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The second branch produces a higher stabilization in the range of high currents which may lead to current
transformer saturation. Its base point is set at address 2044 BASE POINT 2. The gradient is set at address
2043 SLOPE 2. The stability during current transformer saturation can be influenced by this parameter branch.
A higher gradient results in a higher stability. The default setting of 0.5 has proven to be a good value.
Figure 2-42
Add-On 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 entering and leaving the protected zone, i.e. that it is twice the actually flowing cur-
rent. The default setting of 4.00 I/InO should therefore be kept. The maximum duration of the additional stabi-
lization 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
20 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 timer 2026 T I-DIFF> is started when an internal fault in the generator or the
motor has been detected. 2036 T I-DIFF>> is the time delay of tripping stage I-DIFF>>. A separate time
stage is provided for each differential protection stage 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.
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
Parameters Determining the Shape of the Tripping Characteristic
2.14 Differential Protection and Its Protected Objects
Functions
117
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