GE 845 Instruction Manual page 228

SYSTEM
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The first two columns (40 points) correspond to the RESET curve. The other 4 columns, with
80 points in total, correspond to the OPERATE curve. The reset characteristic values are
between 0 and 0.98xPKP, and the operation values are between 1.03 and 20xPKP.
The final curve will be created by means of a linear interpolation from the points defined
by the user. This is a separate process for the RESET and the OPERATE curve.
The definition of these points is performed in a separate module from the relay, using a
configuration program included in EnerVista 8 Series Setup software, which incorporates a
graphical environment for viewing the curve, thus making it easy for the user to create.
The relay using a given FlexCurve applies linear approximation for times lying between the
user-entered points. Special care must be taken when setting the two points that are close
to a Pickup multiple of 1; that is, 0.98*I
two times to a similar value, otherwise, the linear approximation may result in undesired
behavior for the operating quantity that is close to 1.00*I
FLEXCURVE CONFIGURATION WITH ENERVISTA 8 SERIES SETUP SOFTWARE
The EnerVista 8 Series Setup software allows for easy configuration and management of
FlexCurves and their associated data points. Prospective FlexCurves can be configured
from a selection of standard curves to provide the best approximate fit, then specific data
points can be edited afterwards. Alternately, curve data can be imported from a specified
file (.csv format) by selecting the Import Data From setting.
Curves and data can be exported, viewed, and cleared by clicking the appropriate buttons.
FlexCurves are customized by editing the operating time (ms) values at pre-defined per-
unit current multiples. Note that the pickup multiples start at zero (implying the "reset
time"), operating time below Pickup, and operating time above Pickup.
and 1.03*I
pickup pickup
pickup
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
. It is recommended to set the
.