ABB MMCO-2 - Page 2

I
.
L
.
41
-
121.2
TABLE
1
:
MMCO
APPLICATIONS
RELATED
TO
INVERSE
TIME
CURVES
TYPICAL
APPLICATIONS
DESCRIPTION
CURVE
TYPE
1
)
Differential
protection
where
saturation
of
current
transformers
is
not
expected
,
or
where
insensitive
setting
and
delayed
tripping
is
permissible
.
2
)
Overcurrent
protection
,
phase
or
ground
,
where
coordination
with
downstream
devices
is
not
involved
and
2
to
60
cycle
trip
-
ping
is
allowable
.
MMCO
-
2
Short
Motor
-
locked
rotor
protection
where
allowable
locked
rotor
time
is
approximately
between
10
and
70
seconds
.
MMCO
-
5
Long
Overcurrent
protection
where
coordination
with
downstream
devices
is
not
involved
and
MMCO
-
2
is
too
fast
.
The
operating
time
of
this
relay
does
not
vary
greatly
as
current
level
varies
.
MMCO
-
6
Definite
1
)
Overcurrent
protection
where
coordination
with
other
devices
is
required
,
and
generation
varies
.
2
)
Backup
protection
for
relays
on
other
circuits
.
MMCO
-
7
(
IEC
-
A
)
Moderately
MMCO
-
8
Inverse
MMCO
-
9
(
IEC
-
B
)
Very
Inverse
Motor
protection
where
allowable
locked
rotor
time
is
less
than
10
seconds
.
Overcurrent
protection
where
coordination
with
fuses
and
reclos
-
ers
is
involved
,
or
where
cold
-
load
pickup
or
transformer
inrush
are
factors
.
MMCO
-
11
(
IEC
-
C
)
Extremely
Inverse
display
•
Read
data
for
pervious
16
fault
cases
(
tar
-
gets
)
.
•
Make
all
settings
using
password
entry
.
The
following
types
of
INCOM
devices
are
available
:
Options
are
provided
for
a
real
-
time
clock
and
exter
-
nal
directional
control
.
An
external
3
-
phase
device
(
e
.
g
.
,
KD
-
10
or
H
3
)
is
required
to
supervise
phase
tripping
,
and
a
single
ground
directional
unit
(
e
.
g
.
,
KRC
,
KRP
or
KRD
)
is
required
to
supervise
ground
tripping
.
When this
option
is
included
and
selected
as
being
operative
,
timing
will
not
start
until
the
external
contact
closes
.
An
alternate
option
allows
resetting
to
be
accomplished
externally
(
without
using
the
com
-
munication
channel
)
,
but
only
when
directional
con
-
trol
is
not
supplied
.
Options
for
current
are
as
follows
:
•
INCOM
PONI
(
to
access
MMCO
relay
through
INCOM
network
)
•
RS
-
232
PONI
(
to
access
MMCO
relay
through
RS
-
232
lines
)
2
.
CONSTRUCTION
•
3
PH
Ground
•
3
PH
No
Ground
•
2
PH
Ground
The
MMCO
is
a
microprocessor
-
based
relay
consist
-
ing
of
5
printed
circuit
modules
which
are
packaged
in
a
standard
FT
-
22
flexitest
case
(
see
Figure
2
)
.
Refer
to
I
.
L
.
41
-
076
for
detailed
information
on
the
FT
-
22
case
.
The
5
modules
are
as
follows
(
see
Section
6
CIRCUIT
DESCRIPTIONS
)
:
An
INCOM
communications
device
may
be
pur
-
chased
separately
to
allow
for
access
to
the
MMCO
relay
,
using
an
access
code
.
•
Power
Supply
•
Current
Transformer
(
ct
)
•
Microprocessor
•
Display
The
following
remote
operations
may
be
performed
using
an
INCOM
communications
device
:
•
Read
all
information
available
on
front
panel
2
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