CHAPTER 7: PROTECTION
CONTROL ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
377
Figure 314: Digital counter scheme logic
FlexCurves™
There are four user-programmable FlexCurves™ available with the D90
Plus
system, labeled
A, B, C, and D.
The curve shapes for the four FlexCurves are derived from the following equations.
Eq. 40
Eq. 41
In the above equations,
T
operate
represents the operate time in seconds, TDM represents
the multiplier setting,
I
represents the input current,
I
pickup
represents the value of the
pickup current setting,
T
flex
represents the FlexCurve™ time in seconds, and
T
reset
represents the reset time in seconds.
FlexCurve™ settings
Select the
Settings > Protection > Control > FlexCurves > FlexCurve A
menu item to
access the FlexCurve™ A settings. The same group of settings is available for FlexCurves™
B, C, and D.
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