Basler Electric DGC-2020HD - Manual (Page 150)

140 9469300990 Rev B
Caution
For 1 A current sensing, current shall not exceed 3 amperes for 30
seconds or 4 amperes for 1 second. For 5 A current sensing, current
shall not exceed 15 amperes for 30 seconds or 20 amperes for 1
second. Exceeding the above limits may result in equipment damage.
If an overcurrent pickup condition persists for the duration of the calculated time, the element Trip output
becomes true. In BESTlogicPlus, the Trip output can be connected to other logic elements or a physical
relay output to annunciate the condition and initiate corrective action.
If the pickup condition subsides before the calculated time expires, the timer is reset, no corrective action
is taken, and the element is rearmed for any other occurrences of overcurrent.
Per Unit
Settings which are related to machine ratings can be set in either actual units of current or in per unit
values. When a native unit is edited, BESTCOMSPlus automatically recalculates the per unit value based
on the native unit setting and the rated data parameter (on the System Parameters, Rated Data screen)
associated with it. Conversely, when a per unit value is edited, BESTCOMSPlus automatically
recalculates the native value based on the per unit setting and the rated data parameter associated with
it.
Once all per unit values are assigned, if the rated data parameters are changed, BESTCOMSPlus
automatically recalculates all native unit settings based on the modified rated data parameters.
The following settings have native units of Secondary Amps, and the rated data associated with it is
Rated Secondary Phase Amps (on the System Parameters, Rated Data screen).
•
Overcurrent 51-x Three-Phase Pickup
•
Overcurrent 51-x Single-Phase Pickup
Low-Line Scale Factor
A low-line scale factor setting is used to automatically adjust the overcurrent pickup settings in
applications that might utilize more than one type of genset connection. The scale factor setting is
implemented when the DGC-2020HD is determined to be in a low-line configuration. If the Low-Line
Override function is assigned to a contact input via the Programmable Functions screen, the state of the
contact input and the detected configuration are ORed. This means, if one or both are true, then the
system is determined to be configured for low-line. 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-
2020HD and the scale factor setting is 2.000, the pickup setting will be doubled (2.000 x PU).
Alarm Configuration
An overcurrent annunciation can be user-selected to trigger a pre-alarm (warning) or alarm (shutdown). It
can also be user-configured to close a programmable output.
Element status is available in BESTlogicPlus programmable logic when “Status Only” is selected.
Programmable Curves
Each 51 overcurrent element has a Curve setting. See the Time Curve Characteristics chapter for details
on each of the curves available. The user can select integrating reset timing to make the protective
element use integrated reset and emulate an electromechanical induction disk reset characteristic. An
available programmable curve can be used to create a custom curve by selecting coefficients in the
inverse time characteristic equation.
Inverse overcurrent characteristics for trip and reset programmable curves are defined by Equation 1 and
Equation 2. These equations comply with IEEE Std C37.112-1996, IEEE Standard Inverse-Time
Characteristics Equations for Overcurrent Relays. The curve-specific coefficients are defined for the
standard curves as listed in the Time Curve Characteristics chapter. When inverse time overcurrent
characteristic curve P is selected, the coefficients used in the equation are those defined by the user.
Definitions for these equations are provided in Table 45.
Generator Protection DGC-2020HD