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.

1. INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &
Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
TECHNOLOGY (IJEET)
17 – 19, July 2014, Mysore, Karnataka, India
ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 5, Issue 8, August (2014), pp. 64-75
© IAEME: www.iaeme.com/IJEET.asp
Journal Impact Factor (2014): 6.8310 (Calculated by GISI)
www.jifactor.com
IJEET
© I A E M E
WAVELET BASED DOUBLE- LINE AND DOUBLE LINE -TO- GROUND
FAULT DISCRIMINATION IN A THREE TERMINAL TRANSMISSION
CIRCUIT
J.Uday Bhaskar1, Sk. Abdul Gafoor2, J.Amarnath3
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,
64
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

2. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
17 – 19, July 2014, Mysore, Karnataka, India
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.
65
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 (t) and wavelet (t) are
defined by the following equations.
(t) = 2h(n) (2t-n),
(t) = 2g(n) (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.

3. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
17 – 19, July 2014, Mysore, Karnataka, India
66
3. FAULT DISCRIMINATION
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=0.1888/km,R1=0.02/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

4. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
17 – 19, July 2014, Mysore, Karnataka, India
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.
67

5. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
17 – 19, July 2014, Mysore, Karnataka, India
Figure-5. A-B fault from T23T2 at 600 inception angle
Figure-6. A-B-G fault from T23T2 at 600 inception angle
Figures 5,6 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 T2 along its path towards terminal T3 with
variation in distance.
Figure-7. A-B fault from T31T3 at 600 inception angle
68

6. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
17 – 19, July 2014, Mysore, Karnataka, India
Figure-8 .A-B-G fault from T31T3 at 600 inception angle
Figures 7,8 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 T3 along its path towards terminal T1 with
variation in distance.
Figure-9.A-B fault from T12T1 at 100km.
Figure-10.A-B-G fault from T12T1 at 100km
69

7. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
17 – 19, July 2014, Mysore, Karnataka, India
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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8. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
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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

9. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
17 – 19, July 2014, Mysore, Karnataka, India
CASE-2. A-B-G fault with 600 FIA and Rf =5 Ohms along T12T1
Distance, km Ia Ib Ic Th
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
CASE-3. A-B fault with 600 FIA and Rf =5 Ohms along T23T2
Distance, km Ia Ib Ic Th
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
CASE-4. A-B-G fault with 600 FIA and Rf =5 Ohms along T23T2
Distance, km Ia Ib Ic Th
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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10. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
17 – 19, July 2014, Mysore, Karnataka, India
CASE-5. A-B fault with 600 FIA and Rf =5 Ohms along T31T3
Distance, km Ia Ib Ic Th
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
CASE-6. A-B-G fault with 600 FIA and Rf =5 Ohms along T31T3
Distance, km Ia Ib Ic Th
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
CASE-7. A-B fault with 600 FIA and Rf =5 Ohms along T12T1
Fault inception
Ia Ib Ic th
Angle(Degrees)
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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11. Proceedings of the 2nd International Conference on Current Trends in Engineering and Management ICCTEM -2014
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CASE-8. A-B-G fault with 600 FIA and Rf =5 Ohms along T12T1
74
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.
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