Why Protection Relays Drift Out of Calibration
Protection relays are the backbone of industrial and utility power systems. They are designed to detect faults and protect equipment. Most engineers assume relays stay accurate once calibrated. In reality, protection relays drift out of calibration over time due to multiple factors: aging electronics, environmental stress, secondary circuit issues, firmware/software changes, and operational conditions. Drift is progressive and can lead to false trips, delayed fault clearance, protection blind zones, miscoordination, and major reliability problems. This article addresses the top questions about relay calibration drift , providing detailed answers and actionable insights. 1. Why do protection relays drift over time? Relays drift because all measurement systems contain components that degrade over time. Even digital relays have analog front-end circuits like ADCs, voltage references, and signal conditioning modules. Capacitors, resistors, and reference voltages gradually chang...