9400200990 Rev I DGC-2020 BESTCOMSPlus Software 4-39
CT secondary side (DGC-2020). When a single-phase override contact input is received by the DGC-
2020, the overcurrent protection settings automatically switch from the three-phase settings to the single-
phase overcurrent protection settings.
When any of the phase currents increase above the pickup setting
A
for the duration of the overcurrent
time delay, an overcurrent condition is annunciated. An overcurrent annunciation can be user-selected to
trigger a pre-alarm
B
(warning) or alarm
B
(shutdown). An overcurrent annunciation can also be user-
configured to close a programmable output.
The overcurrent time delay is controlled by a time dial setting
C
and a curve setting
D
. The curve setting can
be set at F (fixed) or one of 16 inverse time characteristic curves can be selected. When the fixed curve
setting is selected, the time dial setting determines the overcurrent time delay with no regard to the
generator current level. When one of the inverse time characteristic curves is selected, the time dial
setting, along with the level of measured generator current, determines the overcurrent time delay. As
overcurrent protection settings are entered in BESTCOMSPlus, a plot
E
of the settings is automatically
created to illustrate the overcurrent pickup curve. The available time characteristic curves are listed below
and illustrated in Appendix A, Time Overcurrent Characteristic Curves.
• A, standard inverse • I2, inverse
• A, standard inverse • I2, inverse
• B, very inverse • L1, long inverse
• C, extremely inverse • L2, long inverse
• D, definite • M, moderately inverse
• E1, extremely inverse • S1, short inverse
• E2, extremely inverse • S2, short inverse
• G, long inverse • V1, very inverse
• I1, inverse • V2, very inverse
A low-line scale factor setting
F
is used to automatically adjust the overcurrent pickup settings in
applications that may utilize more than one type of genset connections. The scale factor setting is
implemented when the DGC-2020 senses a contact closure at a contact input programmed to activate
scaling of the protection settings. The value of the scale factor setting serves as a multiplier for the pickup
settings. For example, if a scale factor contact input is received by the DGC-2020 and the scale factor
setting is 2.000, the pickup setting will be doubled (2.000 × PU).
The graph can be set
G
to display the 1 Phase or 3 Phase curve as determined by the settings on the left
side of the chart.
BESTCOMSPlus overcurrent protection settings (DGC-2020, Generator Protection, Overcurrent) are
illustrated in
Figure 4-37. The 51-1 element is shown.
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