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. Defining Performance The performance of a relay element or relaying scheme is described using the terms selectivity, speed, and sensitivity. These are more commonly known as the three Ss. Selectivity is a measure of how well a relay element can differentiate between an in-zone and an out-of-zone. Selective short-circuit protection can be achieved in different ways, such as: Time-graded protection Time- and current-graded protection A straightforward way of obtaining selective protection is to use time grading. Equivalent circuit of the protected object during three-phase c on the HV side of the unit: Rf, transient resistance at the fault lo-cation; xf, coordinate of the fault location. Common calculations. This technical report refers to the electrical protections of all 132kV switchgear. Protection selectivity is partly.
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