Wavelet based double line and double line -to- ground fault discrimination in a three terminal transmission circuit

Proceedings of the 2nd

International Conference on Current Trends in Engineering and Management ICCTEM -2014

17 – 19, July 2014, Mysore, Karnataka, India

64

WAVELET BASED DOUBLE- LINE AND DOUBLE LINE -TO- GROUND

FAULT DISCRIMINATION IN A THREE TERMINAL TRANSMISSION

CIRCUIT

J.Uday Bhaskar1, Sk. Abdul Gafoor

2, J.Amarnath

3

1Department of EEE, DMS SVH College of Engineering, Machilipatnam A.P,India

2Centre for INFORMATION AND COMMUNICATION TECHNOLOGIES,

Indian Institute of Technology, Jodhpur, Rajasthan, India, 3Department of EEE, University College of Engineering, JNTUH, Hyderabad,

ABSTRACT

In this paper, an accurate method to discriminate double line and double line to ground faults

in a three terminal transmission circuit based on wavelet transforms is presented. The proposed

algorithm uses the fault indices of three phase currents of all terminals. Fault indices are obtained by

1st level decomposition of current signals using Bior 1.5 mother wavelet considering the variations

in fault resistance, fault inception angle and distance along the transmission circuit. The entire test

results clearly show that the variation in the value of fault index of the healthy phase with the

presence of ground and constant value in the case of non- presence of ground which discriminates

double line fault from the double line to ground faults in the path along one terminal towards the

other terminal with variations in fault inception angle and fault resistance. The algorithm is proved to

be effective and efficient in detection and discrimination of faults.

Keywords: Double Line Fault, Fault Inception Angle, Fault Indices, Multi Terminal Lines, Wavelet

Transforms.

1. INTRODUCTION

Three terminal lines usually provide right, smart, technical and environmental advantage over

two-terminal lines. Three terminal transmission line protection is complicated as compared with two-

terminal transmission lines since three terminal lines experience additional problems due to the in

feed current from the third terminal, or an out feed to the terminal, differences in line lengths and

source impedances [1]. Much work is done considering two terminal lines with less attention on

three terminal lines. High frequency travelling wave information contained in the post-fault voltage

and current signals are used for the protection of three terminal lines[2]. The main problems in this

method are, it requires high sampling rates and difficulties in distinguishing travelling waves from

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fault and from remote end of the line. In direction comparison method, the polarity of the fault

generated transient current signals is detected at each end of the circuit and sent to line remote ends

through communication channels[3]. Fault location algorithm for locating unbalanced faults based on

negative sequence quantities from all line terminals for two or three terminals is presented [4]. There

are a number of protection schemes for multi-terminal transmission circuits such as unit and non-unit

schemes. The unit schemes require extensive communication channels between the line ends [5].The

non-unit schemes such as distance protection, experience under-reach and over-reach problems [6].

Brahma and Girgis proposed a fault location scheme for a multi-terminal transmission line using

synchronized voltage measurements at all terminals [7]. If there is a variation in system conditions

and faults involving high arc resistances, the scheme’s effectiveness decreases. Different directional

comparison techniques for multi-terminal lines, which compare the polarity of fault generated

transient current signals are proposed by various researchers [8].

Differential protection scheme for tapped transmission lines has been proposed by B.Bhalija

and R.P.Maheswari where out feed current in case of internal and external faults was considered [9].

Al-Fakhri proposed differential protection scheme for multi-terminal lines using incremental currents

[10].

Villamagna and Crossley presented a current differential protection scheme for high

resistance faults, based on the symmetrical component based current quantities. The accuracy and

effectiveness cannot be guaranteed for the protection of multi-terminal lines [11].

Nagasawa et al used current differentials at terminals to reduce multi-terminals lines to a two-

terminal line. This reduction procedure was very complicated [12]. Funabashi et al utilized

synchronized current inputs from all terminals and developed two different methods to locate the

fault[13]. It failed to report results for three-phase and two-phase to ground faults. Prarthana

Warlyani et al used voltage and current signals of each section of teed circuit to detect and classify

L-L-G faults and the detection was in one cycle [14]. There must be some innovative methods to be

developed for three terminal transmission line protection. In this paper, wavelet multi-resolution

analysis is used for detection and classification of faults on three-terminal transmission circuit. Detail

D1 coefficients of current signals at all the three ends are used to detect and classify the faults. The

current signals are analyzed taking into consideration that sum of the current coefficients at all the

three terminals.

2. WAVELET ANALYSIS

Wavelet Transform (WT) is an efficient means of analyzing transient currents and voltages.

Unlike DFT, WT not only analyses the signal in frequency bands but also provides non-uniform

division of frequency domain i.e. WT uses short window at high frequencies and long window at low

frequencies .This helps to analyze the signal in both frequency and time domains effectively. A set of

basis functions called wavelets, are used to decompose the signal in various frequency bands, which

are obtained from a mother wavelet by dilation and translation Hence the amplitude and incidence of

each frequency can be found precisely. Wavelet Transform is defined as a sequence of a function

h(n)(low pass filter) and g(n) (high pass filter). The scaling function ⱷ(t) and wavelet Ψ(t) are

defined by the following equations.

ⱷ(t) = √2Σh(n) ⱷ(2t-n),

Ψ(t) = √2Σg(n) ⱷ(2t-n)

where g(n) = (-1) n h(1-n). A sequence of h(n) defines a Wavelet Transform. There are

many types of wavelets such as Haar, Daubachies, Symlet etc. The selection of mother wavelet is

based on the type of application. In the following section a novel method of discrimination of faults

using Multi Resolution Analysis of the transient currents associated with the fault is discussed.




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3. FAULT DISCRIMINATION

T1 110KM 110KM T2

110KM

T3

Figure-1. Single line diagram of the system.

Figure-2. Simulink model of the transmission circuit.

The scheme is evaluated using 400KV, 50Hz three terminal transmission system whose line

parameters are R0=0.1888Ω/km,R1=0.02Ω/km, L0=3.5Mh/km,L1=0.94mH/km,C0=0.0083µf/km.,

C1=0.012µf/km.

A sampling frequency of 16KHZ is chosen to capture the high frequency content of current

signals .The system is modeled in Matlab Simulink environment.

The network is simulated for L-L AND L-L-G fault situations occurring at different locations

along the paths of Terminal 1 to Terminal 2, Terminal 2 to Terminal 3 and from Terminal 3 to

Terminal 1. For the types of fault at a particular location, the fault inception angle is varied to




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evaluate the performance of the proposed scheme. Influence of fault resistance also being considered

with value of 5ohms.The three phase currents at all the three terminals are analyzed with Bior 1.5

mother wavelet to obtain the detail coefficients D1 over a moving window of half cycle length.

These D1 coefficients are then transmitted to the remote end.

The performance of the scheme in discriminating the. line-to-line, double-line-to ground is

evaluated. The fault inception angle is varied from 150

to 1800 for the faults. The simulations show

that the fault inception angle has a considerable effect on the phase current samples and therefore on

Wavelet Transform output of post-fault signals.

Figure-3. A-B fault from T12T1 at 600 inception angle.

Figure-4. A-B-G fault from T12T1 at 600

inception angle

Figures 3, 4 indicate that the the variation of fault indices with distance and changes in the

healthy phase without and with the presence of the ground which clearly shows that for the fault

involving the ground, the healthy phase fault index value varies while for the non-ground fault it

remains constant, which is considered for the terminal T1 along its path towards terminal T2 with

variation in distance.




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Figure-5. A-B fault from T23T2 at 60

0 inception angle

Figure-6. A-B-G fault from T23T2 at 60

0 inception angle

Figures 5,6 indicate that the the variation of fault indices with distance and changes in the


involving the ground , the healthy phase fault index value varies while for the non-ground fault it



Figure-7. A-B fault from T31T3 at 600

inception angle




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Figure-8 .A-B-G fault from T31T3 at 60

0 inception angle

Figures 7,8 indicate that the the variation of fault indices with distance and changes in the


involving the ground , the healthy phase fault index value varies while for the non-ground fault it



Figure-9.A-B fault from T12T1 at 100km.

Figure-10.A-B-G fault from T12T1 at 100km




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Figures 9,10 indicate that the the variation of fault indices with inception angle and changes

in the healthy phase without and with the presence of the ground which clearly shows that for the

fault involving the ground , the healthy phase fault index value varies while for the non-ground fault

it remains constant, which is considered for the terminal T1 along its path towards terminal T2 with

variation in fault inception angle.

Figure-11. Current waveforms for-L-L fault

Figure-12. Current waveforms for-L-L-G fault.

Figures 11,12 show the simulated current waveforms in all the Phases and the variations in healthy

phase.




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4.FLOW CHART

The flow chart shows the proposed algorithm to discriminate L-L and L-L-G faults with

increase in the distance.

5.SIMULATED RESULTS

CASE-1. A-B fault with 600

FIA and Rf =5 Ohms along T12T1

Distance, km Ia Ib Ic Th

20 961.11 914.41 158.92 400

40 953.5 906.82 158.92 400

60 945.42 898.73 158.92 400

80 937.01 890.33 158.92 400

100 928.17 881.49 158.92 400

120 928.56 881.89 158.92 400

140 938.17 891.49 158.92 400

160 947.31 900.62 158.92 400

180 956.11 909.42 158.92 400

200 964.43 917.73 158.92 400




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CASE-2. A-B-G fault with 600



20 1256.4 993.3 203.6 400

40 1258.8 981.3 201.8 400

60 1262.1 968 207.1 400

80 1264.8 954.2 201.2 400

100 1269.7 942.7 200.4 400

120 1266 944.2 199.6 400

140 1256.8 956.2 199.8 400

160 1255.8 967.8 211 400

180 1256 978.9 221.2 400

200 1262.6 989.2 233.6 400




20 1048.7 920.7 230.3 400

40 1040.4 911.7 230.3 400

60 1031.6 902.9 230.3 400

80 1022.5 893.7 230.3 400

100 1012.9 884.5 230.3 400

120 1012 883.2 230.3 400

140 1019.8 891.1 230.3 400

160 1027.2 898.5 230.3 400

180 1034.4 905.6 230.3 400

200 1041 912.3 230.3 400




20 1170.8 949.3 258.2 400

40 1165.2 940.9 244.9 400

60 1165.9 930.2 233.2 400

80 1167.8 919 218.2 400

100 1177.6 905.5 203.8 400

120 1181.8 907 189.4 400

140 1176.9 919.8 191 400

160 1174.2 933.5 197.5 400

180 1170.8 946.8 192.2 400

200 1168.4 958.8 199.5 400




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20 1129 922.9 216.7 400

40 1122.4 916.2 216.7 400

60 1115.2 909.1 216.7 400

80 1107.8 901.6 216.7 400

100 1099.9 893.8 216.7 400

120 1100.5 894.9 216.7 400

140 1109.3 903.7 216.7 400

160 1117.7 912.3 216.7 400

180 1125.8 920.9 216.7 400

200 1133.4 929.6 216.7 400




20 1066.6 908.1 156.9 400

40 1056.9 895.9 148.6 400

60 1054 879.7 143.9 400

80 1050.8 863.8 142 400

100 1054.5 847 145.9 400

120 1054.2 843.3 160.9 400

140 1049.9 861.5 169.7 400

160 1052.5 877.4 180.2 400

180 1054.6 893.3 189.1 400

200 1063.4 903.9 199.3 400



Fault inception

Angle(Degrees)

Ia Ib Ic th

15 1732.1 1607.6 230.3 400

30 1726.1 1616.5 230.3 400

45 1733.7 1605 230.3 400

60 1734.1 1623 230.3 400

75 1732 1609 230.3 400

90 1741.8 1616.1 230.3 400

105 1735.3 1622.6 230.3 400

120 1742 1613.7 230.3 400

135 1740.8 1622.4 230.3 400

150 1741.9 1619.6 230.3 400

165 1738.2 1620 230.3 400

180 1743.2 1614.4 230.3 400




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Fault inception

angle(Degrees)

Ia Ib Ic th

15 1576.4 2023.9 236.5 400

30 1587.1 2017.6 229.3 400

45 1580.2 2026.7 229.1 400

60 1581.6 2026.3 228.3 400

75 1591 2023.6 227.3 400

90 1576.9 2035.8 235.8 400

105 1589.1 2038.8 244.4 400

120 1591.2 2027.2 249.5 400

135 1589.5 2036.5 271.2 400

150 1589.5 2036.5 271.2 400

165 1591.9 2020.8 268.7 400

180 1581 2034.6 259.1 400

In all the cases above, the detection of l-l and l-l-g faults is performed with consideration of

threshold value where the healthy phase lies below the threshold value and faulty phases lie above

the threshold value which clearly indicate the type of faults and the discrimination is done by

considering the variations in the fault index value of healthy phase for the double line faults

involving the ground and constant value in the case of double line faults without involvement of the

ground.

6. CONCLUSIONS

The wavelet based double line and double line to ground faults discrimination is done by

considering the variations in distance and fault inception angles along the paths from terminal to

terminal which clearly gives the variations in healthy phase and shows promise in discrimination of

faults and can be applied to discriminate l-l-l faults from l-l-l-g faults within less than half cycle.

7. REFERENCES

[1]. R.K.Aggarwal,D.V.Coury, A.T.Johns and A.Kalam “A practical approach to accurate fault

location on extra high voltage teed feeders’’. IEEE transactions on power delivery, vol.8,July

1993, pp.874-881.

[2]. P.G.Mclarenn, S.Rajendra “Travelling wave technique applied to the protection of teed

circuits: Principle of travelling wave technique”. IEEE transactions on power apparatus and

systems, vol. PAS-104,No.12 December 1985,pp 3544-3550.

[3]. Mao,P.L; BO.Z.Q;Mao,L.Z; Li.R.M, “Protection of teed transmission circuits using a new

directional comparison technique.”Proceedings of international conference on power system

technology(Powercon); 18-2, August 1998,vol.2, pp.1111-1115.

[4]. D.A.Tziouvarous, J.B.Robrts, and G.Benmouyal “ New multi-ended fault location design for

two or three terminal lines.” Proceedings of IEE Development in powersystems protection

conference,2002, pp.395-398.

[5]. Bo, Z.Q.; ‘‘A new non-communication protection technique for transmission lines,’’ IEEE

Trans. Power Deliv., 1998, 13,(4), pp. 1073-1078.




75

[6]. Bhalija,B.,and Maheswari,R.P,; “High resistance faults on two terminal parallel transmission

line; analysis, simulation studies, and an adaptive distance relaying scheme’’, IEEE Trans.

Power Deliv., 2007, 22, (2), pp. 801-812.

[7]. Brahma, S.M and Girgis, A..A.;, ‘‘Fault location on a transmission line using synchronized

voltage measurements,’’ IEEETrans.PowerDeliv.,2009,(4)1619-1622.

[8]. Lyonette,D.R.M.,Bo,Z.Q.,Weller, G., and Jiang,G,; ‘‘A new directional comparison

technique for the protection of teed transmission circuits’’. Power Eng. Soc.Winter Meeting,

IEEE., January 2000, vol.3, pp. 1979-1984.

[9]. Bhalija,B., and Maheswari, R.P; “New differential protection scheme for tapped transmission

line”. IET Gener.Transm. Distrib., 2008 , 2,(2), pp. 271-279.

[10]. Al-Fakhri,B,; ‘‘The theory and application of differential protection of multi-terminal lines

without synchronization using vector difference as restraint quantity-simulation study.”

8th

IEE Int.Conf. dpsp, april 2004, vol.2, pp. 404-409.

[11]. Villamagna, N., and Crossley, P.A.,; “Design and evaluation of a current differential

protection scheme with enhanced sensitivity for high resistance in- zone faults on a heavily

loaded line.” 8th

IEE Int. conf.DPSP, April 2004, vol.2, pp. 410-413.

[12]. T.Nagasawa,M.Abe,N.Otsuzuki,.Emura,Y.Jikihara and M.Takeuchi, “Development of a new

fault location algorithm for multi terminal two parallel transmission lines,” IEEE

Trans.Power Deliv., vol-7. 3, pp. 1516-1532, July-1992.

[13]. T.Funabashi, H.Otoguro, Y.Mizuma, L.Dube, and A.Ametani, “Digital fault location

algorithm for parallel double- circuit multi terminal transmission lines.,” IEEE Trans. Power

Deliv., vol.15. 2, pp. 531-537 April-2000.

[14]. Prarthana Warlyani, Anamika Jain, A.S.Thoke, R.N.Patel “Fault classification and faulty

section identification in Teed transmission circuits using ANN”. International Journal of

Computer and Electrical Engineering, Vol.3, No.6 Dec-2012.