Overcurrent Elements

The 889 can be used to provide backup protection for transformer

and adjacent power system equipment. Instantaneous overcurrent

(IOC) elements can be used for fast clearing of severe internal and

external (through) faults. Up to six time overcurrent protection

(TOC) elements per winding allow to coordinate with the adjacent

protection zones and act as backup protection.

• IOC protection functions are provided for phase, neutral &

ground currents

• TOC protection functions are provided for phase, neutral and

ground currents. A variety of standard time curves including

IEEE, IEC, GE Vernova IAC, I2t, definite time are provided

• FlexCurves to coordinate with adjacent protections (including

fuses) as well as transformer damage curves and thermal/

damage curves for downstream equipment Directional

protection functions are provided for phase, neutral and ground

currents. The voltage memory function enables a more reliable

relay operation, especially for faults close to the VTs.