Eee 306 Lab Documents

8/11/2019 Eee 306 Lab Documents

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EEE 306

Power System I Laboratory

Experiment 1

Study of the transmission line models

Objective: To study the characteristics of a transmission line at no-load and full-load.

To construct the models of short, medium and long transmission lines and

evaluate their performance in terms of voltage regulation, transmission efficiency

etc.

Introduction:

Electric power has three major areas of interest:a) Power generation

b) Power transmission

c)

Power utilization

The experiment is concerned with the transmission of power between a source (power

generator) and a remotely located load (power utilization).

Theory:

A transmission line has four parameters R, L, C and G distributed uniformly along thewhole length of the line. The resistance, R and inductance, L form the series impedance.

The capacitance, C and conductance, G existing between conductors and/or neutral formshunt paths throughout the length of the line. Depending on the length of the line,

transmission lines are classified as

I. Short transmission line: When the length of a transmission line up to 80 km, it isusually considered as a short transmission line. Due to smaller length, the shunt

paths can be neglected. The short length line model is shown below.

Z = zl

Load~

Gen

+

-

Vs

IsIL

+

-

VL


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2

where,r = series resistance per unit length(m) per phase;

L = inductance per unit length(m) per phase;C = shunt capacitance per unit length(m) per phase;

z = r + j L = series impedance per unit length(m) per phase;

l = length of the transmission line;

II. Medium transmission line: When the length of the transmission line is about 80-240

km, it is considered as a medium transmission line.

Medium length line( ) model:

where,y = shunt admittance per unit length(m) per phase to neutral

Y = yl = j Cl = total shunt admittance per phase to neutral

III. Long transmission line: When the length of a transmission line is more than 240km, it is considered as a long transmission line.

Long line model:

sinhZ l

l

LoadVs

IL

+

-

VL2

Y

Is

-

2

Y

Z = zl

LoadVs

IL

+

-

VL2

Y

2

Y

~Gen +

-

Is

~

+Gen


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3

where ,tanh( )

2

2 2 ( )2

l

Y Y

l

and = zy = propagation constant.

Typical arrangement of a double line three phase transmission line is shown in Fig. 1.

Fig. 1. : Typical arrangement of conductors of a parallel-circuit three phase line

The transmission line parameters are

r = 0.0962 /km at 50 Hz

L= 6.13 x 10-7

H/m per phase

Cn= 6.3462 x 10-12F/m per phase to neutral

We will use these values to model a l = 208 km transmission line using short, medium

and long transmission line model.

Note: The ratio of the actual transmission line and simulated model parameters are

Voltage ratio: 500

Current ratio: 1000Power ratio: 500000

10/

10/

18/

18/

21

/

a

a/

b

c/

b

c


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4

Procedure:

1. Calculate the circuit parameters of the above-mentioned transmission line usingshort and medium line models.

Table 1 : Parameters of the transmission line models

Type of the

model

Series

resistance, R

Inductive

impedance, XL

Shunt

admittance, Y

short lengthline

Medium lengthline

2. Construct the equivalent circuit of the transmission line using short length line

model as shown in Fig. 2.

Use load of 400 .

Measure the voltages of source and load end voltages and currents at no-load and

full-load conditions. Calculate the values of line voltage drop, voltage regulation,line loss, transmission efficiency and sending end power factor.

Table 2 : Calculation for short length model

Loading

condition Vs Is VL IL

voltage

drop

Voltage

regulation

Line

loss

efficiency Sending

end pf

No-load

Full-load

~Voltage

source230V, 50 Hz

Is

Vs

R + j XLA A

V V

IL

VL Load


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5

3. Repeat step 2 for medium length model keeping the same load current obtained in

the short line model.

Table 3 : Calculation for medium length model

Loadingcondition Vs Is VL IL

voltagedrop

Voltageregulation

Lineloss

efficiency Sendingend pf

No-load

Full-load

Report:

1. Calculate the voltage regulation, line loss and sending end power factor for thesame load using long transmission line model.

2. Give comparison of the voltage regulation obtained using the three different

models? What is the limitation of modeling a long transmission line using a shortline model?


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Power System Laboratory, Dept. of EEE, BUET

Pslab05/labsheet/January2001/experiment4.doc Page 1 of 3

EEE 306: Power System l Sessional

Expt. No. 2Load flow Study o f a Power System

Introduction

The performance of a power system in steady state condition is of primary importance

for utility agencies. Given a specified load condition, the basic question to be

answered are:

What are the line and transformer loads throughout the system?

What are the voltages throughout the system?

We are particularly interested in answering these questions as we evaluate proposed

changes in an existing system such as:

New generation sites

Projected load growth

New transmission line

Load flow solution of a system provides these essential information.

Objectives

In this experiment, load flow study for a 7-bus system will be made. CYMEPSAF

software will be used for this purpose.

Application of the software to be used

Follow the steps described bellow:

Open the software PSAF 2.81

From file menu, select the new study. Then select tabular format or one-line

option to study the network.

From Database menu select New Blank Database Directory to create your own

database.

From File menu, set preferences to identify the path of database and network.

Complete the network by sing either tabular format or one-line format.

Studies on a 7-BUS system

1.

Following the steps described earlier, create network shown in figure.


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Pslab05/labsheet/January2001/experiment4.doc Page 2 of 3

#1 #2 #4 #3

T12 T34

T56

#5 #6 #7

Fig 4.1 : Single line diagram of a 7-bus system

Line Data:

ID KV level Ampacity1 R1 X1 B1

Tag (/Unit length) (/Unit length) ( Siemens/Unit length)

L1 132 800 0.4 2.4 155.5

Fixed tap transformer Data:

ID Nominal MVA Primary Secondary Pos. Seq. X/R Max Load (MVA)

Tag KV KV Z (PU)

T12 400 11 132 0.015 12.5 400T34 500 11 132 0.012 12.0 500

T56 250 11 132 0.024 12.0 250

Generator Data:

ID Type Rated Rated Active Max. MVAR Min. MVARTag KV MVA Generation

G1 SWING 11.0 650 - - -

G3 VOLTAGE 11.0 750 500 400 -300

CONTRILLED

G5 VOLTAGE 11.0 400 200 140 -100

CONTRILLED

Line connections and their lengths

From To Line Type Length(km)

Bus Bus2 6 L1 104 7 L1 10

2 4 L1 6.52

6 7 L1 6.52

G1

G5

G3


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Power System Laboratory, Department of EEE, BUET

EEE 306

Power System I LaboratoryExperiment -3

Study of Microprocessor Controlled Power Factor Improvement

(PFI) Plant

Introduction:

For fixed power and voltage, the load current is inversely proportional to the powerfactor. Lower the power factor, higher the load current and vice-versa. At lower

power factor the KVA rating of the equipment has to be increased, making the

equipment larger and expensive. Moreover, if an amount of power is distributed at

low power factor line losses increases and also to cater for greater current conductor

size has to be increased Therefore, low power factor is not allowed in supply systems.

The low power factor is mainly due to the fact that most of the industrial loads are

inductive and therefore take lagging currents. In order to improve the power factor,some devices taking lagging current should be connected in parallel with the load.

One of such device could be capacitance. In this experiment, study will be made on a

PFI plant controlled by a microprocessor activated relay where capacitor bank

switches are turned ON or OFF according to the power factor such that nearly unitypower factor is achieved.

Features of the microprocessor controller:

The reactive and active portions of power are continuously calculated within the

control relay using the measured value of the supply voltage and current.

In the case of lagging power factor one or more control contacts of the control relayare closed after an adjustable time delay.

This causes the controller to switch capacitor in steps, as and when required, in order

to achieve the programmed target power factor. If the inductive reactive current

portion of the load is reduced, the excess of reactive current causes the capacitors to

be switched off. The control relay allows a variety of possible settings to meet the

condition on site.

Procedure:

1. Connect the load with the PFI plant and arrange the supply for the combination.

2. Examine the wiring inside the PFI plant. Also notice the connections of themicroprocessor relay. Draw the connection diagram of the complete set-up.

3. Vary the load and observe the switching of the capacitors. Also notice the overallpower factor.


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Connection Diagram:

N

L 1

L 2

L 3

3 Pase CB

CT

L 2 L 3

Megnatic

Contructor

MegnaticContructor

Megnatic

Contructor

CT

Ratio -2:1

MC.Coil-1

MC .Coil-2

MC .Coil-3

MC-1 MC-2 MC-3Common

Microprossor Controlled

Unit

Fuse

Fuse

(R)

(L)

VariableInductive load

Fixed Resistive

LoadMicroprocessor Contorlled Power

Factor Improvement Plant( PFI)

C=17.5 Mfd

C=35 Mfd

C=52.5 Mfd


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4. For each set of load, take reading of the load currents, overall power factor, serialno. of capacitor switched on according to the format below.

Resistive current:

Inductive current:

Total current:

Observationno

Total Current(Load )

PF ( COS) Ind/Cap -C/+C Indicator Lamp

# 1 # 2 # 3

5. Manual operation:

Press the button to switch to the manual mode. The man LED would

start to blink. Press the or the buttons for at least 10 seconds to

increase or decrease system capacitance. Press the button again to

switch to automatic operation mode.

Report:

1. Explain the connection diagram.2. Explain the operation of PFI plant.

3. An industry has a maximum load of 200KVA. The minimum load of theindustry is half of its rated load. It is assumed that the reactive power

requirement of the industry is 40% of its KVA demand. A -P based PFI-

plant provide with a fixed base compensation together with variable

compensation. The targeted power factor is 0.95. You have a 6-step switching

module to switch on/off the capacitances. Design the switching sequences and

the KVAR steps for optimum pf control. What would be the worst scenario

with this system.

automan

Iw+

Iw--

automan


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Pslab05/labsheet/January2001/experiment6.doc Page1 of 61

EEE 306: Power System I Laboratory

Experiment. No. 4

Short Circuit Study for a Test Network

IntroductionThe normal operating mode of a power system is balanced three-phase ac. A number of

undesirable but unavoidable incidents can temporarily disrupt this condition. If the

insulation of the system should fail at any point, or if a conducting object should come in

contact with a bare power conductor, a short circuit or fault is said to occur. The

causes of faults are many: - they include lighting, wind damage, trees falling across lines,

vehicles colliding with towers or poles, birds shorting out lines, small animals Entering

switching gear. Power system faults may be categorized as one of four types in order of

frequency of occurrence: single line to ground, line to line, double line to ground, and

balanced three phases. The first three types constitute severe unbalanced operating

conditions.

It is important to determine the values of system voltages and currents during faultedconditions so that protective devices may be set to detect and minimize the harmful

effects of such contingencies. Therefore, it is necessary to analyze the power system

operating in unbalanced modes. The time constants of associated transients are such that

sinusoidal steady state methods may still be used. The method of symmetrical component

is admirably suited to unbalanced system analysis.

System Configuration & Data

The single line diagram of the test network is shown in the figure 4.1. It comprises of 2

generators connected to 3 load buses through transformers.

Figure 4.1:Single line diagram of the test network.

G1

G2

1

2

34

56

T43

T65


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Use the following tables to construct the network.

Bus Data:

Bus No. Bus Name Base kV Operating kV

1 B1 69 69

2 B2 13.8 13.83 B3 13.8 13.8

4 B4 69 69

5 B5 13.8 13.8

6 B6 69 69

Transformer Data:

ID

Tag

Primary

kV

Secondary

kV

Rating

(MVA)

Z1

(p.u.)

X1/R1 Z0

(p.u.)

X0/R0 Standard

Loading

Limit(MVA)

Connection

type

T43 69 13.8 100 0.133 13.3 0.133 13.3 100 Yg-D

T65 69 13.8 100 0.3 30 0.3 30 100 Yg-D

Generator Data:

ID

Tag

Rated

kV

Rated

MVA

Active

generation(MW)

R//

(p.u.)

X//

(p.u.)

R/

(p.u.)

X/

(p.u.)

R

(p.u.)

X

(p.u.)

Winding

connection

G1 69 100 0 0.01 0.085 0.01 0.12 1.20 0.00005 D

G2 13.8 50 10 0.005 0.075 0.005 0.12 1.20 0.008 Yg

Here G1 is swing generator and G2 is fixed generation generator.

Line Data:

ID Tag kV level Loading

limit(Amps)

R1(ohm/km) X1(ohm/km) B1(micro

siemens/km)

Length

(km)

L14 69 800 0.4 2.4 155.5 10

L16 69 800 0.4 2.4 155.5 5

L32 13.8 800 0.4 2.4 155.5 5

L52 13.8 800 0.4 2.4 155.5 7


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Load Data:

ID Tag P (MW) Q (MVAR)

LOAD3 10 5

LOAD5 10 2

LOAD6 20 4

Studies:

From the study menu, select Fault selected buses and solve the network for

LLL, LG, LL, and LLG faults and monitor the necessary parameters.

Sliding fault on lines:

The following studies are to be carried out.

Line ID Fault

location, %

Fault type

L14 5 LLL, LG, LL, LLG













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Note:

First ring contribution

The first ring contributions are fault currents from links adjacent to the fault bus.

Figure 4.2:First ring contribution.

Report:

1.

Explain all the results that you have obtained from the experiment.

2.

Choose the rating of circuit breakers for the lines connected to a bus on which faults

have been simulated.

Reference

1.

Elements of Power System Analysis William D. Stevenson

Prepared by-

Nahid-Al-Masood

Lecturer, EEE, BUET

1St

ring bus1St

ring bus

1St

ring bus

fault


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EEE 306

Experiment 5

Study of BUET Power Plant and Sub-station

Objective

The objective of this study is to get an exposure to a realistic small power plant and LT substation.

Introduction

BUET has a small (2 MW) power plant and its own distribution network and sub-stations to meet its

electrical energy demand. The power plant is located at West Palasy campus of BUET and uses gasas its primary source of energy. The power plant supplies electricity to three sub-stations through

under ground cable at 11 kV. The sub-stations distributes to each building, pump, street lighting at230 V.

The peak demand of BUET campus at present is 1750 kW. The power plant supplies electrical

energy to BUET campus from early morning till mid-night and from mid-night till early morningelectrical energy is taken from the DESA distribution system. The changeover is done automatically

by Automatic Transfer Switches (ATS) located at each sub-station.

Figure 1 shows in block diagram the layout for the BUET electricity generation and distributionsystem.

Figure 1. Block diagram of BUET power generation and distribution system

Power Plant

The BUET power plant consists of two 1 MW gas turbine generators and very soon another 2 MW

generator will be incorporated in the system. The plant is fully automated with control andmonitoring panels. It has protection system for generator overload and underload, generator short

circuit, high radiator temperature, low gas pressure etc. The plant has noise suppressor to reducenoise.

BUET Power Plant

ATS ATS ATS ATS ATS

Main SS

(Panel 1)

Main SS

(Panel 1)

Main SS

(Panel 1)

NI Hall SS Rashid Hall

SS

11 kV Underground cableDESA 11 kV

Feeder


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Sub-station

All BUET substations consists of mainly the following components:

1. Step down transformer

2. Incoming and outgoing feeders3. HT and LT panel

4.

Circuit breaker5. Automatic Transfer Switch

6. Relays7.

Metering instruments (CT, PT and meter)

Record the following readings

1. Record all incoming and outgoing feeder data for the power plant and Panel-3 at the mainsubstation in a table as shown below.

Table for feeder data record

Date and

Time

Feeder

name

Incoming/

Outgoing

Voltage,

V

Current,

A

Power,

kWpf

2. Record the ratings of transformer, ATS, LT panel, PFI, circuit breaker at the power plant and at

the main sub-station and at Rashid Hall sub-station.

Report

1.

Calculate the total current and power from the outgoing feeders and compare it with theincoming feeder readings.

2. Draw the complete system of the BUET power plant using block diagram.3. Describe briefly the power plant protection system.