ABB RELION 620 Series Technical Manual page 607

1MAC504801-IB E
6.4.6
620 series ANSI
Technical Manual
Overload / System short circuit condition
It is required that any overload or short circuit conditions after a CT failure should block
the function. During overload or short circuit condition, the phase current increases
beyond its rated value; if any phase current on any set of current transformer exceeds the
set limit, the function is blocked internally. Also in case of an unsymmetrical fault, the
negative-sequence current increases. If the negative-sequence current increases beyond
the set limit, the function is blocked internally. The overcurrent and negative-sequence
current setting both can be set equal to the overcurrent and negative-sequence protection
function pickup value.
The internal blocking is thus useful for avoiding false operation during a fault situation.
Signals
Table 433: MCS 3I,I2 Input signals
Name Type
I_A1 SIGNAL
I_B1 SIGNAL
I_C1 SIGNAL
I2_1 SIGNAL
I_A2 SIGNAL
I_B2 SIGNAL
I_C2 SIGNAL
I_A3 SIGNAL
I_B3 SIGNAL
I_C3 SIGNAL
I2_3 SIGNAL
BLOCK BOOLEAN
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 Negative-sequence current from set 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
0 Current ID for getting current values for phase 3, tertiary
side or LV restraint
0 Negative-sequence current from set 3
0=False Block signal for activating the blocking mode
Section 6
Supervision functions
601