DSLC Digital Synchronizer and Load Control
Manual 02007
74
Woodward
If the Load/Unload contact input was closed when the CB Aux contact was
closed, the soft loading ramp will be started immediately. Otherwise, load sharing
at the derated load will continue. When the loading ramp is activated, the soft
loading function compares the load on the oncoming unit with the load on the
load sharing system. The load ramp then linearly increases the load on the unit
at the rate set by the Load Ramp Time set point. When the loads match, the
ramp is shut off. In the case of an unloaded system, or when derated shared load
is below the unload trip level, the unit enters load sharing without the ramp
function. The pause command may be used to hold the ramp if desired.
Soft Unloading from a Load Sharing System
The unload sequence is initiated by opening the Load/Unload contact. The DSLC
control then ramps the load down to zero at the preset rate. When the load
reaches the Unload Trip Level set point, the low side driver for the Breaker Open
relay, terminal 22, is momentarily deactivated to initiate the opening of the
generator breaker. This command can be used to separate the engine generator
set from the paralleled system.
Base Loading Against a Utility
The base load function is selected by connecting the Base Load contact input,
terminal 50, to a set of utility breaker auxiliary contacts. The CB Aux contact
input, terminal 47, is connected to a set of generator breaker auxiliary contacts.
When both generator and utility breakers are closed, the unit load will be set to
the unload trip level. When the Load/Unload contact connected to terminal 51 is
closed, the load ramp starts and the unit load is increased to match the base
load set point. The base load can be adjusted up or down while in the base load
mode with the Raise Load and Lower Load contact inputs. The Load Raise and
Lower inputs cannot adjust the base load reference above the High Limit PU or
below the Low Limit PU (Menu 2). The load will follow at a rate set by the
appropriate raise or lower rate set points. When both the Raise and Lower Load
contacts are closed, the external 4–20 mA load setting input will take precedence
over the internal base load set point when above 2 mA (0.5 Vdc).
The Load/Unload input, terminal 51, will initiate the unload sequence. Opening
the unload switch contacts commands the ramp to decrease the demand on the
generator to the unload trip level. When the trip level is reached, the breaker
open command relay is momentarily deactivated to separate the generator from
the utility. When the CB Aux contacts open, the DSLC control will remove the
bias signal from the speed control and reset the loading function for the next
breaker closure.
Base Load and Load Sharing Systems
When the generator is paralleled and load sharing, closing the Base Load
contact to terminal 50 activates the base load function. Load on any parallel load
sharing units is disregarded. Load will ramp in the increasing or decreasing
direction until the unit load matches the Base Load set point. The load will follow
at a rate set by the appropriate load or unload time set points. The base load can
be adjusted up or down while in the base load mode with the Raise Load and
Lower Load contact inputs. The load will follow at a rate set by the appropriate
raise or lower rate set points.