DESIGN CALCULATION FOR VOLTAGE IMPROVEMENT IN … DESIGN-CALCULATION-FOR-VOLTAGE...DESIGN CALCULATION FOR VOLTAGE IMPROVEMENT IN PRIMARY SUBSTATION BY USING MATHCAD ... in this paper

DESIGN CALCULATION FOR VOLTAGE

IMPROVEMENT IN PRIMARY SUBSTATION BY

USING MATHCAD

Khin Trar Trar Soe1

1

Ministry of Science and Technology, Electrical Power research Department, Mandalay Technological

University, Mandalay, Myanmar, [email protected]

Received Date: February 11, 2013

Abstract

Main objective of this paper is to analyze the design of the reactive power compensation in primary

substation by using MATHCAD. This paper describes generally theory, application and design

characteristics of power factor correction and voltage improvement with shunt capacitor banks. The

locations of power factor improvement with capacitor bank at high tension side are Myaungta Gar -

Hlaw Gar- Thake Ta -Hlaingthar Yar - Bayint Naung 230 kV primary Substation in Myanmar. This

paper has been calculated by variable data. Their transmission line configuration are twin bundle

single circuit and single circuit three phase. Calculation results for capacitor bank selection

program are showed with table, chart and curve with variable data by using MATHCAD

calculation. In this paper, a plant consisting of five numbers of primary substation poor voltage

regulations is taken as a designed plant from variable data. The design plant is constructed any

condition. Capacitors have no moving parts, initial cost is low, upkeep costs are minimal, and they

are compact, reliable, and highly efficient and can be installed basically three possibilities to

correct loads individually, in groups or centrally. Therefore, in this paper capacitor banks are used

in Myanmar more than any other. Finally, suitable result selections are explained with bar chart and

curves.

Keywords: MATCHCAD Calculation, Primary Substation, Power Factor, Size of Capacitor

Banks, Transmission Line Configurations, Voltage Improvement

Introduction

Nowadays, power quality is one of the most important topics from electrical energy

consumers’ point of view. Among different power quality factors such as voltage

harmonics, voltage imbalance, voltage sag, voltage swell and flicker, it is possible to say

that voltage magnitude regulation and reactive power compensation is the most common

problems. Capacitor banks are designed for reactive power compensation in primary

distribution substation in Myanmar. They are the most common type to control reactive

power. The main objectives of this paper are to be more economical, effective utilization of

electricity and to get benefits of power factor correction. The system improvement has to

be planned properly with the following objectives in mind. To reduce loss in the distribution and sub transmission system.

To improve the voltage regulation so as to bring it within the prescribed limit.

To improve the power factor in the distribution system so as to get optimum

utilization of distribution capacitors.

Type of distribution system

The distribution system can be classified as follows:

Radial system

ASEAN Engineering Journal, Vol 2 No 1, ISSN 2229-127X, e-ISSN 2586-9159 p.51

mailto:[email protected]

Parallel or loop system

Network or grid system

Radial System

The sub-transmission substation supplies the primary distribution system feeders radiating

from the substation bus. They feed the distribution transformer of substations which step

down the voltage to distribution voltage and supply various loads through distributors.

Parallel or Loop System

From the source of supply such as sub-transmission substation, feeders are laid in parallel

to supply substations from which the secondary distribution of power will be effected. In

this system, the circuit returns to the same point so that there is in affect one feeding point

only. In case of fault in one part of the circuit, an alternative path is available giving mare

reliability than the radial system.

Primary substation

Typical distribution system consists of a primary substation and a number of receiving

substations. A typical distribution system will consist of one or more distribution

substations consisting of one or more feeders. Components of the feeder may consist of the

following:

Three-phase primary main feeder,

Three-phase, two-phase (v phase), and single-phase laterals

Step-type voltage regulators or load tap changing transformer (LTC)

Shunt capacitor banks

Three-phase, two-phase, and single-phase loads.

Network or grid system

This type of system is applicable in large distribution areas with-large loads and where the

system has to be made more reliable for continuity of supply. This is true for primary

distribution systems as well as in some applications to secondary distribution system. In

this paper, there are five primary substations of national grid system namely; Myaungta

Gar, Hlaingthar Yar, Bayint Naung, Hlaw Gar and Thake Ta. These are supplied by 230

kV overhead lines. Lines may start grid configuration from the primary substation as

shown in figure 1.

Myaungta Gar

Athoke

Kamarnat

ThatonHlaw Gar

Ywama

Bayint Naung

Thake Ta

Thanlyin

Thida

Ahlone

Sinmaleik

Hlaingthar

Yar

Figure 1. Single line diagram for primary substation (230 kV operation)


Voltage Control Methods

A power system is said to be well designed only if it gives a good quality reliable supply

i.e. the voltage level should be within certain limits (say within ± 10%). When power is

supplied to a load through a transmission line keeping sending end voltage constant, the

receiving end load voltage undergoes variations depending upon the magnitude of the load

and power factor of the load. The higher the load with smaller power factor, the greater is

the voltage variation. Thus, various methods are adopted for voltage control.

Shunt capacitors

Series capacitors

Synchronous condensers

Tap-changing transformers

Autotransformer tap changing

Booster transformer

Shunt Capacitors

Shunt capacitors installed on a distribution system reduced the current, improve the voltage

regulation and reduce energy losses in every part of the system between capacitors and

generators. There is the capacitor for improving the voltage regulation of the system, as

well as the power factor of the system. The size of the shunt capacitor banks varies from

individual units of 5 to 25 kVA connected to the secondary of primary circuits of a

distribution system to a bank of capacitors of lager size kVA connected to the bus of a

substation at the primary side .

Table 1.Line Data for 230kV primary substation

Line Data for Primary Substation

MG-HY HY-BN MG-HG HG-TKT

Line length(mile) 22.4 6.906 19.14 13.85

Conductor size (mcmil) 605 605 605 795

Configuration Twin

bundle

single

circuit

horizontal

Twin

bundle

single

circuit

horizontal

Twin

bundle

single

circuit

horizontal

Single circuit

Horizontal

Spacing(ft) 25 25 25 25

Bundle spacing (m) 40 40 40 --


a b c

25 ft 25 ft

40 cm 40 cm 40 cm

Figure 2. Configuration conductor between Myaungta Gar and Hlaingthar Yar

a b c

25 ft 25 ft

40 cm 40 cm 40 cm

Figure 3. Configuration conductor between Hlaingthar Yar and Bayint Naung

a b c

25 ft 25 ft

40 cm 40 cm 40 cm

Figure 4. Configuration conductor between MyaungtaGar and HlawGar

25 ft25 ft

Figure 5 . Configuration Conductor between Hlaw Gar and ThakeTa

Capacitive Susceptance:

For short lines, the total capacitive susceptance is so small that is may be omitted. In so far

as the handling of capacitance is concerned, open wire 60 Hz lines less than about 50 mile

long are short lines. Medium- Length lines are roughly between 50 and 150 mile long.

Lines more than 150 mile long require calculation in terms a high degree of accuracy is

required, although for some purposes a lumped parameter representation can be used for

lines up to 200 mile long.

Results Data for Capacitor Banks of MyauntaGar Primary Substation

The line resistance and inductive reactance are 3.8279 and 11.37763 Ω. After power factor

correction (compensation), power factor is 0.966 (lagging). When the receiving end

voltage is 230 kV, the capacitor’s size of 130 MVAR will be installed. However, the size

of capacitor will be installed 30 MVAR which is used in the form of three parallel 10

MVAR capacitor banks when the receiving end voltage is 225 kV because this power

system can be economically convenient.

Figure 6 and 7 show curve and chart of variable data for Myaungta Gar-Hlaingthar Yar

primary substation. If the receiving end voltage improves to 225 kV, size of capacitor is30

MVAR, whereas if receiving end voltage improves to 230 kV, size of capacitor is 130

MVAR for 160 MW and 70 MVAR load as shown in Fig 7. So, size of capacitor must be

chosen small size than large size for economic cost. Moreover, both receiving end voltage

and sending voltage are a little regulation. And then, maximum sending end voltage gets

230.1 kV from data collection of primary substation for one month. So, improve voltage

can choose 225 kV. The more the load increase, the more size of capacitor increase.


225 226 227 228 229 230150

125

100

75

50

25

0

25

50

75

100

Voltage (kV), Vi

Pow

e F

acto

r,S

uppl

y C

urre

nt, S

ize

of C

apac

itors

pfi 100

Isi 100

Qi

Vi

Figure 6. Curve of variable data for Myaungta Gar – Hlaingthar Yar Primary Substation

0

50

100

150

200

250

PL(MW) 160 170 180 190 200

QL(MVAR) 70 80 90 100 110

Qr(MVAR) 30 40 50 70 80

Qr2(MVAR) 130 140 150 170 180

Voltage(kV) 225 225 225 225 225

Voltage2(kV) 230 230 230 230 230

1 2 3 4 5

Figure 7. Chart of variable data for Myaungta Gar – Hlaingthar Yar Primary Substation


Results Data for Capacitor Banks of HlaingtharYar Primary Substation


correction (compensation), power factor is 0.946 (leading). When the receiving end voltage

is 230 kV, the capacitor’s size of 50 MVAR will be installed which is used in the form of

two parallel 25 MVAR capacitor banks because this power system can be economically

convenient. However, the size of capacitor will be installed 270 MVAR when the receiving

end voltage is 225 kV.

Figure 8 and 9 show curve and chart of variable data for HlaingtharYar - Bayint Naung

primary substation. If the receiving end voltage improves to 225 kV, size of capacitor is

270 MVAR, whereas if receiving end voltage improves to 230 kV, size of capacitor is 50



and sending voltage are a little regulation. And then, maximum sending end voltage gets

225 kV from data collection of primary substation for one month. So, improve voltage can

choose 230 kV. The more the load increase, the more size of capacitor increase.

225 226 227 228 229 230100

60

20

20

60

100

140

180

220

260

300

Voltage (kV), Vi

Po

wer

Fac

tor,

Su

pp

ly C

urr

ent,

Siz

e o

f C

apac

ito

rs

pfi 100

Isi 100

Qi

Vi

Figure 8. Curve of Variable Data for Hlaingthar Yar - Bayint Naung Primary Substation


0

50

100

150

200

250

300

PL(MW) 70 80 90 100 110

QL(MVAR) 25 35 45 55 65

Qr(MVAR) 50 60 80 90 100

Qr2(MVAR) 270 260 250 230 220

Voltage2(kV) 225 225 225 225 225

Voltage(kV) 230 230 230 230 230

1 2 3 4 5

Figure 9. Chart of variable data for Hlaingthar Yar - Bayint Naung Primary Substation

Results Data for Capacitor Banks of Hlaw Gar Primary Substation



voltage is 230 kV, the capacitor’s size of 100 MVAR will be installed. However, the size

of capacitor will be installed 10 MVAR which is used in the form of ten parallel 2 MVAR

capacitor banks when the receiving end voltage is 225 kV because this power system can

be economically convenient.

Figure 10 and 11 show curve and chart of variable data for Myaunta Gar - Hlaw Gar

primary substation. If the receiving end voltage improves to 225 kV, size of capacitor is 10




and sending voltage are a little regulation. Then, maximum sending end voltage gets 230

kV from data collection of primary substation for one month. So, improve voltage can

choose 225 kV. The more the load increase, the more size of capacitor increase.


225 226 227 228 229 230150

125

100

75

50

25

0

25

50

75

100

Voltage (kV),Vi

Po

wer

Fac

tor,

Su

pp

ly C

urr

ent,

Siz

e o

f C

apac

ito

rs

pfi 100

Isi 100

Qi

Vi

Figure 10. Curve of variable data for Myaungta Gar - Hlaw Gar Primary Substation

0

50

100

150

200

250

PL(MW) 150 160 170 180 200

QL(MVAR) 55 65 75 85 105

Qr(MVAR) 10 5 20 30 60

Qr2(MVAR) 100 120 140 150 180

Voltage(kV) 225 225 225 225 225

Voltage2(kV) 230 230 230 230 230

1 2 3 4 5

Figure 11. Chart of Variable Data for Myaungta Gar - Hlaw Gar Primary Substation


Results Data for Capacitor Banks of Thake Ta Primary Substation



voltage is 230 kV, the capacitor’s size of 30 MVAR will be installed which is used in the

form of three parallel 10 MVAR capacitor banks because this power system can be

economically convenient. However, the size of capacitor will be installed 90 MVAR when

the receiving end voltage is 225 kV.

Figure 12 and 13 show curve and chart of variable data for Hlaw Gar - Thake Ta

primary substation. If the receiving end voltage improves to 225 kV, size of capacitor is 90


MVAR for 60 MW and 20 MVAR load as shown in Figure 13. So, size of capacitor must

be chosen small size than large size for economic cost. Moreover, both receiving end

voltage and sending voltage are a little regulation. And then, maximum sending end

voltage gets 235 kV from data collection of primary substation for one month. So, improve

voltage can choose 230 kV. The more the load increase, the more size of capacitor

increase.

225 226 227 228 229 230100

80

60

40

20

0

20

40

60

80

100

Voltage (kV), Vi

Po

wer

Fac

tor,

Sup

ply

Curr

ent,

Siz

e of

Cap

acito

rs

pfi 100

Isi 100

Qi

Vi

Figure 12. Curve of variable data for Hlaw Gar - Thake Ta Primary Substation


0

50

100

150

200

250

PL(MW) 60 70 80 90 100

QL(MVAR) 20 30 40 50 60

Qr(MVAR) 30 45 55 70 80

Qr2(MVAR) 90 75 65 50 40

Voltage2(kV) 225 225 225 225 225

Voltage(kV) 230 230 230 230 230

1 2 3 4 5

Figure 13. Chart of variable data for Hlaw Gar - Thake Ta Primary Substation

Conclusions

In this paper, the primary substation Myaungta Gar - Hlaingthar Yar, Hlaingthar Yar -

Bayint Naung, Myaungta Gar - Hlaw Gar and Hlaw Gar - Theka Ta are considered for

improve receiving end voltage by using capacitor banks. Capacitor banks will be used in

this primary substation 230 kV operation. If power system is needed to consider for

economically cost, capacitor bank will be used to control reactive power, power factor,

voltage. Installing capacitor bank at 230 kV voltage side of primary substation for voltage

improvement are benefited to reduce loss, supply current and improve power factor. The

calculated programming language used in this paper is MATHCAD software and easy to

understand, easy to modify for future expansion if necessary.

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Documents

DESIGN CALCULATION FOR VOLTAGE IMPROVEMENT IN … DESIGN-CALCULATION-FOR-VOLTAGE...DESIGN CALCULATION FOR VOLTAGE IMPROVEMENT IN PRIMARY SUBSTATION BY USING MATHCAD ... in this paper