ABB MMCO-2 - Page 7

I
.
L
.
41
-
121.2
5
.
OPERATION
Table
4
indicates
all
values
of
pre
-
determined
param
-
eters
(
To
,
K
,
C
,
P
and
R
)
in
the
program
for
each
curve
.
Parameters
l
0
and
D
are
user
-
selectable
via
pickup
setting
and
time
dial
switches
,
respectively
.
The
MMCO
relay
continually
executes
its
protective
functions
whenever
DC
power
is
applied
to
the
relay
.
Concurrently
with
this
protective
function
,
four
modes
may
be
selected
using
the
front
panel
keypad
switches
.
Table
4
:
TIME
CURVE
PARAMETERS
c
CURVE
K
P
R
To
The
modes
are
:
MMCO
-
2
MMCO
-
5
MMCO
-
6
MMCO
-
7
MMCO
-
8
MMCO
-
9
MMCO
-
11
735
0.675
1.130
1.190
0.800
1.270
1.350
0.500
1
510
112
13769
1
22705
8197
•
Metering
•
Settings
•
Targets
Set
Time
(
Only
with
optional
real
-
time
clock
)
671
1
1475
785
2491
3121
1
525
9200
478
4122
2756
17640
1
9342
310
1
110
2
8875
4.3
.
2
.
IEC
Curves
In
addition
to
the
keypad
switches
which
select
the
relay
modes
,
there
are
three
switches
accessible
from
the
front
panel
dedicated
to
special
functions
.
There
are
three
families
of
IEC
curves
;
IEC
-
A
,
IEC
-
B
,
IEC
-
C
.
Each
family
contains
63
curves
determined
by
the
time
dial
setting
(
see
Figures
11
thru
13
)
.
The
expression
for
the
IEC
curves
is
shown
in
the
equa
-
tion
(
3
)
below
:
These
functions
are
:
•
TRIP
TEST
•
TARGET
RESET
•
EXTERNAL
SCROLL
A
flow
chart
for
MMCO
relay
keypad
operation
is
included
(
Figure
16
)
for
reference
.
T
=
(
K
x
D
/
63
)
/
[
G
/
Gs
)
a
-
1
]
(
3
)
(
3
)
where
T
=
Theoretical
operating
time
(
seconds
)
K
=
constant
characterizing
the
relay
(
seconds
)
D
=
time
dial
setting
from
1
to
63
G
=
value
of
the
characteristic
quantity
(
i
.
e
.
,
current
through
relay
ct
)
.
Gs
=
setting
value
of
characteristic
quantity
(
i
.
e
.
,
pickup
setting
)
a
=
index
characterizing
the
algebraic
function
5.1
.
METERING
MODE
(
“
M
”
IN
UPPER
LEFT
CORNER
OF
DISPLAY
)
When
dc
power
is
applied
to
the
relay
it
displays
the
metering
mode
with
IA
,
IB
,
and
S
(
status
)
appearing
on
the
front
panel
.
When the
relay
is
not
in
the
Meter
-
ing
Mode
the
“
SELECT
”
button
can
be
used
to
go
to
this
mode
.
The
following
additional
information
can
be
displayed
using
the
scroll
button
:
IC
,
I
0
,
and
with
the
real
time
clock
option
:
day
,
date
and
time
.
The
following
values
are
used
for
a
and
K
:
When
in
the
Metering
Mode
,
the
status
,
“
S
”
,
appears
in
the
upper
right
hand
corner
of
the
display
.
When
there
is
an
internal
hardware
or
software
failure
in
the
relay
the
amber
MONITOR
LED
goes
out
and
the
value
of
the
status
indicates
the
cause
of
the
failure
.
The
meaning
of
the
status
coded
(
S
=
“
“
)
are
as
fol
-
lows
:
Very
Inverse
Time
(
B
)
Extreme
Inverse
Time
(
C
)
Standard
Inverse
Time
(
A
)
K
0.14
13.5
80.0
1.0
0.02
2.0
a
7
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