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EENG 457 POWER SYSTEM ANALYSIS I
EXPERIMENT 1
INTRODUCTION TO POWER SYSTEM
Prepared by: Assist. Ahmad ALAhmad
A. Single phase
Phase angle = __________________________
Lagging = _______________________________
Leading: ________________________________
Which one of these is lagging and which one is leading:
Fig 1.1 --------------------------- Fig 1.2. -----------------------------
Power Factor = ___________________________
1
1
1
___________________________________
____________________________________
___________________________________
____________________________________
____________________________________
__________
P
Q
S
__________________________
B. Three Phase
Fig 2.1 : Star connection Fig 2.2: Phasor diagrams for voltages and currents
According to Fig 2.1.
What are the phase voltages: ______________________________________
What are the line voltages: ________________________________________
What is the positive sequence: _____________________________________
LINE PHASEV V
LINE PHASEI I
N R Y BI I I I ------------------------------------------------
According to Fig 2.2.
What is the angle between line voltages: --------------------------------------------
What is the angle between phase voltages: ------------------------------------------
line voltages leads its corresponding phase voltages by : -----------------------
phase current lags its corresponding phase voltage by: -----------------------
line currents lags its corresponding line voltages by : -----------------------
Fig 3.1. Delta or mesh connection Fig 3.2. Phasor Diagram for voltages and currents
According to Fig 3.1.
What are the phase voltages: ______________________________________
What are the line voltages: ________________________________________
What is the positive sequence: _____________________________________
LINE PHASEV V
LINE PHASEI I
According to Fig 3.2.
What is the angle between line voltages: --------------------------------------------
What is the angle between phase voltages: ------------------------------------------
phase current leads its corresponding line current by: -------------------------
line voltages leads its corresponding phase current by : -----------------------
line voltages leads its corresponding line current by : -----------------------
Table 1: Difference between star and delta connections in three phase system
Star Connection Delta Connection
Difference in connection
Neutral point exist
Number of wires
Relation between line currents
and phase current LI LI
Relation between line voltages
and phase voltages LV LV
Total Power of three Phases 3 phP
3 phP
The speeds of Star connected
motors (low or high)
Number of turns (low or high)
Insulation (low or high)
Preferred type of power
system
C. Transformer
Discurss in your class the theory of operation of transformers
Complete the following
Power in primary side and power in secondary side are : ---------------------------------------
What is the purpose of transformer: ------------------------------------------------------
Is the input voltage AC or DC? Why?
Determine the ratings for the primary current and secondary current
Check Circuit diagrams below and discuss its components
Fig.4: Exact circuit diagram of transformer
What is the purpose of referring from secondary to primary or reverse
' 1
2 2
2
' 2
2 2
1
2
' 1
2 2
2
2
' 1
2 2
2
NV V
N
NI I
N
NR R
N
XX X
X
' 2
1 1
1
' 1
1 1
2
2
' 2
1 1
2
2
' 2
1 1
1
NV V
N
NI I
N
NR R
N
XX X
X
Referring from secondary to primary Referring from primary to secondary
Fig.5.1 Transformer equivalent circuit referred to Primary Side
Fig.5.2 Approximation of transformer equivalent circuit referred to primary side
Fig.6.1 Transformer equivalent circuit referred to Secondary Side
Fig.6.2 Approximation of transformer equivalent circuit referred to secondary side
How is the equivalent circuit of transformer in Power system
Transform efficiecny : --------------------------------------
Copper losses: -----------------------------------------------
Three Phase Transformer Connections
Fig.7. Three phase transform connections
Complete the following table
Primary – Secondary
configuration Turns ratio
Star – Star
Star – Delta
Delta - Star
Delta - Delta
D. Synchronous Generators
Inputs are --------------------------
Output is -----------------------
Equivalent circuit per phase:
V -----------------------------------------------------------------------------
Voltage drop = -----------------------------------------------------------------
Voltage Regulation = ----------------------------------------------------------
For lagging (inductive) loads, the phase (and terminal) voltage ------------------------
For unity power factor (purely resistive) loads, the phase (and terminal) voltage ------------------------
For leading (capacitive) loads, the phase (and terminal) voltage---------------------------
Equivalent circuit in three phase:
Power flow diagram for synchronous generator:
The applied mechanical power = -------------------------------------------------------------------
mechanical power converted to electricity = ------------------------------------------------------
Output electrical power = -----------------------------------------------------------------------------
Approximated output electrical power = ------------------------------------------------------------
E. Electrical Load
The electrical load is a device that consumes electrical energy in the form of the current and transforms
it into other forms like heat, light, work, etc.
Three basic types of loads exist in circuits:
1.
2.
3..
Loads consisting of any heating element are classified as -----------------------.
Loads correspond to mechnical are classified as -----------------------------------.
------------------------- ared included at electrical substations to improve the overall "power factor" of the
system.
In resistive load, Voltage and current are ------------------------------
Current lags voltage in -----------------------------------------
Current leads voltage in -------------------------------------------
In case of DC, load is described by level of current. The higher the current, the higher is the load.
However, load in AC is decribed by ----------------------- and ------------------------
For example, load on the generator is 50% at 0.8 pf lagging means--------------------------------------------
----------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------
Power system loads:
F. Transmission lines
Short transmission lines : --------------------------------
Medium transmission lines : --------------------------------
Long transmission lines : --------------------------------
Short Transmission lines Model (ABCD values)
Medium Transmission lines Model (ABCD values)
Long Transmission lines Model ( ABCD values)
G. Electrical Bus-Bar and its Types
Definition: An electrical bus bar is defined as a conductor or a group of conductor used for collecting electric
power from the incoming feeders and distributes them to the outgoing feeders. In other words, it is a type of
electrical junction in which all the incoming and outgoing electrical current meets. Thus, the electrical bus bar
collects the electric power at one location.
Bus-Bar Arrangement
(a) (b)
H. Power system:
I. Per-Unit system
Quantity per unit = -----------------
a) Single phase
Base
Base
Base
Base
V
S
I
Z
b) Three phase
( )
Base
Base
new
I
Z
Z pu
What is the name of the following representation?
a) Find the following
BaseS
Number of zones =
1BaseV
2BaseV
3BaseV
b) Apply the following
2
1
1
2
2
2
2
3
3
Base
Base
Base
Base
Base
Base
Base
Base
Base
KVZ
MVA
KVZ
MVA
KVZ
MVA
c) Inductive load
3
3 cos
/ 3
Load actual
Load actual
Load actualLoad pu
Base
SI
V
VZ
I
ZZ
Z
d) Apply the following
1
3
2
3
3
3
3
3
3
BaseBase
Base
BaseBase
Base
BaseBase
Base
MVAKI
KV
MVAKI
KV
MVAKI
KV
e) Apply this formula if necessary
2
2( ) ( )
old base new base
new old
old basenew base
KV MVAZ pu Z pu
MVAKV
f) What is the name of the following representation?
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