I_LOC_A
I_LOC_B
I_LOC_C
I_REM_A
I_REM_B
I_REM_C
Inrush detector
From remote end
Stabilized low
stage
Instantaneous
high stage
Fail safe
function
BLOCK
BLOCK_LS
ENA_MULT_HS
TRIP
PICKUP
STR_LS_LOC
STR_LS_REM
OPR_LS_LOC
OPR_LS_REM
OPR_HS_LOC
OPR_HS_REM
BLKD2H_LOC
BLKD2H_REM
PROT_ACTIVE
Direct
intertrip
From
remote end
Differential
calculation
Transformer vector
group matching
Zero-sequence
component elimination
GUID-4CA762E0-EC72-417B-AA6C-B5D3F627B483 V1 EN
Figure 221:
Functional module diagram. I_LOC_x stands for current of the local end
and I_REM_x for phase currents of the remote ends.
Stabilized low stage
In the stabilized low stage, the higher the load current is, the higher the differential current
required for tripping is. This happens on normal operation or during external faults. When
an internal fault occurs, the currents on both sides of the protected object flow towards the
fault and cause the stabilizing current to be considerably lower. This makes the operation
more sensitive during internal faults. The low stage includes a timer delay functionality.
The characteristic of the low stage taking the apparent differential current into account is
influenced by various factors:
•
Small tapped loads within the protection zone
•
Current transformer errors
•
Current transformer saturation
•
Small asymmetry of the communication channel go and return paths
•
Small steady state line charging current
•
In-zone transformer no load current
•
Impact of tap changer positions
The timer is activated according to the calculated differential, stabilizing current and the
set differential characteristic.
Section 4
1MAC059074-MB A
Protection functions
462
615 series ANSI
Technical Manual
Summary of Contents for Relion 615 series
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