Functions
2.14 Differential Protection and Its Protected Objects
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
125
The second branch produces a higher restraint in the range of high currents which may lead to current trans-
former saturation. Its base point is set at address 2044 BASE POINT 2 and is referred to the rated power
transformer current. The slope is set at address 2043 SLOPE 2. The restraint during current transformer sat-
uration can be influenced by this parameter branch. A higher gradient results in a higher restraint.
Additional Stabilization During Current Transformer Saturation
Where very high currents flow during an external short-circuit, an add-on stabilization takes effect that is set at
address 2061 I-ADD ON STAB. (saturation stabilization). Please note that the stabilizing current is the arith-
metical sum of the currents through the windings, i.e. it is twice the actually flowing current. The default setting
of should be maintained. The maximum duration of the additional stabilization is set at address 2062 T ADD
ON-STAB. in multiples of one cycle. This time is the maximum duration of blocking after leaving the additional
stabilization area during heavy current external faults. The setting depends under certain circumstances on the
disconnecting time of the upstream contact. The default setting 15 Cycle is a practical value.
Delay Times
In special cases it may be advantageous to delay the trip signal of the differential protection. For this, an addi-
tional delay can be set. The delay timer 2026 T I-DIFF> is started when an internal fault is detected in the
transformer. 2036 T I-DIFF>> is the delay time for the tripping stage 2031 I-DIFF>>. A separate time stage
is provided for each differential protection level and for each phase. The dropout delay is linked to the minimum
trip command duration that is valid for all protection functions. All setting times are additional time delays which
do not include the operating times (measuring time, dropout time) of the protective function.
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