Journal of Energy and Power Engineering 14 (2020) 179-186 doi:10.17265/1934-8975/2020.06.001

A Study on the Protection Relay Test and Analysis

Method of AC Electric Railway Substation

Dae-Seok Kang1, Woo-Sik Won1, Byung-Lib Ahn1 and Byeong-Gon Lee2

1. EntechWorld, Inc., 196 Gasan Digital 1-ro, Geumcheon-gu, Seoul 08502, Korea

2. Korea Railroad Corporation, 240 Jungangno, Dong-gu, Daejeon 34618, Korea

Abstract: Since opening of the Korean high-speed railway in 2004, the rate of electrification has been increasing rapidly, and safety of the supply of AC railways has become very important. And the digital protection relays in railway feeding system need more attention with the expansion of unmanned SSs (substations) and digital SSs. For accident prevention, it is necessary to develop accurate modeling and simulation technology for railway feeding devices of electric railway. And it is also important to continuously improve test methods and develop excellent relay algorithms and apply them to the protection system to prepare for unexpected accidents. In this study, after reduced modeling the AC railway power supply system using PSCAD/EMTDC (Power Systems Computer Aided Design/Electromagnetic Transient DC Analysis), the results were compared and verified with the numerical calculation using the symmetric coordinate method. It also presents a method of using the verified results for simulation and education for various railway accidents. This study result will be used for the construction of new lines as well as existing lines in the future railway business. Key words: Electric railway, digital protection relay, modeling, PSCAD/EMTDC.

1. Introduction

With the opening of the high-speed railway in 2004

in Korea, electric railway technology for safety has

also rapidly developed. However, more fundamental

countermeasures are needed for large and small

accidents that may occur in large-scale personnel

transportation [1]. AC electric railway SSs (substations)

are installed at intervals of about 50 km, and SP

(Section Post) and SSP (Sub-Section Post) are installed

between each SS. The SP and SSP installed between

each SS are for division and extension of the electric

feeding section. These electric rail power supply

devices are monitored in real time by a protection relay

for safety. The protection relay used in the AC electric

railway power system is mostly dependent on foreign

products.

Digital protection relay operation algorithms used for

power system protection are classified into various types

Corresponding author: Woo-Sik Won, Technical Research

Center in Entechworld Inc., research fields: protection relay, fault locator and power quality management.

according to application targets such as transmission

lines, transformers, buses and generators. Recently, the

protection relay has been developing rapidly, but the

relay algorithm currently applied is not perfect yet. In

particular, since the electric train is a moving load, it is

necessary to prepare for unexpected accidents, and to

continuously improve test methods and develop

excellent relay algorithms and apply them to the

protection system. In order to prevent malfunction of

the protection relay and fault locator installed for the

safety of the railway power supply system, modeling

and simulation reflecting the actual field system are

required. In addition, it is necessary to develop various

solutions to increase users’ accident analysis abilities.

In this paper, we investigated the operation and test

method of the electric railway power system protection

relay. And we have developed the new protection relay

for the power supply system evaluation solution based

on PSCAD/EMTDC (Power Systems Computer Aided

Design/Electromagnetic Transient DC analysis). The

developed protection relay evaluation system can be

used for various accident simulation and education.

D DAVID PUBLISHING

A

180

2. Electric

2.1 AC Railw

There are

AT (Auto T

power supp

supplied thr

line, and in t

the feeder l

below.

Fig. 1 is

method. The

and the dista

AT method

SSs are ins

distance betw

is about 10 k

Fig. 1 BT ele

Fig. 2 AT el

In additio

of electric r

called IED

important d

power suppl

is an intelli

Study on the

c Railway D

way Protectio

e BT (Boost

Transformer)

ly method. I

rough the ca

the AT metho

line. The tw

the BT me

e distance bet

ance between

is Korean AC

stalled at int

ween SPs an

km.

ectrical railwa

ectrical railwa

on, there are v

railways, and

(Intelligent E

device for th

ly. IED of a

gent comput

e Protection R

Digital Prot

on Relay

er Transform

method for

In the BT m

atenary line a

od, power is

wo methods a

ethod and Fi

tween BT SS

n AT SSs is

C Railway’s

tervals of ab

d SSPs instal

ay power system

ay power system

various devic

d the digital

Electronic D

he safety of

recent trend

tational relay

Relay Test an

tection Rela

mer) method

electric rail

method, powe

and the sub-

supplied thro

are compared

ig. 2 is the

Ss is about 30

40~100 km.

standard and

bout 50km.

lled between

m.

m.

ces for the sa

protection r

Device) is a v

electric rail

of multifunc

y, which sam

nd Analysis M

ay

and

lway

er is

feed

ough

d as

AT

0 km

The

d AT

The

SSs

afety

relay

very

lway

ction

mples

an i

digi

faul

T

loca

mai

curr

und

Tab

AN

Ov

Un

Ov

Un

Dis

Dif

Fau

V

SP

Tab

Recsec

Tra

Feesec

In

burn

occ

and

prob

failu

due

circ

freq

sect

Method of AC

input at a pre

ital value, an

lt or not by in

Table 1 sum

ations of AC

in AC protec

rent relays, o

dervoltage rel

ble 1 AC railw

NSI device

ercurrent

dercurrent

ervoltage

dervoltage

stance

fferential curren

ult locator

Various accid

and SSP are

ble 2 SS prote

Fa

ceiving ction

ShGr

ansformer InOv

eding ction

ShGrUn

n the electri

nout of trans

ur due to ove

d ground fa

blems of ca

ure due to in

e to overvol

cuit, ground

quent failure

tion [3, 4].

Electric Rail

edetermined p

nd compares

nternal algorit

mmarizes the

C railway prot

tion relays us

overcurrent re

lays and dista

way protection

Numbers

#50/51(O

#37(UCR

#59(OVR

#27(UVR

#21

nt #87

#99(FL)

dents occurrin

summarized

ection relay fai

ault type

hort circuit round fault

nternal problem vervoltage

hort circuit round fault ndervoltage

ic railway s

sformers and

ercurrent acci

aults. In ad

apacity reduc

sulation brea

ltage in the

fault, and un

es in the ca

way Substati

period and co

and determi

thm.

e names and

tection relay

sed in SSs ar

elays, overvo

ance relays [2

n relay.

s Remark

OCR) Feeding

R) SP/SSP

R) Receivi

R) Receivi

Feeding

Transfo

Feeding

ng in electric

in Table 2.

ilure.

Symptoms

Overcurrent

Short circuit

Overcurrent Overvoltage Unable norm

substation, a

d peripheral

idents due to

ddition, there

ction and po

akdown and w

transformer

ndervoltage a

se of the p

ion

onverts it to a

ines whether

d installation

system. The

re differential

oltage relays,

2].

k

g section

P

ing section

ing/Feeding

g section

ormer section

g section

c railway SS,

mal operation

problem of

devices may

short circuits

e are some

ower supply

winding short

r. The short

accidents are

ower supply

a

r

n

e

l

,

,

f

y

s

e

y

t

t

e

y

A

2.2 AC Prote

The diffe

relay #21 o

short circuit

the train to

finding the c

describes the

relay. Fig. 3

the ratio diff

Fig. 3 Test o

In Korea

transformers

#87 is intend

case of an

transformer

primary side

the external

train operati

The differ

between the

transformer

coil in the

transformer

operation. T

suppression

differential c

Study on the

ection Relay

rential curren

operate in the

t accident in

block the fa

cause of the

e differential

3 explains th

ferential relay

of differential c

’s AC powe

s are used. T

ded to protec

n internal fa

protection re

e, the transfo

fault of the

ion.

rential curren

e primary an

in the suppr

e relay for

to determin

Table 3 descr

current co

current relay.

e Protection R

Operation

nt relay #87

e event of a

the power s

ault current a

failure. The

current relay

he operating c

y.

current protec

er railway SS

The different

ct the Scott tra

ault of the

elay should b

rmer should

transformer

nt relay detec

nd secondary

ression coil a

internal pr

ne whether

ribes the cor

orrection con

Relay Test an

and the dista

a ground faul

supply system

and contribut

following bri

y and the dista

characteristic

ction relay.

S, Scott and

tial current r

ansformer. In

transformer,

be cut off on

be inoperativ

or to the nor

cts the differe

y currents of

and the opera

rotection of

the relay is

rrection ratio

nditions of

nd Analysis M

ance

lt or

m of

te to

iefly

ance

cs of

AT

relay

n the

the

n the

ve to

rmal

ence

f the

ation

the

s in

and

the

Tab

Set

Pic

Slo

Slo

HO

F

dist

rela

curr

(pot

outp

dete

the

circ

Fig.

T

each

In

und

mar

Method of AC

ble 3 Differen

tting range

ck-up current

ope 1

ope 2

OC

Fig. 4 describ

tance protect

ay calculates

rent input thr

tential trans

puts TRIP

ermining the

relay install

cuit or ground

. 4 Test of dis

Table 4 descr

h protection

order to p

der-reach in d

rgin of about

Electric Rail

ntial current pr

Differential current (%)

15%

35%~40%

70%

70% of shor

bes the opera

tion relay (#

impedance

rough CT (cu

sducer), and

signal. That

direction and

ation locatio

d fault [5].

stance protecti

ribes the dista

zone of the

prevent mal

distance rela

20% is reflec

way Substati

rotection relay

rt circuit

ating characte

#21). Distanc

value from

urrent transdu

d determines

t is, it is

d electrical d

n to the poin

ion relay.

ance and time

distance prot

lfunction of

ay operation,

cted.

ion 181

y setting.

Restrain current (pu)

1.0

5.0

≥ 10.0

≥ 10.0

eristics of the

ce protection

voltage and

ucer) and PT

s error and

operated by

distance from

nt of a short

e settings for

tection relay.

f over- and

a correction

e

n

d

T

d

y

m

t

r

.

d

n

A

182

Table 4 Diff

Dist

Zone 1 Dist

Tim

Zone 2 Dist

Tim

Zone 1 is

and it is typ

length. Zon

there is no

Operating ti

cycle. Zone

primary line

exact fault

120%~125%

provides su

fault impeda

should note

protection to

3. Protecti

3.1 AC Railw

The digita

and dynamic

test, a simpl

usually ev

characteristi

system accid

Hardware-In

or dynamic c

relay is relat

very comple

so the test m

In electric

involve larg

simulate the

compare it w

Study on the

ferential curre

tance relay setti

tance 85

me 0.0

tance 12

me 0.2

s meant for p

pically set to

ne 1 provide

intentional ti

ime of Zone

1 does not c

e because it

location. U

% of primary

ufficient marg

ance and othe

e that Zone

o a part of the

ion Relay T

way Protectio

al protection r

c characterist

le characteris

valuated, w

ic test, it is us

dents or malf

n-the-Loop (H

characteristic

tively simple

ex accident an

method is also

c railway po

ge fault curren

e fault curre

with the actua

e Protection R

ent protection r

ing P

5%~90% P

05s

20%~125% E

2s

protection of

o cover 80%~

es fastest pro

ime delay as

e 1 can be o

cover the ent

is difficult to

Usually Zon

line impedan

gin to accou

er errors in re

e 2 also pr

e adjacent line

Test and M

on Relay Test

relay test is d

tics. In the sta

stic of the pr

whereas in

sed to check t

functions. Fig

HIL) test pro

cs. The static

but the dyna

nalysis has a

o quite difficu

ower systems

nts. So it is v

ent by each

al value.

Relay Test an

relay setting.

Purpose

Prevent error

Expand protect

the primary

~95% of the

otection bec

ssociated wit

of the order o

tire length of

o distinguish

ne 2 is set

nce Zone 1.

unt for non-

elaying. Also

ovides back

e.

Modeling

t

divided into s

atic character

rotection rela

the dyna

the occurrenc

g. 5 describes

ocedure for s

test of protec

amic test used

variety of inp

ult.

s, most accid

very importan

fault mode

nd Analysis M

tion

line

line

ause

th it.

of 1

f the

h the

t to

This

zero

one

k up

tatic

ristic

ay is

amic

ce of

s the

tatic

ction

d for

puts,

dents

nt to

and

Fig.

F

stat

rela

the

site

amp

pow

stor

CO

In

cha

exte

Om

Fig.

Method of AC

. 5 Protection

Fig. 6 introdu

tic and dyna

ay. The simul

data stored i

e are input

plifier to dete

wer system s

rage data i

MTRADE fi

the test of

annels applied

ernal analo

micron-CMC3

. 6 Protection

Electric Rail

n relay HIL-tes

uces several

amic characte

lation result o

in the protec

to the prote

ermine wheth

imulation ou

is played b

ile and used

this study,

d to the pro

og amplifier

356 (protectio

n relay test syst

way Substati

st procedure.

methods fo

eristics of th

of RSCAD o

ction relay at

ection relay

her there is a

utput data or

back in th

for accident

there were

otection relay

r and the

on relay test s

tem.

ion

r testing the

he protection

or PSCAD or

the accident

through an

a failure. The

the accident

he form of

analysis [6].

two signal

y. One is an

e other is

set).

e

n

r

t

n

e

t

f

.

l

n

s

A

3.2 Electric

The electr

and simulat

V-source an

order to test

V1 and I1

output termi

In the 6-te

between vo

following E

AC electric

Fig. 7 Linea

Power is

sources, tran

time, a vo

impedance o

is %Z, whic

of the line

percentage.

expressed b

the reference

The follo

circuit and

system of th

receives 154

Power Corp

transformer.

Study on the

Railway Pow

rical power sy

ted as a cir

nd I-source b

t electrical fa

of the input

inal, it can be

rminal netw

oltage and c

q. (1), and is

rail power su

ar four-port ne

V1

V1'

I1

I1'

=

a11aa21aa31aa41a

s supplied t

nsmission lin

ltage drop

of each devic

h is importan

voltage drop

Conversion

y Eq. (2) wh

e capacity is

%Z = Q

V2

owing Fig.

simulation c

he AC railro

4 kV from

p.) and transfo

.

e Protection R

wer System M

ystem can be

rcuit configu

based on a 4

aults of the sy

t terminal an

e expressed as

work model,

current is ex

s used for mo

upply system.

twork.

a12a13a14

a22a23a24

a32a33a34

a42a43a44

V2

V2'

I2

I2'

to the load

nes and trans

occurs due

ce. The imped

nt in modeling

p and the ra

of %Z and

hen the line v

Q.

Z2 × 100%

8 shows re

circuit of th

oad. The ele

the KEPCO

forms it into

Relay Test an

Modeling

e simply mod

uration of R

-port networ

ystem. Assum

nd V2, I2 of

s shown in Fi

the relation

xpressed as

odeling the ac

2

2 (1)

through po

sformers. At

to the spe

dance at that t

g. %Z is the r

ated voltage

d ohm value

voltage is V

educed mode

he power sup

ectric railway

(Korea Elec

55 kV in a S

nd Analysis M

deled

RLC,

rk in

ming

f the

ig. 7.

nship

the

ctual

ower

this

cific

time

ratio

as a

es is

and

(2)

eling

pply

y SS

ctric

Scott

(a) M

(b)

Fig.

T

3-ph

M-p

diff

T

tran

to t

betw

rail

sup

resp

In

the

spe

num

met

PSC

ana

Method of AC

Modeling of e

Simulation cir

. 8 Modeling

The Scott tra

hase power

phase and T

ference as sin

The AT rece

nsformer, tran

the feeding li

ween the cate

is connected

plies 27.5 kV

pectively.

n power syste

simulation v

cific acciden

merical calcu

thod and

CAD/EMTDC

alysis.

Electric Rail

electric railwa

rcuit using PS

circuit for AC

ansformer rec

and outputs

T-phase have

ngle-phase ou

eives the 55

nsforms it int

ine. The auto

enary line an

d to its center

V to the cat

em modeling

value were c

nt in the tra

lation using t

the simu

C are compar

way Substati

ay substation

SCAD/EMTD

railway system

ceives KEPC

two 55 kV.

e only 90 d

utputs.

kV output

to 27.5 kV, an

otransformer

nd the feeder

r. In other w

enary-rail an

g, the calculat

compared by

ain feeding

the symmetri

ulation res

red and used

ion 183

DC

m.

CO’s 154 kV

The 55 kV

degree phase

of the Scott

nd supplies it

is connected

line, and the

words, the AT

nd feeder-rail

ted value and

y assuming a

system. The

ic coordinate

sults using

d for accurate

3

V

V

e

t

t

d

e

T

l

d

a

e

e

g

e

A Study on the Protection Relay Test and Analysis Method of AC Electric Railway Substation

184

Table 5 shows the impedance values for the

calculation of 154 kV single line-to-ground fault

current. The numerically calculated single

line-to-ground fault current (Ig) is shown in Eq. (3).

Table 5 154 kV single line-to-ground fault impedance.

Z = R + jX Ω R X

Zero sequence component 1.0296 5.2232

Positive sequence component 0.5853 3.8554

Negative sequence component 0.5853 3.8554

Combined component 2.202 12.934

IG=3E

Z0+Z1+Z2=

3

13.12×

154kV

√3=20.33kA (3)

3.3 Protection Relay Evaluation System Development

RTDS (Real Time Digital Simulator) based

real-time simulators, which have recently attracted

attention as power system simulators, have economic

and technical difficulties. So, in this study, we

developed a relatively simple PSCAD based IED

(Intelligent Electronic Device ; protection relay)

simulator as a pre-test tool prior to RTDS based

simulation as a new solution, and in the future it can

be also used for field education. Fig. 9 is an HIL-test

hardware configuration of the IED simulator for

electric railways developed based on PSCAD in this

study [7, 8].

Fig. 9 HIL-test configuration of IED simulator.

The graphic plots in Fig. 10 are the protective relay

(#87, #21) simulation results obtained from the

HIL-test program developed in this study.

Fig. 10 HIL-test configuration of IED simulator.

The differential current relay (#87) monitors the

current ratio of the primary and secondary sides of the

Scott transformer to check for abnormalities. And the

distance relay (#21) measures and monitors the

impedance of the feeding section to check whether it

is fault or not.

3.4 Fault Simulation of Electric Railway SS

Fig. 11 is a simulation result of accident currents

that may occur in AC railway SS, and these results are

compared with numerical values. It shows the

simulation results using PSCAD/EMTDC, targeting

154 kV single line-to-ground current, 3-phase short

circuit current, 55 kV line-to-line short circuit current,

and 27.5 kV single line-to-ground current.

A

(a) Single lin

(c) Line-to-li

Fig. 11 AC r

Table 6

values of th

kV single

consistency,

was 97.8%,

was 92.9%,

current was Table 6 Fau

Unit: kA (Reference : 100 MVA)

(A)Calculation

(B)Simulation(A)/(B)

The follo

current of th

of the ‘Non

Honam Lin

confirmed th

through the

showed 96.2

in the simula

Study on the

ne-to-ground

ine short circu

railway fault c

compares th

he symmetric

line-to-grou

, the 154 kV

the 55 kV lin

, and the 27

97.0%.

ult simulation c

154 kV

Single line -to-ground

n 20.33

n 22.00 92.4%

owing Fig.

he 27.5 kV c

nsan ~ Bongm

ne in Korea

hat the groun

COMTRAD

2% agreemen

ation.

e Protection R

(b) 3-phase s

uit (d) Single

current simulat

he calculated

coordinate m

und current

V 3-phase sho

ne-to-line sho

7.5 kV singl

current.

154 kV 53-phase Short circuit

InSc

23.04 2

23.56 297.8% 9

12 shows th

catenary line

myeong’ sect

a. The faul

nd fault curre

E file stored

nt with the 5

Relay Test an

short circuit

e line-to-groun

tion result.

d and simul

method. The

showed 92

ort circuit cur

ort circuit cur

le line-to-gro

55 kV 27.5 knternal

Short circuit

Single-to-gro

2.60 5.201

2.80 5.3692.9% 97.0%

he ground f

at the substa

tion of the K

lt current v

ent was 5.57

in the relay,

5.3 6kA obta

nd Analysis M

nd

lated

154

2.4%

rrent

rrent

ound

kV

e lineound

%

fault

ation

KTX

value

7 kA

and

ained

Fig.

4. C

In

incr

quic

con

and

perf

rela

for

PSC

occ

a r

sho

sho

line

27.5

con

calc

circ

but

agre

grou

In

dev

situ

Ac

T

Infr

Rai

Method of AC

. 12 Ground

Conclusion

n a situation

reases and be

ckly and acc

ntinuous data

d software

formance eva

ays was condu

each type

CAD/EMTDC

urring in the

esult, the 15

wed 92.4%

rt circuit cu

e-to-line shor

5 kV single

nsistency. In

culations and

cuit accidents

almost iden

eement with

und fault of

the future,

velopment are

uation analysi

knowledgm

This study wa

rastructure a

ilway Techno

Electric Rail

fault current o

n

where the sc

comes more c

curately resp

accumulation

development

aluation syst

ucted, and sim

along with

C for analys

AC railway

54 kV singl

consistency

urrent show

rt circuit curr

line-to-groun

n the com

d simulations

s, they tend n

ntical. In add

the actual m

the 27.5 kV

the results

e expected to b

is and field tra

ments

as conducted

and Transpor

ology-Project

way Substati

of 27.5 kV cate

cale of the p

complex, it is

ond to incid

n. In this stud

t required

tem for digit

mulations we

reduced mo

sis of vario

power supply

le line-to-gro

y, the 154

wed 97.8%,

rent was 92.

nd current sh

mparison of

for ground fa

not to be 100

dition, it sho

measurement

V catenary lin

s of this r

be used for va

aining.

by the Mini

rt’s Research

(20RTRP-B

ion 185

enary line.

power system

s necessary to

dents through

dy, hardware

to build a

tal protection

ere conducted

deling using

us accidents

y system. As

ound current

kV 3-phase

the 55 kV

.9%, and the

howed 97.0%

f numerical

ault and short

0% identical,

owed 96.2%

result of the

ne of the SS.

esearch and

arious failure

stry of Land,

h Project on

146034-03).

5

m

o

h

e

a

n

d

g

s

s

t

e

V

e

%

l

t

,

%

e

.

d

e

,

n

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