Internati
o
nal
Journal of Ele
c
trical
and Computer
Engineering
(IJE
CE)
V
o
l.
4, N
o
. 2
,
A
p
r
il
201
4, p
p
.
17
9
~
19
2
I
S
SN
: 208
8-8
7
0
8
1
79
Jo
urn
a
l
h
o
me
pa
ge
: h
ttp
://iaesjo
u
r
na
l.com/
o
n
lin
e/ind
e
x.ph
p
/
IJECE
New Techniques for Disconnector Switching VFT Mitigation
in GIS
MA Abd-Allah
1
, A
S
a
id
1
, Ebra
him A Ba
dra
n
2
1
Faculty
of Engineering
at
S
houb
ra, B
e
nha University
,
Eg
y
p
t
2
Faculty
of
Engineering
,
Mansou
ra University
, Eg
y
p
t
Article Info
A
B
STRAC
T
Article histo
r
y:
Received Nov 22, 2013
Rev
i
sed
Jan 16, 201
4
Accepte
d
Fe
b 7, 2014
Switching oper
a
tions in a Gas In
sulated S
ubstations (GIS) generate v
e
r
y
fast
transien
t over vo
ltag
e
s (VFTO) which ar
e dang
erous for the tr
an
sformer and
the s
y
s
t
em
ins
u
lation
be
cause
of th
eir
short
rise
tim
e.
Under spec
ia
l
circum
s
t
anc
e
s
the overvolt
a
ges
can aris
e c
l
os
e to the trans
f
orm
e
r Bas
i
c
Insulation
Lev
e
l (BIL). The red
u
ction
of
VFTO amplitudes is
consider
ed
main challenges. Therefor
e, VFTO in the 220 kV
Wadi-Hoff GIS i
s
analy
z
ed
and the worst
case for disconnector sw
itching is
predic
te
d using
EMTP/ATP
in this paper.
VFTO
m
itigati
on tec
hniqu
es are studied in
this work.
Furtherm
ore, proposed techniqu
es ar
e present
e
d
for m
itigating the VFTO.
The proposed
techn
i
ques can
be used b
y
the mainten
a
nce engineers
,
transformer designers, and GIS
insula
tion manu
factur
es. The results show
that the proposed techniques
hig
h
ly
re
du
ce the V
F
TO in a simple
manner
Keyword:
GIS
VFT
Mitig
atio
n
Tech
n
i
q
u
e
s
EMTP/AT
P
Copyright ©
201
4 Institut
e
o
f
Ad
vanced
Engin
eer
ing and S
c
i
e
nce.
All rights re
se
rve
d
.
Co
rresp
ond
i
ng
Autho
r
:
A Sai
d
,
Faculty of E
n
gineering at
Shou
bra, Benh
a
Un
iv
ersity, Eg
y
p
t
Em
a
il: ab
d
e
lrah
m
a
n
.
g
hon
iem@fen
g
.bu
.
edu
.
eg
1.
INTRODUCTION
GIS is
widely use
d
in electric po
wer syste
m
in recent de
cades beca
use
of its advanta
g
es such as
co
m
p
act size, p
r
o
t
ectio
n
from p
o
llu
tio
n, a
few m
a
in
ten
a
n
ce, and
h
i
g
h
reliab
ility. In
sp
i
t
e o
f
th
ese advan
t
ag
es,
G
I
S
h
a
s
u
n
i
que pr
ob
lem
s
, such
as th
e v
e
r
y
f
a
st vo
ltag
e
increase
due to reflections
of
switch
i
ng
tran
si
en
ts at
v
a
ri
o
u
s
j
u
n
c
tion
s
with
in
th
e
GIS [1-2
]. These tran
sien
ts
are ori
g
inated
within the
GIS any time
there is an
i
n
st
ant
a
ne
o
u
s
chan
ge i
n
v
o
l
t
a
ge.
They
ha
v
e
ve
ry
sh
o
r
t
ri
se t
i
m
e
s, i
n
t
h
e ra
nge
o
f
4 t
o
10
0
ns
, a
n
d
are
n
o
rm
all
y
fo
llo
wed
b
y
o
s
cillatio
n
s
hav
i
n
g
freq
u
e
n
c
ies in
t
h
e rang
e of 100
kHz to
50
MHz [2
]. Th
ey cau
se
trav
eling
wav
e
s in
tern
ally in
sid
e
th
e
GIS, t
r
av
elin
g fro
m
GIS
b
u
sh
i
n
g to
ex
tern
al co
m
p
onents
. T
h
is ca
n lead
to
dam
a
g
e
th
e
in
su
lation
o
f
in
tern
al bu
sb
ar
an
d tran
sf
orm
e
r,
wh
ich
i
n
fl
u
e
n
t
th
e op
erating
reliab
ility o
f
GIS,
accelerate agi
n
g
of tra
n
sform
e
r ins
u
lation a
n
d re
duce tra
n
sform
e
r life [1-3].
Als
o
, VFTO as
sociated with
V
e
r
y
Fast Tr
an
sien
t Cur
r
e
n
t
s (
V
FTC
)
r
a
d
i
ate electr
o
m
a
g
n
e
tic f
i
eld
s
dur
ing
its p
r
op
ag
atio
n
thro
ugh th
e
co
ax
ial GIS
bu
s section
.
The tran
sien
t electro
m
ag
n
e
tic
f
i
el
ds get
co
u
p
l
e
d t
o
t
h
e c
o
nt
r
o
l
eq
ui
pm
ent
or
dat
a
cables of
t
h
e GIS [4].
In fact
,
t
h
e re
spo
n
se be
havi
or of
zi
nc
o
x
i
d
e
(Z
n
O
) s
u
rge arresters to
suc
h
Ve
ry Fas
t
Transie
n
ts
(VF
T
) i
s
n
o
t
wel
l
charact
eri
zed, a
nd t
h
e t
u
rn
-o
n t
i
m
e of Zn
O su
rge a
r
r
e
st
ers m
a
y be m
u
ch l
onge
r t
h
an t
h
e
rise tim
es of t
h
e
VFT
.
T
h
e
r
efore, the t
r
adi
tional Z
n
O
s
u
r
g
e a
rrest
e
r
s ca
nn
ot
s
u
pp
ress
t
h
e w
a
ve
st
ee
pne
ss
because surge
arresters
do not act fa
st enough to prevent t
h
e switchi
ng
transients with
steep front [5].
Thi
s
pa
per i
n
v
e
st
i
g
at
es t
h
e VFTO res
u
l
t
e
d f
r
om
t
h
e operat
i
on o
f
di
sc
on
n
ect
or swi
t
c
he
s at
di
ffere
nt
sen
s
itiv
e po
in
t
s
in
tern
al and
ex
tern
al th
e 220
kV
W
a
d
i
-Hoff GIS. Th
e 22
0
k
V
Wad
i
-Ho
f
f GIS is tak
e
n
as a
case study. T
h
erefore
,
VFTO in the
220 kV
Wadi
-Hoff GIS is analyzed
a
nd t
h
e worst case for disc
onnector
switch
i
ng
is pred
icted
u
s
ing
EMTP/ATP.
VFTO mitig
at
io
n
techn
i
qu
es are stu
d
i
ed
i
n
th
is
work
. Fu
rth
e
rm
o
r
e, in
th
is p
a
p
e
r, p
r
o
p
o
s
ed
t
echni
q
u
es a
r
e
prese
n
t
e
d
f
o
r
m
i
ti
gat
i
ng t
h
e
VFT
O
.
The
p
r
op
ose
d
t
ech
ni
q
u
es ca
n
be us
e
d
by
t
h
e m
a
i
n
tenance
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
IJEC
E V
o
l
.
4, No
. 2, A
p
ri
l
20
14
:
17
9 – 1
9
2
18
0
engi
neers
,
t
r
a
n
sfo
r
m
e
r desi
g
n
ers
,
a
n
d
G
I
S
i
n
s
u
l
a
t
i
on
m
a
nufactures. T
h
e
results s
how that t
h
e
propos
ed
t
echni
q
u
es
hi
g
h
l
y
re
duce
t
h
e
VFT
O
i
n
a si
m
p
l
e
m
a
nner.
2.
MODELING OF
THE 22
0 KV WADI-HOFF
GIS
Du
e to
th
e trav
elin
g
n
a
ture o
f
th
e tran
si
en
ts, th
e d
i
fferen
t co
m
p
on
en
ts can
b
e
mo
d
e
led
b
y
d
i
stribu
ted
p
a
ra
m
e
ter lin
es, su
rg
e im
p
e
d
a
n
c
es an
d
trav
elin
g
tim
es. Eac
h
GIS sectio
n is si
m
u
la
ted
b
y
it
s
equi
val
e
nt
ca
p
aci
t
a
nce an
d i
n
duct
a
nce,
w
h
i
c
h ca
n
be
det
e
r
m
i
n
ed as
fol
l
o
w
s
[6
-7]
.
m
F
o
d
D
/
)
(
ln
2
C
(1
)
m
H
d
D
L
/
2
ln
(2
)
d
D
d
D
C
L
ln
60
ln
2
/
Z
0
(3
)
s
m
LC
v
/
1
(4
)
whe
r
e C a
nd
L are the
capa
c
itance
and the inductance
of the
GIS bu
sb
ar, resp
ectiv
ely. d
is the
out
si
de
di
am
eter
of
t
h
e
G
I
S
b
u
s
b
ar
an
d
D i
s
t
h
e i
nne
r diam
eter of t
h
e
GIS e
n
clos
ure
.
Z
0
is
the
surge
im
pedance
an
d
v i
s
t
h
e
pr
o
p
a
g
at
i
o
n
vel
o
ci
t
y
.
Th
e sing
le lin
e d
i
ag
ram
o
f
th
e su
b
s
tation
un
d
e
r stud
y is i
llu
strated
in
Fig
u
re 1
.
Th
e 220
/66
/
11
kV
Wadi
-Hoff substation unde
r st
udy consists of four inc
o
m
i
ng feede
r
s,
two feede
r
s each of 30
km length, and
t
h
e ot
he
r t
w
o f
eeders eac
h o
f
3 km
l
e
ngt
h.
The s
ubst
a
t
i
o
n
i
n
cl
udes t
h
ree
12
5 M
V
A,
22
0/
6
6
/
1
1 k
V
,
p
o
we
r
tr
an
sf
or
m
e
r
s
. Th
e f
e
ed
er
s are co
nn
ected
in a tw
o
b
u
sb
ar
ar
r
a
n
g
e
m
e
n
t
with
a b
u
s coupler
. The equ
i
v
a
len
t
ci
rcui
t
s
o
f
t
h
e
di
f
f
ere
n
t
G
I
S
com
pone
nt
s a
n
d
t
h
e
val
u
e
s
of t
h
e
di
ff
ere
n
t
param
e
t
e
rs i
n
t
h
e
si
m
u
l
a
t
i
on
are
summ
arized in Table
1.
Fi
gu
re
1.
Ty
pi
cal
si
ngl
e l
i
n
e
di
ag
ram
for
W
a
di
-
H
o
f
f
G
I
S
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
New Techn
i
ques fo
r
Disco
nnecto
r
S
w
itch
i
ng
VFT Mitiga
tio
n
i
n
GIS
(MA
Abd
-
Allah
)
18
1
Tabl
e 1. In
f
o
r
m
at
i
on
f
o
r si
m
u
l
a
t
i
o
n
GI
S Busbar
Z
0
= 70
Ω
and
v=270
m
/
us
Circuit Breake
r
I
n
the closed position: im
p
e
dance of 70
Ω
In the open positio
n: capacitances of 90 pF
(either end to ground)
and 50 pF(between
contacts)
Disconnector
,
and E
a
r
t
hing Switch
I
n
the closed position: im
p
e
dance of 70
Ω
In the open positio
n: capacitances of 30 pF
(either end to ground)
and 30 pF(between
contacts)
Potential T
r
ansfor
m
e
r
Capacitance of 10
0 pF towar
d
s gr
ound
Cur
r
e
nt tr
ansform
e
r
Z
0
= 70
Ω
and
v=270
m
/
µs
Sur
g
e Ar
rester
200 pF in ser
i
es with a gr
ounding r
e
si
stance of 0.
1
Ω
.
Over
head T
r
ans
m
ission L
i
ne
Z
0
= 250
Ω
and v
=
300
m
/
µs
Elbows, Spacers
,
a
n
d
Spherical Shields
lu
m
p
ed capacitance of 15 pF towar
d
s gr
ound
Bushing
Im
pedance of 70
Ω
and 100 pF towar
d
s gr
ound
The
beh
a
vi
or
of t
h
e s
p
ar
k i
n
di
sco
n
n
ect
o
r
ope
rat
i
o
ns ca
n
be
rep
r
ese
n
t
e
d
by
a dy
nam
i
cal
l
y
vari
abl
e
resistance
with a controllable
collapse
t
i
m
e
[1]
.
The
di
sc
o
nnect
or
swi
t
c
h
(D
S)
rest
ri
kes
are m
odel
e
d
as an
exponentially decaying resist
an
ce in series
with a sm
all resistance.
Thi
s
is im
ple
m
ented
using a
Type-91,
TACS
tim
e-varied resistance
in EMTP/ ATP. The
va
riab
le resistan
ce
is calcu
lated
fro
m
th
e fo
llowing
equat
i
o
n:
r
e
R
t
t
)
0
(
)
(
R
(5
)
whe
r
e R
(
0
)
is
12
10
o
h
m
and t
h
e
t
i
m
e
const
a
nt
t
i
s
1
ns
.
r re
prese
n
t
s
t
h
e s
p
ar
k
resi
st
ance
aft
e
r
vol
t
a
ge
b
r
ea
kd
ow
n a
n
d i
s
as
s
u
m
e
d t
o
be
0.
5
Ω
[2
, 3, 8]
. Du
ri
n
g
t
h
e GI
S
D
S
cl
osi
n
g ope
rat
i
o
n,
t
h
e vol
t
a
ge
b
r
eakd
own
takes abou
t 4
n
s
,
so
t
h
e
D
S
clo
s
in
g
ev
en
t
is m
odele
d as
a
n
e
x
ponentially decreasing
resis
t
ance.
The nonlinea
r resistance dec
r
eases
fr
o
m
h
i
gh
v
a
lu
e (1
012
)
to
0.5
Ω
i
n
ab
ou
t 5 ns as
sho
w
n
in Figur
e
2
.
Fi
gu
re
2.
D
S
r
e
si
st
ance be
ha
vi
o
r
du
ri
n
g
cl
o
s
i
n
g
eve
n
t
At h
i
g
h
frequ
e
n
c
ies, t
h
e
wind
ing
o
f
t
r
ansfo
r
m
e
r b
e
h
a
v
e
s lik
e a cap
acitiv
e n
e
t
w
ork
co
n
s
isting
of
series capacita
nces
betwee
n t
u
rns a
n
d coils, and s
h
unt
capacitances bet
w
een turns an
d
co
ils to
th
e grou
nd
ed
core a
n
d t
r
a
n
sf
orm
e
r t
a
nk.
So
, t
h
e t
r
a
n
sf
orm
e
rs are si
m
u
lated
in
th
is
wo
rk b
y
th
eir su
rg
e
cap
acitan
ces.
Th
ese
equi
val
e
nt
ca
p
aci
t
a
nces are i
n
t
h
e
ra
nge
f
r
o
m
2 t
o
10
nF
[
1
,
2,
3]
. T
h
e t
r
ansf
o
r
m
e
r i
s
m
odel
e
d as a
ca
paci
t
o
r
with
2
nF as g
i
v
e
n
in
[2
]. EMTP/ATP is used
to
si
m
u
late
th
e su
b
s
tation
u
n
d
e
r stu
d
y
. Fig
u
re 3
illu
strates th
e
22
0
k
V
Wadi
-
H
o
f
f
G
I
S m
o
d
e
l
i
n
EM
TP/
A
TP.
3.
OVERVOLTAGES OF DI
SCO
N
NECT
OR SWIT
CH
ING
Th
ere are several switch
i
ng o
p
e
ratio
ns to ach
iev
e
som
e
purpose s
u
c
h
as ene
r
gizi
ng
feede
r
s,
energizing tra
n
sform
e
r, CB ma
intenance, e
t
c. At e
n
ergizi
ng
fee
d
er
s
or t
r
ans
f
orm
e
r, di
sco
nnect
or i
s
cl
osed
firstly, and
t
h
en
th
e CB is closed
.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
IJEC
E V
o
l
.
4, No
. 2, A
p
ri
l
20
14
:
17
9 – 1
9
2
18
2
Tabl
e
2 s
h
o
w
s
di
ffe
re
nt
o
p
er
a
t
i
ng m
odes
of
di
sco
n
n
ect
or
s i
n
t
h
e
st
u
d
i
e
d
s
y
st
em
.
At
t
h
e op
erat
i
n
g m
odes of
di
scon
nect
o
r
, t
h
e
VFT
O
i
s
calcu
lated
at th
e in
t
e
rn
al po
in
ts
o
f
GIS (B
B
1
and BB2
), the
trans
f
o
r
m
e
rs term
inals (Tr1,
Tr2
,
an
d Tr
3
)
an
d
th
e
GIS term
in
als su
ch
as at SF6
/air b
u
sh
ing
(
L
1, L2
,
L3,
an
d L4)
.
Figur
e 4 show
s t
h
e V
F
TO
at sev
e
r
a
l
p
o
i
n
t
s
du
e to d
i
ff
er
en
t
op
er
ating
m
o
d
e
s
o
f
di
sco
n
n
ect
or
s
w
i
t
c
hi
n
g
.
It
ca
n
be see
n
t
h
at
m
ode#1 i
s
t
h
e
wo
rst
case
o
f
d
i
scon
nect
o
r
op
erat
i
o
n
i
n
t
h
e s
t
udi
e
d
sub
s
t
a
t
i
on. It
i
s
obse
r
ved t
h
at
t
h
e peak m
a
gni
t
ude
of t
h
e g
e
nerat
e
d VF
T
O
at
Tr1i
s a
b
o
u
t
2.
0
4
p
u
, w
h
i
l
e i
t
i
s
ab
ou
t 1
.
60
pu
at Tr
2
,
1.58
pu at Tr
3
,
1
.
44
pu
at L2
, 1
.
14
pu
at L3
, 1
.
13
pu
at L4
, 1
.
22
pu
at BB1
an
d
1.14
pu
at
B
B
2
.
Al
so
, t
h
e
wave
s
h
ape
of
t
h
e
ge
nerat
e
d
VFT
O
at
T
r
1
i
s
sh
o
w
n
i
n
Fi
gu
re
5.
Fi
gu
re 3.
EM
T
P
/
A
TP
M
o
del
fo
r Wadi
-H
of
f GIS
Tabl
e 2. O
p
era
t
i
ng
m
odes of
vari
ous
di
sc
o
n
n
ect
o
r
s
i
n
2
2
0
kV
M
ode
Power
Supply
Opened CB
Oper
ating DS
#1
line 1 out
CB1
DS 5
#2
line 2 out
CB2
DS 7
#3
line 3 out
CB3
DS 10
#4
line 4 out
CB4
DS 12
#5
All lines connected
CB5
DS 14
#6
All lines connected
CB6
DS 15
#7
All lines connected
CB7
DS 20
4.
VFTO SUPP
RESSI
ON
TECH
N
IQ
UES
Up t
o
date, t
h
e
m
a
in challenges are the re
duction
o
f
V
F
T
O
am
pl
i
t
udes. T
h
e resea
r
c
h
ers
conce
r
ns o
n
fi
n
d
i
n
g t
h
e o
p
t
i
m
u
m
t
echni
que f
o
r s
u
p
p
r
es
si
ng
VFT
O
. S
e
veral techniques are
use
d
to re
duce t
h
e harm
ful
effects of the VFT
O
[2, 5, 7, 8, 9]
. The important techniques are studied
in
th
is wo
rk
to
cho
i
ce th
e su
itab
l
e
tech
n
i
qu
e fo
r
su
ppr
essing
t
h
e V
F
TO
v
a
lu
e to a safe on
e
[9
].
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
New Techn
i
ques fo
r
Disco
nnecto
r
S
w
itch
i
ng
VFT Mitiga
tio
n
i
n
GIS
(MA
Abd
-
Allah
)
18
3
Fi
gu
re
4.
C
o
m
p
ari
s
on
bet
w
ee
n Se
ve
ral
M
o
d
e
s o
f
Di
sco
n
n
e
c
t
o
r
O
p
erat
i
o
n
Fi
gu
re
5.
V
F
T
O
at
T
r
1
(
W
o
r
s
t
C
a
se)
4.1. The
Appr
opriate L
o
ad
Side Terminal
s
The
peak
m
a
gni
t
ude
an
d
fre
que
ncy
c
ont
e
n
t
of
VFT
de
pe
nds
o
n
t
h
e t
e
r
m
i
n
al
com
pon
ent
co
n
n
ect
ed
to
th
e GIS. The ter
m
in
al co
mp
on
en
ts
can
be cab
les, g
a
s-in
su
lated
lin
es (G
IL)
,
or
o
v
er
hea
d
t
r
ansm
i
ssi
on
l
i
n
es
(O
HTL
)
.
Tabl
e
3
gi
ve
s t
h
e
el
ect
ri
c par
a
m
e
ter
s
of th
ese term
i
n
al co
m
p
on
en
ts.
Table
3. T
e
rm
inal com
p
one
n
t data
T
e
r
m
inal co
m
ponent
Sur
g
e im
pedance
(
)
Pr
opagation veloci
ty
,
v, (
m
/µs)
GI
L 70
270
OHT
L 250
300
XL
PE Cable
30
165
Th
e attenu
ation
o
f
VFT
with ti
m
e
d
e
p
e
n
d
s
o
n
th
e typ
e
and
leng
t
h
o
f
lo
ad
si
d
e
term
in
al co
m
p
o
n
en
t
connected to
the GIS
[8].
There
f
ore, the
VFT can be
mitigated
by replacem
ent with the
appropriate
termin
als. Si
mp
licity, lo
w cost i
m
p
l
e
m
en
tat
i
o
n
,
and
m
i
n
i
m
u
m ch
an
g
e
s in
th
e in
stalled
GIS are t
h
e
m
a
in
adva
nt
age
s
of
t
h
i
s
t
echni
q
u
e.
Pract
i
cal
l
y
i
n
Wadi
-H
of
f G
I
S, 5 m
OHTL on t
h
e s
o
urce s
i
de t
e
rm
i
n
al
s and
11
m OHTL on t
h
e loa
d
side t
e
rm
inals are used.
It is cl
ear that the lowe
st values
occu
r
wi
t
h
usi
n
g
c
a
bl
e
t
e
rm
i
n
at
i
ons.
Al
so, t
h
e pea
k
val
u
es dec
r
ea
sed wi
t
h
i
n
c
r
e
a
si
ng t
h
e ca
bl
e
l
e
ngt
h
.
These
can be ex
pl
ai
ned as;
th
e cab
le
atten
u
a
tes th
e
VFTO
d
u
e to its cap
acitan
c
e
t
o
gr
o
u
n
d
,
w
h
i
c
h e
ffect
i
v
el
y
re
duce
d
t
h
e
VFT
O
m
a
gni
t
ude
. Fi
gu
re 6 s
h
o
w
s t
h
e effe
ct
of t
e
r
m
i
n
al
l
e
ngt
h o
n
VFTO
peak
at Tr1. It is
clearly seen that with
len
g
t
h
in
creases th
e VFTO
red
u
c
es. Also
, Fig
u
re 7
illu
st
rates a co
m
p
arison
b
e
tween
th
e
VFTO at Tr1
in
two
load te
rm
inal c
a
ses; 11 m
OHTL and
11 m
cable.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
IJEC
E V
o
l
.
4, No
. 2, A
p
ri
l
20
14
:
17
9 – 1
9
2
18
4
Fi
gu
re
6.
The
peak
o
f
t
h
e
VFTO at Tr1
term
in
al Vs th
e l
o
ad
-si
d
e term
in
al len
g
t
h
4.
2. T
h
e
Cap
a
ci
tance
a
t
T
r
a
n
sf
ormer T
e
r
m
i
n
al
Lum
p
ed s
h
unt
capacitance
is
use
d
t
o
dam
p
the
VF
T
O
i
n
m
a
ny applications. The
ca
pacitance is
arisin
g
in
surge arrestors, cap
acitiv
e vo
ltage tran
sf
o
r
m
e
rs (CVT), cab
les, o
r
ad
d
ition
a
l cap
acito
r on th
e
trans
f
orm
e
r terminals. The ca
pacitan
ce
value is change
d ac
cording to t
h
e
specifications
of t
h
e system
.
Many
researc
h
es
use
the capacitanc
e with diff
e
r
en
t
val
u
es [
2
,
1
0
]
.
Tabl
e 5
gi
ve
s the effe
ct of t
h
e shunt capac
itance
at th
e tran
sformer ter
m
in
als. It is
clearly s
een that,
by increasing the ca
pacitance, the VFT
O
due to
DS re
-
strik
i
ng
will b
e
fu
rt
h
e
r red
u
c
ed
at t
r
an
sfo
r
m
e
rs term
in
al
s (Tr1, Tr2, and
Tr3
)
. Th
is effect
is g
r
eatly sho
w
n
for
capacitance
val
u
es
from
0.1 nF to
10
nF, whereas the
val
u
e
s
above
10
nF
d
o
no
t affect
on
th
e resu
lts.
Fi
gu
re
7.
C
o
m
p
ari
s
on
bet
w
ee
n t
h
e
V
F
T
O
at
Tr1
i
n
ca
se
of
OHT
L a
n
d
C
a
bl
e l
o
a
d
t
e
rm
i
n
al
s
Table
4. E
f
fect of lum
p
ed ca
pacitance on
VFTO a
n
d
VFTC
Capacitance
(n
F)
Tr1
Tr2
Tr3
VFT
O
(
pu)
VFT
C
(
pu)
VFT
O
(
pu)
VFT
C
(
pu)
VFT
O
(
pu)
VFT
C
(
pu)
W
ithout
2.
04
0.
87e-
1
5
1.
60
0.
21e-
3
1
1.
58
0.
61e-
1
5
0.
1
1.
49
0.
14e-
1
4
1.
21
0.
12e-
1
4
1.
30
0.
13e-
1
4
0.
8
1.
11
0.
30e-
1
4
1.
06
0.
89e-
1
4
1.
06
0.
89e-
1
4
1.
0
1.
08
0.
90e-
1
4
1.
06
0.
91e-
1
4
1.
06
0.
90e-
1
4
10
1.
01
0.
72e-
1
3
1
0.
67e-
1
3
1.
06
0.
67e-
1
3
50
1
0.
89e-
1
3
1 0.
10e-
1
2
1 0.
95e-
1
3
100
1
0.
62e-
1
2
1 0.
62e-
1
2
1 0.
62e-
1
2
Zoo
m
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
New Techn
i
ques fo
r
Disco
nnecto
r
S
w
itch
i
ng
VFT Mitiga
tio
n
i
n
GIS
(MA
Abd
-
Allah
)
18
5
Fi
gu
re
8 sh
o
w
s t
h
e i
n
fl
uence
of t
h
e c
a
paci
t
a
nce
com
p
one
n
t on the
VFT
O
and the
VFTC at Tr1.
Fi
gu
re
8 ca
n b
e
use
d
t
o
p
r
o
v
i
d
e a s
o
l
u
t
i
o
n
f
o
r c
h
oo
si
ng
the op
ti
m
u
m
v
a
lu
e
o
f
t
h
e capa
c
itance com
p
onents
.
Th
is op
tim
u
m
p
o
i
n
t
is ach
ieved
at th
e in
tersectio
n
po
in
t
of th
e two
cu
rves. So
,
t
h
e adding an e
x
tra
surge
arrester whic
h has
a
ca
pacitance
around 10 nF
(t
he op
tim
u
m
v
a
lu
e) can
help
to ach
iev
e
t
h
e
o
p
tim
u
m
p
o
in
t at
Tr
1, Tr
2, an
d
Tr
3.
In
o
r
de
r t
o
re
d
u
ce the
V
F
T at
the
po
we
r tra
n
sfo
r
m
e
r,
th
e app
licatio
n
o
f
su
rg
e cap
acito
rs i
s
a feasib
le
alternative
due to s
p
ace limita
tion and
cost, if t
h
e
s
u
itable capacit
a
nce
value is
selected. Bec
a
use
of
i
m
p
o
ssib
ility o
f
add
i
ng
cap
acitan
ce in
h
i
gh
v
o
ltag
e
sy
stems, th
e cou
p
ling cap
acito
r vo
ltag
e
tran
sfo
r
m
e
r with
cap
acitan
ce
o
f
1
0
n
F
is
u
tilize
d
instead
o
f
poten
tial tran
sformer [2
].
Fig
u
re 9
illu
strates a co
m
p
arison
b
e
t
w
een
th
e
VFTO
at Tr1
in
case o
f
with
ou
t
an
d
with
a
cap
acitan
ce
o
f
1
0
nF.
It is clearly seen
t
h
e
h
i
g
h
redu
ctio
n of o
s
cillatio
n
s
and
th
e v
a
l
u
e
o
f
VFTO.
Fi
gu
re
8.
I
n
fl
u
e
nce
of
C
a
paci
t
a
nce C
o
m
p
o
n
e
nt
o
n
VF
TO
a
n
d
V
F
TC
at
T
r
1
Fi
gu
re
9.
C
o
m
p
ari
s
on
bet
w
ee
n t
h
e
V
F
T
O
at
Tr1
in
case
o
f
with
ou
t an
d wi
th
sh
un
t cap
acitan
ce
4.
3. Shu
nt Res
i
stor Disc
onne
ctor
Switchin
g
The s
w
itching
resistance is connecte
d
in
parallel w
ith the contacts of the
disconnector
s
w
itch.
W
i
t
h
the arc to be s
h
unted
by the resistan
ce, a part of the arc c
u
rrent fl
ows th
rough the re
sistance, the arc c
u
rrent
will
d
ecreases an
d
th
e rate o
f
d
e
ion
i
zatio
n
of
th
e arc
p
a
th
will b
e
in
creased [9
,
10
].
The i
n
st
al
l
a
t
i
on
of
o
p
eni
n
g
and
cl
osi
n
g
re
si
st
or
has a ce
rt
ai
n ap
pl
i
cat
i
o
n
i
n
or
der
t
o
i
nhi
bi
t
t
h
e
gene
rat
e
d
VFT
O
i
n
G
I
S [
9
]
.
The s
h
u
n
t
resi
st
or act
s as
a bufferi
ng elem
e
n
t to the
tra
n
sient process
,
leaking
the rem
a
ining charge a
nd a
b
s
o
rbing the
ove
rvoltage e
n
ergy. Shunt resis
t
ance accel
erates the decay of the
transient proce
ss.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
IJEC
E V
o
l
.
4, No
. 2, A
p
ri
l
20
14
:
17
9 – 1
9
2
18
6
Fig
u
r
e
10
show
s th
e V
F
TO
w
h
en
th
e shunt r
e
sisto
r
is u
s
ed
. Th
e eff
ect o
f
ch
an
g
i
n
g
t
h
e r
e
sistan
ce
val
u
e
on t
h
e V
F
TO at
se
veral
poi
nt
s i
n
G
I
S
i
s
used
. The a
m
pli
t
ude o
f
V
F
TO i
s
de
crea
sed as t
h
e s
w
i
t
c
hi
n
g
resistance inc
r
eases.
W
ith i
n
creasing the s
w
itching re
sist
ance from
0 to 400 oh
m
,
the VFT
O
noticeably
d
ecr
eases. A
s
t
h
e
sw
itch
i
ng
r
e
sistan
ce
in
cr
eased
b
e
yond
4
0
0
o
h
m
,
th
e V
F
TO
d
ecr
eased slo
w
ly.
It
i
s
show
n t
h
a
t
at
t
h
e swi
t
c
hi
ng r
e
si
st
ance o
f
40
0
Ω
, an
o
p
ti
m
u
m so
lu
tion
is g
e
t. Furtherm
o
r
e, th
e
maxim
u
m
voltage t
o
ground
at each
c
o
m
p
onent
and t
h
e
percenta
ge
of voltage i
n
creasi
n
g are
gi
ve
n in Tabl
e
6. Fi
g
u
r
e 1
1
sh
ows t
h
e com
p
ari
s
o
n
bet
w
ee
n
t
h
e vol
t
a
ge wa
vef
o
rm
s of Tr
1
i
n
case of wi
t
h
an
d wi
t
h
o
u
t
shu
n
t
resistance.
Table
6. E
f
fect of Shunt Resis
t
ance on
VFT
O
Case
VFT
O
(
pu)
Tr1
Tr2
Tr3
L1
L2
L3
L4
BB1
BB2
W
ithout shunt r
e
sistor
2.
04
1.
60
1.
58
0
1.
44
1.
14
1.
13
1.
22
1.
14
W
ith shunt r
e
sistor of 400
Ω
1.
14
1.
09
1.
08
0
1.
04
1.
03
1.
04
1.
04
1.
04
% Reduction
44
31
31
0
27
19
9
14
9
Fi
gu
re
1
0
.
VF
TO at
GI
S Te
r
m
i
n
al
s Vs s
w
i
t
c
hi
n
g
resi
st
or
val
u
e
Fi
gu
re
1
1
.
VF
TO at
T
r
1
wi
t
h
an
d
wi
t
h
o
u
t
s
h
unt
resi
st
ance
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
New Techn
i
ques fo
r
Disco
nnecto
r
S
w
itch
i
ng
VFT Mitiga
tio
n
i
n
GIS
(MA
Abd
-
Allah
)
18
7
4.4. Ferrite Ri
ngs
Tec
hnique
Ferri
t
e
i
s
a hi
gh
-f
re
que
ncy
no
nl
i
n
ea
r m
a
gnet
i
c
m
a
t
e
ri
al
. The fe
rri
t
e
ri
ngs i
s
use
d
a
r
o
u
nd
GI
S
co
ndu
ctor
s to
ab
sorb
th
e trans
i
ent energy when the DS restrikes to
i
nhi
bi
t
t
h
e VF
TO
. The
fer
r
i
t
e
ri
ngs ca
n be
si
m
p
lif
ied
to
a
n
o
n
lin
ear
inductan
ce an
d a
no
n
lin
ear
r
e
sistan
ce, i
n
ser
i
es
w
ith
G
I
S co
ndu
ctor
[7
, 8
]
.
A fer
r
i
t
e
ri
n
g
s
of l
e
n
g
t
h
o
f
0.
47 m
wi
t
h
an eq
ui
val
e
nt
d
i
am
et
er of 0.
1
5
m
,
havi
ng a
n
eq
ui
val
e
n
t
resistor of
70
Ω
an
d a
n
e
qui
v
a
l
e
nt
i
n
d
u
ct
a
n
c
e
o
f
0.
02
m
H
i
s
use
d
i
n
t
h
i
s
st
udy
.
Tabl
e 7
sh
o
w
s
t
h
e va
ri
at
i
on
o
f
V
F
TO at
se
v
e
ral
p
o
i
n
t
s
due
t
o
usi
ng m
a
ny
fer
r
i
t
e
ri
n
g
s.
The re
sul
t
s
show t
h
at the
increasi
n
g of
t
h
e n
u
m
b
er o
f
ri
ngs
f
r
o
m
1 t
o
3
gi
ves
g
r
eat
e
ffect
on
re
d
u
ci
ng
t
h
e
VF
TO
.
M
o
r
e
ri
n
g
s gi
ves s
m
al
l
effect
on
t
h
e VFT
O
. S
o
, t
h
e
opt
i
m
um
resul
t
i
s
fo
un
d
wi
t
h
usi
n
g 3
ri
n
g
s. Fi
g
u
re
12
illu
strates th
e
VFTO
wh
en 3
ferrite ring
s
are u
s
ed
at
Tr1
.
It is clearly seen
fro
m
Tab
l
e 7 th
at th
e redu
ctio
n
of
the VFT
O
is
20% at T
r
1,
7%
at Tr2,
6% at
T
r
3,
7%
at L
2
,
2% at L3 and
L
4
, a
n
d
2% at B
B
1 a
n
d BB2.
Tabl
e 7. Vari
at
i
on o
f
VFT
O
wi
t
h
t
h
e
n
u
m
b
er of fer
r
i
t
e
ri
n
g
s
No of r
i
ngs
VFT
O
(
pu)
Tr1
Tr2
Tr3
L1
L2
L3
L4
BB1
BB2
1
1.
45
1.
23
1.
20
0
1.
17
1.
08
1.
10
1.
09
1.
10
2
1.
33
1.
17
1.
14
0
1.
11
1.
06
1.
08
1.
07
1.
08
3
1.
23
1.
14
1.
12
0
1.
08
1.
05
1.
06
1.
06
1.
07
4
1.
20
1.
12
1.
11
0
1.
06
1.
04
1.
05
1.
05
1.
06
5
1.
18
1.
11
1.
10
0
1.
05
1.
04
1.
04
1.
05
1.
05
6
1.
15
1.
10
1.
09
0
1.
04
1.
03
1.
03
1.
05
1.
05
Fig
u
re 12
. VFTO
at
Tr1
with
and
with
ou
t ferrite
ri
n
g
s
4.
5. R
C
Fi
l
t
er
RC filters (R i
n
p
a
rallel with
C) h
a
v
e
b
e
en wid
e
ly
u
s
ed
to
pro
t
ect lo
ads. Also, th
ey h
a
v
e
b
e
en
widely used in vacuum circuit breaker
s to
suppress the over vo
ltag
e
s of th
e arcing
[7]. R
is u
s
ed
to
m
a
k
e
en
erg
y
attenu
ates and
C
reduces th
e ci
rcu
it
o
s
cillatio
n
frequ
en
cy.
In th
is wo
rk
RC
filter is
u
s
ed
as a sh
un
t
com
pone
nt
ne
xt
t
o
t
h
e m
a
i
n
trans
f
orm
e
r t
o
pr
ot
ect
i
t
.
R
i
s
vari
e
d
f
r
o
m
50
Ω
to 400
Ω
an
d C is
c
h
ang
e
d
fro
m
0
.
0
1
to
0
.
2
µ
F
[7
].
Th
e
o
p
timu
m
mitig
atio
n
o
f
th
e
VFTO i
s
fo
und
at R eq
u
a
l t
o
50
Ω
a
n
d
at
C
e
qual
t
o
0.
0
1
µF.
Tab
l
e 8 shows th
e variatio
n o
f
VFTO at
sev
e
ral
po
in
ts d
u
e to
u
s
ing th
e RC filter. Also
, th
e
p
e
rcen
tag
e
redu
ctio
n in ov
er vo
ltag
e
s is giv
e
n
.
It is
clearly seen that
this
techn
i
que on
ly pr
o
t
ect
s th
e
tran
sform
e
rs, wh
ereas t
h
e
o
t
h
e
r
po
in
ts i
n
GIS
d
o
no
t
affected
.
Figu
re
13 illu
strates th
e
co
m
p
ariso
n
b
e
tween
VFTO at Tr1
i
n
case of
with
an
d withou
t the RC filter.
Zoo
m
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
IJEC
E V
o
l
.
4, No
. 2, A
p
ri
l
20
14
:
17
9 – 1
9
2
18
8
Tab
l
e
8
.
Variat
io
n
of
VFTO at sev
e
ral
po
in
ts du
e to using
t
h
e RC
filter
Case
VFT
O
(
pu)
Tr1
Tr2
Tr3
L1
L2
L3
L4
BB1
BB2
W
ithout shunt RC filter
2.04
1.60
1.
58
0
1.44
1.14
1.13
1.22
1.14
W
ith shunt RC filter
1.008
1.0071
1.006
0
1.44
1.14
1.
13
1.22
1.14
% Reduction
50
37
36
0
0
0
0
0
0
Fig
u
re 13
.
C
o
m
p
ariso
n
b
e
tween
VFTO
at Tr1 with and
with
ou
t RC Filter
5.
THE PROPOSED TECHNIQUES
FO
R VFT
MITI
GAT
I
ON IN
GIS
In
creasing
t
h
e sh
un
t resistor v
a
lu
e g
i
v
e
s
a red
u
c
tion
of
VFTO bu
t th
is is still asso
ciated
with
h
i
gh
o
s
cillatio
n
s
, as g
i
v
e
n
in
section
4.3. Th
erefore, th
ese
o
s
c
illatio
n
s
can
b
e
fitted
b
y
a cap
acito
r
o
r
an
i
n
du
ct
o
r
i
n
series
with
th
e
resisto
r
.
In th
e
fo
llowing
sub
s
ectio
n
s
t
h
e two tech
n
i
q
u
e
s are in
v
e
stig
ated
.
5.1.
Shunted Series RC
Whe
n
resista
n
ce fixed at 400
Ω
and cha
n
ge capacitance value if
inc
r
ea
se capacitance
s
above 1µ
F
f
i
nd
n
o
ch
ange on
V
F
TO
peak
an
d if
r
e
du
ces cap
aci
t
a
n
ce bel
o
w
1µF
fi
n
d
great
ch
ange
o
n
re
duc
t
i
on
of
V
F
TO
p
e
ak
.
Table 9
gives t
h
e VFTO at the GIS term
inals in cas
e o
f
with
ou
t and
with sh
un
ted
series RC. Also
,
th
e p
e
rcen
tag
e
redu
ction
is g
i
v
e
n. It is
foun
d th
at th
e re
du
ct
io
n
is m
o
re th
an
th
at
wh
en
t
h
e shu
n
t
ed
resisto
r
is
use
d
(a
s
gi
ve
n
i
n
Ta
bl
e
6)
.
Fi
gu
re
1
4
s
h
o
w
s a
com
p
ari
s
on
bet
w
een
t
h
e VF
TO
at
Tr
1 i
n
case
of
w
i
t
h
an
d
with
ou
t shu
n
t
ed
series RC,
wh
ere R is
4
0
0
Ω
and C is
1pF.
Furt
herm
ore,
Fi
gu
re 1
5
gi
ve
s a com
p
ari
s
o
n
bet
w
een
t
h
e VFT
O
at Tr1 whe
n
a s
h
unte
d resistor of
40
0
Ω
i
s
used
and t
h
e
pr
o
pos
ed sh
u
n
t
e
d seri
es R
C
wi
t
h
t
h
e sa
m
e
resistance and C is 1pF. The fi
gure clearly
illu
strates th
e
red
u
c
tion
i
n
bo
th
th
e VFTO mag
n
itud
e
and
oscillatio
n
in
case of th
e pro
posed
tech
n
i
q
u
e
.
Tab
l
e
9
.
VFTO at sev
e
ral po
i
n
ts du
e to u
s
i
n
g
th
e sh
un
ted series RC
Case
VFTO (pu)
Tr1 Tr2 Tr3
L1
L2
L3
L4
bb1
bb2
Without
2.04
1.60
1.58
0
1.44
1.14
1.13
1.22
1.14
With shunted Series RC,
R = 400
Ω
+ C
= 1 pF
1.01
1.01
1.01
0
1.04
1.00
1.00
1.00
1.00
%
Reduction
50 37 36
0
30 20 11 18 12
Evaluation Warning : The document was created with Spire.PDF for Python.