Electrical Power: Synchronous Machine Construction and Operation

This article provides an overview of synchronous machines used in electrical power systems. It explains the constructional features of the stator and rotor, and how direct current excitation is used to generate a rotating magnetic field. The article also discusses the operation of synchronous generators and the equations for induced voltages.

Electrical power 1
ELECTRICAL POWER
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CH4 PARAPHRASING
A4.1
The experimental outcome indicates how it is
possible to use capacitive arranged in parallel
with the load to do voltage compensation by
adjusting these parameters to help balance
both the receiving and the sending voltages.
It can be observed from the recorded
experimental observations that the variation of
the angle through compensation lead to line
power and current moving in the transmission
line. This is not always vivid for some
observations recorded hence there might be
some inaccuracies when noting such data. But
the most significant issue is to ensure that the
basic trend is always right when checked
against the info about the background on the
topic of the studio.
There are some other connections witnessed
within the process, such includes continuous
voltage drop and current drop during the
transmission of power but the scalar value of
receiving and sending the voltage should be
equalized
B4.2
When the voltage flow there is always drop in
voltage in the line of transmission between the
voltages of receiving and sending, the voltage
drop is due to the resistivity of a conductor and
this can be illustrated by the equation below;
R=⍴ L
A
Through noting the number of shunt capacitor
it is possible to regain the value of nominal
voltage. When the shunt capacitors are put at
the transmission line receiving end, it makes the
current line to bisect the shift in phase between
the receiving and sending end voltage. The
output gotten by fluctuating the resistive load in
the line of transmission of the AC voltage acted
as anticipated. There was a surety that the
capacitors were not switched ON at the same
time in the capacitor module.

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Since the nominal voltage needs to be
maintained, at the receiving end there were
some capacitors which were employed to
realize this by increasing the receiving end
voltage. There may be a serious fault in the
gadgets of the line of transmission in case the
loads in the line of transmission are completely
removed from the line. There was a surety that
the capacitors were switched ON at different
times.
B4.2.1
The drop in voltage at the transmission line
receiving end was as expected when there were
no capacitors. The drop in voltage was
witnessed again where the shunt capacitors
were introduced, the network for power was as
well balanced [1]. With this simulation was
completed effectively.
A5.1
After concluding for the transmission line
capacity of the power transmission some of the
things were seen and deduced. Some of these
include; when in need for the active power to
move from the receiving end of the
transmission end, the shift in phase has to exist
in the voltage. In case the sending and receiving
voltage´s sine wave are in phase the
instantaneous voltage value at the receiving
and sending end will be at all times be equal
hence the active power will never flow.
During the experiment, it was seen that
transferred active power through transmission
line are the shift in phase between the receiving
and sending ends will increase until the
maximum value is attained when the shift is
equal to 900 . Nevertheless, optimizing
transferred output power through the voltage
AC voltage compensation in the transmission
line. This is attained by adjusting the shift in
phase until it reaches 900. This phase shift can
produce some unstable system since at this
point voltage cannot be compensated further.

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Therefore it is significant to make sure that the
system of transmission will give the demanded
active power at the same time ensuring that
shift between the receiving and sending end is
much below 900 and in most scenarios, it is 300
The study in this assignment has deduced that
the reactance due to the inductors in a line of
transmission is inversely proportional to the
flow of real power but directly proportional to
the transmission line length [2]. Therefore the
real power optimum flow in the transmission
line, reactance due to inductor and length for
every conductor kilometre have to be
maintained as minimum as possible. This is a
perfect way of real power flow capacity
maximization as well as making sure that the
system keeps to the optimal stability.
A5.1.2
The outcomes from the MATLAB simulation
indicates that a roughly equal real power was
transferred in the AC transmission
compensated system. This was done at a reduce
phase shift in receiving and sending end
voltages and at that point reactance due to
inductors were decreased.
The simulations outcomes then help in doing
the verifications of the practical finding activity.
It was seen during the experiment that for
compensated voltage system, through
decreasing the reactance due to the inductor in
the transmission line, there will be an equal
level of real power in the reduced shift in phase
between the receiving and the sending end
voltage. This has advantages since it reduces
the reactance due to inductance in the line of
transmission [3].
B5.2
For this experiment capacitive load was
connected first then inductive load as well as
resistive load was connected to the system to
help analyse the drop in voltage and also phase
angles in the compensated line. In case the

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shunt capacitive load is used in the connection
then the outcome was that receiving voltage
was lagged by sending voltage. This implies that
the voltage receiving end was much less due to
the absorption voltage from the inductance.
But if we connect a load which is restive the
result gave no lag or lead-in phase. Hence the
sending end voltage is roughly equal to the
voltage at the receiving end. It can hence be
concluded that adding these shunt capacitors is
an appropriate way to give the optimum
reactive power in the transmission line [4].
A6.1
From the experiment done there was a vivid
indication that autotransformers can be
employed for adjusting the receiving and
sending voltage phase angles to help in power
flow regulations in two transmission lines. This
is realized in either direction so long as the
power level transmitted and relative phase
angles are involved.
B6.2
In case the receiver and sender voltage are in
phase to one another in the AC line of
transmission, then the real power is transmitted
through the reactive and line power is given in
similar quantity to the line of receiving and
sending voltage ends. The more the angle of
phase shifts the more the reactive power
engrossed by the transmission line
When the shift fluctuates to 150 and -150, the
real flow of power direction is altered. There
were no modifications of voltage hence it was
seen that there existed no flow of power in the
AC line when the power shift was 0. Hence to
ensure that for the transferred power in more
areas it is needed that they must have a phase
shift to help share the electrical power [5].
If we use an autotransformer is employed as a
step up transformers, it has the ability to reduce
or increase reactive power through the

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incoming phase shift voltages. The anticipated
values of decreased and increased voltage are
met through employing several taps on the
windings of the transformer and this is with
accordance with turn’s ratio.
A7.1
In the whole session of the practical, the
working and employment of a STATCOM to help
compensate voltage in transmission line was
illustrated and thoroughly scrutinized.
If the STATCOM was put in the transmission
line´s receiving end resistive load resistance was
confirmed and the correct information was
noted down. This indicates that a STATCOM
could be quickly and precisely compensate and
respond to the system through feeding required
amount of reactive power to make sure that the
voltage at the receiver end is almost the same
as that at the sender end [6].
The compensation speed was seen to be
between the two and one cycles of the sine
wave that is roughly instantaneous. This is a big
quality to efficiency of STATCOM compensation
voltage.
When the STATCOM I put at the receiver end
still of the line of transmission, therefore in the
middle of the line shunt capacitor was put.
During the experiment, it was clear that when
the shunt capacitor was included in AC line of
transmission, there was no consequence on the
appropriate compensation system of the
STATCOM.
In summary, it was approved that
compensating reactive power was very
operative when STSTCOM was used in the
whole transmission line [7].
A8.1
There are scopes which follow these activity´s
description of the simulation and illustrate the
variation in the power and how the

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compensation varies the voltage through the
STATCOM unit.
The first scope illustrates the early process of
stabilization process which is followed by some
variations where there is the production of
current and amendment to do the
compensation of the voltage.
The second scope illustrates variations and also
0.2 where there some current drop to surge and
negative in the reactive power which is then
compensated to 0.3 for this process till the
nominal value of the voltage moves to 0.4.
And in the third scop it illustrates the process at
0.2 where there are trivial power changes on
the 1 st records then the prominent act of the
STATCOM in the process since there is a rise in
current and voltage waveform in the final
readings in the scope.
A8.1.2
“Data Acquisition station 1:”
Since the real power is often checked in the
trace illustrates that it increasing from zero to 1
pu it again reduces to about 1.5 s when the
power reduces to 0.95 pu.
The real power illustrates an initially jumped
market as ramp up system which is followed by
a marked variation at 1.5 s in which the reactive
power reduces hence it will be correct the
system for the system reactive capacitance. It
was then witnessed that the system was stable
there was more system with a few small
variations was enacted [8].
“Data Acquisition station 2:”
On the trace two direct current voltages after
the initial stabilization rests at about 1pu till it
reaches 1.5s and this goes on till there is
variation where there are voltage drop and
oscillation for the same period. Therefore at 2.5
s, it will drop gradually again because of the

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fluctuations but this elections must be close to
1pu which is a reference point.
A8.1.3
The simulation is done on these three gadgets
allows giving an illustration on how the
operating in regulating current, voltage,
reactive and real power in the transmission line.
The SVS and STATCOM system are perfectly
simulated to illustrate how the compensation
for the load variation and decrease or increases
in the systems reactive power to make the
stable power remain stable in the network [9].
The system of HVDC must deal with variations
as it transfers it in direct current form again
when it is reversed back to thigh AC voltage to
be used in power grid. The design illustrated the
voltage compensation to keep the transmission
in the needed pu parameters.

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ARTICLE 1
Synchronous machine
While in steady state, the rotation of a
synchronous machine is at a constant speed.
Direct current (ac) excitation is provided to the
field that winds to the rotor whereas the
alternating current is supplied in the armature
winding. Synchronous machines can use either
a motor or a generator.
Constructional features
The machine comprises of cylindrical stator and
cylindrical rotor that are coaxial and made of
materials that are highly permeable.
Figure 1: Layout
Figure 2: Stator and Rotor

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Stator
The stator is made of 3 distributed winding
where the main voltage is supplied. Its design is
for high voltage and current.
Figure 3: Cross Sectional view
Figure 4: Circuit of stator
Rotor
The rotor comprises a field winding that is
mainly an electromagnet. A direct current
voltage is induced to the winding to achieve
rotor flux. Salient pole and cylindrical or non-
salient pole rotor are the 2 common types of
rotor for low speed and high speed applications
respectively [10].

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Figure 5: Salient pole rotor
Figure 6: Cylindrical or non-salient motor
“Synchronous generator”
Direct current is induced to the winding of the
rotor thus generating a magnetic field. A
rotating magnetic field is produces a 3- phase
voltages set.

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Figure 7: voltages equations
Figure 8: induced voltages
The excitation voltages are expressed as below;
The induced voltage is given by

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Figure 9: rotor speed and frequency of induced voltage
Figure 10: Synchronous speed
Equivalent circuit model for synchronous
machine

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Figure 11: equivalent circuit model
Performance characteristics Illustration of a voltage regulation characteristic
of a standalone synchronous generator
Figure 12: “Synchronous generator”

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Figure 13: Voltage characteristic

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ARTICLE 2
“Reactive and active control of power flow”
“Control of active power flow in interconnected
power networks”
Active power control basically involves
regulating the highest shift in phase to levels
that can ensure the highest power of the
alternating current line of transmission is not
surpassed as well as enabling a stable operation
[11].
Figure 14: interconnected power network diagram
Figure 15:
Direction of
active power
flow
Reactive power flow in ac transmission lines
The reactive power level engrossed by the
corresponding inductor relies on the current
that is moving in the line. The greater the
current, the
higher the level of reactive power that is
absorbed by the line of transmission. It is easier
to calculate both the reactive power at the
receiver and at the sender when the line
current value is known [12]. The difference

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between the two values of reactive power gives
the reactive power that is engrossed by the line
of transmission.
Figure 16: “voltage flow in ac
transmission line”
Figure 17: Phasor diagram
Figure 18: calculation of reactive and
active power values
“Control of reactive power flow in
interconnected power lines”
Lowering or raising the voltage at each end of
an alternating current line of transmission
results to control of levels of reactive power
that the receiver and sender ends supply to the
line. This technique enables the modification of
reactive power that the receiver and sender
end supplies to the desired level [13].
Figure 19: voltage flow
Figure 20: calculation of both reactive
and active power value

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“Effect of the line resistance on the operation
of ac transmission lines”
The resistance for most ac transmission lines is
basically high enough to resent a noteworthy
influence on the voltage values, power and
current values in the circuit. There are different
current and voltage figures in the ac line of
transmission whenever a resistance is inserted
into the line.
Control to the regulating autotransformer
A “regulating autotransformer” has the
capability to perform as either a buck-booster
or a phase-shifting transformer, or even both at
each given time. The ability of different
performance allows it to control the active and
reactive flow of power into the line of
transmission.
Figure 21: regulating autotransformer circuit

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Figure 22: showing phasor diagram when acting as phase-shifting transformer

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ARTICLE 3
Compensation of Voltage
“Compensation of Voltage at the receiver end
of an AC transmission line”
A connection of either a resistive load or an
inductive load to an alternating current line of
transmission will lead to a fall in voltage at the
end of the receiver. The voltage drop value is
proportional to the load. Shunt capacitors are
devices that have the ability to raise the voltage
at the receiver end. Effective switching of shunt
capacitors equally leads to compensation of the
disparity in voltage at the receiver end [14].
Figure 23: phasor diagrams
Figure 24: calculating capacitive
resistance
Voltage compensation calculations

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1. AC transmission line with
uncompensated receiver voltage
Figure 25 : calculating value of voltage
and current
2. AC transmission line with
compensated receiver voltage
Figure 26: calculations for compensated
receiver voltage
3. AC transmission line with
compensated voltage receiver when
the line current rises.
Figure 27: compensated voltage receiver
when line current rises
“Load loss in compensated ac transmission
line”
The usage of shunt capacitors for the purpose
of compensating the receiver voltage has got a
limitation. Whenever the connected load to the
line reduces or is lost, there will be a
development of a massive overvoltage across
the line. This occurs because whenever the
resistive receiver end load is withdrawn, the ac
line of transmission is exclusively linked to a
capacitive load which further raises the voltage
at the receiver end [15].

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Figure 28: “Calculating receiver voltage
and line current across resistive load”
Figure 29: “parameters calculating of the
ac transmission line”
ARTICLE 4
“Active power flow in ac transmission line”
In order to transmit active power from one end
of the sender to the other end of the receiver of
an ac line of transmission, the voltage of the
receiver should stay behind the voltage of the
sender. This is mainly because whenever the
sine waves voltages at either line of
transmission end are in phase, their resulting
prompt values are same every time. This implies
that no current can flow at either ends of the
line. The active power which is transmitted from
the sender to the receiver can be found from
the following calculations;
Figure 30: Calculating active power
A graphical presentation of the active power
that is transmitted by each voltage
compensated phase of a line of transmission is
as shown;
Figure 31: maximal active power
percentage

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From the figure above, an instance that the shift
in phase between the voltage of the receiver
and the sender is zero, then it implies no
existence of active power transmitted from one
end of the sender to the other end of the
receiver. The following equation signifies the
maximal level of active power that is able to be
transmitted by each compensated voltage
phase of an alternating current line of
transmission [16].
Figure 32: “Calculating maximal amount
of active power”
From the equation, it can be argued that the
lesser the inductive resistance of a
compensated voltage line of a transmission, the
greater the maximal level of active power that
is possible to transmitted by the line. A
representation of the typical active power
curves that can be transmit with varying
reactance values is s shown below;

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Figure 33: typical curves of active power

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ARTICLE 5
AC transmission lines
Transmission lines serve the purpose of
transmitting electrical power from the stations
that generate power to the network of
distribution which further supplies it to the
consumers. They basically symbolize the second
step of electrical energy transfer.
Figure 34: Showing network of generation, transmission and distribution
Several lines of transmission transmit 3-phase
alternating current and is comprised of 3 line
wires with no neutral wire. They are usually
aerial given that it is cheaper to install and
maintain than underground [17].
Characteristics of regulation of Voltage
Equivalent circuit of ac line of transmission
The common characteristics that different
transmission lines share are their resistance,
capacitive reactance and inductive reactance.
These components are basically distributed
over the ac line of transmission.

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Figure 35: equivalent circuit
Figure 36: reactive and active flow of power
Characteristics of regulation of Voltage
The voltage measured at the end of the receiver
varies depending on the supplied load type and
current that is moving through the line of
transmission.
Figure 37: Typical voltage regulation
characteristics

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Calculations for resistive load voltage
Receiver voltage reduces whenever the line
current increases
Calculation of inductive load voltage
Receiver voltage reduces whenever there is a
rise in the current line.
Calculation of capacitive load voltage
The receiver load increases whenever there is a
rise in the current line
Regulation of voltage in ac transmission lines
This represents the level to which the receiver
voltage varies whenever the connected load to
the alternating current line of transmission also
changes [18]. It is achieved whenever the ac
line of transmission is operating at full load. The
calculation of voltage regulation is s below;
Figure 38: Calculation of voltage
regulation

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ARTICLE 6
Flexible AC systems of transmission
Technologies of “flexible ac transmission
systems (FACTS)” are designed to promote
flexibility, capacity and security of transmission
of power. They offer faster regulation of voltage
as well as control of power flow. It is a
substitute to developing new lines of power
transmission and facilities for generation of
power.
Figure 39: transmission system with
shunt and series compensation
Transmission line with series compensation
Whereas FACTS are needed for compensation
of series; it equally modifies the impedance line.

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The impedance line is therefore reduced in a
bid to raise the transmittable real power [19].
Figure 40: reactive and real power
Figure 41: phasor diagram
Series capacitor leads to increase in the stability
of transmission system hence the capacity to
transmit electric power is increased.
Transmission line with shunt compensation
The FACT device is has a parallel connection to
the power system and functions as a controlled
source of current.
Figure 42: Transmission line with shunt
compensation
“Static VAR Compensator (SVCs)”
This is a product that is used to offer fast-acting
reactive power on increased networks of
transmission. They have the ability to regulate
voltage, stability harmonics and transmission
systems power factor [20].

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Figure 43: simplified SVCs diagram
“Static synchronous compensator (STATCOM)”
This is a shunt controlling device that makes use
of power electronic devices. They can acts as a
sink or source of reactive power to a network of
electricity. They are much faster than the SVCs
with reduced harmonic emission. Their duty is
to supply precise, fast-acting and modifiable
level of reactive power to the ac system of
power.
Figure 44: A typical STATCOM
ARTICLE 7
STATCOM Controller Operation
The design for STATCOMs is either for the
reactive power compensation requirement for a

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power system or to compensate the voltage
over a power system [21].
Automatic control of voltage
When used for compensating voltage over a
system of power, the voltage over the
STATCOM can be controlled using a voltage
control loop that is applied in controller of the
STATCOM. The controller is able to regulate the
voltage over the STATCOM for the step-down
transformer.
Figure 45: STATCOM for voltage compensation
Automatic reactive power control
When used for correction of correction of
dynamic power factor, the reactive power
which can be exchanged by the application with
the power network is controlled such that it is
kept constant at zero var. this is attained
through regulating the line currents reactive
component that flows between the power input
and power network of the output.

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Figure 46: STATCOM designed for correction of dynamic power factor
The controller within a STATCOM that performs
automatic reactive control of power basically
comprises of a voltage control loop, a current
control loop as well as a 3-phase PWM
inverter/rectifier controller [22].
Reactive power control loop
It is applicable in keeping constant the level of
reactive power that the connected industrial
application exchanges with the network of
power at 0 var. this is attained by ensuring the
line current reactive component that flows
between the power network and the
application is kept at 0A.

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Figure 47: STATCOM controller for automatic reactive control of power

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