ABB Relion REC670, Applications Manual

Page: 148 / 658

( )
3
2000
200 0 3 50 60 10 .100
5
IP approx A
-
= ° + × - ° × £
EQUATION1887-ANSI V1 EN-US
(Equation 17)
where
100 mA is the current drawn by the IED circuit and
10 mA
is the current drawn by each CT just at pickup
20 mA is current drawn by metrosil at pickup
The magnetizing current is taken from the magnetizing curve for the current
transformer cores which should be available. The current value at
TripPickup is taken.
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.
7.1.4.4 Tertiary reactor protection
M16850-118 v5
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 (87) can be used to protect the tertiary reactor
for phase faults as well as ground faults if the power system of the tertiary winding is
direct or low impedance grounded.
Section 7
1MRK 511 401-UUS A
Differential protection
142 Bay control REC670 2.2 ANSI
Application manual