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The SLY81 relay utilizes a three input phase angle comparator for
the phase distance measurement.
measurements are:
(a)
(I A - Ia)
(b)
(C)
V AB
( I A - I
where
T V AB
+
K V AB l
V AB
The
use
of
polarizing signal results in a relay characteristic of the "variable
mho"
type�
that
impedance
behind
accommodation
of
component
of
voltage
directional integrity of the distance measurement.
The
third
supervision function.
above load
current but below the minimum
provide security from mis-operation due to potential failure.
The SLY81 has a characteristic which is adjusted by means of the
setting
on
the
characteristic
unusually
heavy
large
reach
settings
recommended.
GENERAL
Type
SLY81A
operation
in
ambient
standard C37. 90.
be damaged if operated in an ambient up to 65°C.
The current circuits of the relays which are rated five amperes
( 5 amps}
rms
will carry
amperes for one second (1 sec).
APPLICATION
GEK-49861
Z a1
Z a1
- T
V AB
+
K V AB l
a)
are the currents in the faulted phases.
is
the
impedance angle of 85° .
is
the
multiplied by the restraint setting T.
is
the faulted
times the positive
K
the faulted phase-to-phase voltage.
design constant equal to 0. 3 per unit.
the
positive
is,
the
characteristic
the
relay
increasing
arc
in
the
input
of
the
This input is adjustable so that it can be set
characteristic
is
recommended,
load
transfer,
are
applied,
and
SLY81B
temperatures between
I n addition, these relays will not
10 amperes continuously and
The three inputs for the phase A-B
Operating Quantity
Polarizing Quantity
Overcurrent Supervision
base
reach
faulted
phase-to-phase
phase-to-phase
sequence
component
expands
increases,
providing
impedance.
polarizing
signal
comparator
provides
fault current in order to
timer.
For
short
but,
for
longer
or
three
terminal
RATINGS
a
lens
shaped
relays
are
designed
-20° C
The current circuits of the relays
4
impedance
with
voltage,
voltage
sequence
component of
of
voltage
as
the
an
automatic
The
positive
sequence
also
improves
an
overcurrent
lines
a
circular
lines,
lines
lines
where
characteristic
for
continuous
and
+55° C
per ANSI
malfunction nor
will
carry 250
an
plus
K
is a
in
the
source
the
with
very
is
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