Modelling and Testing of a Numerical Pilot Distance Relay for Compensated Transmission Lines

International Journal of Scientific Research and Engineering Development-– Volume 3 Issue 6, Nov-Dec 2020
Available at www.ijsred.com
ISSN : 2581-7175 ©IJSRED: All Rights are Reserved Page 776
Modelling and Testing of a Numerical Pilot Distance Relay for
Compensated Transmission Lines
Mohammad M. Almomani*, Seba F. Algharaibeh**
*
Electrical Engineering Department, Engineering College, Mutah university, Jordan,
**
Electrical Engineering Department, Engineering College, Mutah university, Jordan
*
Tel.: +00-962-796515220
----------------------------------------************************----------------------------------
Abstract:
Flexible AC transmission system (FACTS) technologies are wildly used in the high voltage and
extra-high voltage AC transmission systems to control the power flow. The existence of FACTS devices in
the transmission lines makes a misoperationof the traditional distance relay. In this paper, a new special
pilot distance protection scheme is presented for any compensated transmission line. This scheme is valid
for any type of FACTS device (shunt, series, and compound) and different operation points (capacitive
mode or inductive mode). The proposed scheme is modeled and tested in MATLAB 2020a/Simulink. The
model includes a fault detection algorithm, phase selection, measured impedance, and five zones mho
characteristic. The proposed scheme includes two additional reversed zones with the three traditional
zones. The model is verified under deferent fault scenarios, includingsingle-line to ground faults, double-
line faults, double-line to ground faults, and three-phase faults. The results show the model robustness for
different FACTS devices, including Static synchronous compensator (STATCOM), static synchronous
series compensator (SSSC), and unified power flow controller (UPFC) as examples on the shunt, series,
and compound FACTS devices respectively. All results show that the relay operates correctly under
different FACTD device locations, different types of faults, different types of FACTS devices, and
different operation points.
Keywords:FACTS device, Distance Relay, compensated transmission line, modeling, UPFC.
----------------------------------------************************--------------------------------
1. INTRODUCTION
Selectivity, sensitivity, and time of tripping are
the most important criteria in any protection
system. In the high voltage and ultra high voltage
transmission system, these criteria are more
important than other systems due to the stability
limitation in addition to its thermal capability. In
the modern interconnected power systems, the
FACTS devices are widely used to achieve
optimal load flow with minimum losses and
maximum loadability. The traditional distance
relay will operate incorrectly (under/overreach)for
compensated transmission lines due to the device
impedance.
Different researchers present the performance
of the distance relay in compensated transmission
lines [1-10]. The impact of different FACTS
devices including SSSC, STATCOM, and UPFC
on the apparent impedance by the distance relay is
discussed in [1].The results show that the
apparent impedance of the fault is highly
dependent on the presence of the FACTS device,
their type, and control parameters setting. In [2],
the impact of delta connection MMC STATCOM
on the distance protection using hardware in the
loop is presented. In this study different operation
points of the STATCOM are not considered, so
only the under-reach problem is observed. From
RESEARCH ARTICLE OPEN ACCESS

this study, the Impact of STATCOM on distance
relay in case of external fault is less than in the
case ofan internal fault. At the certain operation
point (and control parameter setting) the under
reach problem is observed higher in three-phase
fault than single-phase fault. The impact of shunt
transmission line capacitance on distance relay for
SSSC compensated transmission line in case of
single-phase fault is presented in [9]. The result
shows that the analysis of the apparent impedance
is less accurate when the shunt transmission line
capacitance is ignored. The effect of shunt
capacitance depends on the compensation level.
So, some under reach cases may be observed if a
fault is accrued in the first zone (if the shunt
capacitance is ignored) and overreach problem in
case of a fault occurs in second and third zones.
In summary, the traditional relay still not be able
to detect the zones boundary correctly in
compensated transmission lines. The modeling of
the traditional distance relay in
MATLAB/SIMULINK is proposed in [11-15]. In
[11], a three-zone mho characteristic is modeled
in MATLAB/Simulink. The results show that the
software (MATLAB) is capable of being used to
simulate any protection relays. Researchers in
[12] presented a model of three stepped zones
mho distance relay. The model is valid for
different types of faults and different locations.
The basic principles of a digital distance relay and
some related filtering techniques are described in
[13].Three zones mho type distance relay is
implemented using the SimPowerSystem toolbox
in MATLAB in [14]. In this research, the non-
pilot distance relay for the uncompensated
transmission line is modeled and tested for
different fault types and locations.
In this paper, a new pilot distance scheme is
proposed to increase the robustness of the
distance relay in a compensated transmission line.
Modeling of a digital distance relay is also
presented to validate the proposed scheme. The
structure of the paper is prepared as
follows:principle operation of the digital distance
relay is proposed in section II. Section III presents
the proposed scheme. Modeling and simulation of
the proposed scheme are shown in section IV.
Validation tests for different faults at different
locations for different types of FACTS
compensated lines are presented in section V.
2. PRINCIPLE OPERATION
A distance protective relay detects the
faultbased on the measuring impedance between
the current transformer point and fault location.
To apply this simple concept, it is necessary to
identifyseven loops to coverall types of faults. For
all loops the basic equation is used:
= (1)
The measured impedance ( )is based on the
measured voltage ( ) and current ( ). The
relation between measured impedance in the
secondary side (of the current and voltage
transformers, CT and VT) and the actual
impedance is given by:
= (2)
Where : the actual line impedance. The
difference between the loops is the definition of
the measured voltage and the measured current,
. The table below shows the measured
voltageand current, which areused in equation (1)
for the seven loops.
TABLE I
MEASURED QUANTITY DEFINITION OF THE SEVEN LOOPS.
Fault loop Measured
voltage ( )
Measured
current ( )
A-G +
B-G +
C-G +
A-B / A-B-G − −
B-C / B-C-G − −
C-A / C-A-G − −
A-B-C !" !" !" !"
Where =
#$%#&
#&
, , (: zero andpositive
sequence impedance and :zero sequence
current.
When a fault occurs on the line,fault with
impedance, the measured impedance is given by:
= ) + *+
Where) = ,
, -+: the distance between relay
point and fault location. L: total length of the
protected line.*+: Fault resistance. The measured
impedance when a fault occurs is very less than
the measured impedance at normal load. Based on
this concept, the distance relay characteristic can
be implemented. To ensure the correct fault
direction, the first quarter of the R-X plane refers
to the forwarded fault, and the third quarter refers
to reverse fault location. MHO-characteristic is

one of the most common distance relay
characteristics. Figure (1) shows the traditional
three-stepped zones mho characteristic.
Z1
Z2
Z3
R
X
θ
Fig.1. three zones MHO characteristic
Zone (1) is the main protection to the line;
typically, it covers 80-85 % of the line and trips
instantaneously. Zone (2) and (3) are the backup
for the next station and the next line. Thesezones
are typically set to cover 120-150% and 180-
220% of the line,respectively. The time operation
of the second and third zones may set to 0.25-0.4s
and 0.35-0.45s, respectively.
The existence of a series FACTS device (line
impedance compensator) on the transmission line
decreases/increases (based on its operation) the
measured impedance by the distance relay. For
example,if a series-FACTS device absorbs
reactive power, the measured impedance will be
greater than the actual impedance, and the relay
will operate under-reach. If the device delivers
reactive power, the measured impedance will be
less than the actual, and the relay will operate
overreach. In addition to that, the measured
impedance argument will change clockwise or
counterclockwise based on the operation point of
the device. For more details, the FACTS device
may be divided into:
Voltage regulators: change the magnitude of the
voltage at the sending end to control both real and
reactive power flows. e.g., STATCOM, SVC,
TCVR, SVS-based voltage regulator. These
controllers should have a shunt part to inject
current (so reactive power) to the system at a
controlled point. The shunt impedance, which is
parallel with the actual impedance, will
increase/decrease the measured impedance based
on its operation.
Line Impedance compensators: induce a
controlled capacitance or inductance in series
with the line. e.g: TCSC, SSSC. These devices
should have a series-part to inject voltage out of
phase to the line current by ±90 . So the
measured impedance and its angle may be greater
than the actual, or less than the actual.
Phase angle regulation (Phase shift): these types
of FACTS devices change the angle of voltage,
and the magnitude does not change. These
devices change the measured impedance
argument only positively or negatively.
Unified power flow controller (UPFC): this
special configuration may change all line
parameters to control both real and reactive power
independently. This configuration has series and
shunts VSC connected via a DC link (capacitor).
Based on the operation principle of the FACTS,
the mho characteristic is better than other
characteristics if the phase angle regulator is used.
Otherwise, all characteristics (MHO, quadratic
…) will be affected by the FACTS.
3. PROPOSED SCHEME
The proposed scheme is based on a pilot
distance relay to overcome the problem of
under/overreach of distance relay due to the
FACTS device. The proposed scheme uses a
block comparison signal (BCS) and trip
communication channel: permissive under/ over
reach trip (PUTT/POTT) and direct trip.
Referring to figure (2) The proposed scheme is
summarized as follow:
RA
RB
FACTS
Communication channel
Fig.2. single line diagram of the compensated transmission line protected
by a pilot distance relay.
If the FACTS device was installed at the end of
the line (behind relay RA)
BCS: if any relay (A or B) detects a fault in the
reverse region, it will send a block signal to the
other relay. If a relay receives a block signal,it
should deactivate its forward zones.
Trip scheme: if relay RB detects a fault in its
zone 1, it will send a direct trip to relay RA. If
relay RB detects a fault in its zone 2, it will send a
permissive trip to relay RA. If relay RA detects a

fault in its zone 1 or 2, it will send a permissive
trip to relay RB. Any relay receives a direct trip;
it will trip without any condition. Any relay
receives a permissive trip and feels the fault in its
forward direction; it will trip instantaneously.
If the FACTS device is installed at the middle
of the line:
BCS: same as the previous case.
Trip scheme: if any relay detects a fault in its
zone 1 or 2, it will send a permissive trip to the
other relay. If any relay receives a permissive trip
and feels the fault in its forward direction, it will
trip directly.
For both previous cases, two additional reverse
zones are needed to cover the traditional zone 2
and zone 3. Figure 3 shows the additional zones.
The reach setting of the zone (R1) equal to the
(Z2-ZL) with tripping time equal to the traditional
zone two operation time. For zone (R2), the reach
impedance equal to (Z3-ZL) with tripping time
equal to the traditional zone three operation time.
Where Z2: reach impedance of the traditional
zone 2. Z3: reach impedance of the traditional
zone 3. ZL: protected line impedance.
Fig.3. Proposed impedance diagram
Modeling of the proposed scheme
In this section,modeling, simulation, and testing
of three zones of traditional distance relay and the
proposed scheme are presented. The model of the
distance relay consists of:
Pre-Processing Block: this block consist of a
low-frequency filter and phase-locked loop in
addition to a Fourier analyzer, which is needed to
get a fundamental signal of the measured voltage
and current.
Fault detection: detect the faulty phase during a
fault.
Phase selection: to select a faulty loop based on
fault detection technique.
Measured impedance: for a faulty loop, the
measured impedance can be calculated based on
table1.
The fault detection algorithm compares the
impedance for each phase with the impedance of
zone 3 with the margin factor. The mask
parameters and relay settings are seen in figure 5.
Figure 6 shows the faulty phase detection
algorithm. The loop selection technique (fault
type classification) is shown in figure 7. This
algorithm uses the Karnaugh-Maps technique
[16]. One faulty loop should be selected in this
block (table 1).
The measured impedance block of loop A-G
and the trip algorithm block are shown in Figures
8 and 9. Figure 8 applied the equations in table 1.
Each faulty loop has its measured impedance
block. The proposed tripping characteristic, figure
3, is used in figure 9. It can be easily seen in
figure 9 all tripping zones (Z1, Z2, Z3, R1, and
R2). The permissive receive signal is an effect on
the operation time of the second and third zones,
it is seen in the figure. Finlay from this figure, it
can be seen the block algorithm, when a fault is
observed in the reverse direction. The seven-loop
blocks are shown in figure 10. This model is
tested for non-compensated transmission lines at
all fault types and different locations in each zone
and the edge of each zone.The result in table 2
shows that the relay works correctly in all zones
for any type of fault. Where Z1, Z2, and Z3 refer
to zone 1, 2, and 3 operate respectively. N/O: not
operate. The relay setting is shown in figure 5.
Fig. 4. System understudy
-10 -5 0 5 10
R (ohm)
-5
0
5
10
15
Impedance Diagram
Line angle
Zone 1
Zone 2
Zone 3
Zone R1
Zone R2
Pilot Distance relay
Pilot Distance relay
A Block send
B Per. send
C Block rec.
N Per. rec.
Z1 Z3P
Z2 R1
Z3 R2
21
A Block send
B Per. send
C Block rec.
N Per. rec.
Z1 Z3P
Z2 R1
Z3 R2
C
c
C
C
C
c
C
C
C
c
C
C c C c
C
c
C
C
C
C
C
c
C
c
C c
C
c
C

Fig. 5. Parameter setting of the relay mask
Fig. 6. The faulty phase detection block
Fig. 7. Fault type classification
Fig. 8. Measured impedance block (A-G loop)
Fig. 9. Tripping algorithm block (loop A-G)
Fig. 10. Seven loops block diagram
Fig. 11. Measured impedance in zone one.
The measured impedance is drowned in the R-
X plan in Figure 11. This figure shows the
measured impedance in zone 1 without the
FACTS device. The effect of a FACTS device in
the line may increase or decrease the measured
impedance by the relay based on its operation.
TABLE III
Test results of the proposed model
Fault type Fault Location
79% 80% 119% 120% 149% 150%
A-G Z1 Z
2
Z2 Z3 Z3 N/
O
B-G Z1 Z
2
Z2 Z3 Z3 N/
O
C-G Z1 Z
2
Z2 Z3 Z3 N/
O
A-B Z1 Z
2
Z2 Z3 Z3 N/
O
A-B-G Z1 Z
2
Z2 Z3 Z3 N/
O
B-C Z1 Z
2
Z2 Z3 Z3 N/
O
u1
1 1
u1
1 1
u1
1 1
u1
1 1
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
[C]
[N]
<= Z(1)/100*abs(R(1)+j*2*pi*f *X(1))*L/2
<= Z(2)/100*abs(R(1)+j*2*pi*f *X(1))*L/2
<= Z(3)/100*abs(R(1)+j*2*pi*f *X(1))*L/2
Reciev e
<= (Z(3)-100)/100*abs(R(1)+j*2*pi*f *X(1))*L/2
<= (Z(2)-100)/100*abs(R(1)+j*2*pi*f *X(1))*L/2
1
2
3
permissive
Meas Impedance R-X
send
1
2
3
permissive
Meas Impedance R-X
send
1
2
3
permissive
Meas Impedance R-X
send
[meas_CG]
1
2
3
permissive
Meas Impedance R-X
send
1
2
3
permissive
Meas Impedance R-X
send
[meas_BC]
1
2
3
permissive
Meas Impedance R-X
send
[meas_CA]
1
2
3
permissive
Meas Impedance R-X
send
[meas_ABC]
[meas_CG]
[meas_BC]
[meas_CA]
[meas_ABC]
impedance
-T- -T- -T-
-T-
-T-
-T-
-T-
1 GT
-T-
-T-
-T-
-T-
-T-
-20 0 20 40 60
R (ohm)
0
10
20
30
40
50
Impedance Diagram
Zone 1
Zone 2
Zone 3
Zm

B-C-G Z1 Z
2
Z2 Z3 Z3 N/
O
C-A Z1 Z
2
Z2 Z3 Z3 N/
O
C-A-G Z1 Z
2
Z2 Z3 Z3 N/
O
A-B-C Z1 Z
2
Z2 Z3 Z3 N/
O
4. MODEL VALIDATION AND RESULTS
In this section, UPFC, SSSC, and STATCOM
are selected to validate the proposed scheme. Two
Different locations of the FACTS device are
studied; at the line end and in the middle of the
line. Figures 12 shows the single line diagram of
the first scenario. F1, F2, F3, F4, and F5 are
different fault locations. The relays RA and RB
have the same setting: zone 1 reach = 80 km, zone
2 reach =120 km, zone 3 reach =150 km. zone 2
time operation= 400ms Zone 3 time operation=
800ms. For different fault types, this study is
conducting using traditional distance relay and
proposed schemes at different operation points of
the FACTS. Table 3 shows the power flow intwo
different operation cases.Tables4, 5, 6, and 7
show the results of different scenarios.
Tables 4 and 5 show the misoperation of the
traditional three zones mho characteristic relays
(yellow labels). All these misoperations are
solved by the proposed scheme (tables 5-6). The
results show that the proposed scheme can solve
any under/overreach in the relay for any FACTS
device. From tables 5 and 6, Z2P and Z3P are the
permissive zone 2 and 3 respectively. The trip
time of the permissive forward zones are
instantaneous, so it is similar to the first zone time
operation. The corrections in the proposed
scheme, tables 5 and6, are shown in the green
label. Some of these corrections are improved the
traditional relay operation for the uncompensated
transmission lines. This scheme can handle the
faults with resistance better than the traditional
relays
RA
FACTS RB
0 40 70 90 100 130
30
Distance (Km)
F1
F2 F3 F4
F5
Fig.12. Single line diagram of the first scenario.
Table III
power flow for two different operation points.
Case Operation point
Without FACTS S= 100 MW+ j 50 MVAR
UPFC case 1 S= 130 MW+ j25 MVAR
UPFC case 2 S= 80 MW+ j 75 MVAR
STATCOM case 1 Q= 25 MVAR
STATCOM case 2 Q= 75 MVAR
SSSC case 1 Injection voltage = +0.1 Pu
SSSC case 2 Injection voltage =-0.1 Pu
Table IV
Traditional Relay operation zones, operation point 1.
Fault location Fault
type
Without FACTS UPFC SSSC STATCOM
RA RB RA RB RA RB RA RB
F1(30km) A-G N/O Z3 N/O N/O N/O N/O N/O Z3
B-C N/O Z3 N/O N/O N/O N/O N/O Z3
A-C-G N/O Z3 N/O N/O N/O N/O N/O Z3
A-B-C N/O Z3 N/O N/O N/O N/O N/O Z3
F2(40 km) A-G Z1 Z1 N/O Z1 N/O Z1 Z1 Z1
B-C Z1 Z1 Z2 Z1 Z2 Z1 Z1 Z1
A-C-G Z1 Z1 Z2 Z1 Z2 Z1 Z1 Z1
A-B-C Z1 Z1 Z2 Z1 Z2 Z1 Z1 Z1
F3(70 km) A-G Z1 Z1 N/O Z1 N/O Z1 Z1 Z1
B-C Z1 Z1 Z3 Z1 Z3 Z1 Z1 Z1
A-C-G Z1 Z1 Z3 Z1 Z3 Z1 Z1 Z1
A-B-C Z1 Z1 Z2 Z1 Z3 Z1 Z1 Z1
F4(90km) A-G Z2 Z1 N/O Z1 N/O Z1 Z2 Z1
B-C Z2 Z1 Z3 Z1 Z3 Z1 Z2 Z1
A-C-G Z2 Z1 Z3 Z1 Z3 Z1 Z2 Z1
A-B-C Z2 Z1 Z3 Z1 Z3 Z1 Z2 Z1
F5(130km) A-G Z3 N/O N/O N/O N/O N/O Z3 N/O
B-C Z3 N/O N/O N/O N/O N/O Z3 N/O
A-C-G Z3 N/O N/O N/O N/O N/O Z3 N/O
A-B-C Z3 N/O N/O N/O N/O N/O Z3 N/O
Table V
Traditional Relay operation zones, operation point 2.
type

F1(-30km) A-G N/O Z3 N/O N/O N/O N/O N/O Z3
B-C N/O Z3 N/O N/O N/O N/O N/O Z3
A-C-G N/O Z3 N/O N/O N/O N/O N/O Z3
A-B-C N/O Z3 N/O N/O N/O N/O N/O Z3
F2(40 km) A-G Z1 Z1 Z3 Z1 Z2 Z1 Z1 Z1
B-C Z1 Z1 Z2 Z1 Z3 Z1 Z1 Z1
A-C-G Z1 Z1 Z2 Z1 Z3 Z1 Z1 Z1
A-B-C Z1 Z1 Z2 Z1 Z3 Z1 Z1 Z1
F3(70 km) A-G Z1 Z1 Z3 Z1 Z2 Z1 Z1 Z1
B-C Z1 Z1 Z3 Z1 Z3 Z1 Z1 Z1
A-C-G Z1 Z1 Z3 Z1 Z3 Z1 Z1 Z1
A-B-C Z1 Z1 Z3 Z1 Z3 Z1 Z1 Z1
F4(90km) A-G Z2 Z1 Z3 Z1 Z3 Z1 Z2 Z1
B-C Z2 Z1 Z3 Z1 Z3 Z1 Z2 Z1
A-C-G Z2 Z1 Z3 Z1 Z3 Z1 Z2 Z1
A-B-C Z2 Z1 Z3 Z1 Z2 Z1 Z2 Z1
F5(130km) A-G Z3 N/O N/O N/O N/O N/O Z3 N/O
B-C Z3 N/O N/O N/O N/O N/O Z3 N/O
A-C-G Z3 N/O N/O N/O N/O N/O Z3 N/O
A-B-C Z3 N/O N/O N/O N/O N/O Z3 N/O
TableVI
proposed scheme Relay operation zones. (operation point 1)
type
F1(-30km) A-G R3 N/O R3 N/O R3 N/O R3 N/O
B-C R3 N/O R3 N/O R3 N/O R3 N/O
A-C-G R3 N/O R3 N/O R3 N/O R3 N/O
A-B-C R3 N/O R3 N/O R3 N/O R3 N/O
F2(40 km) A-G Z1 Z1 Z3P Z1 Z3P Z1 Z1 Z1
B-C Z1 Z1 Z2P Z1 Z2P Z1 Z1 Z1
A-C-G Z1 Z1 Z2P Z1 Z2P Z1 Z1 Z1
A-B-C Z1 Z1 Z2P Z1 Z2P Z1 Z1 Z1
F4(90km) A-G Z2P Z1 Z3P Z1 Z3P Z1 Z2 Z1
B-C Z2P Z1 Z3P Z1 Z3P Z1 Z2 Z1
A-C-G Z2P Z1 Z3P Z1 Z3P Z1 Z2 Z1
A-B-C Z2P Z1 Z3P Z1 Z3P Z1 Z2 Z1
F5(130km) A-G N/O R3 N/O R3 N/O R3 N/O R3
B-C N/O R3 N/O R3 N/O R3 N/O R3
A-C-G N/O R3 N/O R3 N/O R3 N/O R3
A-B-C N/O R3 N/O R3 N/O R3 N/O R3
Table VII
proposed scheme Relay operation zones. (operation point 2)
type
F1(-30km) A-G R3 N/O R3 N/O R3 N/O R3 N/O
B-C R3 N/O R3 N/O R3 N/O R3 N/O
A-C-G R3 N/O R3 N/O R3 N/O R3 N/O
A-B-C R3 N/O R3 N/O R3 N/O R3 N/O
F4(90km) A-G Z2P Z1 Z3P Z1 Z3P Z1 Z2P Z1
B-C Z2P Z1 Z3P Z1 Z3P Z1 Z2P Z1
A-C-G Z2P Z1 Z3P Z1 Z3P Z1 Z2P Z1
A-B-C Z2P Z1 Z3P Z1 Z2P Z1 Z2P Z1

F5(130km) A-G N/O R3 N/O R3 N/O R3 N/O R3
B-C N/O R3 N/O R3 N/O R3 N/O R3
A-C-G N/O R3 N/O R3 N/O R3 N/O R3
A-B-C N/O R3 N/O R3 N/O R3 N/O R3
(a) (b)
(c) (d)
(e) (f)
(g) (h)
(i) (j)
Fig.13. The measured impedance at different locations (F1, F2, F3, F4, F5)
of the Double phase-to-ground fault which seen by relay A and relay B for
the non-compensated transmission line.
Figures 13-16 show the measured impedance of
different fault locations of the non-compensated,
UPFC compensated, SSSC compensated and
STATCOM compensated transmission line,
respectively.
Figure 13 shows the measured impedance by
local (RA) and remote (RB) relays for different
fault locations of Double phase to ground (A-C-
G) fault. From the figures, it can be seen that the
correct operation of both A (left) and B (right)
relays at different fault locations based on the
measured impedance. This figure validates the
operation of the modeled distance relay for all
five zones faults.
(a) (b)
(c) (d)
(e) (f)
(g) (h)
(i) (j)
Fig. 14. The measured impedance at different locations (F1, F2, F3, F4, F5)
of Double phase fault seen by relay A and relay B for a UPFC-
compensated transmission lineat operation point 1.
Figure 14 shows the measured impedance of the
UPFC- Compensated transmission line. Different
X
(Ohms)
X
(Ohms)
X
(Ohms)
X
(Ohms)
X
(Ohms)
X
(Ohms)
-20 -10 0 10 20 30 40
R (Ohms)
-20
-10
0
10
20
30
40
50
F4,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohms)
-20
-10
0
10
20
30
40
50
F4,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohms)
-20
-10
0
10
20
30
40
50
F5,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohms)
-20
-10
0
10
20
30
40
50
F5,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F1,RA
Z1
Z2
Z3
R1
R2
Z
m
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F1,RB
Z1
Z2
Z3
R1
R2
Z
m
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F2,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F2,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F3,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F3,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F4,RA
Z1
Z2
Z3
R1
R2
Z
m
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F4,RB
Z1
Z2
Z3
R1
R2
Z
m
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F5,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F5,RB
Z1
Z2
Z3
R1
R2
Zm

fault locations of double phase (B-C) fault are
presented. From this figure, the impact of the
UPFC on the measured impedance is seen in
subfigures b, c, e, g, i. Based on these subfigures,
we can observe some notes:
o
(a) (b)
(c) (d)
(e) (f)
(g) (h)
(i) (j)
of Single phase to ground fault seen by relay A and relay B for an SSSC-
compensated transmission line at operation point 2.
o Relay A in 14-a and relay B in 14-ido not
affect by the UPFC, because the location of
the relay is between the device and the fault.
So, we can observe that the UPFC doesn’t
impact the relay if it isn’t in the path of the
fault. Refer to this comment, if a fault
occurred between the relay and the UPFC,
the relay should not be affected, see
subfigures d, f, and h.
o The underreach problem is seen in 14-b and
14-i. in the first case relay, B didn’t feel the
fault in its zones due to the UPFC.
o Overreach problems with a significant
change in the impedance angle are seen in
14-c, 14-e, and 14-g.
o The overreach problem and the underreach
problem may be seen if the fault is near or
far from the relay location respectively. It is
very important to mention here that the relay
may not operate in the first zone while the
overreach problem in the measured
impedance is observed. That happens
because of the significant change in the
measured impedance makes it out of the
first zone. This note is not observed in the
previous tables 4-7. The same general
comments are observed in the second
scenario, UPFC in the middle of the line.
The SSSC-Compensated transmission line
measured impedance of single-phase to ground
faults at different locations is presented in figure
15. From the figure, we can observe some other
comments:
• The main problem in the SSC compensated
transmission line is the underreach problem.
No overreach problem is observed.
• The SSSC impacts the measured impedance
either if it is between the relay and the fault or
not. From a, d, f, and h, we can see that the
pre-fault impedance angle is changed.
Figure 16 shows the measured impedance at
different locations of three-phase fault in a
STATCOM-Compensated transmission line.
From the figure, we can say that the effect on the
STATCOM on the distance relay can be ignored.
This result is matched with the previous tables
4,5. For this fault case (three-phase fault), no
difference can be observed between the
STATCOM compensated transmission line and
the non-compensated transmission line. For other
faults, single-phase, or double-phase faults, a
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F1,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F1,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F2,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F2,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F3,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F3,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F4,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F4,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F5,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F5,RB
Z1
Z2
Z3
R1
R2
Zm

small difference can be observed, but still can be
ignored. The second scenario, STATCOM in the
middle of the transmission line, has small
difference observations, but these observations
were not affected on the relay operations.
(a) (b)
(c) (d)
(e) (f)
(g) (h)
(i) (j)
of the Three-phase fault seen by relay A and relay B for the STATCOM-
compensated transmission line at operation point 1.
The impact of the STATCOM compensated
transmission line on the distance operation is very
effected by the fault resistance. The effect of the
fault resistance on the other FACTS compensated
transmission line is less than the STATCOM.
The second scenario, FACTS in the middle, is
simulated for the three FACTS devices in both
operation cases. The same general comments are
observed in the second scenario. For the SSSC
compensated transmission line, an adaptive
directional relay block may be generated based on
the operation point of the FACTS device to
overcome the directional issue. This scheme is
also tested for different fault resistance at
locations, the results show that the proposed
scheme is better than the traditional for the non-
compensated transmission line also.
5. CONCLUSION
In this paper, the impact of FACTS devices
(UPFC, STATCOM, and SSSC) on the distance
relay operation is clarified. A lot of general
comments on the operation point of the FACTS
device is cleared. A new pilot distance scheme is
presented to overcome the problems of under or
overreach in the distance relay for the
compensated transmission line. The proposed
scheme can be used for non-compensated
transmission lines also. The problem of fault
resistance should be covered in this scheme. The
modeling of a numerical distance relay in
MATLAB/ Simulink is presented in this paper.
The model is tested for different types of fault at
different locations. The results show that the
MATLAB/ Simulink is a very good environment
to model different protective relays. In this
project, the relay is modeled in both the discrete
mode solver and the phasor model. Both modes
give good accuracy for the zones' reach.Different
FACTS devices (UPFC, STATCOM, and SSSC)
are considered as examples of FACTS devices.
The results show that the proposed scheme is a
comprehensive solution for the under/overreach
problems in distance relays. The proposed scheme
is tested for different FACTS- Compensated
transmission line. The problem of
under/overreach may occur for non-compensated
transmission lines in case of high resistance fault.
This scheme is primness for this case in addition
to the compensated transmission lines.
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F1,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F1,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F2,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F2,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F3,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F3,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F4,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F4,RB
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F5,RA
Z1
Z2
Z3
R1
R2
Zm
-20 -10 0 10 20 30 40
R (Ohm)
-20
-10
0
10
20
30
40
50
F5,RB
Z1
Z2
Z3
R1
R2
Zm

REFERENCES
[1] Sadhu, Rajib, and P. S. Bhowmik. "Different Setting of Unified
Power Flow Controller (UPFC) and Its Effect on Performance of
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[2] Guan, Rui, Ying Xue, and Xiao-Ping Zhang. "Advanced RTDS-
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protection." The Journal of Engineering 2018.15 (2018): 1038-1042.
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