This relay serves as a fundamental backup or primary protection device in medium-voltage (MV) and high-voltage (HV) networks. Its core principle is to measure the current via connected Current Transformers (CTs) and, if the current exceeds a preset threshold for a duration defined by an inverse time curve, it mechanically closes its output contacts to trip a circuit breaker. Its self-powered nature makes it exceptionally reliable and ideal for critical protection where control power failure must not compromise safety.

The ABB 3HAC021761-001 is a precision control component designed for advanced industrial automation systems. Tailored for applications requiring high accuracy and reliability, it integrates seamlessly into complex manufacturing processes.

The ICS Triplex T3411F is a high-performance monitored digital input module designed for industrial automation systems, providing reliable signal monitoring and data acquisition.