Manual 26174
EGCP-2 Engine Generator Control Package
Woodward
125
Base Load Against the Mains
Base Load is a method of setting a base or fixed load on a machine operating in
parallel with the mains. The EGCP-2 control operates the generator set in base
load whenever the generator is in parallel with the utility, unless a process control
mode of operation is selected through the Process discrete input. This is
accomplished by using an isochronous load control and providing a reference
level at which to control the load. The governor will force the generator output to
increase or decrease until the output of the load sensor is equal to the reference
setting. The base load reference is set in the Real Load Control tuning menu of
the EGCP-2. At this point, the system is in balance.
The advantage of base loading over droop is that when separating from a Mains,
there is no frequency change. Simply removing the bias signal required to
maintain the base load reference on breaking from the Mains (mains CB Aux
open) returns the system to isochronous load control.
The EGCP-2 is only allowed to parallel with the mains in a Mains Parallel
operating mode. When configured for this type of operation, the EGCP-2 will
operate in either a base load or process control mode while in parallel with the
mains. The EGCP-2 automatically switches between base load and isochronous
operation depending upon whether or not the Mains Breaker CB Aux input is
closed at the same time the Generator CB Aux input is closed. If both the Mains
and the Generator CB AUX are closed, then the EGCP-2 realizes it is in parallel
with the mains, and operates in a base load control mode. The EGCP-2 will
operate in a process control mode, which is discussed later in this section, if both
the Process and Run with Load discrete inputs are active (on).
Automatic Generator Loading Functions
The automatic generator loading functions of the EGCP-2 control will work with
the speed control to automatically control the loading and unloading of the
generator. This accomplishes a bumpless transfer when paralleling the generator
to a load sharing or infinite bus system, or when separating a generator from a
system.
Process Control Description
The process control function of the EGCP-2 control will control any process
where the controlled parameter is determined by the generator load, and the
controlled parameter can be monitored as a 4–20 mA or 1–5 Vdc input signal.
The control compares the Process Input signal to the Process Reference set
point in the Process menu of the EGCP-2. This set point uses milliamps for units,
so that it is easily related to the 4–20 mA or 1–5 Vdc input signal. The EGCP-2
then adjusts the generator load to maintain the desired value. The EGCP-2 will
only operate in a process control mode if it is configured to be a Mains Parallel
unit, and receives an Auto, Run With Load, and Process discrete inputs. Also,
the EGCP-2 can operate in a process soft transfer mode if the Load Control
Mode set point in the Real Load Control menu is set for Soft Transfer, and the
Test discrete input is closed with the Auto, Run with Load and Process discrete
inputs. In a soft transfer mode, the EGCP-2 will load the generator(s) (depending
on the application) to the process reference level. Upon reaching the reference
value on the 4–20 mA or 1–5 Vdc input signal, the EGCP-2 will open the mains
breaker. This Soft Transfer mode is used to transfer the supply of power for the
load from the mains to the generator(s).