Signals - ABB RELION REX640 Technical Manual

Section 4
Protection functions
4.3.3.9
654
If the actual burden of the current transformer (S
enough to provide a sufficient value for F
• A current transformer with a higher rated burden S
means a higher rated accuracy limit F
• A current transformer with a higher nominal primary current I1
rated burden) can be chosen.
Example 2
Assuming that the actions according to the current transformer with a higher nominal
primary current I1 (but the same rated burden) are taken to improve the actual
n
accuracy limit factor (F
a
I = 1000 A Rated secondary current of the transformer
rTR
I = 1500 A Rated primary current of the CT on the transformer secondary side
rCT
F = 30 Rated accuracy limit factor of the CT
n
F = (I / I ) ⋅ F Actual accuracy limit factor due to oversizing the CT
a rCT rTR n
= (1500/1000) ⋅ 30 = 45
F
a
In differential protection it is important that the accuracy limit factors (F
of the phase CTs correspond with each other, that is, the burdens of the CTs on both
sides should be as equal as possible. If high inrush or start currents with high DC
components flow through the protected object when it is connected to the network,
special attention should be paid to the performance and the burdens of the CTs and to
the settings of the function block.

Signals

Table 597: TR3PTDF Input signals
Name Type
I3P1 SIGNAL
I3P2 SIGNAL
I3P3 SIGNAL
BLOCK BOOLEAN
BLK_OPR_LS BOOLEAN
BLK_OPR_HS BOOLEAN
TAP_POS INT8
a
, there are two alternatives.
a
) or
n
):
Default Description
- Three-phase currents 1
- Three-phase currents 2
- Three-phase currents 3
0=False Block
0=False Blocks operate outputs from biased stage
0=False Blocks operate outputs from instantaneous stage
0 Tap position indication
1MRS759142 C
) in Equation 120 cannot be reduced
can be chosen (which also
n
(but the same
n
) at both sides
a
Technical Manual
REX640