ABB CIRCUIT SHIELD 87T - Page 16

Transformer
Differential
Relay
IB
7.6
.
1.7
-
4
Page
16
B
_
.
Instantaneous
Unit
Tests
:
in
the
testing
and
calibration
of
the
instantaneous
unit
,
high
currents
are
Apply
test
current
for
only
a
short
time
in
order
to
avoid
thermal
damage
.
shut
off
the
current
source
and
review
Selection
lowest
tap
value
(
2.9
A
)
for
the
initial
testing
will
reduce
the
test
current
CAUTION
:
required
.
If
the
expected
operation
is
not
obtained
,
your
connections
and
procedures
.
Wait
30
seconds
before
repeating
a
test
,
of
the
required
.
Typical
test
connections
are
shown
in
Figure
10
.
If
you
are
using
an
electronic
current
source
test
set
it
may
be
necessary
to
place
two
of
the
independent
sources
in
parallel
in
order
to
obtain
the
necessary
current
level
.
Be
sure
that
both
sources
are
set
for
the
same
phase
angle
and
connected
with
the
same
polarity
so
the
currents
add
together
at
the
relay
input
terminals
.
(
Alternate
method
:
for
test
sets
with
limited
capacity
,
the
required
test
current
will
be
reduced
to
one
-
half
of
normal
by
connecting
two
relay
input
windings
in
series
:
test
current
into
terminal
1
,
out
2
,
into
5
,
and
out
terminal
6
.
)
To
verify
the
factory
tting
of
10
x
tap
,
it
is
not
necessary
to
separate
the
upper
and
lower
circuit
boards
;
however
,
if
you
plan
to
recalibrate
the
relay
,
the
adjust
-
ment
potentiometer
R
119
is
located
on
the
lower
circuit
board
as
shown
in
the
circuit
board
layout
on
page
19
.
Use
of
the
18
point
extender
board
will
allow
easier
access
to
this
adjustment
.
-
a
Locate
the
connector
pins
labelled
1
through
5
on
the
module
board
-
see
circuit
board
layouts
on
page
19
.
To
defeat
the
operation
of
the
main
differential
unit
,
a
jumper
must
be
connected
temporarily
between
pins
3
and
5
.
(
Take
care
to
prevent
shorting
to
any
of
the
other
pins
.
)
Only
the
instantaneous
unit
will
remain
active
.
Apply
rated
dc
control
voltage
to
the
relay
.
The
relay
is
If
the
2.9
A
Increase
the
test
current
until
the
relay
operates
and
note
the
value
,
factory
calibrated
for
an
operating
point
of
10
x
tap
(
tolerance
+
/
-
15
%
)
.
tap
is
being
used
,
a
trip
should
be
obtained
at
25
-
33
A
.
and
repeat
the
test
until
the
desired
operating
point
is
obtained
.
If
necessary
,
readjust
R
119
At
the
completion
of
this
test
,
remove
the
temporary
jumper
.
C
.
Harmonic
Restraint
Tests
:
The
Type
87
T
uses
2
nd
harmonic
restraint
to
block
relay
operation
on
transformer
inrush
upon
energization
.
The
factory
calibration
is
restraint
for
2
nd
harmonic
content
of
15
%
and
above
.
and
it
is
not
necessary
to
separate
the
upper
boards
;
however
,
if
you
plan
to
recalibrate
the
relay
,
the
adjustment
potentiometer
R
217
is
located
on
the
module
board
of
the
lower
circuit
board
as
shown
Use
of
the
18
point
extender
board
will
To
verify
the
factory
setting
of
15
%
lower
circuit
in
the
circuit
board
layouts
on
page
19
.
allow
easier
access
to
this
adjustment
.
The
procedure
to
be
used
to
verify
the
harmonic
restraint
function
depends
on
the
type
of
test
set
being
used
:
the
more
modern
electronic
current
-
source
,
or
,
the
older
style
voltage
-
source
.
Most
electronic
current
-
source
units
can
be
set
up
to
provide
one
output
current
at
the
fundamental
and
another
output
at
the
second
-
harmonic
frequency
.
When
using
voltage
-
source
sets
,
the
relay
’
s
built
-
in
diode
is
used
to
generate
second
-
harmonic
.
1
,
Electronic
_
current
-
source
testing
:
a
.
Connect
the
relay
as
shown
in
Figure
11
.
Apply
rated
dc
control
volts
.
b
.
Set
the
taps
at
2.9
A
.
%
Diff
and
Minimum
Restraint
:
any
settings
.
c
.
Apply
4.0
amperes
of
fundamental
current
.
The
relay
should
close
its
output
contact
.
d
.
Apply
2
nd
harmonic
current
and
increase
its
value
until
the
output
Iznd
/
Ifu nd
X
100
.
Percent
2
nd
for
restraint
contact
drops
out
.
For
the
4.0
A
fundamental
,
restraint
should
occur
for
hnd
The
2
nd
harmonic
current
may
be
increased
and
decreased
to
determine
the
restraint
and
release
points
,
and
R
217
may
be
readjusted
as
needed
to
obtain
the
desired
restraint
point
.
0.58
-
0.66
A
.
continued
on
page
20
.
2
.
.
.
.
.
.
Vo
1
tage
-
source
testing
:
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