GE MDP

GEK
-
100682
The
use
of
a
separate
grounid
-
overcurrent
function
is
advantageous
because
it
can
generally
be
adjusted
to
provide
faster
and
more
sensitive
protection
for
single
-
phase
-
to
-
ground
faults
'
than
the
phase
-
overcurrent
functions
.
Typical
connections
for
such
an
application
are
shown
in
Figures
9
and
10
,
This
safety
factor
can
be
reduced
to
0.07
second
if
the
time
unit
is
instead
set
to
the
desired
time
accurate
tests
.
by
#
The
instantaneous
-
overcurrent
unit
can
be
applied
in
many
instances
to
reduce
the
fault
-
clearing
time
for
high
-
fault
currents
.
This
unit
is
normally
set
to
pick
up
only
on
internal
faults
in
the
protected
zone
.
Significant
transient
overreach
can
be
experienced
under
certain
conditions
,
and
this
must
be
taken
into
account
by
selecting
a
pickup
setting
that
is
higher
than
that
which
would
be
dictated
by
the
maximum
steady
-
state
external
-
fault
current
.
The
pickup
setting
of
the
MDP
time
unit
should
be
chosen
so
that
it
will
operate
for
all
short
circuits
in
the
protected
zone
,
and
also
provide
back
-
up
protection
for
short
circuits
in
the
immediately
-
adjacent
system
element
when
possible
.
The
time
-
unit
pickup
should
be
set
low
enough
to
ensure
that
the
minimum
fault
current
is
at
least
1.5
times
the
setting
.
IMPORTANT
NOTE
If
one
unit
(
instantaneous
or
inverse
)
operates
,
the
other
unit
(
inverse
or
instantaneous
)
will
also
operate
.
The
MDP
’
s
fault
report
will
record
the
first
fault
that
occurred
.
When
the
fault
is
cleared
the
MDP
’
s
fault
LED
’
s
will
display
Phase
-
Phase
,
Phase
-
Ground
,
Instantaneous
and
inverse
time
faults
.
See
display
section
on
how
to
interpret
the
display
for
various
fault
conditions
.
The
MDP
will
generate
a
new
fault
report
when
the
fault
current
drops
below
the
pick
-
up
value
and
a
new
fault
occurs
.
The
time
-
delay
adjustment
of
the
time
unit
should
be
chosen
to
assure
selectivity
with
the
protection
on
the
adjacent
system
elements
.
This
adjustment
should
be
made
for
the
condition
that
yields
maximum
fault
current
at
the
relay
location
.
The
time
delay
is
determined
by
the
adjacent
relay
operating
time
for
this
condition
,
plus
a
coordinating
time
allowance
that
includes
the
adjacent
circuit
-
breaker
maximum
operating
time
and
a
safety
factor
to
accommodate
any
uncertainties
.
Since
the
MDP
time
unit
has
insignificant
overtravel
,
the
only
relay
variation
that
needs
consideration
in
the
safety
factor
is
the
tolerance
on
the
time
curves
.
A
0.17
-
second
safety
factor
is
generally
used
if
the
relay
time
is
determined
by
selecting
a
time
-
dial
setting
from
the
time
curves
.
i
Contact
converter
input
CC
1
and
the
output
-
select
switch
of
the
MDP
allow
a
Zone
Selective
Interlocking
of
the
MDP
relays
.
This
scheme
provides
instantaneous
operation
(
with
a
minimum
time
delay
)
of
the
upstream
relay
for
faults
between
the
upstream
and
downstream
relays
.
Refer
to
Figure
11
for
a
typical
scheme
and
settings
considerations
.
Note
that
all
the
feeders
must
be
radial
,
with
no
,
or
very
weak
,
source
.
TECHNICAL
SPECIFICATIONS
Nominal
frequency
:
25
/
50
/
60
Hz
t
!
Nominal
current
:
1
or
5
amps
24
-
48
VDC
(
19
to
60
VDC
)
48
-
125
VDC
/
AC
(
38.5
to
150
VDC
/
AC
)
35
to
120
AC
110
-
250
VDC
(
88
to
285
VDC
)
85
to
240
AC
0.1
-
0.875
/
0.3
-
2.65
=
0.09
/
,
2.8
°
at
60
Hz
(
2.25
VA
at
5
A
)
0.1
-
0.875
/
0.3
-
2.65
=
0.09
/
,
2.4
°
at
50
Hz
(
2.25
VA
at
5
A
)
0.5
-
4.375
/
1.5
-
13.25
=
0.01
/
,
11.5
°
at
60
Hz
(
0.25
VA
at
5
A
)
0.5
-
4.375
/
1.5
-
13.25
=
0.01
/
,
9
,
7
°
at
50
Hz
(
0.25
VA
at
5
A
)
Less
than
3
watts
at
all
voltages
,
quiescent
Less
than
4.5
watts
at
maximum
voltages
Auxiliary
power
supply
:
AC
Burden
:
DC
6
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