Download WEEK 1: OVERVIEW, DC CIRCUIT REVISION

Electrical Machines I
WEEK 1: OVERVIEW, DC CIRCUIT REVISION
Course Contents
1
Review on electric circuits (DC circuits)
2
Magnetic circuits
3
DC Machines (1): DC machines: construction-applications-theory of operation.
4
DC Machines (2): DC machines: equivalent circuit-excitation-voltage control.
5
DC Machines (3): DC motors: performance and speed control.
6
Review on electric circuits (AC circuits)
7
Transformers (1): construction-applications.
8
Transformers (2): theory- equivalent circuits-tests.
9
Transformers (3): voltage regulation- efficiency.
10
Three Phase Induction Motors (1): construction-applications.
11
Three Phase Induction Motors (2): rotating magnetic field-theory of operation-equivalent circuit.
12
3-phase induction motor (3): characteristics-performance-starting.
13
Synchronous Machine (1): construction- applications-equivalent circuit.
14
Synchronous Machine (2): synchronous alternator: theory of operation-characteristics-synchronization.
15
Synchronous Machine (3): synchronous motor.
Power System Components
1- Generation System: source of power, ideally with a
specified voltage and frequency
 Generators:
•
•
•
•
•
Thermal (water steam by burning Coal, Oil, NG)
Nuclear (water steam by Uranium or Plutonium fission)
Geothermal
Hydroelectric
Wind
• solar
2- Transmission Network: transmits power; ideally as a
perfect conductor
 Primary Transmission system
 Secondary Transmission system
3- Distribution Network: consumes power
 Distribution Lines
 Loads
Additional components include protection and control
Electrical Power System Layout
Station switch yard
13.8 kV
Power Plant
Step up
transformer
220 kV rural feeder
Step down
transformer
66 kV su transmission line
11 kV rural feeder
Step down
transformer
Large
industrial
customer
Secondary distribution
substation
11 kV feeder
Step down
transformer
11 kV feeder
66/11 kV
Commercial /
industrial
customer
66 kV sub
transmission line
220/66 kV
13.8/220 kV
Primary distribution
substation
Other 66 kV sub
transmission lines
Sub transmission
sub station
11 kV/ 400 V
11 kV feeder
66 kV
400 v
Radial distributor
Step down
transformer
11 kV/ 400 V
Ring distributor
Generating Station:
The place where electric power produced by parallel connected three phase alternators/generators is called Generating Station. The Ordinary
generating voltage may be 11kV, 11.5 kV 12kV or 13kV. But economically, it is good to step up the produced voltage to 132kV, 220kV or 500kV or
greater by Step up transformer (power Transformer).
Primary Transmission:
The electric supply (in 132kV, 220 kV, 500kV or greater) is transmit to load center by overhead transmission system.
Secondary transmission:
Area far from city which have connected with receiving station by line is called Secondary transmission. At receiving station, the level of voltage
reduced by step-down transformers up to 132kV, 66 or 33 kV, and Electric power is transmit by three phase three wire overhead system to different
sub stations.
Primary Distribution:
At a sub station, the level of secondary transmission voltage (132kV, 66 or 33 kV) reduced to 11kV by step down transforms. Generally, electric
supply is given to those heavy consumer whose demand is 11 kV. For heavier consumer (at large scale) their demand is about 132 kV or 33 kV, they
take electric supply from secondary transmission or primary distribution and then step down the level of voltage by step-down transformers in their
own sub station for utilization ( i.e. for electric traction etc).
Secondary Distribution:
Electric power is given by to distribution sub station. This sub station is located near by consumers areas where the level of voltage reduced by step
down transformers 440V by Step down transformers. These transformers called Distribution transformers, three phase four wire system). So there is
400 Volts (Three Phase Supply System) between any two phases and 230 Volts (Single Phase Supply) between a neutral and phase (live) wires.
Residential load (i.e. Fans, Lights, and TV etc) may be connected between any one phase and neutral wires, while three phase load may be
connected directly to the three phase lines.
Egyptian Network
‫ الشبكة الموحدة‬220 kV
Any electrical network usually feeds a certain zone or location. In
case any power failure in the network, all services will be
interrupted and leads to disconnection of loads. The unified grid
solves such problems since it connects a number or a group of
networks together. In case of any power failure in one network
occurs, the rest of the network feeds the loads and prevents their
cut out. There Egyptian grid consists of the following:
Generation : 24- 30 kV ‫محطات التوليد‬
Transmission : ‫محطات الرفع ألغراض النقل علي أكثر من مستوي‬

220 kV: )‫ سيناء‬-‫ حدود مصر‬-‫ وجه بحري‬-‫ القاهرة الكبري‬-‫معظم الجمهوريه (شرق الدلتا – غرب الدلتا‬

500 kV:‫ كم‬950 ‫خط رابط بين أسوان و القاهرة طوله تقريبا‬
Egypt is connected to Jordan with a marine underground
cable at 400 kV and is connected to Lybia with an overhead
line that is at 220 kV
 ‫ كيلو فولت تم إختيارها بهذه القيمة الن المسافة بعيدة بين الصعيد ووجه بحري و بالتالي المقاومة الكلية للكابالت ممكن تؤدي النخفاض‬500 ‫شبكة ال‬
‫ تقريبا‬500 ‫ أو ال‬440 ‫ إلي‬220 ‫التيار للنصف تقريبا و بالتالي الجهد سيزداد للضعف من‬
‫‪Egyptian Grid Useful Statistics‬‬
‫‪%‬إجمالي الطاقة الكهربية المنتجة‬
‫البيان‬
‫الطاقة المائية‬
‫‪7.94‬‬
‫طاقة الرياح‬
‫‪0.79‬‬
‫الطاقة الشمسية‬
‫‪0.07‬‬
‫كهرباء مولدة من المحطات الحرارية المربوطة بالشبكة‬
‫‪91.02‬‬
‫كهرباء مولدة من المحطات الغير مربوطة بالشبكة‬
‫‪0.14‬‬
‫كهرباء مشتراة من فائض الشركات الصناعية‬
‫‪0.04‬‬
‫إجمالي (مليون ك‪.‬و‪.‬س)‬
‫‪168069‬‬
‫تقرير وزارة الكهرباء عم ‪2014-2013‬‬
What do we see???
Generation:
ELECTRICAL:
Generators & Turbines
Transformers
320 MW generator
Steam turbine
Current Transformer
Circuit breaker
Capacitor banks
Switches
Busses
Circuit Breakers
Capacitor banks
Measuring devices
Power Transformer
Potential Transformer
Bus bars
switches
What do we see???
Transmission:
 Transmission lines typically carry voltages of 110 kV, 230 kV, or even higher. The wires are not insulated, so they are kept
high off the ground and well separated from each other, to prevent arcing (sparks) and injury or people or animals.
 Why use such high voltages? Using very high voltages on the transmission lines reduces the amount of energy wasted
heating up the wires.
 And why is that so? Transformers cannot add energy, so if the voltage is increased, the current (in amps) must decrease.
The charges flowing through the wires constantly collide with the atoms, losing energy and heating the wire. We call this
resistance. Recall that the power (energy per time) lost to that heating is given by the equation P=I2R. If the current is
reduced, the power used in heating the wire is reduced.
Transmission lines
Substation
What do we see???
Distribution:
ELECTRICAL:
Distribution transformer
 Protection
Cables
 Loads
Electrical loads
Illumination
Pole mounted
Pad mounted transformer
Motors
LV switch gears
Circuits Rules:
“At any junction in a circuit, the total
current leaving the junction is equal
to the total current entering the
junction. This rule is also known as
Kirchhoff’s current law.”
Series
means:
connection
of
components
The current entering a component is the
same as the current leaving the component
 Components do not use up current
 The current passing through two or
more components in series is the same
through each component
“For two or more components in series,
the total potential difference across all
the components is equal to the sum of
the potential differences across each
component”
Total current into the junction =
0.5 A
Total current out of the junction
= 1.5 A
Therefore wire 3 must have
1.0 A INTO the junction
“The potential difference
across components in
parallel is the same.”
The total current through the two resistors,
I is equal to the sum of the individual
currents:
I = I1 + I2
For any complete loop in a circuit, the sum of the
emfs round the loop is equal to the sum of the
potential drops round the loop.