Marine Online
Completion of this section the student
should have a good understanding of how
power is produced and a mutuality
between the prime movers and the
alternator's a pre-requisite for
satisfactory parallel operation is equal
speed on the prime movers Diesel's the
speed of the diesel engines is
controlled by their governors there are
different types of controllers on the
market but the principle is the same the
purpose of the controllers is to
maintain the speed at all loads and for
load sharing of active load in the
example below the generator use is a six
pole generator and the nominal frequency
is 60 Hertz this means that the speed of
the diesel engine has to be 1,200 rpm if
a kilowatt load such as heating is
switched on to the alternator then
energy is drawn from the alternator and
converted into heat this energy must be
provided by increasing the rate of fuel
to the prime mover this happens
automatically in the following way
as for the voltage regulation reactive
load sharing the diviners are adjusted
to have a speed drop from zero to full
load as we can see in the characteristic
the RPMs have dropped to 1152 of the
ends at full load if the idle speed is
set to 1,200 rpm and the speed droop is
four percent the frequency will drop
proportionally with a speed 250 7.6
hurts let's parallel shift the droop so
that the generator is at its nominal
speed at fifty percent load this is done
by changing the speed set point as we
can see the RPM is at 1200 rpms at fifty
percent load and the frequency will be
60 Hertz let's see what happens when we
change the speed roop to two percent we
still wish to retain the nominal
frequency at fifty percent slowed to
obtain a nominal frequency fifty percent
load we also have to change the speed
set point let's keep the focus and group
setting
and the governor adjusted nominal
frequency 60 Hertz at fifty percent load
start the generator by pressing the
start button on the DG one control panel
as you can see the generator has reached
idle speed connect the generator by
pressing the connect button on the DG
one control panel load the generator to
fifty percent each click on the increase
or decrease button will change the load
by ten percent as you can see we have
nominal frequency at fifty percent load
continue to load the generator two
hundred percent the RPM and frequency is
at 1176 and 58.8 respectively at full
load to maintain the nominal frequency
we must add more fuel to the diesel by
the means of the governor press the up
button on the governor we want to
connect generator 2 to the main bus in
order to share the load the governor has
the same speed droop characteristic as
number one start dg2 by pressing the
start button in the dg2 control panel
adjust the frequency of dg2 and it is
slightly above the main bus frequency by
pressing the down button the frequency
for the incoming connects dg2 by
pressing the connect button in the dg2
control panel the main best frequency
will decrease if we do not decrease DG
one simultaneously let's adjust both the
governor's to the nominal frequency at
this point it should be obvious what
will happen if we tamper with a speed
group and speed setting let's have a
look at a few examples changing the
speed set point Edwards on DG one will
result in DG one taking more of the
total load than dg2 there will be a
constant load deviation between DG 1 and
dg2 changing the speed droop on governor
one to eight percent will cause DG one
to take half as much load 50g to hear
both the speed setpoint and speed droop
is changed on DG one with these new
settings we get balanced load sharing
only at fifty percent load note that
these settings have been adjusted doing
the generator trials and should not be
tampered with if you are not fully aware
of what you are doing note that on
modern electrical power plants there is
an automatic frequency controls which
have take the Devon as app down
according to a preset point the
procedures in this chapter of a manual
adjustment of frequency and load sharing
in the following page
is it is