ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
Power Swing Protection of Series Compensated Transmission
Line
Saptarshi Roy
Dr. Suresh Babu Perli
Student M.Tech-PSE
Department of Electrical Engineering
NIT Warangal, WARANGAL,INDIA
Assistant Professor
Department of Electrical Engineering
NIT Warangal, WARANGAL,INDIA
power restoration. Power Swing is caused
by large disturbances in power system,
which if not blocked caused mal-operation
of distance relays and undesired tripping of
breakers,change in load impedance,
unwanted relay operations at different
locations of the network, major poweroutages or even power blackout. If a fault
occurs during the power swing, the relay
must detect the fault and operate quickly.
The detection of faults in a seriescompensated line during power swings is
more challenging due to different
frequency components in the fault signals
which depend on the fault location,
type,level of compensation etc cause the
apparent impedance seen by the relay to
oscillate and imposes difficulty to
distinguish faults from the power swing.
This paper proposes a technique for
detecting faults in a series-compensated
line during the power swing. During
unbalanced faults, the negative-sequence
components become significant and due to
transients in current signals in the initial
period, a negative sequence component is
present even in three-phase faults. To
detect the faults during swing in a seriescompensated line, a cumulative sum
(CUSUM) of change in the magnitude of
the
negative-sequence
current-based
approach is proposed in this paper[5]. The
performance is tested for numerous cases
for an SMIB system and a 9-bus system
simulated
with
SIMULINK/PSCAD.
ABSTRACT- Fault detection during
power swing condition is a challenge for
stable operation of power system due to
several reasons like protection problems,
Voltage/current inversion,sub-harmonic
oscillations and transients especially if it
is series compensated modulation of
voltage and current waveforms with
swing frequency etc. This paper proposes
a
negative-sequence
current–based
technique for detecting presence of fault,
classification of fault occurred, estimated
zone and location of the fault occurred
and the fault inception time with respect
to system reference clock during the
power swing condition in a series
compensated line. In proposed work
negative sequence current was analysed
as it keeps the other parameters in the
system in healthy state. The technique is
tested for different series-compensated
power systems including a SMIB system
and a WSCC-9bus-3machine power
system with their different configurations
and contingency combinations. Power
swing caused by various faults are
simulated with PSCAD / EMTDC and
MATLAB/SIMULINK and compared
with available techniques to prove the
effectiveness of the proposed technique
algorithm.
INDEX TERMS : fault detection, power
swing, series compensation, negative
sequence current, fault classification &
location.
INTRODUCTION:
Fast and accurate determination of a fault
in electrical power system is a vital part in
466
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
Fig3:Current Waveforms during Power Swing
Further we detected the classification of
the fault using fine tuning method and
detected the location of the fault.
Fig4: Voltage Waveforms during Power Swing
PROPOSED FAULT
TECHNIQUE :
DETECTION
The computation steps for the method are
provided
Fig1:Implementation of a Transmission Line using PSCAD
Software
(1)
I2=negative
sequence
current;alpha=exp(j2*pi/3) and Ia,Ib and
Ic are phase currents.
Sk=del(I2k)=I2k-I2k-1.
(2)
For Sk >epsilon,
gk =max (gk-1+Sk-epsilon,0)
(3)
gk = fault index and epsilon = the drift
parameter in it .
A fault is registered if gk>h
(4 )
h is a constant and ideally zero. Epsilon
provides the low-pass filtering effect and
influences the performance of
the
detector. When Sk > epsilon, the gk value
increases
by a factor of difference
between Sk and epsilon.After each fault
detection index g is reset to zero. The
selection of epsilon and h is important for
determining the performance of the
algorithm. Epsilon is a very small quantity
which having a value greater than zero.The
value of h is set such that the algorithm
can maintain the balance between
dependability versus security and speed
versus accuracy requirements of the
relaying scheme.Considering all extreme
fault situations during the power swing we
worked
with
(h)max=0.48
and
(epsilon)max=0.05 value. The proposed
method is based on the CUSUM approach
and, therefore, a distinctly much higher
index value is obtained during the fault.
FAULT DETECTION CHALLENGES
DURING POWER SWING IN SERIESCOMPENSATED LINES:
Series compensation imposes protection
problems.The use of series capacitors in
transmission lines results voltage/current
inversion,sub-harmonic
oscillations,transients, sub -synchronous
oscillations[10].
Fig2: 400KV SMIB Test System.
A test system shown in Fig. 1 is
considered[2]. Both Line-1 and Line-2 are
40% compensated and the capacitors are
placed [10] . The system details are
provided in Appendix A. The system with
the distributed line model is simulated
using
SIMULINK/PSCAD. The
traditional fault detection techniques, like
the sample-to-sample or cycle-to-cycle
comparison of current (or voltage) signals
cannot be reliable during the power
swing[9].
CASE-1:SMIB SYSTEM:
TEST AND RESULTS
467
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
The fault is detected after 4.75 ms of fault
initiation. At the time of fault inception the
fault index g glows enormously high.
Output shows 1 after inception of the fault
and 0 before inception.
The algorithm is tested for different
conditions including balanced and
unbalanced
faults
etc.
Using
SIMULINK/PSCAD with distributed
parameter line model data was generated.
The data-sampling rate was maintained at
4 kHz for the 50-Hz power system.
Line-to-Ground Fault in the SeriesCompensated Line
a)healthy Signal g -t plot b)LG Fault :I2 With Low R
Fig5 : Implementation of SMIB Test System Using PSCAD
c) LG Fault :I2 with fault resistance100 ohm
a)g - t plot
b) output-t plot
Fig6 :(a &b):LG fault Analysis
Fig :8(a,b,c)Performance Analysis of a healthy signal and a
signal containing LG fault
Fault Detection During Single-Pole
Tripping
Initially phase-a of Line-1 is out of service
following an ag- fault occurring during
normal operation. It introduced swing into
the system. A line-to-ground fault of bgtype with a fault resistance 100 Ohm is
created at 0.2s at a distance of 160 km
from the relay location toward bus N
during swing. For this case, and the fault
detection is possible after 0.6-ms fault
inception.
Fig:7 : SIMULINK Implementation of SMIB system
Algorithm is tested for a line to ground
fault of ag–type with a fault resistance of
0.1 ohm initiated at 0.34 sec for 0.04 sec
duration at a distance 240KM from bus1.
a) g - t plot during single pole tripping
468
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
b) I2 - t during Single Pole tripping
Fig:9(a,b):Performance Analysis during Single Pole tripping
condition
Fault Detection During Double-Pole
Tripping
a) g2 vs t plot
b)Fig: I2 - t plot
Fig:10(a,b) Here fault detection is possible after 0.55 ms.
CLASSIFICATION
DETECTED FAULT :
OF
THE
Classification or type of detected fault can
be detected by tracking the absolute
variation of fault index g and the variation
of variation of fault index g (fine tuning
of g).
a) Del g - t for LG fault
b) Delg - t plot for LLLG
c) Del g vs t plot for LL
469
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
segregate LL, LLL from LLG, LLLG
fault.
CLASSIFICATION
FAULTs :
OF
PHASE
The variation of (Variation of) g gradually
diminishes to zero towards the end of fault
duration and this tendency of variation
declining towards zero rapidly increases
w.r.t if any additional Line or ground
involved in the fault.
d) Delg - t plot: LLG fault
e)Delg - t plot : LLL
Fig:11(a,b,c,d,e)Variation of g vs time
CLASSIFICATION OF LG AND NONLG FAULTs :
a) Del(Del g) vs t plot for LL fault
The variation of g in case of a LG fault is
very less with compared to other
case.The maximum variation of fault
index g in case of LG fault 0.16 unit
here,for other fault the value of
(gmax)var goes beyond 0.3 and above
unit.
CLASSIFICATION
FAULTs :
OF
b) Del (Del g) - t plot in case of LLL fault
Fig : 12(a,b): LLL fault the local maxima is missing.
NON-LG
CLASSIFICATION OF
FAULTs :
The trick of the detection is the nature of
the g-variation curve. The variation of g
gradually diminishes to zero towards the
end of fault duration and this tendency of
variation declining towards zero rapidly
increases with respect to if any additional
line or ground involved in the fault. See
the similarities between the plot of gvariation in case of LL and LLL & LLG
and LLLG.In case of LL and LLL there is
a set of
local maxima other than the
global maxima variation (local maxima
approx. 60% of global max.).This is
missing in case of LLG or LLLG.So, by
seeing the local maxima in the plot we can
GROUND
The variation of (Variation of) g gradually
diminishes to zero towards the end of fault
duration and this tendency of variation
declining towards zero rapidly increases ,
if any additional Line or ground involved
in the fault..
a) LLG Del (Del g) - t
470
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
b) LLLG Del (Del g) - t plot
Fig: 13(a,b) :Del(Delg)-t plot for ground involved faults
PREDICTION OF ZONE AND
LOCATION OF THE DETECTED
FAULT :
Fig: 15: WSCC-9 bus System Implementation Using PSCAD
Zone is a function of fault distance. By
analying the time delay to sense the fault
after actual time of inception of the
fault,we can predict the Zone of the fault.
A WSCC-3-machine-9-bus configuration
is considered for the study where a
modification has been incorporated by
providing 40% compensation at the
beginning of line 7–8.The system details
are given in Appendix B.A three-phase
fault is created in line 5–7 at 0.1 s. The
fault is cleared at 0.3 s by opening breaker
B3 and B4.The removal of line caused
swing condition.Different faults are
simulated on line
7-8 to test the algorithm.
Fig: 14: LLG fault detection:time delay vs percentage length
Plot for the SMIB System
Line Length= 320 KM
Trick to find location is to
find fault
impedance .
Zf=( Vf/If) Ohm
Fault Location= (Zf/ Z 1ohm/Km) KM
As it is a 3-Zone Protection scheme
,impedances and time Constants of the
relays varies zone to zone ,so, sometimes it
becomes problematic to detect the exact
location of the fault but of course zone of
the fault we can predict. More the length
increases the algorithm for fault location
identification gives more accurate value.In
case of fault impedance, during healthy
state positive sequence impedance (Z1)
present in the system and the value is
given in the paper. Vf and If can be
obtained from the sampling of the
waveforms we got.
Fig16:Current and Voltage Waveforms of relay bus during the
power swing
a) I2 vs t Plot During Single Pole Tripping Condition
CASE-II-WSCC-9BUS SYSTEM:
TEST AND RESULTS
471
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
with a ground fault resistance of 0.1 is
created at 0.3 s on line
7–8 during the power swing at a distance
of 160 km from the relay location.
b) g - t plot during Single Pole Tripping
Fig:17. Single pole tripping
a) g2 vs t
b)
I2 vs t
Fig 20(a,b): Fault detection.
ANALYSIS
SEQUENCE
CURRENTS
Fig18: Single-Line Diagram of
System
USING
POSITIVE
COMPONENTS
OF
If we replace Ib with Ic and Ic with Ib in
the
negative
sequence
Current
expression,we will get positive sequence
current.We can achieve the same feet
here,if we use positive sequence
components of currents instead of negative
sequence components of currents in our
algorithm.But the use of positive sequence
component of current incurs fault
detection(protection) sensitivity problems,
specially incase of detection of High
Impedance faults (HIFS),low fault current
levels and ground fault detection in case of
involvement of non-linearity in the ground
path[13]-[4]-[14].It
may
imposes
insulation problem also during practical
implementation.
the Modified WSCC 9-bus
Case-1: Line-to-Ground Fault:
An ag- fault with a fault resistance of
0.1ohm is created during the power swing
on line7–8 at a distance of 160 km from
the relay location at
0.3 s. The index increases to a higher value
at the inception of the fault. The technique
is able to detect the fault within half-acycle of its inception.
a) g - t plot
b) I2 - t plot
Fig19(a,b):LG fault analysis
Case-2: Double Line-to-Ground Fault:
The performance of the algorithm for a
double-line-to-ground fault of abg-type
a)g vs t
Fig 21(a,b):LG Fault
components of currents
472
b)I2 vs t
Analysis using positive sequence
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
c) Del (Del g) - t plot
Fig 23(a,b,c):LLG fault Analysis
By analysing the Delg & Del (Delg) - t
plot we got this is a non-LG ground fault
and less inclined to zero . i.e from Delg vs
t plot it is clear that it is either LLG or
LLLG fault and from Del(Delg) vs t, it is
coming as LLG fault.By sampling the
fault
voltages
and
performing
calculations,the fault location was obtained
at 241.07 km with actual fault location of
240 Km.
Accuracy:
Error in measurement of fault distance
from the proposed algorithm is computed
as follows.
a)g vs t
b)I2 vs t
Fig 22(a,b):LLL Fault Analysis using positive sequence
components of currents
CONCLUSIONS
In this paper we have developed a novel
fault detection technique for detecting the
classification and location of the fault.
LLG fault is created at 240 KM distance
during power swing condition. After
analysing it we got below waveform.
Accuracy=(100%-((241.07240)x100%)/240)= 99.554%
Proposed novel fault detection technique
for the series compensated line during the
power swing is presented in this paper to
detect the location and classification of the
fault. It uses fine tuning or the nature of
variation of fault index to detect the
classification of the fault and the fault
impedance calculation for the location of
the fault. The performance of the proposed
algorithm is tested for balanced and
unbalanced faults for different series
compensated systems.
a) Voltage and Current Waveforms
APPENDIX A
System data for SMIB
Geneator:
600MVA,22KV,50HZ,H=4.4MW/MVA
Xd=1.81p.u, Xd’=0.3p.u, Xd’’=0.23p.u,
Td0’=8s,Td0’’=0.03s,X0=1.76p.u.
,Xq’’=0.25p.u,Tq0’’=0.03s,Ra=0.003p.u,
Xp(Potier reactance)=0.15p.u.
b) Del g - t plot
473
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
[3] A. Esmaeilian, A. Ghaderi, M.
Tasdighi, and A. Rouhani, “Evaluation
and performance comparison of power
swing detection algorithms in presence of
series compensation on transmission
lines,” in Proc. 10th Int. Conf.
Environment Elect. Eng., May 8–11, 2011,
pp. 1842–1848.
[4]Normann
Fischer
and
Daqing
Hou,”Methods For Detecting Ground
Faults
in
Medium
Voltage
DistributionPowerSystems”,[2006].[Onlin
e].Available:https://www.selinc.com/Work
Area/DownloadAsset.aspx?id=2385.
[5] F. Gustafsson, Adaptive Filtering and
Change Detection. NewYork: Wiley, 2000.
[6]S. Lotfifard,J. Faiz, and M. Kezunovic,
“Detection of symmetrical faults by
distance relays during power swings,”
IEEE Trans. Power Del., vol. 25, no. 1, pp.
81–87, Jan. 2010.
[7] X. Lin, Y. Gao, and P. Liu, “A novel
scheme to identify symmetrical faults
occurring during power swings,” IEEE
Trans. Power Del., vol.23, no. 1, pp. 73–
78, Jan. 2008.
[8] S. R. Mohanty, A. K. Pradhan, and A.
Routray, “A cumulative sum-based fault
detector for power system relaying
application,”IEEE Trans. Power Del., vol.
23, no. 1, pp. 79–86, Jan. 2008.
[9] R. J. Marttila, “Performance of
distance relay mho elements on
MOVprotected series-compensated lines,”
IEEE Trans. Power Del., vol. 7,no. 3, pp.
1167–1178, Jul. 1992.
[10] Abdolamir Nekoubin,”Simulation of
Series Compensated Transmission Lines
Protected with Mov”, World Academy of
Science, Engineering and Technology
58,pp.1002-1006 2011.
[11] P. K. Nayak, A. K. Pradhan, and P.
Bajpai, “Detecting fault during power
swing for a series compensated line,”
presented at the Int. Conf. Energy, Autom.,
Signal, Bhubaneswar, Odisha, India, Dec.
28–30,2011.
[12] A. Newbould and I. A. Taylor, “Series
compensated
line
protection:System
Transformer:
600MVA,22/400KV,50HZ,D/Y,X=0.163p
.u,
Xcore=0.33p.u,Rcore=0.0p.u,Pcopper=0.0
0177p.u
Transmission lines:
Length=320Km
Positive-sequence impedance=0.12+j0.88
Ohm/Km
Zero-Sequence Impedance=0.309+j1.297
Ohm/Km
Positive-sequence
capacitive
reactance=487.723x1000 Ohm-Km
Zero-sequence
capacitive
reactance=419.34x1000 Ohm-Km.
APPENDIX B
System data for
3-machine 9-bus
configuration:
Gererators
Gen-1: 600 MVA,22KV,50HZ
Gen-2: 465 MVA,22KV,50HZ
Gen-3: 310 MVA,22KV,50HZ
Transformers
T1: 600 MVA,22/400KV,50HZ,D/Y;
T2: 465 MVA,22/400KV,50HZ,D/Y;
T3: 310 MVA,22/400KV,50HZ,D/Y;
Transmission line:
Length of
line 7-8=320Km.,line
9=400Km,line
7-5=310Km.,line
4=350Km,line
6-4=350Km,line
9=300km.
Loads
Load A=300MW+j100MVAr.
Load B=200MW+j75MVAr.
Load C=150MW+j75MVAr.
Other parameter used
are same
APPENDIX A
856-
as
REFERENCES
[1] H. J. Alture, J. B. Mooney, and G. E.
Alexander,
“Advances
in
series
compensated line protection,” 2008.
[Online].
Available:
www.selinc.com/20081022, TP6340-01
[2] S. M. Brahma, “Distance relay with
out-of-step blocking function using wavelet
transform,” IEEE Trans. Power Del., vol.
22, no. 3, pp.1360–1366, Jul. 2007.
474
www.ijaegt.com
ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
Vol-2, Issue-2, February 2014
in Crompton Greaves Limited from 2009
to 2010 and associated with Tata
Consultancy Services Limited from 2011
to 2012. Currently he is pursuing second
year of M.Tech in Power Sysem
Engineering in the department of Electrical
Engineering,
National
Institute
of
Technology,Warangal,India. His area of
interest is power system protection.
modeling and relay testing,” in Proc. 4th
Int. Conf.Develop.Power Protect., 1989,
pp. 182–186.
[13]John P.Nelson,”System Grounding
and
Ground-Fault
Protection
in
Petrochemical Industry:A need for a better
Understanding”,IEEE Transactions on
Industrial Applications,Vol.38,No.6,Nov.Dec 002,pp.1633-1640.
[14]A.M.Sharaf,L.A.Snider
and
K.Debnath,”A Neural Network Based
Relaying Scheme for Distribution System
High
Impedance
FaultDetection”,[1993].[Online].Availabl
e:
www.researchgate.net/...fault_detection/...
/79e41510b7791025bb.pd
Dr. Suresh Babu Perli:
Currently he is working as
an Assistant Professor,in
Department Of Electrical
Engineering,
National
Institut of Technology,Warangal. His area
of interest is Power System Protection.
BIBLIOGRAPHY
Saptarshi Roy: Received
the
B.E
degree
in
Electrical
Engineering
from Jadavpur University,
West Bengal,India in
2009. He was an Engineer
475
www.ijaegt.com