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Describtion Parallel
Operation Switching
Devices PLC
Matlab
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 Operation Of
Single Generator
Any
generator coubled to the bus must have addiational instrument .
Before
starting the prime over , make sure the generator breaker is open . and
then close the disconnect
links
the purpose of “disconnects” is to allow the complete isolation of the
breaker from the bus for the purpose of test ,maintenance and repair.
 Warnning
The
circuit breaker must always be opened0 before opening or closing the disconnect
switch or links
 Procedure For
Single Generator Operation
-
1-make
sure that the generator is open.
2-close the disconnect link
3-start the turbine or engine and bring up It to speed
4-using the governer control switch ,adjust the frequency to the rated name
plate frequency
5-adjust the automatic voltage regulator to obtain rated voltage
6-close the circuit breaker manually or automatic
Procedure
Of Parallel Operation
when
the load On an AC system exceeds
the amount that can be supplied by a single generator
additational
generator must be connected to the system to supply the required energy.
The
incoming machine must be paralleled in a manner that enable each machine to
supply its proper
Proportion
of the active and re active power to the common load .
Condition
For Parallel Operation
The
following condition must be fulfilled before an incoming alternator can but in
parallel with bus bar :-
1-the
voltage of the incoming machine must be the same as that of the bus
bar
2-the
frequency of the incoming alternator must be the same as the bus bar frequency
3-the
phase of the voltage of the incoming alternator must be identical
with the phase of
the
bus bar voltage with respect to the external circuit.
4-the
phase sequence of the voltage of the incoming alternator must be the same as
that of the bus bar voltage.
the
condition of the same phase sequence is checked by the phasing out test during
the commissioning of the alternator .
the
other three condition have to be checked each time the alternator is to be put
in parallel
with
the bus bar (this is done with the help of synchronoscope) .
The
Procedure Of Operation
1-make
sure that the breaker of the incoming machine is opened
2-
close the disconnect links
3-switch
the turbine or engine and bring up to speed
4-using
the governer control switch . adjust the frequency of the
incoming machine to
approxmately 0.1 cycle higher
than the bus frequency
5-
adjust the automatic voltage regulator so that the voltage of the incoming
machine is approxmately to or slightly higher than the bus voltage
6-switch
the synchroscope to the incoming machine ,and adjust the frequency until the
synchroscope pointer revolves slowly in the “fast ” direction
7-close
the circuit breaker at the instant of the synchroscope
pointer passing into zero
position
8-turn
the synchroscope switch to
“off”.
9-turn
the governer switch of the incoming machine to ”Raise ” and the machine in
the bus to ”lower” until the
(KW) loaded
is divided equally between machines .
If
the machine is not identical. the (KW
) should be divided between the machine in
Proportion
to their (KW) rating
10-
if the power factor or the Kvar reading of to machine are not equally adjust the
var control .turning that of
the incoming machine in “raise voltage” direction and the other
in the “lower voltage” until they are
equalised .
in
factories ,hotels, or large shopes
which required two or three generator in parallel
the
connecting load .its good operating practice to balance both the KW
and the Kvar
of loads in
proportion to the KW ratings of the machine by doing so .transient over current
and short circuit in the distribution system are shared by the generator
reducing the probability of one generator tripping .the tripping of one
generator due to over current
will
throw the entire load on the remaining unit
or units causing them to trip and
blocking the plants
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