08 – 707 POWER SYSTEM LAB L/T/P : 0/0/4 Credits : 4

Hardware Tests

√1. Power frequency testing of electrical equipment like insulators, fuses, AB switches,

lightning arresters etc.

2. Determination of string efficiency of string insulators.

√3. Calibration of HV measuring equipment using sphere gap

√4. Impulse voltage test on insulators, lightning arresters etc.

√5. Measurement of dielectric strength of air, solid and liquid insulating materials.

√6. Determine the characteristic , pick up time etc. of different types of electromagnetic

relays

√7. Determine the characteristic, pick up time etc. of different types of static relays.

√8. Measurement of earth resistance and soil resistivity.

√9. Testing of insulation of 3 core and 4 core cable

√10. Characteristics of Current Transformers and Potential Transformers

√11. Power measurement using current transformer & potential transformer.

√12. Power factor improvement with capacitor banks.

13. Testing of energy meters

14. Ferranti Effect and its mitigation

15. Transient stability study

Software Simulation Tests

16. Load flow analysis- Gauss Siedal Method ,Newton Raphson Method, Fast

decoupled method, Of test systems with buses not exceeding 6 numbers.

17. Short circuit studies – 3 phase LG, LL, LLG fault.

18. Simulation of FACTS devices (Shunt Compensation).

19. Analysis of Transient stability and Voltage stability of power systems (using Power

angle and PV curves respectively).

20. Simulation of AGC for single area and two area systems using SIMULINK.

21. Formulation of Ybus matrix with mutual coupling using MATLAB.

Note: (i) Ten of the twelve Hardware Experiments and all the Six Software Experiments are

to be conducted.

(ii) University Question paper will contain one hardware and one software question for the

exam. Each student must answer both parts.

Note:

For University examination, the following guidelines should be followed regarding award of

marks

(a) Circuit and design -30%

(b) Performance -30%

(c)Result -20%

(d) Viva voce -20%

POWER SYSTEM LAB

Index

Ex.No.

Title

Date

Page No.

1 Power frequency testing of Insulators.

2 Measurement of dielectric strength of air & solid

insulating materials.

3 Measurement of dielectric strength of liquid

insulating materials.

4 Measurement of insulation resistance of 3-core &

4-core cables

5 Testing of Electromagnetic Over Current Relay.

6 Testing of Current Transformer and Potential

Transformer

7 Short Circuit Analysis I - Mi Power

8 Short Circuit Analysis II - Mi Power

9 Short Circuit Analysis III - Power World

10 Study of MATLAB

11 Measurement of Earth Resistance& Soil Resistivity

12 Impulse testing of Insulators.

13 Calibration of High Voltage Equipment

14 Power factor Improvement

15 Power measurement using CT & PT.

16 Testing of Static Over current relay

17 Study of Relay Tester Sverker 760

18 Testing of Earth Fault current relay

19 Automatic Generation Control - Simulation of

Single Area and Two Area System - Simulink

20 Load Flow Analysis I - Mi Power

21 Load Flow Analysis II - Mi Power

22 Load Flow Analysis III - Power World

23 Simulation of FACTS devices (Shunt Compensation).

24 Transient stability and Voltage stability

LIST OF EXPERIMENTS

Ex.No. Title

Cycle-I

1 (i) Power frequency testing of Insulators.

(ii) Measurement of dielectric strength of air & solid insulating

materials.

2 (i) Measurement of dielectric strength of liquid insulating

materials.

(ii) Measurement of insulation resistance of 3-core & 4-core cables

3 Testing of Electromagnetic Over Current Relay.

4 (i) Testing of CT

(ii) Testing of PT

5 Mi Power – Short Circuit Analysis I

6 Mi Power – Short Circuit Analysis II

7 Power World - Short Circuit Analysis III

8 Ybus Formation using MATLAB

Cycle-II

9 (i) Measurement of Earth Resistance& Soil Resistivity

(ii) Impulse testing of Insulators.

(iii) Calibration of High Voltage Equipment

10 (i) Power factor Improvement

(ii) Power measurement using CT & PT.

11 Testing of Static Over current relay

12 Testing of Earth Fault current relay

13 Simulation of single area and two area AGC System.

14 Mi Power – Load Flow Analysis I

15 Mi Power – Load Flow Analysis II

16 Power World – Load Flow Analysis III

Cycle-III

17 Simulation of FACTS devices (Shunt Compensation).

18 Analysis of Transient stability and Voltage stability of power systems (using Power angle and PV curves respectively).

Experiment No. 1

(i) Power frequency testing of Insulators.

(ii) Measurement of dielectric strength of air & solid insulating materials

(i) Aim: Power frequency testing of Insulators:-

a) To study the power frequency test set up.

b) To find the power frequency with stand voltage of the given 11 kV disc

insulator.

c) To find the power frequency flashover voltage of the given 11 kV disc insulator.

(ii) Aim: Measurement of dielectric strength of air & solid insulating materials

a) To measure the breakdown voltage of air in uniform and none uniform fields.

b) To measure the breakdown voltage of solid insulation in uniform fields.

THEORY

The main focus of high voltage engineering is that to design a reliable and economic

insulation system. It is therefore important to know how an insulating material turns itself

in to a conducting one (i.e. breakdown of insulating material). Breakdown theory in gases

can be explained by using Townsend’s breakdown theory. Townsend’s mechanism is

based upon

(i) Ionization by collision in the gas and

(ii) Ionization on the surface of cathode

Townsend used a parallel plated electrode system enclosed in a glass chamber

containing a gas at low pressure. An U.V light source was used to irradiate the cathode

surface to emit photoelectrons in the gaseous medium. A variable source of potential was

connected externally across the electrodes in series with an electrometer to measure small

current. There are four distinct regions in the current growth curve.

Townsend’s mechanism can be explained as follows (Fig)

In region 1 current through the air gap increases proportionally with gap voltage till it

reaches V1. This is because with increasing gap voltage more and more emitted photo

electrons from cathode reach the anode .

In region 2 current remains essentially constant between V1 and V2, all the

photoelectron emitted per second from the cathode reach the anode per second giving a

saturation current. , N0 is number of photoelectron liberated per second.

In region 3 current gross exponentially beyond v2 and up to v3,with the increase in

gap voltage, the electric field stress E, in the gap increases and hence an electron leaving

the cathode experience more force and acceleration. This result in higher kinetic energy

of the electrons as it travels to the anode. Therefore probability of ionization increases

due to the collision of electrons with uncharged particle.

Anode current .

Towson’s introduces a quantity called (Townsend’s first ionization constant). It is

defined as the average number of ionizing collision made by one electrode per cm drift in

the duration of electric field. Here is the electron avalanche and represents

the number of electrons produced by one electron while travelling from cathode to anode.

NA is number of electron reaching anode per second.

In region 4 as the voltage reaches V4 the anode current increases very sharply and is

limited only by the external resistance. The current doesn’t change even if the u.v light

source is removed. The gas is now said to have broken down Townsends postulated that a

second mechanism in addition to the primary process must be affecting the current.

There may be three secondary processes as follows.

1. The positive ions liberated in an avalanche may cause ionization by collision

while moving towards the cathode.

2. The positive ion may liberate electron from the cathode surface when they

impinge on it.

3. The excited atoms or molecules in the avalanche may emit photons when these

atoms returns to normal state and these photon may cause photo ionization.

The steady state current may derived as

Where α and γ are both dependent on electric field stress

Townsend’s criterion for spark breakdown:

If α and γ reaches such a values so that the denominator become zero, the current

become independent on N0 and indeterminate (1 to )

Townsend’s criterion for the breakdown gases is , is very large and

hence reduce to .

For voltages above V3 and below V4, . Hence the condition for

breakdown is not satisfied but the current is contributed by the electrons produced by

both α and γ processes, the later being significant beyond V3 .At V4, the denominator tends

to be zero and steady state electron flow ceases. V4 is denoted as breakdown voltage (Vb)

of the gap and the corresponding field stress is known as the electron field stress, Eb .For

voltages equal to or more than V4 ,the circuit current is determined by resistance.

Factors affecting breakdown voltage:

Electrode separation.

Electrode effects.

Frequency of applied voltage.

Pressure effects.

Time lags.

Eternal circuits.

Recovery of insulating property.

Non metallic electrodes and surface coating.

Flashover test on air gaps

Adjust the air gap at suitable gas distance (say 3cm). Make sure that all

connections between various elements like control unit, HV transformer, test specimen

and earth are ok. Keeping the control knob at minimum position, switch on the control

unit. Increase the voltage across the air gap using the control knob at 2KV/sec. When the

breakdown of the air gap occurs, not down the voltage from the peak voltmeter, bring

back the knob to zero position and wait for 2 minutes. The experiment can be repeated in

the same way and take 5 set of readings. From this the average value of the breakdown

strength of air can be calculated.

Arrangement of disc insulator for test set up.

i) String insulated unit is suspended from an earthed metal cross arm.

ii) The length of cross arm should be at least 1.5 the length of the string being tested

and should be at least equal to 0.9m on either side of the axis of string.

iii) No other earthed objects should be nearer the insulator string than 0.9m and 1.5

times the length of sting whichever is greater

iv) A conductor of actual size to be in use in service or diameter not less than1.0 cm

and length 1.5 times the length of the string is secured in the suspension.

v) The high voltage of the transformer is connected to the conductor and capacitance

voltage divider using insulated wire.

Power Frequency Testing of HV equipment

The HV equipment is connected at the test position as in service (figure 1). To do

the withstand test, specified value of voltage is applied across the equipment by means of

the HV test set up, the voltage is raised in steps of 2kV/second the voltage is maintained

for 1 minute. For conducting break down test, the voltage is raised in steps of 2kV/second

till there is a breakdown across the equipment.

Figure 1

Determination of Dielectric Strength of air

The test circuit is done as given in the figure. The electrodes are connected

instead of across the HV equipment. If the electrodes are both flat, the field between the

electrodes is uniform. The field is non uniform when the electrodes are either rod or flat

and rod. Sphere gap also can be used. The voltage is gradually raised as done for the

power frequency test and the value of voltage at which, the breakdown occurs is

determined. The ratio of the breakdown voltage to the distance between the electrodes in

cm, will give the dielectric strength of air.

PROCEDURE:

(i) Power frequency voltage is applied to the insulator and the voltage is increased to

specified value and maintains it for one minute.

(ii) The voltage is increased gradually till flashover occurs.

(iii) The experiment is repeated for 5 times.

(iv) The mean of 5 consecutive flashover voltages must be less than the specified

value.

Observations

Uniform field (Plane to Plane)

Air Gap (cm)

Breakdown voltage (KV)

Mean (KV/cm)

1cm

2cm

Non Uniform field ( Point to Plane)

Air Gap (cm)

Breakdown voltage (KV)

Mean (KV/cm)

2cm

3cm

Withstand voltage of _ _ _ KV disc insulator :_ _ _ _ _ _KV

Flashover voltage of _ _ _ KV disc insulator :_ _ _ _ _ _KV

Result:

Inference:

Experiment No. 2

(i) Measurement of insulation resistance of 3-core & 4-core cables.

(ii) Measurement of dielectric strength of liquid insulating materials.

(i) Aim: Measurement of insulation resistance of 3-core & 4-core cables.

a) To study the Insulation resistance Test Megger BM11D.

b) To measure the insulation resistance of the given under ground cables-

(i) HT 11 kV (ii) LT 1100 V cables.

c) To measure the insulation resistance and polarization index of the given

transformer.

(ii) Aim: Measurement of dielectric strength of liquid insulating materials.

a) To study the transformer oil test kit.

b) To measure the dielectric strength of the given samples of transformer oil.

Measurement of Insulation Resistance of Cables

Procedure for measurement

1. Open the Meggering Instrument BM11D and connect the red, blue and

black leads as specified in the manual: Red to the positive and black

lead to the negative terminals. Blue lead is required when guard

connection is required.

2. Switch On the Megger using the ON/OFF switch and wait till is ready

to use.

3. Check the status of the battery and choose the test voltage using the

select keys, required for the cable under test.

4. To start test process, the red button is pressed for more than 1second.

The red LED will be flashing indicating that the test is in progress.

5. When the timer reads 60seconds, press red button again and note the

final reading.

6. Polarization index is the ratio of Insulation resistance in 60 seconds to

the Insulation Resistance in 10 seconds.

4-core cable

Observations

HT Cable

Test

Voltage

Description

Insulation

Resistance

5000

LT Cable

Test Voltage Description Insulation

Resistance

1000

Inference

Experiment No. 3

Testing of Electromechanical Over Current Relay.

Aim:

a) To study the relay test unit Sakova.

b) To study Electromechanical Over current relay – Type CDG11

c) To conduct the pick up test on all taps and determine the percentage error.

d) To obtain the time current characteristics (Operating time characteristics)

with time multiplier settings at 0.1, 0.5 & 1.0.

THEORY

A protective relay is a device that detects the fault and initiates the operation of

circuit breaker to isolate the defective section from the rest of system. In some cases it

may give an alarm or visible indication to alert operator. Protective relays are broadly

classified in to three depending on the technology they use for their construction and

operation as electromagnetic relay, static relay and microprocessor based relay.

Electromagnetic relay operate on electromagnetic principle i.e. an electromagnet attracts

the magnetic moving part or a force is exerted on a current carrying conductor when

placed in a magnetic field or a force is produced by principle of induction. Moving ion,

moving coil, attracted armature, induction disc and induction cup type relays come under

this group of relay.

A protective relay which operates when the load current exceeds a preset value is

called an overcurrent relay. The value of prêt current above which the relay operate is

known as its pick-up value. An overcurrent relay is used for protection of distribution

lines, large motors, power equipments etc. A scheme which incorporate overcurrent

relays for the protection of an element of power system is known as an over current

scheme. At present electromagnetic relays are widely used for this. A wide verity of time

current chara is available for over current relay.

A definite time overcurrent relay operates after a predetermined time when the

current exceeds its pick up value. The operating time is constant irrespective of

magnitude above pick-up value.

An instantaneous relay operates in definite time when the current exceeds its pick-

up value and there is no intentional delay. It operates in 0.1s or less. An inverse time

overcurrent relay operates when the current exceeds its pick-up value. The operating time

depends on the magnitude of operating current. Operating time decreases as current

increases.

Current setting

The current above which an overcurrent relay operates can set. If the relay is set at

5A, it will then operate when current exceeds 5A. An overcurrent relay which is used for

phase to phase protection can be set at 50% to 100% of rated current in steps of 25. The

current at which it can set are 2.5, 3.75, 5, …, 10A. The actual rms relay current is

expressed as multiple of the setting current (pick up current) which is known as plug

setting multiplier.

Time setting

The operating time of a relay can be set at a desired value. In induction disc type

relay the angular distance by which the moving part of the relay travels for closing the

contact can be adjusted to get different operating time. There are 10 steps in which

current can be set.Time multiplier setting is used for these steps. The value of TMS

are0.1, 0.2,…….,0.9, 1.0. Suppose that at a particular value of current or PSM,the

operating time is 4s with TMS as 1, the operating time for same PSM with TMS as 0.5

will be 4 0.5 = 2 sec.

Relays and Relay Testers

Tests for Relays

Relays are devices used in systems especially in power systems for preventing or

avoiding unintended situations that may lead to the damage of equipments or personnel.

Relays can be Analog or Digital based on the measurement methods. They can be

Electromagnetic, Electromechanical, Static or Numeric based on the method by which

the trip signal is produced to be sent to the Circuit breakers. All these relays have to go

through a routine testing procedure to ensure security during their operating life time.

Some tests are specific for each relay as specified by the corresponding manufacturers.

But a few are common to each and every relay irrespective of their operating nature.

Only those tests are conducted in this laboratory to test the relays. These tests are

1. Pick up Test

2. Drop out Test

3. Operating Time Determination Test

Basic operation of a relay

Relay Testers

All relays can be tested by certain universal testers capable of supplying the

actuating quantity (current or voltage). For an overvoltage or undervoltage relay, the

tester should be capable of supplying voltages ( ac or dc depending on the type of relay)

with capability to change the magnitude of voltage. This can be very easily achieved by

a variable voltage source. Whereas for current actuated relays (overcurrent relays, earth

fault relays, impedance relays etc.) the relay tester should be a current injection unit. In

this laboratory, two types of relay testers are used. They are capable of current injection

and voltage injection. Read the details of each relay testers from the corresponding

manuals – SAKOVA model RTS – 03 and Sverker 760.

Testing Procedures

1. Pick up Test

This test is done to find out the minimum value of the actuating quantity for

which the relay is about to start the process of tripping. For overcurrent relays, the

current is injected to the current carrying terminals and the value of current is gradually

increased by the current varying knob of the relay tester. The picking up of the relay

can be identified by any of the following methods. For an electromagnetic relay, the

Pick up value is the value corresponding to which the Aluminum disc begins to rotate.

Whereas for a static relay, pick up value is the value corresponding to which, the trip

LED gives the first blink.

2. Drop Out Test

This test is done to find out the maximum value of the actuating quantity for

which the relay stops the tendency to trip. For this test, initially the relay is made to

pick up as done in the pick up test. The current injection to the overcurrent relay is

reduced gradually till the disc stops rotating or till the LED stops blinking. It is quite

obvious that in both these tests, the speed of current variation certainly affects the

value. So, utmost care should be taken to change the value of current injection at the

slowest pace.

The relays should be supplied with the DC voltage to energies the tripping

circuit by connecting the 110V DC from the relay tester to the voltage point of the

relays. This is done by rotating the knob of auxiliary DC supply in Sakova to

110V. The trip circuit of the relay and the tester are also to be connected.

3. Operating Characteristics Determination Test

This is the most important test for determining the quality of a relay. Each

Manufacturer will provide a set of operating characteristics for different time multiplier

settings. Current injection should be given to the relay as given in the circuit below for

few specified values of current or voltage and the time taken by the relay to trip in each

case is determined.

First, set the DC Voltage to 110V. Then switch off the DC supply. Set the time

multiplier to the required value by rotating the disc of CDG11. Now slowly inject the

currents by the ON and OFF push buttons alternately till it reaches the specified values

of currents for overcurrent relays as CDG 11, MCT12A or TSA 111. Then switch on

the DC supply, switch On the Timer and then press the ON push button. The relay will

trip after some time. Note the time shown in the timer (AT).

Points to be noted: The N/C N/O switch should be in the N/O position for testing

CDG11. The timer switch should be in INT position. Don’t inject the current with DC

ON for doing the current setting for the Operating time determination.

Observations

Pick Up and Drop Out Test

Pick Up test should be done for each tap setting for CDG11

Current

Setting

Is (A)

Pick Up

Current

Ip (A)

Percentage Error

((Ip – Is)/Is)*100

Drop Out

Current

Id (A)

Percentage Error

((Id – Is)/Is)*100

Operating Time Characteristics

Find the Curve time (CT), the time set by the manufacturer for each value of current from

the manual. It is also given on the front panel of CDG11. Few values are given in the

table.

Plot the graph for Operating Characteristics with Plug Setting Multiplier on X axis

(Multipliers of Is) and Tripping Time on Yaxis.

Current

setting Is

(A)

Time

Multiplier

Setting

Tripping Time in Seconds

2Is 4Is 6Is 8Is 10Is

CT AT CT AT CT AT CT AT CT AT

2.5A

0.1 1 0.3

0.5 5 1.5

1.0 10 3

Typical time current chara of a relay

Experiment No. 4

Testing of Current Transformer and Potential Transformer

Aim

a) CT testing

i) To obtain the magnetizing characteristics of the give CT and to

determine the knee point voltage.

ii) To determine the CT ratio

iii) To determine the polarity of the primary and secondary

windings.

iv) To measure the resistance of the secondary winding.

v) To measure the CT burden when feeding the given relay.

b) PT testing

i) To determine the insulation resistance of the given PT.

ii) To determine the polarity of the primary and secondary

windings of the given PT.

iii) To determine the PT ratio.

Procedure:

i) To obtain the magnetizing characteristics

Wire up the circuit as shown in figure. Initially connect the ammeter to

one of the CT secondaries. Also connect the digital voltmeter across

output of autotransformer. Supply a small voltage using autotransformer.

Note the meter reading. Repeat this procedure until a small rise in voltage

leads to a sudden/large increase in current. Repeat the procedure until

saturation is reached. Perform the procedure in second set of CT

secondaries.

a) Measuring CT

b) Protection CT

c) CT ratio

5.2

50

2

1

I

IRatio

ii) To obtain CT/PT ratio.

Wire up the circuit as shown in the figure. The circuit that injects current

at CT primary is obtained from the relay test set. Keep the circuit dc off.

Apply a current of 50A into the primary. Note the digital primary

ammeter reading (I2) when the primary current is 50 A(I1). CT ratio is I1/

I2. For PT, 230 (V1) 1- ac supply is given at primary and secondary

voltage is observed V2. The PT ratio is V2/V1.

iii) Polarity test.

For CT, the secondary is connected to centre zero ammeter with

S1connected to +ve and S2 connected to –ve. A battery is connected

across P1 ,P2 terminals of CT primary. Now when CT primary is

connected on ammeter. A +ve deflection indicates that selection of S1and

S2 is correct. In case of –ve deflection reverse the connections of S1and

S2 for the +ve deflection. For PT the connection are made as shown in

figure. For subtractive polarity meter should real (V1 - V2 ) voltage and for

additive polarity meter should read (V1 + V2 ) voltage. If both conditions

are satisfied the polarity is correct.

iv) To measure the resistance of secondary winding of CT.

A multimeter is set in ohms range and the probes are placed across S1 and

S2 of Ct secondary winding. The digital display given winding resitance.

v) To determine CT circuit burden.

The relay test set was made to inject current to CT. Hence burden of this

circuit is to be measured. For this, one end of the digital ammeter is

connected to relay trip circuit and the circuit is completed through relay

trip circuit and ammeter. A 5A current is not injected into circuit and

voltmeter reading is noted. The product of current and voltage given

burden of CT circuit.

vi) To measure insulation résistance.

Insulation resistance can be measured using BM 11D Megger.

iii) Polarity

iv) CT Burden Measurement

v) Polarity (PT)

vi) PT Ratio

2.237

1.140Ratio

a) Measuring CT b) Protection CT

Injection

Voltage (V)

Current

(mA)

Injection

Voltage (V)

Current

(mA)

`

c) Insulation Resistance

Test Voltage (V) Description Insulation Resistance

(M )

Result:

Inference:

Questions:

1 2 3 4

G1 T1 T2 G2

TL

L

Experiment No. 5

Mi Power – Short Circuit Analysis I –Simple System

Aim

(i) To Study the Power System Simulation Software Mi Power

(ii) To Draw the Single Line Diagram of the given system in Mi Power

(iii) Obtain the fault current and fault MVA for a symmetrical three phase fault at

bus no. 3 analytically and verify it using Mi Power

(iv) Obtain the fault contributions for a line to line fault on the transmission line at

60 % distance from bus no. 2

Single line diagram

G1,G2: 100 MVA, 11 kV, Xd’=0.15 p.u.

T1,T2: 100 MVA, 11/110 kV, X=0.1 p.u., R – negligible

TL: X=0.02 p.u.

L: P=20 MW, Q= 10 MVAR

MiPOWER

Power System Simulation Software

How to draw single line diagram

Click Mipower on desktop. Then open power system network editor. Select menu

option Database→ configure. Configure Database dialog is popped up as shown below.

Click Browse button.

Browse the desired directory and specify the name of the file. Open it verify.

Click ok in the configure database dialog box. Another window appears. Uncheck the

power system libraries and standard relay libraries. Now a GUI pattern will get displayed.

Select grid from the top shown tool bar.

To draw Bus

Click on bus icon provided on power system tool bar on the RHS. Draw a bus and

a dialog appears prompting to give the bus ID and bus name. Click OK. Data base

manager with corresponding Bus Data form will appear. After entering data click save

which invokes Network Editor. Follow the same procedure for remaining buses. (Here

Bus1, Bus2 & Bus3).

If ratings (11kV for Bus1, 110kV for Bus2 & Bus3) are other than the default one,

modify them. After entering data, click save. The right clicks to avoid bus option.

To draw transmission line

Select transmission line from tool bar. To draw the line click between the two

buses (here Bus 2 & Bus 3) to connect the ‘from bus’ double click on the from bus and

do the same for ‘to bus’. Now an element ID dialog box will appear.

Enter element ID number and Click OK. Database manager with corresponding

Line/Cable Data form will be open.

Enter the details of that line as shown below.

Enter Structure Reference number as 1 and click on Transmission Line Library. Line

& cable library form will appear. Enter the data (X=0.02 pu other values are set to zero).

Then save and close the library. Click save.

If there is more than one transmission lines with same parameters enter Structure

Reference number as 1 for all transmission lines. If there is more than one transmission

lines with different parameters (R, X &B/2) use different Structure Reference number (2,

3, 4 etc).

To draw Generator

Click on Generator icon provided on power system tool bar. Connect it to bus 1

by clicking the left mouse button on Bus 1. The Element ID dialog will appear Enter ID

number and click OK. Data base with corresponding Generator Data form will appear.

Enter details as :- Give De-Rated MVA as 100 and Scheduled Power as 80 MW

(assume power factor as 0.8).

Note: If specified voltage is given, click Compute Volt button and enter that value.

Voltage will be calculated and appear in the specified voltage field.

At slack bus, only voltage and angle are mentioned. Schedule power, real power

minimum and maximum constraints do not have much importance.

If the bus is a PV bus, then scheduled power, specified voltage, minimum and

maximum real & reactive power data is must.

Enter Manufacturer Reference number as 1 and click on Generator Library

button. Generator Library form will appear.

Enter MVA Rating as 100,MW Rating as 80 and kV Rating as 11.

Also give Direct Axis Transient Reactance (Xd’) as 0.15 pu.

After entering data save and close. In Generator Data form click save. Network Editor

screen will be invoked.

If there is more than one generator with different data, give different

Manufacturer Reference number otherwise give the same Manufacturer Reference

number.

To draw Transformer

Click on Two Winding Transformer icon provided on power system toolbar. To

draw the transformer click in between two buses (here bus 1 and bus 2) and to connect to

the From Bus, double click left mouse button on the from bus and join to another bus by

double clicking the mouse button on the To Bus. Element ID dialog will appear Click

OK.

Note: - Care should be taken to connect the two winding transformer between buses.

High Voltage side should be connected to From Bus ( Here From Bus (HV side-

primary ) is bus 3).

Transformer Element Data form will be open. Enter the Manufacturer

Reference Number as 1. Enter transformer data in the form as shown below. Click on

Transformer Library.

Transformer Library form will be open. Enter the data. Save & close library

screen.

Transformer element data form will appear. Click save button, which invokes

network editor.

To draw the Load

Click on Load icon provided on power system toolbar which is also shown by the

position of the arrow in the figure shown above. Connect it to bus 3 by clicking the left

mouse button on Bus 3. The Element ID dialog will appear Enter the details of the load,

the real and reactive power, click OK and save to return to the editor.

Attach Transformer T2, Generator G2 as described before to complete the single

line diagram given. Since the ratings of the two generators are same, one need to save

only one generator library with one manufacturer reference number. The same can be

done for the transformers also.

Options for short circuit analysis

To solve the short circuit analysis, click Solve on Menu bar and choose short

circuit studies from the scroll menu. Now there is choice for fault on bus and fault on

line. There is choice for different types of faults also. All types of faults can be selected

from the scroll menu provided. In the case of fault on line, the distance at which the fault

occurs can also be selected.

By giving proper output options, now the short circuit study can be executed and

the result can be observed in the standard format.

Experiment No.8

YBUS FORMULATION

Aim:-

Form the YBUS of the given network by transformation method. Display the

matrices A, Yprimitive and YBUS .

(a) Without mutual coupling

(b) With mutual coupling

(c) Also find EBUS of the system if J=[ -0.6+j3.0

0

-0.4+j5.0

0

0 ];

| Ele | From | To | X |

| No | Bus | Bus | pu |

linedata = [ 1 ref 1 j0.3

2 2 ref j1.0

3 ref 3 j0.2

4 1 2 j0.03

5 3 2 j0.02];

| Ele | From | To | X | Mutual Cop. | X |

| No | Bus | Bus | pu | with element | p.u |

linedata = [ 1 ref 1 j0.3 - -

2 2 ref j1.0 - -

3 ref 3 j0.2 - -

4 1 2 j0.03 5 -j0.01

5 3 2 j0.02 4 -j0.01];

3 2 1

1

1

2

1 3

1 5 4