Siemens Static Trip III - Ground Fault Sensing Diagrams

Ground
Fault
Sensing
Diagrams
Ground
Fault
Sensing
Diagrams
iH"lriiirj^*Ln
-0"
"oit'g";;
to
accommodate
the
followins
oround
faulL
sensing
scnemes'
I
3-Pha.",
3-Wire
Residual
.
3-Phase,
4-Wire
Residual
.
Direct
Ground
.
ZeroSequence
The
following
are
brief
descriptions
of
the
ground
f ault
sensing
schemes
as
they
r"rutu
iJir'5
siatic
Trip
l'il
trip
units
Detailed
technical
and
applicatiJn
rnfot"tion
on
the.
oround
fault
sensino
schemes
i.
"onilin"iln
in?
s-i"nn"nt
rlitrical
Prod-
uits
Siecitication
Guide
(SG 3061)'
Residual
(3-Phase,
3-Wire)
-
Under
normal
system
conditions'
(withoul
the
presence
oiu
gto;O
l'yl.:f ,vector
sum
of
thenhaseCUrrentsbelngmonitoredbythetripunitiszero.This
i."rf#i;;i;;;;
th;
Jondition
of
ah
overc.urrent
phase-to-
ohase
fault
and
phase t'nOutun""
condrtion
When
a
phase{o-
Xl';;;ii;;ii";i*i,
L1"""ioi
"'
or
the
phase
currents
is
Xl;:i,,
f
t"p"iiiiJi,o
tne
magnitude
or
the
sround
rault
rhe
trip
unit's
microprocessot
"Jt
this
vector
sum
data
in
the
execution
of
the
grounJiu*
ptt""tion
function
The
trip
unit
,illr"tiH"
,i"in"ur
nt"ux"i
current
sensors
No
external
cur-
rent
sensors
are
required'
Circuit
breaker
current
sensors
are
available
with
separate
2000A
grouno sensor*]iJ'gi
t"
Orovile-tt1
1200A
maxi-
;"u"ri';;";;;-fault
pickup
'"itins
iequired
bv
NEC
Article
230-95
for
service
"ntt'i""
app-lications
Wiring
diagrams
for
the
two
3-Phase,
i-Wit"
glo'1d
fa{!
sensing
schemes
are
given in
the
Curre'nt'S"ntlot
Wiring
Diagrams
section
ln
either
case,
tr,e
curreni
t"ntott
are
ilounGd
on
the
circuit
6t"rx"t.
N.i
external
current
sensors
are
required'
Residual
(3-Phase,
4-Wire)
-
ln
the
3
Phase'^4
Wire
Residual
scheme
a
fourth
",""nt-J"nior
is
connected
in
the
neutral
conductor
to
Sense"lormat
neutrat
currents
Under
normal
svstem
conditions
tf'e
vector
sum
of
the
currents
in
all
phases
:'"",;;i.';;
.;;i;rl
;r;;;iThis
is also
true
under
the
condition
;i#;";;"r;[n]
pr'tut"
io-phase
fault
and
phase
unbalance
condition.
When
a
phase-to-ground
fault
occ-Lrrs'
the
fault
current
returns
uiu
u
putt't"Jtf'Lrif'an
tfre
neutral'
Therefore'
the
vector
sum
of
the
phaJe
currents
no
longer
equals
the
neutral
current.
frris
c'lrieni
ditferentiat
is
detected
by
the
i,",'t.*it
*J
uied
in
the
execution
of
the
ground
fault
pro-
i"E,i""
i,l".i,Jn.
6rr.,."ni
#n#i
wit.t
separate
2000A
NEC
;;;;;st-
,;;-usable
toi
t"n's
ilnsins
scheme'
iust
as
for
3-
pHr.","5
wiie
residual
giorno
sens'ing
(see
current
sersor
Wiring
Diagrams),
Direct
Ground
-
ln
this
scheme'
the
phase
c,urrents
are
not
used
in
detecting
unO
plJ""ittg
grornd
faults
The
trip
unit
;H.ji;;
il;g';,,n0
ti'ii
p'Li""iiJ"
runcrron
based
on
data
from
a
ground
current
Jenloi
if
':
:"L:.:^t^is
located
on
the
neutral
connection
to
gio'nO
at
the
service,entrance'
and
is
connected
to
tne
appr6[t't"l"p't
terminals
on
the
trip
unit
(see Current
Sensor
Wiring
lJiagrams'7
Zero
Sequence
-
This
scheme
is
very
similar
to
the
Residual
6"rlirll"i|le
traoitionaimethod
is
touse
a
core
balance
tvpe
current
sensor
wf,icn
lncircl6s
all
phase
conductors
and
neutral
on
a
four
wire
tVJ"'
UnO"r
nolmal
:I:t"'
conditions
"t
"
rf.lrt"
i"-phase
iauti
conOltion'
there
is
no
output
from
;h"'#;r;;
i"
TH"
liip
,"ii
o"ta"e
the
vector
sum
of
the
currents
through
tne
selsor
winJow
is
z.ero.,lf
a
ground
fault
occurs,
the
ground
"'ii"i
it
not
s""n
by,the
sensor'
which
t*,".
tl,
,f-rJ
*,t""
by
I
patn
ottrer
than
through
the
sensor
*"i"d;.1'h;."n.o,
oZt"its
this
current
rmbalance
and
pro-
vides
the
data
requirei'OV
jn"
tiip
unit
to
execute
l?
g]"^Y:d
irr["pi"t#i"n
lunction
The
zeto
sequence
sensor
rs
con-
nected
to
the
appropiut"
inp't
t"tminals
of
the
trip
unit
(see
Crii"nt
Sensor'Wirlng
Diagrams)'
Alternatively,
three
orfour
current
sensors
orstandard
CT's
can
be
connected
togetnll,
"
*'tft
the
Besidual
Schemes
de-
scribed
above.
tn
tl^'ls
JasJ]ho*"u"t'
only
the
electrlcal
sum
of
the
sensor
outputs
it"it"lj
us
Jite"t
input
to
the
trip
unit's
oround
fault
circuit
tlrminats
(the
sensors
are
not
used
for
X;;u.
";;;"i
l.prtl"iHills
tr'e
etectrical
equivalent
of
the
it;;il;;i
.ugndti"'"o,,e
balance
summation'
Breaker
Mtd
C!rrefl
Sensors
N.!lral
Bus
Cur:ent
Sensors
Residual
Sensing,
Circuit
Breaker
Wiring
for
Ground
Protection
(3-
Phase,
4-Wire
SYstem
Shown)
18
Direct
Ground
Current
Sensing
Aiernate
Pcs
t
on Oi
Zero
Seque:.e
Sefso'
Nelta
D
sconnact
Lnr
Zero
Sequence
Ground
Fault
Protectlon