ABB RELION REX640 Technical Manual page 1726

Section 12
Requirements for measurement transformers
1720
F (IrCT / IrTR) * Fn (actual accuracy limit factor due to oversizing the CT) = (1500/1000) * 30 = 45
a
In TR2PTDF and TR3PTDF, it is important that the accuracy limit factors F
phase current transformers at both sides correspond with each other, that is, the
burdens of the current transformers on both sides are to be as equal as possible. If high
inrush or start currents with high DC components pass through the protected object
when it is connected to the network, special attention is required for the performance
and the burdens of the current transformers and for the settings of the function block.
1MRS759142 C
of the
a
REX640
Technical Manual