87nd neutral differential protection, Restrained differential (87ndpu, 87ndt), Pickup accuracy – Basler Electric BE1-CDS240 General Information User Manual
Page 24: Tap setting range, Restraint slope, Automatic setting group characteristics, Switch level, Switch timer, Bestlogic, General specifications
Figure 1-9. Typical 87 Response Characteristic Curves
87ND Neutral Differential Protection
Restrained Differential (87NDPU, 87NDT)
Pickup Accuracy
5 Ampere CT ............................................................ ±4% or ±75 mA, whichever is greater
1 Ampere CT ............................................................ ±4% or ±25 mA, whichever is greater
TAP Setting Range
5 Ampere CT ............................................................ 2 to 20 A
1 Ampere CT ............................................................ 0.4 to 4 A
Minimum Pickup (1 or 5 Ampere CT)
Setting Range .......................................................... 0.10 to 1.00 per unit
Restraint Slope
Setting Range (1 or 5 Ampere CT) .......................... 15 to 60%
Automatic Setting Group Characteristics
Number of Setting Groups:
4
Switch Level
Range ............................................................................. 0-150% of the setting group 0 #51 Phase, Neutral,
or Negative-Sequence pickup setting
Accuracy ......................................................................... ±2% or ±50 mA (5 A), ±2% or ±10 mA (1 A)
Switch Timer
Range ............................................................................. 0-150% of the setting group 0 #51 Phase, Neutral,
or Negative-Sequence pickup setting
Accuracy ......................................................................... ±0.5% or ±2 s, whichever is greater
BESTlogic
Update Rate .................................................................... ¼ cycle
General Specifications
AC Current Inputs
5 Ampere CT
Continuous rating ............................................................ 20 A
One second rating .......................................................... 400 A
For other current levels, use the formula I = (K/t)
½
where t = time in seconds and K = 160,000.
Begins to Clip (saturate) ................................................. 150 A
Burden ............................................................................ <10 mΩ at 5 Aac
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
R
esp
on
se
Ti
me (
cycl
es)
Multiple of Pickup
Unrestrained
Restrained
1-22
BE1-CDS240 General Information
9365200990 Rev M