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?