Distance relays are fed from the secondary's of line CT's & Bus PT's /Line CVT's. The CT and PT ratios are inter related. 1 Line Impedance Calculation The positive sequence impedance (Z₁) of the. Pick Up Current Definition: The current level at which the relay begins to operate, overcoming the controlling force. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions. The selection and applications of. Generally zones Z1, Z2, Z3 are taken as forward direction and Z4 is taken as reverse direction with time settings as T1, T2, T3 and T4 respectively. Stepped distance relay scheme is. 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.
