ABB REC670 Applications Manual page 144

Section 7
Differential protection
3·Id
IEC05000176 V3 EN-US
Figure 53: Application of the1Ph High impedance differential protection HZPDIF function on a reactor
138
Setting example
It is strongly recommended to use the highest tap of the CT
whenever high impedance protection is used. This helps in utilizing
maximum CT capability, minimize the secondary fault, thereby
reducing the stability voltage limit. Another factor is that during
internal faults, the voltage developed across the selected tap is
limited by the non-linear resistor but in the unused taps, owing to
auto-transformer action, voltages much higher than design limits
might be induced.
1MRK 511 401-UEN A
IEC05000176-3-en.vsd
Bay control REC670 2.2 IEC
Application manual