.
[PDF Version]