GE GCX51A - Calculation of Settings

GEI
-
98328
Complete
potential
burden
data
with
No
.
1
taps
and
E
2
taps
on
100
%
and
with
the
input
tap
on
100
%
are
given
in
Table
VIII
:
TABLE VIII
MAXIMUM
POTENTIAL
BURDENS
IMPEDANCE
P
.
F
.
WATTS
FREQ
.
VOLTS
V A
HI
OHM
120
ITby
+
jO
1245
+
jl
540
1460
+
jO
515
+
j
109
170
1273
1273
120
0.66
4.6
7.3
MHO
Restraint
MHO
Polarizing
Total
Relay
60
60
120
1.0 10.0
10.0
120
60
0.98 26.8 29.6
The
DC
potential
burden
of
the
OX
transfer
relay
circuit
is
given
in
Table
IX
for
the
3
DC
voltage
taps
:
TABLE IX
VOLTS OHMS
40
000
125
2000
4000
250
CALCULATION
OF
SETTINGS
Table
X
illustrates
qualitatively
how
to
set
the
three
zones
of
the
relays
when
they
are
applied
in
straight
distance
schemes
,
applications
,
see
GEK
-
7384
.
For
directional
comparison
TABLE
X
SETTINGS
ON TWO
TERMINAL
LINES
UNIT
SETTINGS
ON
THREE TERMINAL
LINES
Set for
90
%
of
the
reactance
to
the
nearest
remote
terminal
.
Do
not
include
the
effects
of
infeed
.
or
Set for
90
%
of
the
total
line
.
With
all
three terminal
breakers
closed
,
calculate
the
effective
reactance
seen
by
this
unit
for
a
three
-
phase
fault
at
one
of
the
remote
terminals
.
Repeat
for
a
fault
at
the
second
remote
terminal
.
Include
the
effects
of
infeed
in
both
cases
.
Select
the
larger
of
the
two
reactances
and
set
this
unit
for
at
least
110
%
of
this
reactance
.
02
Set
for
at
least
110
%
of
the
total
line
reactance
.
Since
the
MHO
unit
supervises
first
-
and
second
-
zone
tripping
,
it
must
be
set to
reach
at
least
as
far
as
the
second
-
zone
reactance
unit
.
Actually
the
reach
setting
should be
long
enough
to
provide ample
arc
resistance
accommodation
at
the
balance
point
of
the second
zone
.
Any
additional
reach
would
only
provide
for
additional
back
-
up
protection
for
faults
on
remote
lines
.
M
12
Courtesy of NationalSwitchgear.com