lab1 eps fina

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LAB 1: Transmission and Distribution Systems

NURUL SHAFINA BT RAZALI

EA11053(SECTION: 03)

DATE: 22 APRIL (SEM 2 2013/14)

[email protected]

ABSTRACT Electric-power transmission is the

bulk transfer of electrical energy, from

generati ng power plants to electr ical substations

located near demand centers. Thi s is distinct f rom

the local wir ing between high-voltage substations

and customers, which is typical ly referred to as

electric power distribution. Transmission lines,

when interconnected with each other, become

transmission networks. The combined

transmission and distr ibution network i s known

as the " power gr id" in the Uni ted States, or just

" the grid" . In the Uni ted Kingdom, the network is

known as the " National Grid"

INTRODUCTION

Distribution is a part of the electrical utility system

between the bulk power source and the consumersservice switches and normally operated below 100

kV.

Sub transmission system deliver energy from bulk

power sources to the distribution substations. The

voltage is about between 34.5 and 138 kV. Thedistribution substation reduces the sub

transmission voltage to a lower primary system

voltage for local distribution (using power

transformer)

There are three basic types of distribution system

designs that is Radial, Loop, or Network.

We can use combinations of these three systems,and this is frequently done.

Electric utilities aim to provide service tocustomers at a specific voltage level, for example,

220V or 240V. However, due to Kirchhoff's Laws,

the voltage magnitude and thus the service voltageto customers will in fact vary along the length of a

conductor such as a distribution feeder.

Jn order to maintain voltage within tolerance unchanging load conditions, various types of devi

are traditionally employed

a load tap changer (LTC) at the substat

transformer, which changes the turns ratio

response to load current and thereby adjusts voltage supplied at the sending end of the feeder

voltage regulators, which are essentia

transformers with tap changers to adjust

voltage along the feeder, so as to compensate the voltage drop over distance; and

capacitors, which reduce the voltage drop alo

the feeder by reducing current flow to lo

consuming reactive power.

Radial Distr ibut ion Systems

The Radial distribution system is the cheapestbuild, and is widely used in sparsely popula

areas. A radial system has only one power soufor a group of customers. A power failure, shcircuit, or a downed power line would interr

power in the entire line which must be fixed bef

power can be restored.

Electricity suppliers normally use rad

distribution in rural areas where the load

randomly distributed, separated by areas with lior no habitation, and back up supplies are norma

not available. The length of feeder is typica

limited to 500 m or less. In the radial distributsystem, feeders supplying the consumers are all from a central point (the substation) as shown

Figure 1. There is no looping of the feeders.


2/13

FIGURE 1

Ring Di str ibution Systems

A loop system, as the name implies, loopsthrough the service area and returns to the original

point. The loop is usually tied into an alternatepower source. By placing switches in strategic

locations, the utility can supply power to the

customer from either direction.

If one source of power fails, switches are thrown

(automatically or manually), and power can be fedto customers from the other source.

The loop system provides better continuity ofservice than the radial system, with only short

interruptions for switching. In the event of power

failures due to faults on the line, the utility hasonly to find the fault and switch around it to restore

service. The fault itself can then be repaired with a

minimum of customer interruptions.

The loop system is more expensive than the radial

because more switches and conductors are

required, but the resultant improved system

reliability is often worth the price.

This is commonly used in urban areas with high

housing density. In such a system, LV cables from

neighbouring distribution substations are either

looped together or are terminated very close to oneanother where an interconnection of cables can be

made. This system is normally used when a high

degree of reliability of load supply is required andback up substations is made available. Figure 2

shows a schematic diagram for a ring distribut

network.

FIGURE 2

Voltage Regulation

Voltage regulation is a measure of change in

voltage magnitude between the sending

receiving end of a component, such astransmission or distribution line. Volt

regulation describes the ability of a system

provide near constant voltage over a wide range

load conditions.

A voltage phasor diagram can be drawn for equivalent circuit as shown in Figure 3,

considering the current, I, to be equal to the sum

two currents, Ip and Iq, that are at right angles

each other. Ip is in phase with Vr and Iq lags Vr900.

Figure 3: Generator Feeding a Large Pow

System


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The resulting phasor diagram for a lagging p.f.

load is shown in Figure 4.

Figure 4: Resulting Phasor Diagram for a lagging

p.f load

From this diagram,

222

qprs VVVV (1.1)

If is small,

rs VV = qpp XIRIV (1.2)

And, therefore,

r

qp

pV

QIPIV

(1.3)

If the load is capacitive or leading p.f. load, the

plus sign becomes a minus sign. Similarly, it is

seen that:

r

qpqV

QRPXRIXIV

(1

Thus, if X/R > 1, the flow of reactive power

determines the voltage drop and the flow of powP, determines the transmission angle and th

statements are substantially independent of e

other.

The objectives for this Lab 1 are to investig

the effect of loading and feeder length on

voltage regulation in a radial distribution netwfeeding a resistive load, to investigate the eff

that the inductive and capacitive loads have up

the voltage regulation of a radial feeder andinvestigate the voltage regulation for a simple r

distribution network when it supplies resisti

inductive and capacitive loads. Also, to mak

comparison between the results obtained with

corresponding results for the radial network.

I. PROCEDURE

Experiment 1: Single-Phase Radial Netw

Feeding a Resistive Load

Procedure A: One Section of the Feeder

1)

One phase of the supply line and the neu

line is connected to one phase of resistive loas shown in Appendix A. Ensure that

secondary of the CT is short-circuited.2) CB1 and CB2 have been closed to connect

circuit.3)

The Neutral Switch has been closedconnect the circuit to the ground

4) The supply is switched on and the load is se

25%. This should give the load current roug1.25A. The readings for load (receive) volt

Vr, supply voltage Vs and load current, I h

been taken.5) Step (3) is repeated for 50%, 75% and 10

and recorded it in Table 1.

Procedure B: Two Section of the Feeder

1) Procedure A is repeated, but with two secti

of the line 1 connected in series and the t


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sections of the Neutral line are connected in

series as shown in Appendix B. The resultsare recorded in Table 2.

Experiment 2: Single-Phase Radial Network

Feeding I nductive and Capaciti ve Loads

Procedure A: Inductive Load

1) On the three-phase circuit of the trainer, two

sections of the red phase and the neutral linesare connected to one phase of the inductive

load as shown in Appendix C. Ensure that the

secondary of the CT is short-circuited.2)

CB1 and CB2 are closed to connect thecircuit.

3) The Neutral Switch has been closed to connect

the circuit to the ground4)

The supply is switched on and the load is set

to 25%. The readings for load (receive)voltage Vr, supply voltage Vsand load current,

Ihave been taken.5) Step (3) is repeated, for 50%, 75% and 100%

and recorded it in Table 3.

Procedure B: Capacitive Load

1) A blank table is created as in Table 3 and

replaced the inductive load by a capacitiveload, repeat Procedure A.

Experiment 3: Ring Distribution Network

Supplying Resistive, Inductive and Capacitive

Loads

Procedure A: Resistive Load

1)

A resistive load is connected to the midpoint(TP4) of the red phase sections that are fed

from the two points (TP2) and (TP3) as shown

in Appendix D.2)

Temporarily disconnected the load, the supply

is switched on and no load receive voltage

(VnL) reading has been taken. CB1 and CB2 are

closed to connect the circuit.3) The load is reconnected and the load is set to

25%. The readings for load (receive) voltage

Vr, supply voltage Vs and load current, I h

been taken.4) Step (3) is repeated, for 50%, 75% and 10

and recorded it in Table 4. The central mete

used to measure Vr.

Procedure B: Inductive Load

1) A blank table is created as in Table 4.

2) The resistive load is replaced with an induct

load and Procedure A is repeated.

Procedure C: Capacitive Load

1) A blank table is created as in Table 4.

2)

The inductive load is replaced with a capacitload and steps (3) and (4) in Procedure A

repeated.

II. RESULTS


Feeding a Resistive Load

Table 1: One Section of the Feeder.

Load I

25% 132.10 V 131.26 V 1441.5 m

50% 131.76 V 130.03 V 2.81 A

75% 131.05 V 128.23 V 4.29 A

100% 130.52 V 127.09 V 5.58 A

Table 2: Two Sections of the Feeder in

Series.

Load I

25% 132.17 V 130.89 V 1429.0 m

50% 131.43 V 128.67 V 2.754 A

75% 130.85 V 125.90 V 4.213 A

100% 130.30 V 123.79 V 5.423 A


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R

Generator

1 2

X21

Resis

Load

Experiment 2: Single-Phase Radial Network


Table 3A: Inductive Load.

Load I

25% 132.44 V 127.11 V 1202.5 mA

50% 132.35 V 120.96 V 2.396 A

75% 132.17 V 114.93 V 3.581 A

100% 130.01 V 111.00 V 4.418 A

Table 3B: Capacitive Load.

Load I

25% 133.88 V 140.48 V 1525.5 mA

50% 133.30 V 149.28 V 3.285 A

75% 133.47 V 145.69 V 5.232 A

100% 133.67 V 150.64 V 7.385 A

Experiment 3: Ring Distribution Network

Supplying Resistive, Inductive and Capacitive

Loads

Table 4A: Ring Network with Resistive Load.

= 132.05 V

Load I%

Regulation

25%132.36

V

130.68

V

143.5

mA0.26

50%131.93

V

130.48

V

2783.8

mA0.41

75%131.13

V

128.65

V

4270.0

mA1.84

100%130.65

V

127.31

V5.557A 2.91

Table 4B: Ring Network with Inductive Load.

= 132.41 V

Load I%

Regulation

25%132.77

V

129.96

V

1234.6

mA1.89

50%132.51

V

126.38

V

2519.4

mA4.77

75%132.28

V

123.09

V

3839.8

mA7.57

100%132.09

V

120.67

V

4.828

A9.73

Table 4C: Ring Network with Capacitive Loa

=133.10 V

Load I%

Regulati

25%133.21

V136.92

V1492.8

mA2.79

50% 133.34V

141.10V

3080.4mA

5.67

75%133.71

V145.43

V4.781

A8.48

100%133.89

V

149.55

V

6.594

A10.99

III. DISCUSSIONS

Experiment 1: Single-Phase Radial NetwFeeding a Resistive Load

Procedure A: One Section of the Feeder

Circuit diagram obtained from the connection

Appendix A;


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The percentage regulation using the Equation 1.5

for each load setting;

% Regulation = 100

r

rs

V

VV (1.5)

For load: 25%

For load: 50%

For load: 75%

For load: 100%

The percentage regulation against load cur rent;

Graph 1.1

As we can see from the Graph 1.1, the

percentage regulation is increases due to the load

current increases. Regarding to Ohms Law, V=IR

it states that current flowing is directlyproportional to the voltage and inversely

proportional to the resistance. Therefore, if the

voltage is increased, the current will increase if the

resistance of the circuit does not change. Sa

goes to the increasing resistance of the circuit wlower the current flow if the voltage is

changed. This formula shows that there

relationship between this three variable.

Procedure B: Two Section of the Feeder

The circuit diagram obtained from the connectio

in Appendix B;

The percentage regulation using the Equation

for each load setting;

For load: 25%

For load: 50%

For load: 75%

For load: 100%

0

2

4

6

0 1 2 3 4 5 6Percentageregulation(%)

Load current (A)

Percentage Regulation against load current for one

section of the feeder


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X2

1 2

R

Generator

1 2

X21

R221

Inductive

Load

The percentage regulation against load current;

Graph 1.2

Compar ison of the regulation- load current

curves obtained when one section and two

sections of the feeder are used to supply the load;

Graph 1.3

In the Graph 1.3, the line curve percentageregulation for two sections of the feeder is higher

than line curve percentage regulation for onesection of the feeder. Based on the Ohms Law. the

voltage will be higher as the impedance is increase

and that will lead to the higher percentageregulation. In this experiment, the impedances for

two feeders, are higher rather than one feeder,

Based on the results, current is one of

factors that determine the voltage regulation . the percentage of load current is negative,

percentage regulation will be increase. Length

the feeder also one of the factors that will affect

voltage regulation. The percentage regulation wbe increase if we increase the length of the feede

So, we can see the effect of loading feeder length on the voltage regulation in a rad

distribution network feeding a resistive load.



Procedure A: Inductive Load

The circuit diagram obtained from the connectio

in Appendix C;

The percentage regulation using the Equation 1.for each load setting.

% Regulation = 100

r

rs

V

VV (1.6)

For load: 25%

For load: 50%

For load: 75%

0

1

2

3

4

5

6

0 1 2 3 4 5 6

Percentageregulation(%)

Load current(A)

Percentage Regulation against load current for two

section of the feeder

0

2

4

6

0 1 2 3 4 5 6Percentageregulation(%)

Load current(A)

Percentage regulation against load current for one and

two section of the feeder.

one section of

the feeder

two sections of

the feeder


8/13

For load: 100%

Graph 2.1

Compar ison of the regulati on- load cur rentcurves obtained for inductive load and resistive

load;

Graph 2.2

As we can see in Graph 2.2, inductive l

having higher percentage regulation than resistload. It is show that inductive load has m

voltage loss when compared to resistive load.

Procedure B: Capacitive Load

The percentage regulation using the Equation 1.for each load setting.

For load: 25%

For load: 50%

For load: 75%

For load: 100%

0

2

4

68

10

12

14

16

18

20

0 1 2 3 4 5


Load currents(A)

Percentage regulation against load current for inductive

load

0

2

4

6

8

10

12

14

16

18

20

0 1 2 3 4 5 6

Percentage

regulation(%)

Load current (A)


load and resistive load

inductive load

resistive load

0

2

4

6

8

10

12

0 2 4 6 8


Load current (A)

Percentage regulation against load current for capacitive

load


9/13

X2

1

2

R

Generator1

2

X

2

1

R2

2

1

Resistive

Load

Graph 2.3

Compar ison of the regulati on- load cur rent

curves obtained for capacitive load and inductive

load;

Graph 2.4

Based on calculation, capacitive load actually

having negative percentage regulation. So,

theoretically, the percentage regulation for

capacitive load is less than inductive load.

For the inductor, assume the current through is

it same as resistor, and the voltage across theinductor is

which transforms to the phasor,

but , and , thus

showing that the voltage has a magnitude of

and a phase of The voltage and current

are out of phase. Specifically, the current lthe voltage by .

For the capacitor, assume the voltage acros

is while the current throuthe capacitor is

And by referring to steps as we took for inductor, we obtain

showing that the current and voltage are ouphase. To be specific, the current leads the volt

by . And this explain why capacitive loresults in less voltage regulation than induct

loads.

Experiment 3: Ring Distribution Netw

Supplying Resistive, Inductive and Capaci

Loads

Procedure A: Resistive Load

The circuit diagram obtained from the connect

in Appendix D (for resistive load);

The percentage regulation for each load using expression;

% Regulation = 100

r

rnL

V

VV (1.7

0

2

4

6

8

10

12

14

16

18

20

0 2 4 6 8


Load current (A)


load and inductive load

inductive

capacitive

load


10/13

InductiveLoadGenerator

2

1

1

2

X2

1

2

R R2

2

1

X

For load: 25%

For load: 50%

For load: 75%

For load: 100%

Comparison results for the voltage regulation

with the corr esponding resul ts obtained from the

radial feeder in Experiment 1;

Graph 3.1

As can be seen in Graph 3.1, radial feeder

curve is slightly different than ring feeder. Thepercentage regulation are almost the same for the

second , third and fourth point of the radial and

ring network.

Procedure B: Inductive Load

The circuit diagram obtained from the connect

in Appendix D (for inductive load);

The percentage regulation for each load using

expression 1.6;

For load: 25%

For load: 50%

For load: 75%

For load: 100%

Comparison results for the voltage regulat

with the corresponding resul ts obtained from

radial feeder in Experiment 2;

0

0.5

1

1.5

2

2.5

3

3.5

0 1 2 3 4 5 6


load current (A)

Percentage regulation against load current for radial

network resistive load and radial network resistive load

radial

network

resistive load

ring network

resistive load


11/13

CapacitiveLoadGenerator

2

1

1

2

X2

1

2

R R2

2

1

X

Graph 3.2

Referring to Graph 3.2, radial feeder curve

regulation-load current is rising higher than ring

feeder for each point.

Procedure C: Capacitive Load

The circuit diagram obtained from the connection

in Appendix D (for capacitive load);

The percentage regulation for each load using the

expression 1.6;

For load: 25%

For load: 50%

For load: 75%

For load: 100%

Comparison results for the voltage regulat

with the corresponding resul ts obtained from radial feeder in Experiment 2;

Graph 3.3

The effect of load power factor upon volta

regulation for each of resistive, inductive a

capacit ive loads;

0

2

4

6

8

1012

14

16

18

20

0 2 4 6

Percentageregula

tion(%)

Load current (A)


load in radial and ring feeder

radial

networkinductive

load

ring network

inductive

load

0246810

12141618202224

0 2 4 6 8


Load current (A)


load in radial and ring feeder

radial

network

capacitive

load

ring netwo

capacitive

load


12/13

Graph 3.4

In this experiment, we can calculate the"power factor", which is defined as the cosine of

this angle based on the phase difference betweenthe voltage and current signals. In an electricpower system, a load with a low power factor

draws more current than a load with a high power

factor for the same amount of useful power

transferred. The higher currents increase theenergy lost in the distribution system, and require

larger wires and other equipment. Because of the

costs of larger equipment and wasted energy,electrical utilities will usually charge a higher cost

to industrial or commercial customers where there

is a low power factor.

Linear loads with low power factor (such as

induction motors) can be corrected with a passive

network of capacitors or inductors. Non-linearloads, such as rectifiers, distort the current drawn

from the system. In such cases, active or passive

power factor correction may be used to counteractthe distortion and raise the power factor. The

devices for correction of the power factor may be

at a central substation, spread out over a

distribution system, or built into power-consumingequipment.

In a purely resistive AC circuit, voltage and

current waveforms are in step (or in phase),changing polarity at the same instant in each cycle.

All the power entering the load is consumed (or

dissipated). Where reactive loads are present, suchas with capacitors or inductors, energy storage in

the loads results in a time difference between the

current and voltage waveforms.

If a load had a capacitive value, induct

(also known as reactors in this context) connected to correct the power factor. In

electricity industry, inductors are said to consu

reactive power and capacitors are said to supply

even though the energy is just moving back forth on each AC cycle.

When the load is inductive, the inducta

tends to oppose the flow of current, storing ene

then releasing it later in the cycle. The currwaveform lags behind the voltage wavefo

When the load is capacitive, the opposite occu

and the current waveform leads the volt

waveform.

So, lagging and leading is another way o

saying the net reactance is either inductive or

capacitive.

IV. CONCLUSION

As a conclusion, we can say since the volt

drop for the ring network is lower than radnetwork, it means that the ring distribution netw

is better than radial network. All the objectives

this experiment are achieved as we assure

managed to investigate the effect of loading

feeder length on the voltage regulation in a raddistribution network feeding a resistive load,

effect that the inductive and capacitive loads hupon the voltage regulation of a radial feeder,

the voltage regulation for a simple ring distribut

network when it supplies resistive, inductive a

capacitive loads. Other than that, we also mcomparison between ring and radial networks.

V. REFERENCES

1. http://en.wikipedia.org/wiki/Power_f

or

2. http://www.allaboutcircuits.com/vol_2

pt_11/3.html

3.

http://en.wikipedia.org/wiki/Electric_p

er_transmission

0

12

3

4

5

6

7

0 2 4 6 8

Percentageregulations(%)

Load current (A)

Percentage regulation against load current for resistive,

inductive and capacitive load

resistive load

inductive load

capacitive

load
http://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Power_factorhttp://www.allaboutcircuits.com/vol_2/chpt_11/3.htmlhttp://www.allaboutcircuits.com/vol_2/chpt_11/3.htmlhttp://www.allaboutcircuits.com/vol_2/chpt_11/3.htmlhttp://www.allaboutcircuits.com/vol_2/chpt_11/3.htmlhttp://www.allaboutcircuits.com/vol_2/chpt_11/3.htmlhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://www.allaboutcircuits.com/vol_2/chpt_11/3.htmlhttp://www.allaboutcircuits.com/vol_2/chpt_11/3.htmlhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Power_factor


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4. http://epb.apogee.net/foe/home.asp

5. http://yourelectrichome.blogspot.com
http://epb.apogee.net/foe/home.asphttp://epb.apogee.net/foe/home.asphttp://yourelectrichome.blogspot.com/http://yourelectrichome.blogspot.com/http://yourelectrichome.blogspot.com/http://epb.apogee.net/foe/home.asp

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