Relay protection setting of line impedance
The feature is useful where line impedance characteristics change between sections or where hybrid circuits are used. Direction: Forward Typically the zone 1 reach is required to be 80% - 90% of the line. They are used for direct tripping (Zone 1), in directional comparison pilot schemes, and in step distance protection schemes. 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.
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