Relay Test Set Accuracy and Calibration Explained
0.1 class, 0.2% datasheet accuracy and 0.5 class field minimum are three different things. What each means and what a calibration certificate must prove.
Standards & Test Practice
How Often Should Protection Relays Be Tested?
DL/T 995 fixes intervals by technology, NERC PRC-005 ties them to monitoring, and NETA leaves them to the owner. How to choose and defend an interval.
Relay Testing Standards Compared: IEC, IEEE, NETA, DL/T
Four standards, four different jobs: how IEC 60255, IEEE C37.233, NETA and DL/T 995 divide relay testing, and why their criteria cannot be swapped.