EasyManua.ls Logo

ABB Modures LZ92-1 - DIRECTION OF MEASUREMENT SETTINGS

ABB Modures LZ92-1
72 pages
To Next Page IconTo Next Page
To Next Page IconTo Next Page
To Previous Page IconTo Previous Page
To Previous Page IconTo Previous Page
Loading...
3.5
Arc
resistance
compensation
The
ratio
R/X
can
be
set
between
1
and
5
in
steps
of
1
on
a
control
on
the
front
of
the
main
processing
unit.
The
actual
setting
depends
on
the
value
of
arc
or
earth
resistance
to
be
expected
in
relation
to
the
reactance
of
the
line.
Typical
settings
for
overhead
lines:
R/X =
1,
2
or
3.
A
setting
of
R/X = 1
is
permissible
in
cable
systems,
since
high
arc
resistance
are
not
to
be
expected.
Where
the
phase-angle
of
the
positive-sequence
impedan-
ce
is
less
than
40°
the
ratio
R/X
is
set
to
1
and
the
RL
is
used
for
grading
the
relays.
According
to
van
C.
Warrington
arc
resistance
can
be
calculated
from:
=
where
28700
d
Il.4
d
length
of
the
arc
in
m
I
current
in
A
RB
arc
resistance
in
ohms
In
the
impedance
plane
it
can
be
seen
that
the
influence
of
arc
resistance
varies
with
the
kind
of
fault,
because
the
unit
is
ohms
per
phase.
A
given
fault
resistance
RF
in
the
R/X
plane
is
as
follows:
-
earth
fault
-
phase-to-phase
fault
R = RF I
(1
+ I k I )
R = RF I 2 °
(for
overhead
lines)
In
grounded
systems
R
will
be
greatest
for
an
earth
fault.
For
a
given
line
impedance
Z =
RL
+
j/
the
required
arc
resistance
compensation
thus
becomes:
L . L
R/X
RL
+ R
3.6
Direction
of
measurement
The
direction
of
measurement
is
determined
by
the
position
of
switch
Sb
on
PCB
8
of
the
main
processing
unit
(up
to
order
number
HESG
439
686,
see
Section
3.12).
From
order
number
HESG
440
718
(PCB
8)
provision
is
made
for
selecting
the
direction
of
measurement
on
the
frontplate
of
the
main
processing
unit
with
the
control
marked
I
~
(see
Figures
9.6
and
9.8).
In
either
case
there
is
no
influence
on
the
starting
units.
With
the
switch
in
position
I -
and
the
relay
connected
according
to
the
wiring
diagram,
i.e.
with
the
neutral
of
the
c.t's
at
the
ends
of
the
windings
nearest
the
busbars,
the
relay
measures
into
the
line.
21

Related product manuals