Inputs
Current single-line diagram; maximum and minimum fault levels at each bus (from a short-circuit study); CT ratios, classes and knee-points; relay models and firmware; transformer, cable and motor data including damage curves and inrush; and the network operator's settings at the point of connection.
Outputs
A settings schedule for every relay function, time-current coordination curves showing grading margins, a list of assumptions, and identified risks where coordination cannot be achieved. Settings should be issued as controlled documents with revision history.
Common pitfalls
Using maximum fault levels only, so relays fail to operate for minimum faults; ignoring transformer inrush and cold-load pickup; CT saturation for high-current faults; insufficient grading margins for breaker and relay operating times; and settings that are never checked against the relay as-installed.
Verification
Secondary injection testing of each relay with the issued settings, trip-circuit checks, and review of settings files loaded to the relay against the approved schedule. Discrepancies should be closed before energisation.