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ABB Distribution Protection Unit 1500R
Customer-Programmable Curves
An external PC-based program, CurveGen, is used to create and program time-current curves for the DPU1500R. With
CurveGen you can program time-overcurrent curves other than the ones currently provided in the DPU1500R (see Tables
1-1 and 1-2). You can manipulate the curves in the time and current domains just like any other curve currently programmed
into the DPU1500R. CurveGen generates all of the necessary variables for the user-defined curves to be stored in the
DPU1500R (i.e. the alpha's, beta's and pointers to the curve table). The method of accomplishing this task is curve
definition.
The standard curve entered into the DPU1500R has the form of:
A
t =
+ B [ ( 14n - 5 ) / 9 ]
p
M
- C
To define the curve, you must define the variables in this equation.
There are two ways to do this:
•
Enter variables by hand: With the CurveGen program you can define all four variables by hand. This is designed for
users who do not want curves based on already established functions but instead are ready to define curves
through mathematical manipulation.
•
Determine variables via curve fitting: Define a series of time versus current points and fit them to the standard
equation listed above.
With the CurveGen program you can enter these series of time/current points from an already defined curve. CurveGen
then fits the four variables to these points. There are two ways to enter these points into the CurveGen program:
•
Enter all sampled points by hand. The ability to remove, sort, plot, edit and view points gives you total power over
the curve to be generated.
•
File entry: CurveGen can also read files with points defined in them. The ability to remove, sort, plot, edit and view
points gives you total power over the curve to be generated.
Once all the points are entered, the CurveGen program is cued to fit a standard curve. After A, p, C and B have been
determined, you can plot the curve against the points given as well as determine the overall error of the curve versus the
plotted points.
After all four variables have been determined, you can generate a linear approximation of the curve. A maximum error
criteria must be satisfied before CurveGen can determine the coefficients needed for the DPU1500R. Errors and warnings
indicate whether or not the error criteria can be met or if the number of entries in the curve table is above the maximum
value allowed.
When the curve tables have been defined by CurveGen, download them into the DPU1500R. When you want a customer-
defined curve, select "Export Option" from the File Menu in WinECP.
10-10
M is the per-unit current
above the pickup value
t is total trip time at M
A, p, C and B are variables
to be defined.
website:www.abb.com/papd
9/99
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