Use this Protection Relay Setting Calculator to calculate pickup current, time multiplier settings (TMS), operating time, coordination time interval (CTI), and plug setting multiplier (PSM) using fault current, CT ratio, and IEC 60255 curve parameters. Protection relays employ a wide range of configurable parameters to identify defects & trip the breaker in a controlled & selected manner. Understanding each setting facilitates proper relay coordination. When developing a protection philosophy, clear indication should be given for special cases where. Coordinating overcurrent relays across multiple protection zones is one of the most consequential tasks in power system design — get it wrong and a single downstream fault trips an entire substation. For thermal overload protection (ANSI Device 49), the pickup is typically set at 115% to 125% of motor full-load amps depending on service factor. For overcurrent. What's the best way to determine optimal settings for power system protection relays? Power system protection relays are devices that monitor and control the operation of electrical networks, such as transmission lines, transformers, generators, and motors. All calculations are based on the available documentation/ information. These settings may be revaluated during the commissioning, according to actual and/or measured values.