ABB Circuit Shield 87B - OTHER APPLICATIONS; Restricted Earth-Fault Protection

High
-
Impedance
Differential
Relays
IB
7.6
.
1.7
-
7
Page
15
OTHER
APPLICATIONS
The
following
diagram
shows
the
typical
connections
of
the
Type
87
B
high
-
impedance
relay
in
a
scheme
that
provides
ground
fault
protection
for
transformer
or
generator
windings
.
This
arrangement
is
sometimes
referred
to
as
"
restricted
earth
-
fault
Protection
"
.
The
scheme
provides
sensitive
ground
-
fault
detection
for
its
zone
of
protection
,
and
is
stable
for
faults
outside
the
zone
.
All
four
ct
’
s
must
have
the
same
ratio
,
and
be
dedicated
to
the
87
B
relay
.
iZ
.
(
-
)
(
)
iri
0
*
7
06
j
—
OG
O H
TYPE
67
B
r
-
86
2
86
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-
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Courtesy of NationalSwitchgear.com