Tertiary Reactor Protection - ABB Relion REC670 Applications Manual

1MRK 511 358-UEN A
The magnetizing current is taken from the magnetizing curve for the current transformer
cores which should be available. The current value at
dependent resistor current the peak value of voltage 200 ˣ √2 is used. Then the RMS current is
calculated by dividing obtained current value from the metrosil curve with√2. Use the value
from the maximum metrosil curve given in Figure
It can clearly be seen that the sensitivity is not so much influenced by the selected voltage level
so a sufficient margin should be used. The selection of the stabilizing resistor and the level of
the magnetizing current (mostly dependent of the number of turns) are the most important
factors.
6.1.4.4

Tertiary reactor protection

Reactive power equipment (for example shunt reactors and/or shunt capacitors) can be
connected to the tertiary winding of the power transformers. The 1Ph High impedance
differential protection function HZPDIF can be used to protect the tertiary reactor for phase
faults as well as earth faults if the power system of the tertiary winding is direct or low
impedance earthed.
3·Id
IEC05000176 V3 EN-US
Figure 37: Application of the1Ph High impedance differential protection HZPDIF function on a reactor
Application manual
U>Trip is taken. For the voltage
38
Section 6
Differential protection
M16850-118 v5
IEC05000176-3-en.vsd
97