Basler Electric BE1-851 - Manual (Page 73)

Table 4-8. Definitions for Equations 4-1 and 4-2
Parameter Description Explanation
T
T
Time to trip Time that the 51 function will take to time out and trip.
D Time dial setting Time dial setting for the 51 function.
M Multiple of pickup
Measured current in multiples of pickup. The timing algorithm has a
dynamic range of 0 to 40 times pickup.
A
Coefficient specific
to selected curve
Affects the effective range of the time dial.
B
Coefficient specific
to selected curve
Affects a constant term in the timing equation. Has greatest effect
on curve shape at high multiples of tap.
C
Coefficient specific
to selected curve
Affects the multiple of PU where the curve would approach infinity if
allowed to continue below pickup. Has greatest effect on curve
shape near pickup.
N
Exponent specific
to selected curve
Affects how inverse the characteristics are. Has greatest effect on
curve shape at low to medium multiples of tap.
K Constant Characteristic minimum delay term.
T
R
Time to reset Relevant if 51 function is set for integrating reset.
R
Coefficient specific
to selected curve
Affects the speed of reset when integrating reset is selected.
Curve coefficients can be entered using BESTCOMS. Alternately, curve coefficients can be entered using
the SP-CURVE (Settings Protection-programmable curve) command. Table 4-9 lists the programmable
curve settings.
Table 4-9. Programmable Time Current Characteristic Curve Coefficients
Setting Range Increment Default
A Coefficient 0 to 600 0.0001 0.2663
B Coefficient 0 to 25 0.0001 0.0339
C Coefficient 0.0 to 1.0 0.0001 1.0000
N Coefficient 0.5 to 2.5 0.0001 1.2969
R Coefficient 0 to 30 0.0001 0.5000
Curve coefficients are entered by selecting the Curve Coefficients button on the 51 or 151 tab in the
Overcurrent screen (refer to Figure 4-14). The Curve Coefficients screen will appear. See Figure 4-15.
Enter the calculated values for each constant and select Done.
Figure 4-15. Curve Coefficients Screen
9289900990 Rev R BE1-851 Protection and Control 4-17