Offset Mho Relay For Loss of Excit p22 PDF
Offset Mho Relay For Loss of Excit p22 PDF
Offset Mho Relay For Loss of Excit p22 PDF
A DISSERTATION
Submitted in partial fulfillment of the
requirements for the award of the degree
of
MASTER OF TECHNOLOGY
In
ELECTRICAL ENGiN"EERING
(with Specialization in Power System Engineering}
By
CHOKKAKULA BUTCHIM NAI:DU
V C~A066~j ~4 L,
ICS Ala ................. -G
?-e Jf6f14
Dates$ l.1... 1.410.. ......
I hereby declare that the work that is being presented in this dissertation
report entitled "Development of Restricted Mho Relay and Offset Mho Relay"
submitted in partial fulfillment of the requirements for the award of the degree of
Master of Technology in Electrical Engineering with specialization in "Power
System Engineering", submitted in the Department of Electrical Engineering,
Indian Institute of Technology Roorkee, is an authentic record of my own work
carried out, under the guidance of Shri. Bharat Gupta, Assistant Professor,
Department of Electrical Engineering, Indian Institute of Technology, Roorkee.
The matter embodied in this dissertation thesis has not been submitted by me
for the award of any other degree.
C~,bnaZC6
Date:
Place: Roorkee (Chokkakula Butchim Naidu)
CERTIFICATE
This is to certify that the above statement made by the candidate is
true to the best of our knowledge.
Page No.
Candidate's Declaration
Acknowledgement
Abstract
Contents iv
List of Figures vi
List of Tables x
1 INTRODUCTION I
1.1 Importance of protection systems 1
1.2 Introduction to protective relays 2
1.3 Literature review 6
2 DISTANCE RELAY BASICS 8
2.1 Introduction 8
2.2 Distance relay schemes 8
2.3 Advantage of Mho Relay 11
2.4 Drawbacks in Mho Relay 11
2.5 Application of Restricted Mho Relay 11
2.6 Applications of Offset Mho Relay 11
3 TRANSMISSION LINE DISTANCE PROTECTION 12
3.1 Introduction 12
3.2 Distance Relay Protection Zones 12
3.3 Computation of the Apparent Impedance 14
3.4 Generalised Mathematical Expression for Distance Relays 17
iv
3.5 Restricted Mho Relay Characteristics 19
3.6 Offset Mho Relay Characteristics 20
4 PSCAD SIMULATION AND RESULTS 21
4.1 Introduction 21
4.2 Simulation Model 21
4.3 Simulation Flow Chart 23
4.4 Simulation Results 24
4.4.1 Restricted mho Relay Results 24
4.4.2 Offset Mho Relay Results 30
5 EMULATED MODEL OF RESTRICTED MHO RELAY AND OFFSET MHO
RELAY 36
6 WORKING OF RESTRICTED MHO RELAY AND OFFSET MHO RELAY
AND TEST RESULTS 41
6.1 Introduction 41
6.2 Program Flow Chart for Restricted Mho Relay 42..
6.3 Program Flow Chart for Offset Mho Relay 45
6.4 Test Results 46
6.4.1 Restricted mho relay 46
6.4.2 Offset mho relay 53
7 CONCLUSIONS AND FUTURE SCOPE 61
7.1 Conclusions 61
7.2 Future Scope 61
REFERENCES 62
APPENDIX A: SOURCE AND TRANSMISSION LINE DATA 64
APPENDIX B: NI DAQ 6212 SPECIFICATIONS 65
APPENDIX C: LEM MODULE LA 50-P 68
APPENDIX D: PSCADIEMTDC SOFTWARE 70
u
LIST OF FIGURES
VI
4.5 Voltage, current waveforms at restricted mho relay 26
location and trip Signals for BC fault
vii
5.3 Analog input Pin assignment of the DAQ card 38
5.4 NIUSB6212DAQcard 39
viii
ix
LIST OF TABLE
x
CHAPTER 1
INTRODUCTION
The importance of the services that power systems offer and the high
amount of investments that represent the facilities and equipments, make the
normal and constant operation of power systems critical and strategic for every
society. Faults and failures normally occur in power systems. Due to the great
amounts of energy involved, faults represent a threat to the operation and
security of power systems if the faults are not promptly corrected. Power
systems need an auxiliary system that must take corrective actions on the
occurrence of a fault. This auxiliary system is known as protection system.
1
1.2 Introduction to protective relays:
One of the most important equipments employed in the protection of
power systems are protective relays. These are one of the most flexible,
economic and well-known devices that provide reliable, fast and inexpensive
protection.
2
The developments in digital technology led to the incorporation of
microprocessors in the construction of relays. Digital and numerical relays are
sophisticated, multiple purpose equipment with the capacity to record signals
during faults, monitor themselves and communicate with their peers. Numerical
relays employ microprocessors especially constructed to process digital
signals, which make them faster and more powerful, while preserving their
economic advantages.
3
prototypes and faster realization of finalized design. From the point of view of
utilities and industrial plants, the availability of a software model is useful to
expedite comprehensive test studies before subjecting the actual relay to
various tests. In this manner, crucial test conditions are thus first identified and
the physical relay is tested only for these conditions. The software model can
also be a very useful training tool.
4
Power
log
Ana Digital Digital
Input Input output
Subsystem Subsystem Subsystem
Analog I Registers
• Interface and I I RAM ROM /
CtIp Memoy
-- I
I t I
e Control CP C 1111 ions
• a.... - - s - - . . s • • • • s - • . . . - - s r a •
f
Micro-computer
Power
supply
7
CHAPTER 2
DISTANCE RELAYS BASICS
2.1 Introduction:
E3
b) Reactance Relay: The reactance relay as shown in figure 2.2 measures
only the reactive component of impedance. The characteristic of a reactance
relay in the R-X plane is a straight line parallel to the R axis. The reactance
relay must be supervised by another function to ensure directionality and to
prevent tripping under load.
c) Mho Relay: The characteristic of the mho relay as shown in figure 2.3 is a
circle whose circumference passes through the origin. The relay operates if the
measured impedance falls within the circle.
d) Offset mho Relay: The characteristic of an offset mho relay •as shown in
figure 2.4 is a circle that is shifted and includes the origin, thus, providing better
protection for close-in faults. This unit, when used to trip, must be supervised by
a directional unit or be time-delayed.
f) Restricted mho Relay: The restricted mho relay as shown in figure 2.6 is
similar to the mho relay, except it is lens-shaped rather than circular, thus
providing more sensitivity to load.
Figure 2.3: Mho Characteristics Figure 2.4: Offset Mho Characteristics.
ZONE 3
ZONE 2
ZONE I
10
2.3 Advantage of Mho Relay:
The term Mho given to a group of directional-impedance measuring
relays which are ideally suited for distance protection. The term Mho is derived
from the fact that the relay characteristic when plotted on admittance, instead of
impedance, diagram gives a straight line. When plotted on an impedance
diagram, in a similar manner to the impedance relay, the circle for operation
cuts the intersection of the X and R axis. With such a characteristic the relay
measures distance in one direction only. A Mho unit, therefore, combines
directional action with impedance measurement, and thus combines both
functions in one unit.
11
CHAPTER 3
TRANSMISSION LINE DISTANCE PROTECTION
3.1 Introduction:
Distance protection has been widely used for protecting transmission
and subtransmission circuits because of its suitability, simplicity, economy and
reliability. In addition, selectivity and remote back-up protection are natural
advantages of this type of protection. Distance relays use voltages and currents
acquired at the relay location to calculate the apparent impedance of the
protected line. The calculated apparent impedance is compared with
predetermined impedance that is called reach of the relay. During normal
operation, the apparent impedance must be larger than the impedance-reach of
the relay. If the apparent impedance is less than the impedance-reach, then it
is concluded that a fault has occurred in the protected line between the relay,
location and the impedance reach of the relay. Under these conditions, the
distance relay energizes the circuits to trip appropriate circuit breakers to
isolate the faulted line from the rest of the system. Generally mho relay is used
to protect long transmission lines.
The impedance reach of zone-1 is usually set between 80% and 90% of
the transmission line impedance, leaving the remaining 20% to 10% of the line
impedance as a safety margin. This is done because errors are introduced by
12
inaccuracies of current and voltage transformers and processes used in the
relay for calculating impedances. These errors could make the relay over-reach
causing the relay to operate for faults in other than its own protection zone. No
intentional delay is provided to zone-1 protection. It essentially provides primary
protection.
Z3
Z2
Z1
T~ T2
A I Instantaneous B I C
Adjacent
Line under
Line
cosideration
13
X
Most distance relays incorporate six operating elements per zone, one
for each of the phase-phase and phase-ground loops. The voltage and current
phasors are used to estimate the impedance between the relay and the fault.
The impedance estimates are determined using six relay elements: - three for
phase faults (faults AB, ABG,BC, BCG, CA, CAG, ABC)and three for earth
faults (faults AG, BG, CG). Each of the six elements is presented with the
appropriate voltage and current phasors.
14
Table 3.1: Relay Elements and Signals used for Impedance Estimation
Measuring Unit Equations
• AG VA /[IA + k1o ]
BG VB /[IB + kIo ]
CG Vc /[Ic + k1o ]
AB [VA -VB]/[IA -Is]
BC [VB - Vc]/[IB - IC]
CA [VC — VA]/[IC — IA]
When the distance relays receive discrete voltage and current signal, it
has to convert them to phasor. The Discrete Fourier Transform (DFT) is the
most popular method to estimate fundamental phasors for digital relaying. The
full-cycle DFT is described as following equation (3.2):
2 N-1 - 2nk N
X = N ~k-0 Xk (3.2)
Where X is complex phasor, Xk is the sample discrete data of the signal, and N
is the number of samples per cycle.
15
In addition, when a fault occurs on transmission lines, the voltage and
current signals are severely distorted. These signals may contain decaying dc
components, subsystem frequency transients, high frequency oscillation
quantities, and etc. The higher frequency components can be eliminated using
low pass anti-aliasing filters with appropriate cut-off frequency, but the anti-
aliasing filters cannot remove decaying dc components and reject low
frequency components. This makes the phasors very difficult to be quickly
estimated and affects the performance of digital relaying. Therefore, we usually
use the mimic filter to remove the dc-offset components. The mimic filter can be
developed by digital method. Here, we want to pass the fundamental frequency
signal (50Hz) by the filter. Then, assuming the gain K equals 1 and the samples
frequency is fs ( fs = IlTs ), finally, we obtain a formula (3.3)
K = FM2+N2) (3.4)
Where
a *ir *so
M=1+ -rfs — ifs cos fs (3.5)
N = zfs
sin( 2* fs sa) (3.6)
16
3.4 Generalised Mathematical Expression for Distance Relays:
Zr—Zo
r= Z (3.7)
Where
The centre of the mho circle is offset from the origin by,
Zr+Zo
c= 2 (3:8)
17
If Z = R+jX is the impedance seen by the relay, then the operating conditions
for the offset mho relay with positive offset is given by,
z-c<=r (3.9)
Zr + Zo Zr — Zo
( z
_ 2 ) ~ 2
Rr+Ro 2 Xr +Xo 2 Rr
( —Ro l2 Xr— Xo)21
(R_ ) +(x_
2 _
2 ) < 2 J + 2
Rr, Ro, Xr and Xo are constants for a particular characteristic and hence the
above expression can be written in the generalised form as
Rr+RO
k1 =
2
Xr+XO
k2=
2
11:1
(Rr — Ro Z Xr — Xo)Z
k3 — ~ +(
2 2
;1
►
cle I
Is
Where
Rr1
k11= 2
19
Xrl
k21 = 2
k31= () + (X21
2 ) 2
G~~3TRAL'
ZACC No .................
Date ....................
Equation for mho circle 2 is given by
K T RnnR1tC~~
(R+K12)2 + (X—K22)2 5 K32 (3.12)
Where
Rr2
k12 = 2
k22= -Xr2
2--
ME
X
(R—K1)2 + (X—K2)2 <— K3 (3.13)
Rr—Ro
k1 = 2
Xr — Xo
k2 = 2
~ (Rr+Ro)2+(Xr +Xo)Z
k3=
2 2
21
CHAPTER 4
PSCAD SIMULATION MODEL AND RESULTS
4.1 Introduction:
In this a set of simulation tests were carried for the test model of a power
system as shown in Figure 4.1. The power system has 0.400kV transmission
line with single end feeding source. The data of transmission line and sources
are given in appendix A.
T.
1I RL RR A TL-SEC2
~ 81
0.0018 [MWJ
22
4.3 Simulation Flow Chart:
START
If
NO
Zcal<=Zset
END
23
4.3 Simulation Results:
I 23.7921+j48.2651
II -12.7990+j52.2659
Main: Graphs
-vi
V\1?IIW
0.40
0.30 __.. . ._ ._......__._._.......__.. ._.... . _ .....;...... _... _.. X 0.084
0.20
0.10 ..... ..._..... ...
0.00
0.10
0.20' ._........__.._ . .... ................_........ T.
-0.30
-0,40 _ _... _ .__. .,. . _
0.0100
X -0.001
0.0080
_.-._. . .__.. . . . . _.
..
0.0060 O 0.001
—
00040 . O.002
._. __ __....__ ......
..
0.0020 . i
0.0000 — .. __....._... _._, _._..._......._. _W ..._
-0.0020
-0.0040 ......................................................:..... ................. .......... . .
-4.0060
_ .
2.no
• Feul Signal .... ......... TripSignell (01) : - Breaker open ►
X 0.587
1.75
01.000
1.50
1.25: A0.413 ..:<
1.00 Min 1.000.
,0.75 - Max 1.000
0.50
0.25
0.00
t(sec) 0.1U0 0.1>50 0.0 0.250 0.300 It 0.350 0.400 X 0.200.'
x
- - U 0 0.332: .
s . ► X 0.133
Figure 4.3: Voltage, current waveforms at restricted mho relay location and trip
25
=25
-50
-100 :. -75 -50 -25 50 75 .100
Aperture Width 0.6
0.000s 0.600s Position 0.000
Figure 4.4: Impedance trajectory seen by restricted mho relay for AG fault
25
Main: Graphs
1 1:~
1 1i1
1 11.
•
.ill1
iii i
— T iii
• 111
.1°
111
11
- 111
1 1
1.1
1 1 1 I I 1 1 11
'n'';1 '1
a I.
Figure 4.5: Voltage, current waveforms at restricted mho relay location and trip
26
cbn 1MP_CALC_COMP : IMPEDANCE TR. CTORIES BY: PHASE FAULT RELAY
X Coordinate V Coordinate
■Rab }Cab .
•a Rbc Xbc
Rca Xca
50
25
-25-
-50-
y
,, X100 _ _ -75 -50 -25 0 25 50 75. 100
Aperture Wdth 0.6
0.000s 0.600s Position 0.000
Figure 4.6: Impedance trajectory seen by restricted mho relay for BC fault
27
Main: Graphs
1 1:~
1 1 iiIIIlIIHIHhI.11hIIIIH.IIiiIIiUHhIIIU.flIiIII
1l~ii~'I'Itj1~1j 1n1~11't~'I~~llyj~iTIIN 1 •1
;1; D~~1H1i~~L1f111,T1t~~~i~I1~I1~11 i~1ui11~Rh~jl~ln~lftfil(11~11f L &.
!1
1 1 11
1 1 1:1 1 11
~~~~ ~■~
iFlZi1~~~~~~~1~T a 1 11 1
1.
1 1111 1~,( 111~A1! ~~ j ~rr
/~~~~~r~r~~~Y~~~1~~1~~ ~~~~ , P I I 1 'P
~~ ~
III ~ 1 ~t~
1 11.1
1 11'1 ~ ! 1
•11
• 111
a1
11 Ili
1 1
III
1 1 1 ~I1 1 1 r 11
Figure 4.7: Voltage, current waveforms at restricted mho relay location and trip
28
cbn_IMP_CALC_COMP : IMPEDANCE TRAJECTORIES BY PHASE FAULT RELAY.
Coordinate Y Coordinate
Figure 4.8: Impedance trajectory seen by restricted mho relay for ABC fault
For offset mho relaying simulations are carried out for different fault types.
Settings of offset mho relay are shown in table 4.2.
Impedance Setting
Zo 0.687+j6.2832
Zr 5.496+j50.2656
Main:
A x0.055
0-0.217
i d =0.272
...Min-O.13
Figure 4.9: Voltage, current waveforms at offset relay location and trip
30
cbn_IMP_CALG COMP IMPEDANCE TRAJECTORIES BY GROUND FAULT
50
25
Figure 4.10: Impedance trajectory seen by offset mho relay for CG fault
Figure 4.9 shows Voltage, current waveforms at offset mho relay location
for CG fault. Here setting impedance is 80% of the transmission line length and
fault is applied at the location of 75% of line length. Impedance trajectory seen
by offset mho relay for CG fault is shown in figure 4.10
31
Main :'Graphs
—
■V1 r
x o.os
o.3a
0-0.158
a.2a
0.10
.Y o.oa I Min -0.317 F
o -0.10 Max 0.317
-0.20
tf
'a.3a j
1
-0.40
0.0080 — 1
x -0.001
o.aoso
I o 0.000
0.0040
H020 a0,001=
0.0000 i Mn -0.003 I
C -0.0020 Max 0.003
L) -0.0040
0.0060
-0.0080
Figure 4.11: Voltage, current waveforms at offset relay location and trip
32
cbn_IMP_CALC COMP :IMPEDANCE TRAJECTORIES BY GROUND FAUL...
X Coordinate Y Coordinate
0Ia Xe
=Rb .. Xb
Rc }{c
50
25
_25
-50
Aperture jj _ INfdth a6
0.000s 0.600s Position 0.000
Figure 4.12: Impedance trajectory seen by offset mho relay for BCG fault
33
Main: Graphs
II
11
j 1 11
111.• , r /}i~ilJl~tT111~#11fL1111TN1
i1,li .1
111 1 - ,'i•,',- ii,a~ L1i~~.~~1l
lIUIf ~~
111.
1 111 ~~
Y~ ~1 ~i~~~~~~~~~~l~il~l~I +i~ ~
~ill~lrl~}i11~~1u1l1~i11tL~i~![i~~
I if - 1
11
Eli
• I11
H1
► 111
11 1 111
111
II
1 11
1 11 1 1 1p 11 •J'1 0.300 1 1 1 II 1 11
■ • f
■
Figure 4.13: Voltage, current waveforms at offset relay location and trip
34
*. cbn 1MP CALC_COMP :IMPEDANCE TRAJECTORIES BY GROUND FAUL...
X Coordinate '(Coordinate
=Rb Xb
m Rc Xc
I . 1
I L
Figure 4.14: Impedance trajectory seen by offset mho relay for ABCG fault
35
CHAPTER 5
EMULATED MODEL OF RESTRICTED MHO RELAY
AND OFFSET MHO RELAY
Figure 5.1 shows the connection diagram of the transducer and the
variable resistance is used in order to calibrate the value of voltage attained for
a known current flowing across the current transducer.
Figure 5.2 shows emulated for voltages fed to the DAQ card from step
down transformers. The transformers isolate the voltage at the primary side to
the voltage at the secondary side. The voltage rating of primary is 230v and
secondary side is 3v.The connections are shown in the figure below in which
common star point is taken as common and connected to the ground and three
terminals representing each phase voltage is connected to analog input
channels of DAQ card. Figure 5.3 shows analog input assignment of the DAQ
card.
36
Channel-1
~ Channel-2
I I Ground
Channel-3
Figure 5.1: Voltages given to the DAQ card from LA 50-P current transducers
37
0 To Channel -.5
To Channel -6
C To Channel - 7
Figure 5.2: Voltages given to the DAQ card from 230/3v step-down
transformers
Al
Al l Al 2 Al 3 ASN Al 4 Al 5 Al 6 All
GND
+ - + - + - + - + - + - + -
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
38
To USB
Current, IA 1
Current, IB 2
Current, IC 3
Voltage, VA 5
Voltage, VB 6
Voltage, VC 7
39
CHAPTER 6
WORKING OF RESTRICTED MHO RELAY AND OFFSET
MHO RELAY AND TEST RESULTS
6.1 Introduction:
Restricted mho relay is less affected to power swings and provides
more sensitivity to transmission line. Offset mho relay is provides bus-bar back-
up protection and protects synchronous generator during loss of excitation.ln
this chapter working of restricted mho relay and offset mho relay are
implemented in MATLAB code. Flow charts developed for the operation of
above said relays.
41
6.2 Program Flow Chart for Restricted Mho Relay:
Start
42
A
Calculate (X-K21 )2
b
Figure 6.2: Flow chart for restricted mho relay part-II
43
Calculate (R+K12)2
Calculate (X-K12 )2
Sum = (R+K12)2+(X-K12)2
NO / Is
x Sum<=
K2?
YES
stop
44
6.3 Program Flow Chart for Offset Mho Relay:
Start
Calculate (R-K1 )2
45
Figure 6.5: Flow chart for restricted mho relay part-II
46
6.3.1 Restricted mho relay:
VI =
Zincomplex =
1.Oe+002
4.8123 + 2.67191
• 4.9077 + 1.6272i
4.0049 + 2.21771
4.6449 + 2.20281
4.5652.+ 2.33441
4.4934 + 2.20221
Voltages Currents
V I =
Zincomplex =
4.9498 +46.29551
2.8004 +40.6240i
2.6505 +42.98141
3.1968 +46.79641
4.3215 +45.64321
2.0342 +45.24821
ABC Fault
>>
47
Figure 6.6 shows test results of restricted mho relay for ABC fault which
is created at 75% of the transmission line. Figure 6.7 shows Impedance
trajectory seen by AB element of restricted mho relay for ABC fault. Here
restricted 'mho relay operated for ABC fault.
100
80
60
40
20
-20
-40
-100
-100 -80 -60 -40 -20 0 20 40 60 80 100
48
Z1ncomplex
1.0e002
4.7371 + 2.7019i
4.7749 + 1.6488i
3.9252 + 2.0919i
4.5301 + 2.24051
4.4058 + 2.24771
4.4575 + 2.13821
Currents
Voltages
Til I =
Zincomplex
1.Oe+002
0.4665 + 0.46301
0.3326 + 0.47311
3.2299 + 2.08091
0.0422 + 0.45801
0.7952 + 0.5245i
1.3180 + 0.6385i
AB fault
49
Figure 6.8 shows test results of restricted mho relay for AB fault which is
Treated at 75% of the transmission line. Figure 6.9 shows Impedance trajectory
seen by AB element of restricted mho relay for AB fault. Here restricted mho
relay operated for AB fault.
100
80
60
40
20
-20
-40
-60
--80
-100
-100 -80 -60 -40 -20 0 20 40 60 80 100
50
[7 I
Zincomplex =
1.Oe+002
4.7709 + 2.56141
4.9140 + 1.93721
4.0748 + 2.23441
4.6777 + 2.21091
4.5649 + 2.37451
4.4843 + 2.20071
Voltages Currents
V I =
3.6252 154.3493
175.4070 -110.2816
177.8459 5.8966 3.6756 -89.2018
171.9267 125.3151 3.8577 33.4104
Zincomplex
4.9784 +48.11011
4.2554 +48.76721
1.1853 +44.3633i
4.4155 +48.2179i
3.6535 +45.63911
1.9190 +47.24721
ABCG Fault
1 »
51
Figure 6.10 shows test results of restricted mho relay for ABCG fault
which is created at 75% of the transmission line. Figure 6.11 shows Impedance
trajectory seen by AB element of restricted mho relay for ABCG fault. Here
restricted mho relay operated for ABCG fault.
100
80
60
40
20
-20
-40
-60
-80
-100
-100 -80 -60 -40 -20 0 20 40 60 80 100
52
6.4.1 Offset mho relay:
V I
Zincomplex
1.Oe+002
5.1339 + 2.94411
5.3317 + 2.00751
• 4.3268 + 2.26121
5.0001 + 2.40691
4.6726 + 2.4787i
4.8739 + 2.33761
Voltages Currents
V1
Zincompl.ex =
1.Oe+002
• 4.3793 + 2.65091
0.4865 + 0.54131
0.3276 + 0.47661
1.4085 + 0.59091
0.0500 + 0.49941
0.8508 + 0.5680i
BC fault
f._>>
100
80
60
40
20
-20
-40
-60
-80
-100
-100 -80 -60 -40 -20 0 20 40 60 80 100
Figure 6.13: Impedance trajectory seen by BC element of offset mho relay for
BC fault
54
File Edit Debug Desktop Window Help
... _. _....__..... _ ... ...........................................................................I._..............__....._.............:.......r.................................._..................._...,...,....,......................................I................:.................
0 New to MATLAB? Watch this Video. see Demos, or read Getting Started.
VOlrages Currents
11
Zincomplex =
1.Oe+002
7.8343 + 4.55351
7.9425 + 2.2738i
5.9797 + 3.4548i
7.3770 + 3.30371
7.3121 + 3.64791
7.0591 + 3.41931
Voltages Currents
V I =
Zincomplex =
5.4507 +49.79041
3.3560 +51.81141
1.6987 +47.26041
3.8162 +50.16441
3.7842 +48.96471
2.8085 +49.56701
ABC
55
Figure 6.14 shows test results of offset mho relay for ABC fault which is
created at 75% of the transmission line. Figure 6.15 shows Impedance
trajectory seen by AB element of offset mho relay for ABC fault. Here offset
mho relay operated for ABC fault.
100
80
60
40
20
-20
-40
-60
-80
-100
-100 -80 -60 -40 -20 0 20 40 60 80 100
Figure 6.15: impedance trajectory seen by AB element of offset mho relay for
ABC fault
56
File Edit Debug Desktop Window Help
........................._ ..__...................:...._.._._..._ .._......._....._.........._..................__....................,......................................._._.................................:._._........._....._......._...._,_ _..._._...,.......
0New to MATLAB? Watch this Video. see Demos. or read Getting Started.
Voltages Currents
VI
Zincomplex =
1. Oe+002
• 5.2203 + 3.00711
• 5.2594 + 1.95251
4.2374 + 2.20091
4.9657 + 2.43701
4.7959 + 2.41061
4.8963 + 2.27721
Voltages Currents
V I
Zincomplex =
4.7091 +49.7568i
3.1840 +52.29461
2.5159 +46.53241
3.1980 +50.54081
4.4681 +49.09921
2.6798 +46.72341
ABCG Fault
1 >>
150
100
50
-50
-100
-100 -80 -60 40 -20 0 20 40 60 80 100
Figure 6.17: Impedance trajectory seen by BC element of offset mho relay for
ABCG fault
58
f f r f I f I f
tom 1 mm 25M _000 amo ,000 asap sm
-1
-2
-3
A rr r r r -
—Y 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
59
o.e
OA
as
aA
.0.8
0 500 1000 1508 2000 2500 2 2500 Imo imn wn
Figure 6.18 shows relay voltage samples before filter, in this it contains
voltage harmonics. By using butterwort low pass filter voltage harmonics are
eliminated. Figure 6.19 shows voltage samples after passing through filter.
Figure 6.20 shows relay current samples.
CHAPTER 7
CONCLUSIONS AND FUTURE SCOPE
7.1 Conclusions:
In this report microprocessor based restricted mho relay and offset mho
relay are implemented. In laboratory transmission line is modelled and different
types of faults are created. Test results of restricted mho relay and offset mho
relay operating characteristics are presented for different types of faults.
For the same transmission line PSCAD simulations were done for
restricted mho relay and offset mho relay. Simulation results are presented and
analysed for different types of faults.
61
REFERENCES
63
APPENDIX A
SOURCE AND TRANSMISSION LINE DATA
64
APPENDIX B
NI DAQ 6212 SPECIFICATIONS
Analog Input:
Number of channels : 8 differential or 16 single ended
ADC resolution :16 bits
Sampling rate : 400 kS/s single channel,
400 kS/s multichannel
Input coupling : DC
Input range : 10, ±5, ±1, ±0.2 V
Maximum working voltage
For analog inputs (signal +
Common mode) : ±10.4 V of Al GND
Input impedance
Device on
AI+ to Al GND : >10 G'/2 in parallel with 100 pF
Al- to Al GND : >10 G1/2 in parallel with 100 pF
Device off
AI+ to AI GND :1200%
Al- to AI GND :1200%
Input bias current : ±100 pA
Crosstalk (at 100 kHz)
Adjacent channels : -75 dB
Nonadjacent channels : 90 dB
Input FIFO size : 4,095 samples
Scan list memory : 4,095 entries
Data transfers :NI signal streaming on USB
Analog Output:
Number of channels :2
DAC resolution :16 bits
Maximum update rate
1 channel 250 kS/s
2 channel 250 kS/s per channel
Timing accuracy 50 ppm of sample rate
Timing resolution 50 ns
Output range ±10 V
Output coupling DC
Output impedance 0.2 1/2
Output current drive :±2mA
Output FIFO size :8,191 samples shared
among channels used
Data transfers :NI signal streaming on USB,
Calibration (Al and AO):
Recommended warm-up time 5 minutes
Calibration interval 1 year
Digital I/O/PFI
Static Characteristics:
Number of channels
Digital input/output
USB-6212mass terminal : 24
Ground reference : D GND
Direction control Each terminal individually
Programmable as input or output
Pull-down resistor
USB-6212 : 50 kY2 typical, 20 k%2 minimum
Bus Interface:
USB Hi-Speed USB or full-speed USB
NI signal streaming 4 high-speed data streams;
Can be used for analog input,
analog output, counter/timer 0,
Counter/timer 1
Power Requirements:
USB port : 4.5 to 5.25 V in configured state
Caution: Do not exceed 16 mA per DIO pin.
67
APPENDIX C
LEM MODULE LA 50-P
Definition:
The LEM Module LA 50-p is a current transducer for the electronic
measurement of currents: DC, AC, IMPL. It has galvanic isolation between
primary and the secondary circuits.
Electrical data:
Nominal current : 50A rms
Measuring range 0 to ± 70A
Measuring resistance Rm min. Rm max.
With ±15V at ±50A 5052 1000
at ±70A : 50U 700
Nominal analog output current : 50A
Turns ratio 1:1000
Overall accuracy at +25 deg. C ± 0.5% of nominal current
Supply voltage ±15V
Isolation between primary and secondary:
2 kV rms/5OHz/1 min.
EMTDC results are solved as instantaneous values in time, but they can
be converted into phasor magnitudes and angles via built-in transducer and
measurement functions (such as true-rms meters or FFT spectrum analyzers),
much the same way real system measurements are performed. In PSCAD V4,
a new component will be available to calculate the impedance vs. frequency
spectrum of any system, from any point of the system.
EMTDC users can easily write their own models, from very simple to
very advanced. They can write in Fortran, C and MATLAB. The PSCAD
Component Workshop also makes the task of designing the visual appearance
of models and the data entry forms easier. All features of the very powerful
MATLAB program can be utilized, including the numerical and graphical
visualization plot libraries.
70