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International Journal of Applied Research and Studies (iJARS)

ISSN: 2278-9480 Volume 3, Issue 1 (Jan - 2014)

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Manuscript Id: iJARS/707 1

Review Paper

Power Flow Analysis of 110/11KV Substation Using ETAP

Authors:

1 Aswani R *, 2

Sakthivel R

Address For correspondence:

1 PG Scholar, Department of Electrical and Electronics Engineering V.S.B Engineering College, Karur 2 Asst. Professor, Department of Electrical and Electronics Engineering, V.S.B Engineering College,

Karur, India.

Abstract— Power flow analysis is the study of Real and

reactive power flow through the various buses and lines in

power system. In this paper power flow of a 110/11kV

Substation is analysed and during the analysis under voltage

and over voltage problems are found, These are reduced by

using capacitor bank at the suitable location .The analysis is

done by using an advanced software known as ETAP 12

version. The inputs given are based on the real time data

collected from a 110/11kV substation under K.S.E.B.

Keywords— Load flow Analysis, ETAP, Voltage

Intensification, Power factor improvement, Reactive Power

compensation

I. INTRODUCTION

In the study of power systems power flow study has the

significant importance. Power flow study deals with the study

of various quantities of the power systems such as real power,

reactive power, and magnitude of voltage and angle of voltage.

Load flow study is done on a power system to ensure that

generation supplies load and losses. From load flow study, we

can ensure that bus voltage should be near to the rated values

and the generation operates within real and reactive power

limits. We can insure that transmission lines and transformers

are not overloaded.

The objective of load flow analysis is in the planning stage

of new networks, adding and erection of a new network to the

existing substation. It gives the nodal voltages and phase

angles, power injection at all the buses and power flows

through interconnecting power channels. It is helpful in

determining the best location as well as optimal capacity of

proposed generating station, substation and new lines. It

determines the voltage of the buses and keeps within the

closed tolerances.

From the load flow analysis the location of maximum

voltage variation can be obtained. Due to load fluctuations

during peak load conditions under voltage problems also will

be present. But during some other load conditions over

voltage or over load conditions may occur. Many software are

available for load flow analysis of huge power system. On

these Electrical Transient Analyzer Program (ETAP) is very

effective.

II. POWER FLOW ANALYSIS USING NEWTON RAPHSON

METHOD

Power flow analysis is the study of power system under

steady state conditions subject to certain inequality constraints

under which the system operates. These constraints may be

load nodal voltages, reactive power generation of the

generators, the tap settings of a tap changing under load

transformer etc. The load flow solution gives the nodal

voltages and phase angles and hence the power injection at all

the buses and power flows through inter connecting power

channels. Load flow solution is essential for designing a new

power system and for planning extension of the existing one

for increased load demand. These analyses require the

calculation of numerous load flows under normal and

abnormal operating conditions.

Load flow solution gives the initial conditions of the system

when transient behaviour of the system to be studied. Load

flow solution can be done for balanced and unbalanced

conditions. The load flow solution of a system involves

mainly three steps.

[email protected] *Corresponding Author Email-Id

mailto:[email protected]



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They are drawing of single line diagram of network,

Formulation of network equations and suitable mathematical

equations for the solution of the equations. The mathematical

techniques include Gauss-Siedel method, Newton raphson

method, advanced newton raphsons method and Fast

decoupled method etc. In this paper load flow problem is

solved by using Newton raphson method.

(1)

(2)

(3)

These three sets of equations are the load flow equations

which are non linear equations in terms of real and imaginary

components of nodal voltages. Here Pp,Qp for a load bus and

Pp ,Vp for a generator bus are specified and eP and fP are

unknown quantities .For n-bus systems ,the number of

unknown are 2(n-1) because the voltage at slack bus is known

and is kept fixed both in magnitude and phase angles. Newton

raphson method is an iterative method which approximates the

set of non linear simultaneous equations to a set of linear

simultaneous equations using Taylor’s series expansion and

the terms are limited to first approximation.Electrical

Transient Analyser program (ETAP) is one of the efficient

software used to analyse the very complex power systems .

The advantage of this method over other method makes it

suitable to our analysis. The number of iterations to be

performed by N-R method is less compared to G-S method.

Also the number of iteration is less dependent on size of the

system. The convergence characteristics of N-R method are

not affected by the selection of a slack bus. So inorder to solve

the problems of large systems like substations, it is very

advantageous to use this method.

II .STUDY SYSTEM

The system under study is one of the 110kV substations

under Kerala state electricity board. It consists of four power

transformers, Circuit breakers, Current transformers, potential

transformers, Lightning arresters ,Isolators, Many feeders etc. This substation is a step down as well as distribution

substation. There are four 110kV feeders. There are two

40MVA 110/66kV transformers .these transformers are

normally operated in parallel. Two 10 MVA transformer are

used to step down 66kV to 11kV.There are two numbers of

20MVAr shunt capacitor bank and are used to improve the

power factor. All 110kV circuit breakers are SF6 and motor

operated. All 66kV circuit breakers are SF6 type out of these

three are and pneumatically operated mechanism.

The sub transmission voltage 66kV line can serve as a

source to distribution substation. Distribution substation is

located near to the end user.

Fig.1 Single line diagram of substation

Distribution substation transformer changes the

transmission or sub transmission voltage to lower level for use

by end user. The distribution voltage is 11kV.

Both 110kV and 66Kv are single bus arrangement. There

are two incomer to 11kV switch gear panel; these are from

both 10 MVA transformer is not meant for parallel operation.

There is a bus coupler arrangement in 11kV panel. Normally

these two buses are working independently. Bus coupler can

close when other incomer is absent. There are six outgoing

feeders including one station auxiliary. The distance of 110kV

line is 40.93KM.

III.SIMULATION OF 110/11 kV SUBSTATION in

ETAP

The Fig 2 is the simulation diagram used to simulate the

above substation. The power grid will supply power to the

110kV Bus 1.Transformer 1 and 2 supply power to 66kV

buses. The transformers 3 and 4 will supply power to 11kV

buses. The six feeders are emanating from bus 7.



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Fig 2.Simulated diagram of 110/11kV substation using ETAP

IV.LOAD FLOW ANALYSIS

Fig. 3 shows the Load Flow Analysis of the 110/11 kV substation carried out using ETAP in which Newton- Raphson

method [5],[6] is used and it is observed that at the Bus 7and

Bus 14 there is under voltage which can be clearly seen

from Fig.4 showing the sectional view of the feeders. At Bus

The above table shows the following details of under

voltage.

Fig 3.Load flow analysis of 110/11kV substation

Fig.4 Sectional view of feeders

From the sectional view it is clear that bus 7 and 14 are at under voltage. Only it operates with 89.3% of rated value.

The red indicates the abnormal condition in ETAP .Here it is

under voltage problem.

Table 1 shows the power flowing through the system; both

real and reactive power can be obtained from this study. The

power factor can be also obtainable from the analysis. From

this it is clear that power factor is very low in the range o.8 is

obtaining. The goal of a power flow study is to obtain

complete voltage angle and magnitude information for each

bus in a power system for specified load and generator real

power and voltage conditions

TABLE I

TABLE II

Description MW MVAR MVA % Power

factor

Swing Bus 7.709 5.445 9.438 81.68 lag

Total Demand 7.709 5.445 9.438 81.68 lag

Total Static Load 1.271 0.745 1.474 86.22 lag

Total Motor Load

6.371 3.735 7.385 86.27 lag

Apparent Losses 0.066 0.965 - -

Transformer T21 0.016 0.0731 - -

Transformer T23 0.016 0.0731 - -

Monitoring

Points

kV

MW

Mvar

%PF

BUS 2*

110

7.709

5.445

81.7

BUS 7

11

3.854

2.722

81.7

BUS 14

11

7.706

5.228

82.4



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Device

Condition Rating Operating kV

Operating % ID

Not at Under

Bus 7 Voltage 11 kV 10.805 98.23

Not at Under

Bus 14 Voltage 11 kV 10.827 98.43

V. LOAD FLOW ANALYSIS WITH VOLTAGE

INTENSIFICATION

The simulation of 110/11kV substation is carried out in

Electrical Transient Analyzer Programme by placing the

capacitor bank at shunt with 11kV feeders .The rating of

capacitor bank is 9 Mvar. Fig 5 shows the load flow analysis

of this arrangement. Fig 6 shows the sectional view of this

arrangement.

Fig 5.Simulated diagram of 110/11kV substation

From the load flow analysis, it can be seen that the

operating voltage of bus 7 has improved from 89.3% to

98.35%.This is shown in fig 6.

Fig.6 Power flow analysis of 110/11kV substation

Fig.7 sectional view of 11kV feeders

Table III on comparing with table I, the voltage profile is

improved and also power factor, real power and reactive

power flows were improved.

TABLE III

Table IV shows demand and losses. These are also

improved due to the presence of shunt capacitor banks.

Therefore voltage profile is enhanced due to the placement of

capacitors at 11 kV side.

TABLE IV

VI.CONCLUSIONS

In this paper power flow study of 110/11kV substation using

ETAP is carried out to overcome the low power factor and

under voltage problem. Load flow study using ETAP software

is an excellent tool for system planning. A number of

operating procedures can be analysed such as the loss of

generator, a transmission line, a transformer or a load. Load

flow studies can be used to determine the optimum size and

Monitoring points

kV MW Mvar %PF

Bus 2 110 7.957 1.4 98.5

Bus 7 11 2.83 1.1 98.18

Bus 14 11 2.83 1.1 98.18



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location of capacitors to surmount the problem of an under

voltage. Also, they are useful in determining the system

voltages under conditions of suddenly applied or disconnected

loads. Load flow studies determine if system voltages remain

within specified limits under various contingency conditions,

and whether equipment such as transformers and conductors

are overloaded. Load-flow studies are often used to

identify the need for additional generation, capacitive, or

inductive VAR support, or the placement of capacitors and/or

reactors to maintain system voltages within specified limits.

REFERENCES

[1] Rohit Kapahi, ”Load flow analysis of 132kV substation using

ETAP software”, International Journal of Scientific

&Engineering Research Volume 4,Issue 2,February 2013 ISSN

2229-5518.

[2] Pravin Chopade1 and Dr. Marwan Bikdash, “Minimizing Cost

and Power loss by Optimal Placement of Capacitor using

ETAP”, 978-1-4244-9593-1/11/ ©2011 IEEE 24.

[3] M.A.Pai, “Computer Techniques in Power System Analysis”,

second edition, ISBN: 0-07-059363-9, Tata McGraw Hill

[22005].

[4] R.O.Gorman and M.A.Redfern,”Voltage Control Problems on

Modern Distribution Systems” Proceedings of the IEEE Power

Engineering Society General Meeting IEEE Publication, ISBN

0-7803-X, Denver, Jul2004.

[5] M.P.Selvan and K.S. Swarup, “Distribution System Load Flow

using Object-Oriented Methodology”,2004 international

Conference

on Power system technology-POWERCON 2004, Singapore,

21-24 Nov.2004.

[6] J.Arrillaga and N.R.Watson “Computer Modelling of

Electrical Power Systems”, second edition, ISBN: 978-0-

471-87249-8, John Wiley and Sons June 2001.

[7] Charles Mozina “Undervoltage Load Shedding”, ISBN: 978-

1-4244-0855-9, IEEE, Page(s): 39-54.

[8] D.M. Tagare Reactive power management Mc-Graw Hill

2000.

[9] Rani and Vijaya, “Distribution system loss reduction by

capacitors”, Proceedings of National Conference on Emerging

Trends in Engineering (2000), Husur.

Distribution Feeders with Distorted Substation Voltages”, IEEE

Trans. on Power Delivery, Vol. 5, No. 2, April 1990, pp. 650-

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