Signals - ABB RELION 620 Series Technical Manual

Section 4
Protection functions
4.6.2.8
450
Example 2
Assuming that the actions according to the current transformer with a higher nominal
primary current I1 (but the same rated burden) is taken to improve the actual accuracy
n
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 ) x F actual accuracy limit factor due to oversizing the CT
a rCT rTR n
F = (1500/1000) x 30 = 45
a
In differential protection it is important that the accuracy limit factors (F
transformers at both sides correspond with each other, that is, the burdens of the current
transformers 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, a special attention should be paid to the performance and the burdens of the
current transformers and to the settings of the function block.

Signals

Table 344: 87T3 Input signals
Name Type
I_A1 SIGNAL
I_B1 SIGNAL
I_C1 SIGNAL
I_A2 SIGNAL
I_B2 SIGNAL
I_C2 SIGNAL
I_A3 SIGNAL
I_B3 SIGNAL
Table continues on next page
Default Description
0 Current ID for getting current values for phase A,
winding 1
0 Current ID for getting current values for phase B,
winding 1
0 Current ID for getting current values for phase C,
winding 1
0 Current ID for getting current values for phase A,
winding 2
0 Current ID for getting current values for phase B,
winding 2
0 Current ID for getting current values for phase C,
winding 2
0 Current ID for getting current values for phase 1, tertiary
side or LV restraint
0 Current ID for getting current values for phase 2, tertiary
side or LV restraint
1MAC504801-IB E
) of phase current
a
620 series ANSI
Technical Manual