# POWER FAULT DETECTION BY VOLTAGE MEASUREEMNT METHOD

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#### POWER FAULT DETECTION BY VOLTAGE MEASUREEMNT METHOD

POWER FAULT DETECTION BY VOLTAGE MEASUREEMNT METHOD

1 M.Tech Scholar, Doon Valley College of Engineering

2 M.Tech Scholar, GITAM Jhajjar

3A.P, Doon Valley College of Engineering

1. INTRODUCTION

Fault location and distance estimation is very important issue in power system engineering in order to clear fault quickly and restore power supply as soon as possible with minimum interruption. This is necessary for reliable operation of power equipment and satisfaction of customer. In the past several techniques were applied for estimating fault location with different techniques such as, line impedance based numerical methods, travelling wave methods and Fourier analysis [1]. Nowadays, high frequency components instead of traditional method have been used [2]. Fourier transform were used to abstract

a

o

fundamental frequency components but it has been

frequency domain. Hence a Discrete Wavelet Transform (DWT) is used in this paper because it is very effective in detecting fault- generated signals as time varies [8]. This paper proposes a wavelet transform based fault locator algorithm. For this purpose, 330KV,300km,50Hz transmission line is simulated using power system BLOCKSET of MATLAB [5].The current waveform which are obtained from receiving end of power system has been analysed. These signals are then used in DWT. Four types of mother wavelet, Daubechies (db5), Biorthogonal (bio5.5), Coiflet (coif5) and Symlet (sym5) are considered for signal processing.

2. WAVELET TRANSFORM

Wavelet transform (WT) is a mathematical technique used for many application of signal processing [5].Wavelet is much more powerful than conventional method in processing the stochastic signal because of analysing the waveform in time scale region. In wavelet transform the band of analysis can be adjusted so that low frequency and high frequency components can be windowing by different scale factors. Recently WT is widely used in signal processing application such as de noising, filtering, and image compression [3]. Many pattern recognition algorithms were developed based on the wavelet transform. According to scale factors used the wavelet can be categorized into different sections. In this work, the discrete wavelet transform (DWT) was used. For any function (f), DWT is written as.

shown that Fourier Transform based analysis

DWT f(m, k) = 1

x(n)<p[k-noboam]

(1)

((J

Jaom n m

sometimes do not perform time localisation of time

varying signals with acceptable accuracy. Recently wavelet transform has been used extensively for estimating fault location accurately. The most important characteristic of wavelet transform is to analyze the waveform on time scale rather than in

Where <p is the mother wavelet [3], amis the scale parameter, n0 , b0 , am are the translation parameters.

0

3. TRANSMISSION LINE EQUATIONS

A transmission line is a system of conductors

connecting one point to another and along which

electromagnetic energy can be transmission lines are a typical transmission lines. The transmission

sent. Power example of line equations

that govern general two-conductor uniform transmission lines, including two and three wire lines, and coaxial cables, are called the telegraph equations. The general transmission line equations are named the telegraph equations because they were formulated for the first time by Oliver Heaviside (1850-1925) when he was employed by a telegraph company and used to investigate disturbances on telephone wires [1]. When

Figure 1 Single phase transmission line model

In this equation, 8 is a complex quantity which is known as the propagation constant, and is given by

one considers a line segment __ with parameters resistance (R), conductance (G), inductance (L), and capacitance (C), all per unit length, (see Figure 3.1)

(12)

Where, ; is the attenuation constant which has an influence on the amplitude of the wave, and the phase

the line constants for segment dx are Rdx, Gdx, Ldx,

and Cdx. The electric flux and the magnetic flux

constant which has an influence on the phase shift of the wave. Equations (7) and (8) can be solved by

created by the electromagnetic wave which causes

the instantaneous voltage U(x,t), & and current i(x,t) are:

(2)

(3)

Calculating the voltage drop in the positive direction of x of the distance one obtains

(4)

If __ '1 cancelled from both sides of equation (4), the voltage equation becomes

(5)

Similarly, for the current flowing through G and the current charging C, Kirchhoffs current law can be applied as

(7)

transform or classical methods in the form of two arbitrary functions that satisfy the partial differential equations. Paying attention to the fact that the second derivatives of the voltage > and current 'functions, with respect to t and x, have to be directly proportional to each other, so that the independent variables t and x appear in the form [1]

(14)

Where Z is the characteristic impedance of the line and is given by

(15)

A1 and A2 are arbitrary functions, independent of x To find the constants A1and A2 it has been noted that when x=0, u(x) = uR and i(x) = ir from equations (13) and (14) these constants are found to be

fact that when the current and propagates & will decrease in increasing .

voltage waves amplitude for

(17)

The expressions of line impedance, Z and admittance Y are given by

(8)

(9)

Differentiate once more with respect to x, the second- order partial differential equations

Upon substitution in equation in (13) and (14) the general expression for voltage and current along a long transmission line become

(19)

The equation for voltage and currents can be rearranged as follows

(21)

(26)

4. RESULTS & DISCUSSION

(23)

(25)

Rewriting the above equations (24) and (25) in term of ABCD constants we have

A MATLAB simulink model for that is shown figure

1. To determine the fault location DCT-DWT algorithm has been used in my case. The current before and after fault occurrence is given to the DCT block which after that passes through DWT. A four level DWT is used with mother wavelet db4 for best results.

Figure 1: Complete MATLAB model for proposed algorithm

-188

x 10

4

3

DWT of Fault Current at Bus1

In my work results for fault location algorithm will be checked with all types of faults along with for different mother wavelets function. Initially a three phase fault

2

Iabc

1

0

0 500 1000 1500

time

2000 2500

is given at a distance of 97 km from sending end. The

DWT of fault current for three types of faults: three phase, double phase to ground, single phase to ground is shown in following graphs. The four level discrete wavelet transform is used with mother wavelet db6.

-188

x 10

4

3

Iabc

2

1

DWT of Fault Current at Bus2

These graphs are shown when fault was at a distance of

0

0 500 1000 1500

time

2000 2500

97 km from the sending end.

Figure 2: DWT of three phase fault current using db6 for three phase fault

speed

 Time Time on Location 296688 0.02105 0.0219 35 34.6 -0.4 296688 0.0209 0.0215 73 73.4936 0.4936 296688 0.02156 0.022 97.50 97.23 -0.27 296688 0.02005 0.0204 111 110.58 -0.42 296688 0.0242 0.02421 160 161 1

-188

x 10

4

DWT of Fault Current at Bus1

3

Iabc

2

1

0

0 500 1000 1500 2000 2500

time

-188

x 10

4

3

Iabc

2

DWT of Fault Current at Bus2

1

0

0 500 1000 1500 2000 2500

time

Figure 3: DWT of double phase fault to ground current using db6

Fault location has been found out at various locations as

-188

x 10

4

3

Iabc

2

1

DWT of Fault Current at Bus1

shown in above table. The results for three phase faults are shown in above table. By using DWT-DCT and even for four scaling of DWT our algorithm works well. A graph between real location and calculated location by

0

0 500 1000 1500 2000 2500

time

our proposed method is shown in figure below.

Graph between calculated distance and actual distance

1

0.8

-188

x 10

DWT of Fault Current at Bus2

180

 Actual Fault Distance alculated Fault Distance

C

160

Iabc

0.6

Fault Distance calculated from Sending Station

0.4 140

0.2

0

0 500 1000 1500 2000 2500

time

120

Figure 4: DWT of single phase fault to ground current using db6 The above graphs for different faults classify the types of faults by using DWT. In three phase faults the wavelet magnitude of all three phases is highest at some points as shown in figure by three different colors indicating three phases, whereas in two phase only two phase wavelet magnitudes is highest at some

100

80

60

40

20

1 1.5 2 2.5 3 3.5 4 4.5 5

Time

points because of fault occurrence at that location and for single phase only single coloured magnitude is showing its highest value at the time of fault occurrence. This is the way to classify and detect the type of fault in transmission line.

The fault location is found out by travelling wave formula as given

d = L v(tr ts)

2

Where d = fault distance from the sender end V = velocity of travelling wave

tr = time at the receiving end ts = time at the sending end L = total length of line

To measure the time of fault occurrence in DWT-DCT transform, the time of first peak of fault is checked. For that the time period taken by fault in reaching to bus 2 is calculated. In our above case that time taken is 0.00044. A table given below shows all factors.

Table1: Fault Location for fault at various positions

Figure 6.4: Graph between calculated fault distance and real fault distance

Above graph clearly shows that our proposed algorithm DWT-DCT fault location detection with the help of travelling wave calculates fault location almost exactly to the actual fault location. These all results classifiy the various types of faults and calculates the fault location from the sending end considering the first peak of wavelet transform.

REFERENCES

[1]. K.G. Firouzjah, A. Sheikholeslami, A Current Independent Method Based On Synchronized Voltage Measurement For Fault Location On Transmission Lines, Simulation Modelling Practice And Theory 17 (2009) 692707

[2]. Adly A. Girgis David G. Hart William L. Peterson, A NEW FAULT LOCATION TECHNIQUE FOR TWO- AND THREE-

TERMINAL LINES, Transactions On Power Delivery, Vol. 7 No.1, January 1992

 Travelling wave Sender Receiver RealLocati Calculated Error(Km)

[3]. Amir A.A. Eisa, K. Ramar, Accurate One-End Fault Location For Overhead Transmission Lines

In Interconnected Power Systems, Electrical Power And Energy Systems 32 (2010) 383389

[4]. IEEE Guide For Determining Fault Location On AC Transmission And Distribution Lines Sponsored By Power System Relaying Committee Of The IEEE Power Engineering Society On IEEE Std C37.114-2004(R2009)

[5]. Carlos Eduardo De Morais Pereira And Luiz Cera Zanetta, Jr., Senior Member, IEEE, Fault Location In Transmission Lines Using One-Terminal Postfault Voltage Data, IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 19, NO. 2,

APRIL 2004

[6]. LI Yongli ZHANG Yi MA Zhiyu, FAULT LOCATION METHOD BASED ON THE PERIODICITY OF THE TRANSIENT VOLTAGE TRAVELING WAVE

[7]. Zijad Galijasevic, Student Member, IEEE, And Ali Abur, Senior Member, IEEE, Fault Location Using Voltage Measurements, IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 17, NO. 2, APRIL 2002