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. 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. All calculations are based on the available documentation/ information. These settings may be revaluated during the commissioning, according to actual and/or measured values. This standard mandates that generator, transmission, and distribution owners establish a process for developing new and revised protection settings and properly coordinate their systems wi h interconnected utilities as part of Requirement 1. The objective is to minimise the impact of electrical faults by ensuring that only the. Relay coordination is the process of selecting settings that will assure that the relays will operate in a reliable and selective way. Instantaneous units should be set so they.
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