GE L30 Instruction Manual page 317

Line current differential system
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CHAPTER 5: SETTINGS
The relay using a given FlexCurve applies linear approximation for times between the user-entered points. Take
care when setting the two points that are close to the multiple of pickup of 1; that is, 0.98 pu and 1.03 pu. It is
recommended to set the two times to a similar value, otherwise the linear approximation can result in undesired
behavior for the operating quantity that is close to 1.00 pu.
5.5.7.2 FlexCurve configuration with EnerVista software
The EnerVista 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 EnerVista Import Data From setting (Settings > System Setup > FlexCurves > FlexCurve).
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.
5.5.7.3 Recloser curve editing
Recloser curve selection is special in that recloser curves can be shaped into a composite curve with a minimum response
time and a fixed time above a specified pickup multiples. There are 41 recloser curve types supported. These definite
operating times are useful to coordinate operating times, typically at higher currents and where upstream and
downstream protective devices have different operating characteristics. The recloser curve configuration window shown
here appears when the Initialize From setting in the EnerVista software is set to "Recloser Curve" and the Initialize
FlexCurve button is clicked.
The Multiplier and Adder settings only affect the curve portion of the characteristic and not the MRT and HCT
settings. The HCT settings override the MRT settings for multiples of pickup greater than the HCT ratio.
5.5.7.4 Example
A composite curve can be created from the GE_111 standard with MRT = 200 ms and HCT initially disabled and then
enabled at eight times pickup with an operating time of 30 ms. At approximately four times pickup, the curve operating
time is equal to the MRT and from then onwards the operating time remains at 200 ms.
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
Figure 5-59: Recloser curve initialization
SYSTEM SETUP
5
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