corresponding 59 time delay, an overvoltage condition is annunciated. Both overvoltage pickup settings
have a range of 70 to 576 Vac and both overvoltage time delay settings have a range of 0 to 30 seconds.
An overvoltage annunciation can be user-selected to trigger a pre-alarm (warning) or alarm (shutdown).
An overvoltage annunciation can also be user-configured to close one or both of the programmable
outputs.
When a Single-Phase Override contact input is received, the DGC-500 automatically switches from the
three-phase overvoltage settings to the single-phase overvoltage settings.
Undervoltage (27)
Two sets of undervoltage settings are provided: one for three-phase generator connections and one for
single-phase generator connections.
When the average of the three-phase voltage (three-phase mode) or the average of the line-to-line
voltage (single-phase mode) decreases below the corresponding 27 pickup setting for the duration of the
corresponding 27 time delay, an undervoltage condition is annunciated. Both undervoltage pickup
settings have a range of 70 to 576 Vac and both undervoltage time delay settings have a range of 0 to 30
seconds.
A frequency-based inhibit setting prevents a 27 trip from occurring during an underfrequency condition
associated with system startup. The frequency-based inhibit function has a setting range of 20 to 400
hertz.
An undervoltage annunciation can be user-selected to trigger a pre-alarm (warning) or alarm (shutdown).
An undervoltage annunciation can also be user-configured to close one or both of the programmable
outputs.
When a Single-Phase Override contact input is received, the DGC-500 automatically switches from the
three-phase undervoltage settings to the single-phase undervoltage settings.
Frequency (81)
Two sets of frequency settings are provided: one for underfrequency (81U) protection and one for
overfrequency (81O) protection.
When the generator frequency decreases below the 81U pickup setting for the duration of the 81U time
delay, an underfrequency condition is annunciated. When the generator frequency increases above the
81O pickup setting for the duration of the 81O time delay, an overfrequency condition is annunciated. For
50/60 hertz sensing, the 81U and 81O functions have a setting range of 45 to 65 hertz. For 400 hertz
sensing, the 81U and 81O functions have a setting range of 360 to 440 hertz. The time delay for the 81U
and 81O functions has a setting range of 0 to 30 seconds.
A voltage-based inhibit setting prevents an 81U trip from occurring during an undervoltage condition
associated with system startup. The voltage-based inhibit function has a setting range of 70 to 576 Vac.
Underfrequency and overfrequency conditions can be user-selected to trigger a pre-alarm (warning) or
alarm (shutdown). An underfrequency and/or overfrequency condition can also be user-configured to
close one or both of the programmable outputs.
Overcurrent (51)
Two sets of overcurrent settings are provided: one for three-phase generator connections and one for
single-phase generator connections.
When any of the phase currents increase above the 51 pickup setting for the duration of the 51 time
delay, an overcurrent condition is annunciated. Controllers with 1 A current sensing (style X1XX) have an
overcurrent pickup range of 0.18 to 1.18 Aac. Controllers with 5 A current sensing (style X5XX) have an
overcurrent pickup range of 0.9 to 7.75 Aac. The overcurrent time delay is controlled by a curve setting
and time dial setting. The curve setting can be set at F, Fixed, or one of 16 inverse timing characteristic
curves can be selected. When the F, Fixed curve setting is selected, the time dial setting (adjustable from
0 to 30 seconds) determines the overcurrent time delay with no regard to the generator current level.
When one of the 16 inverse timing characteristics curves selected, the time dial setting (adjustable from a
multiplier of 0 to 9.9) along with the level of measured generator current determines the overcurrent time
delay.
The available characteristic curves is listed below and illustrated in Appendix A, Time Overcurrent
Characteristic Curves.
• S1, Short Inverse
• S2, Short Inverse
• L1, Long Inverse
• L2, Long Inverse
9355400990 Rev H DGC-500 Functional Description 3-13
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