Modelling and Testing of a Numerical Pilot Distance Relay for … · 2020. 12. 10. · mho distance relay. The model is valid for different types of faults and different locations

International Journal of Scientific Research and Engineering Development-– Volume 3 Issue 6, 2020

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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, Email:[email protected] *Electrical engineering department, engineering college, Mutah university, Jordan

Email: [email protected],[email protected] *Corresponding Author: [email protected] , Tel.: +00-962-796515220

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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 misoperation of 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, including single-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.

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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 this study, the

Impact of STATCOM on distance relay in case of

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external fault is less than in the case of an 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 fault

based on the measuring impedance between the

current transformer point and fault location. To

apply this simple concept, it is necessary to

identify seven loops to cover all types of faults. For

all loops the basic equation is used:

𝑍𝑚 =𝑉𝑚𝐼𝑚

(1)

The measured impedance (𝑍𝑚) is based on the measured voltage (𝑉𝑚) and current (𝐼𝑚). 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:

𝑍𝑚 = 𝑍𝐿 𝐶𝑇𝑟𝑎𝑡𝑖𝑜𝑛𝑉𝑇𝑟𝑎𝑡𝑖𝑜𝑛

(2)

Where 𝑍𝐿: the actual line impedance. The difference between the loops is the definition of the

measured voltage and the measured current,

𝑉𝑚 𝑎𝑛𝑑 𝐼𝑚. The table below shows the measured voltage and current, which are used in equation (1)

for the seven loops. TABLE I

MEASURED QUANTITY DEFINITION OF THE SEVEN LOOPS.

Fault loop Measured

voltage (𝑽𝒎) Measured

current (𝑰𝒎) A-G 𝑉𝐴 𝐼𝐴 + 𝐾0𝐼0 B-G 𝑉𝐵 𝐼𝐵 + 𝐾0𝐼0 C-G 𝑉𝐶 𝐼𝐶 + 𝐾0𝐼0 A-B / A-B-G 𝑉𝐴 − 𝑉𝐵 𝐼𝐴 − 𝐼𝐵 B-C / B-C-G 𝑉𝐵 − 𝑉𝐶 𝐼𝐵 − 𝐼𝐶 C-A / C-A-G 𝑉𝐶 − 𝑉𝐴 𝐼𝐶 − 𝐼𝐴 A-B-C 𝑉𝐴 𝑜𝑟 𝑉𝐵 𝑜𝑟 𝑉𝐶 𝐼𝐴 𝑜𝑟 𝐼𝐵 𝑜𝑟 𝐼𝐶

Where 𝐾0 = 𝑍0−𝑍1

𝑍1 , 𝑍0, 𝑍1: zero and positive

sequence impedance and 𝐼0 :zero sequence current. When a fault occurs on the line, fault with

impedance, the measured impedance is given by:

𝑍𝑚 = 𝑚 𝑍𝐿 + 𝑅𝑓

Where 𝑚 =𝐿𝑓

𝐿 , 𝐿𝑓: the distance between relay

point and fault location. L: total length of the

protected line. 𝑅𝑓: 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.

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Figure (1) shows the traditional three-stepped

zones mho characteristic.

Z1

Z2Z3

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. These zones

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 ±90⁰. 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:

RARB

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





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 Z2 Z2 Z3 Z3 N/O

B-G Z1 Z2 Z2 Z3 Z3 N/O

C-G Z1 Z2 Z2 Z3 Z3 N/O

A-B Z1 Z2 Z2 Z3 Z3 N/O

A-B-G Z1 Z2 Z2 Z3 Z3 N/O

B-C Z1 Z2 Z2 Z3 Z3 N/O

B-C-G Z1 Z2 Z2 Z3 Z3 N/O

C-A Z1 Z2 Z2 Z3 Z3 N/O

C-A-G Z1 Z2 Z2 Z3 Z3 N/O

A-B-C Z1 Z2 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 in two

different operation cases. Tables 4, 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

RAFACTS 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






type



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 Table VI

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)


of Double phase fault seen by relay A and relay B for a UPFC-compensated

transmission line at operation point 1.

Figure 14 shows the measured impedance of the

UPFC- Compensated transmission line. Different

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:





(a) (b)

(c) (d)

(e) (f)

(g) (h)

(i) (j)

Fig. 15. The measured impedance at different locations (F1, F2, F3, F4, F5) 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-i do 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 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.

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Modelling and Testing of a Numerical Pilot Distance Relay for … · 2020. 12. 10. · mho distance relay. The model is valid for different types of faults and different locations