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Initial Release
differential overcurrent pickup set point is being viewed in
the unit’s normal operating mode. The LED will blink red
whenever the load current exceeds the differential
overcurrent pickup set point. If the relay trips on differential
overcurrent, the LED will be continuous red.
Time LED
This LED will blink green, while in the program mode,
when the LED time set point is displayed in the
Settings/Test Time/Trip Cause window. When the time
multiplier is being viewed in the unit’s normal operating
mode, the LED is a constant green.
I
A Diff
, I
B Diff
, I
C Diff
LED’s
The specific phase current LED’s will be a constant green
when that phase differential current is being displayed in
the rms ampere window.
Program LED
This LED is a constant green when the relay is in the
program mode.
Test LED
This LED is a constant green when the relay is in the test
mode.
Display Windows:
Two windows are used to display the
relay’s data, Set Points and messages. One window is
located in the upper portion of the relay’s faceplate and is
labeled RMS Amperes. A second window is located in the
lower portion of the faceplate adjacent to the program and
test LED’s. It is labeled Settings/Test Time/Trip Cause.
RMS Amperes Window
This window has a five digit numeric display and shows:
1. The present phase differential currents.
2. The phase current transformer CT setting (when “View
Settings” pushbutton is used with the relay in the
normal operating mode).
Settings/Test Time/Trip Cause Window
This window is a four character alphanumeric display used
to show the value of the Set Points, the test time and the
cause of trip.
2-2.2 REAR ACCESS PANEL
THE BACK OF MD-3000, WHEN ENERGIZED,
OFFERS EXPOSURE TO LIVE PARTS WHERE
THE HAZARD OF A FATAL ELECTRIC SHOCK IS
PRESENT. ALWAYS DISCONNECT SOURCE AND
CONTROL POWER SUPPLY BEFORE TOUCHING
ANYTHING ON THE REAR OF THE MD-3000.
FAILURE TO DO SO COULD RESULT IN INJURY
OR DEATH.
The rear access panel of MD-3000 is normally accessible
from the rear of an open panel door. All wiring
connections to the MD-3000 Protective Relay are made at
the chassis’ rear. For the sake of uniform identification, the
frame of reference used when discussing the rear access
panel is facing the back of the relay. Become familiar with
the functions and connections involved, especially the
following:
DIP Switches: A set of ten DIP switches is located in the
upper left portion of the rear panel. These switches are
unused in the MD-3000.
Differential Trip contact (TB2 14 and 15) and the Trip
Alarm contact (TB2 6, 7 and 8) change state after a
protection trip operation. The contacts stay in that state
until the “Reset” Pushbutton is pressed. In addition, the
front panel will hold the cause of trip in the “Trip Cause”
window and the fault current magnitude in the “RMS
Ampere” window.
Terminal Block One (TB1)
: TB1 is located on the left side
of the rear panel, and is numbered 1 through 15.
Terminals 5 and 6 are provided for the AC or DC input
control power connections. Terminal 4 is the connection
for equipment ground.
When the relay has input control
power, Terminals 9 and 10 will have this potential on
them.
Terminal Block Two (TB2):
TB2 is located on the right
side of the rear panel and is numbered 1 through 15.
Terminals 6, 7 and 8 are Form “C” contacts on the trip
alarm relay and change state whenever a protective trip is
initiated by the relay. After a protective trip, the contacts
remain in the changed state until the “Reset” Pushbutton is
pressed. These contacts can be fed to the MP-3000 or
MP-4000 discrete input to indicate a differential trip. The
MP-3000 or MP-4000 then can report the differential trip
over either the INCOM or MODBUS network.
Terminals 14 and 15 are a “NO” configurable contact. This
contact closes when the relay detects a need for the circuit
breaker to trip due to a differential current above the user
programmed set point for a period of time in excess of the
user defined time delay setting. These contacts can be fed
to the MP-3000 or MP-4000 discrete input to indicate a
differential trip. The MP-3000 or MP-4000 then can report
the differential trip over either the INCOM or MODBUS
network.
Rear Surface Terminals:
The rear surface terminals,
identified as (A1, A2), (B1, B2), and (C1, C2) provide the
current transformer input connection points and are rated
for 5 ampere inputs. (A1, A2), (B1, B2) and (C1, C2) are
phase A, B, C current inputs respectively.
2-2.3 EXTERNAL HARDWARE
The MD-3000 Protective Relay requires that a customer
supplied source of input control power be wired into the
TB1 terminal block located on the rear panel. Refer to the
typical wiring diagram in Figure 3-1. A power supply can
be either ac or dc voltage within the acceptable voltage
WARNING
