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Initial Release
on the front of the relay, via the two display windows. This
is considered “ON DEVICE” information.
In addition to being able to provide a circuit breaker
“OPEN” or “CLOSED” status to the remote location, the
MD-3000 displays parameters, such as:
•
Individual phase differential currents
•
Magnitude and phase of current causing trip
•
Cause of trip
•
Current transformer ratio
•
Existing set point settings
•
Software Version
1-4 STANDARDS
MD-3000 Protective Relays are “Component Recognized”
by the Underwriters Laboratory, Inc.® under UL File
E154862. Refer to Section 2-3 UL Testing and
Specification Summary for more information.
SECTION 2: FUNCTIONAL DESCRIPTION
2-1 PROTECTION, SETTINGS, AND TESTING
2-1.1 RMS SENSING
MD-3000 Protective Relays provide true RMS sensing for
proper correlation with the thermal characteristics of
conductors and equipment. The root-mean-square (rms)
value is determined by a microprocessor calculation of
discrete sampled points of the current waveform. This rms
value is used for the protection response and metering
displays of the relay.
2-1.2 PICKUP SETTING
A MD-3000 Protective Relay pickup setting is a discrete,
pre-selected value of differential current used to initiate a
tripping action. The available pickup settings are 0.04,
0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24,
0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44,
0.46, 0.48, 0.50, and NONE.
2-1.3 TIME SETTING
A MD-3000 Protective Relay time setting is a pre-selected
time delay initiated when the pickup is exceeded. If the
current value drops below the pickup value, the timing
function resets. Memory is NOT provided. If the current
value does not drop below pickup, the amount of delay
before tripping occurs is a function of only the time setting.
The available time settings are 0.05, 0.10, 0.15, 0.20, 0.25,
0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75,
0.80, 0.85, 0.90, 0.95, 1.00, 1.25, and 1.50 (seconds).
2-1.4 MISCELLANEOUS SETTINGS
TABLE 2.1 MISCELLANEOUS SETTINGS
TYPE SETTING
AVAILABLE SETTINGS
FREQUENCY
50 Hz, 60 Hz
PHASE CT RATIO
5,10, 25, 50, 75,100,150, 200, 250, 300, 400, 500, 600, 630,
800, 1000, 1200, 1250, 1500, 1600, 2000, 2400, 2500,
3000,3200, 4000, 5000
TEST
Phase
Phase Trip
P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P12, P14, P16
P18, P20, P22, P25
P3T, P10T, P25T
System Frequency Selection:
Either 60Hz or 50Hz may
be selected.
Phase CT Ratio Selection:
The available CT ratios,
shown in the above table range from 5:5 to 5000:5.
Defaults:
In the unlikely event that settings are missed or
entered incorrectly, the Operational LED will blink Red and
the relay will display “PRGM” in the Settings Display
window. This means the program settings should be re-
entered and saved.
2-1.5 TESTING
Phase no-trip tests (test Px) and a phase trip tests (PxT)
are provided (see table 2.1).
THE TEST MODE SHOULD NOT BE USED TO
TRIP LIVE CURRENT CARRYING CIRCUITS. IF A
LIVE CURRENT OF GREATER THAN 0.1 TIMES
THE VALUE IS FLOWING IN ANY PHASE, THE
TEST MODE IS AUTOMATICALLY EXITED,
ACCOMPANIED BY AN ERROR MESSAGE IN THE
SETTINGS/TEST TIME/TRIP CAUSE WINDOW.
2-2 PROTECTIVE RELAY HARDWARE
2-2.1 FRONT OPERATIONS PANEL
The operations panel, which is normally accessible from
the outside of the switchgear panel door, provides a
means to program, monitor and test the unit (Figure 1-1).
