Kohler 500EOZCS Operation page 33

Load Control Description
The purpose of Load Control is to permit a generator to
support load which may occasionally exceed the rated
capacity of the generator. In paralleling systems, load
shed permits the bus to stay at rated voltage and
frequency while an additional generator is synchronizing
to it. In single-generator applications, load control may
shed unimportant but highly demanding loads when the
generator is overloaded, preventing a power outage
caused by the generator going offline.
The Load Control in the Decision-Makerr 3500
controller supports 6 load control priorities. These
priorities generate internal notices for the shed
condition. The internal notices are generated any time a
load is shed, but they will only operate a load control
relay if they are configured to a digital output.
Only 4 load control priorities can be configured to the
RDO outputs on the controller (2 in paralleling
applications) but the optional 14 relay dry contact kit will
permit all 6 load control priorities to be accessed and
configured to disconnect 6 different loads (each load
priority can interrupt several devices).
In paralleling applications, the load shed priorities can
be divided between all the generators. For instance,
Generator #1 can support Load Priorities 1 and 4,
Generator #2 can support Priorities 2 and 5 and
Generator #3 can support Priorities 3 and 6. This
configuration does not require the 14 relay dry contact
kit and permits partial load shed functionality even if one
controller is powered down or fails (redundancy).
Load Priority 1 is shed last and added first, the priorities
are added in increasing sequence and shed in
decreasing sequence.
All Load Priorities are immediately shed when load
control is initiated. Load control is initiated when the
system receives a start signal (a system start, a remote
start, or a start by communication). In a paralleling
application, the controller can receive a start signal from
any generator which is connected to the PGEN
communication network. Pressing RUN on the
controller will not cause the loads to shed.
All loads are added immediately when Load Control is
de-activated—this occurs when the start signal is
removed.
Load Control adds loads based on the capacity of the
system—loads will add more quickly if the available
capacity is higher.
Load Control sheds loads based on the degree of
overload of the system—loads will shed more quickly as
the degree of the system overload increases.
TP-7126 5/20
Note: The generator management start % should be
significantly lower than the Gen Overload
Percent so that additional generators will come
online before a load is shed.
An under frequency event will also shed load—the
under frequency threshold is not adjustable from the
User Interface.
The load control will shed subsequent loads more
quickly if shedding a load did not remove the overload or
underfrequency condition.
In a standard application (single generator or generator
controlled by external switchgear) the load control logic
uses the Gen % or Rated kW and the Gen Frequency.
In a paralleling
Decision-Makerr 3500 controller is responsible for
first-on, synchronizing, load sharing, and generator
management) the load control logic uses the Bus % of
Rated kW and Bus Frequency. All generators use the
same start signal, load and frequency values to
determine load control timing, hence each controller will
shed and add a given load priority at the same time
(provided that the load control settings are identical in
each controller).
In a paralleling application
Management is used, some generator sets may be shut
down (turned Off) by Generator Management. Even if
the generator set is Off, it may de-activate its Load
Control outputs to energize those loads. This may seem
counter-intuitive, but the generator sets are acting as a
system. If voltage and frequency of the paralleling bus
are adequate, and Load Add accumulators are met, the
loads will be enabled, even if a particular generator set is
shut down by the Generator Management.
Description of User Adjustable Load Control
Settings
The Load Control
GENERATOR INFO -> PARALLEL OPERATION ->
LOAD CONTROL. Load control is active, even if the
generator is not operating in a paralleling application.
Gen % Max Cap. The load level on the generator (or
paralleling bus, in a paralleling application) that the load
control will not intentionally exceed. If the load is within
15% of this load level, the load control will not add the
next priority until the load decreases (or another
generator starts, synchronizes and closes its paralleling
breaker/contactor, in a paralleling application).
Gen Overload Percent.
generator (or paralleling bus, in a paralleling
application) above which the load Control will start to
consider shedding loads. Loads will shed more quickly if
the generator is heavily overloaded, more slowly if the
application (where
where Generator
settings are found
The load level on the
Section 1 Specifications
the
under
33