The type of ANSI characteristic can be selected under address 3145 51Ns ANSI CURVE. Setting options that
can be selected are Very Inverse, Inverse, Short Inverse, Long Inverse, Moderately Inv.,
Extremely Inv. and Definite Inv..
As dropout time, set under address 3146 51Ns Drop-out Instantaneous or Disk Emulation.
Logarithmic Inverse Time characteristic (Inverse Time)
The characteristic (see Figure 2-53) is set with the parameters 3119 51Ns PICKUP, 3141 51Ns Tmax, 3140
51Ns Tmin, 3142 51Ns TIME DIAL and 3143 51Ns Startpoint. 51Ns Tmin and 51Ns Tmax deter-
mine the tripping time range. The slope of the curve is defined in 3142 51Ns TIME DIAL. 51Ns PICKUP is
the reference value for all current values with 51Ns Startpoint representing the beginning of the curve,
i.e. the lower operating range on the current axis (related to 51Ns PICKUP). This factor is preset to the value
1.1, analogously to the other inverse time curves. This factor can also be set to 1.0 since in logarithmic inverse
curves the tripping time on a current value, which is identical to the specified pickup threshold, does not
approach infinity, but has a finite time value.
[kennlinie-amz-log-invers-050803, 1, en_US]
Figure 2-53 Trip time characteristics of the inverse time ground fault protection with logarithmic-inverse
time characteristic
Logarithmic inverse
t = 51Ns MAX. TIME DIAL - 51Ns TIME DIAL·ln (Ι/51Ns PICKUP)
Note:
For Ι/51Ns PICKUP > 35 the time applies for Ι/51Ns PICKUP = 35
Logarithmic Inverse Time characteristic with Knee Point (inverse time)
The curve (see Figure 2-54) is set by parameters 3119 51Ns PICKUP, 3127 51Ns I T min, 3128 51Ns I
T knee, 3132 51Ns TD, 3140 51Ns T min and 3141 51Ns T max. 51Ns T min and 51Ns T max deter-
mine the range of the tripping time, whereby 51Ns T max of current threshold 51Ns PICKUP and 51Ns T
min of current threshold 51Ns I T min are assigned. In configuration with knee point 51Ns T knee, the
tripping time is determined at transition of the two curve sections with different slopes. The transition point is
defined by current threshold 51Ns T knee. 51Ns PICKUP represents the minimum pickup limit for the
ground fault pickup current of the overcurrent element. As of a maximum secondary current of 1.4 A, the trip-
ping time takes on a constant value. Parameter 51Ns TD serves as a time multiplier for multiplication of the
tripping time.
Functions
2.9 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
136 SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016
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