Relay protection impedance conversion
Relays measure secondary impedance, so we convert using: Zsecondary=Zprimary× (CTratio/VTratio) Example: Zsecondary= (5+j20)×500/1200=2. 1 Zone 1 (Instantaneous, 80-85% Reach) Purpose: Fast tripping for faults within. Protective Relays - Technical Seminar Nov 2016 - Copyright: IEEE 2 Abstract: Protective relays and devices have been developed over 100 years ago to provide "lastline"of defense for the electrical systems. They are intended to quickly identify a fault and isolate it so the balance of the system. The calculated impedances differ under certain circumstances as shown in the following example.
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