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ABB Modures LZ92-1 - LOAD VOLTAGE AND CURRENT CHECKS

ABB Modures LZ92-1
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k , I
0
Voltages
proportional
to
the
phase
currents
taken
from
across
the
replica
impedances
are
available
at
these
three
sockets
(see
Section
6.4
for
details).
Phase
voltages.
The
voltages
are
taken
from
behind
the
input
transformers
(see
Section
6.4
for
details).
Zero-sequence
compensation.
A
voltage
U
can
be
measured
at
this
socket
which
is
proportional
to
th~
product
of
the
neutral
current
IL
and
the
compensating
factor
lk
0
1.
The
relationship
is:
0.125
I
ko
I x I2:
(A)
Input
transformer
units
with
the
part
number
HESG
440
754
resp.
HESG
441 721
have
these
two
sockets
in
addition.
Caution!
The
circuit
breaker
can
be
tripped
by
connecting
these
sockets
and
pressing
one
of
the
starter
test
buttons.
This
procedure
energizes
the
auxiliary
tripping
relay
in
the
EW91
without
the
distance
relay
having
to
measure,
providing
terminal
Ell
of
the
EW91
is
connected
to
terminal
E63
of
the
main
processing
unit
(with
PCB
8
according
to
HESG
440
718).
6.4
Checking
load
voltages
and
currents
Load
voltages
and
currents
can
be
measured
at
the
sockets
on
the
front
of
the
unit
EW91
as
follows:
-
First
switch
on
the
auxiliary
d.c.
supply.
-
The
phase-to-neutral
voltages
are
reduced
by
a
factor
of
15
for
rated
vol-
tages
between
100
and
130
V
(code
Ul)
and
a
factor
of
30
for
rated
voltages
between
200
and
260 V
(code
U2).
- The
load
currents
are
converted
into
proportional
voltages
according
to
the
relationship
0.125
x
I/IN
(V).
- The
neutral
current
should
be
approximately
zero
under
load
conditions.
- The
phase
sequence
of
the
voltages
and
currents
can
also
be
checked
using
an
oscilloscope.
The
voltage
proportional
to
the
current
of
a
particular
phase
lags
the
phase
voltage
by
approx.
90°
if
an
ohmic
load
current
flows
towards
the
protected
line
and
the
relay
is
conected
according
to
Fig.
9.9.
Note:
The
replica
voltages
can
contain
more
harmonics
than
the
primary
currents
due
to
the
physical
properties
of
the
replica
impedances,
but
this
has
no
influence
on
the
operation
of
the
relay.
31

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