M icroVersaTri p Plus™ and PM™ Trip Units
Metering
When the metering function is selected, a number of
standard metering parameters can be viewed on the LCD
display. All of these values are communicated to the POWER
LEADER™ Power Management System. The accuracy of the
metering functions is constrained by the physical size of the
current sensors. Consequently, all metering functions are
designed for load management decisions, and a re not a
substitute for utility revenue metering equipment.
•
Current:
All trip units, including MicroVersaTrip Plus™, pro
vide metering of individual p ha se currents. The user can
select phases 1, 2, or 3. Current displays automatically shift
from amps to kiloamps a bove 999 amps. The minimum
current display resolution is in tenths of a n a m p (e.g., 5 12
AI.
•
Voltage:
The metering display of fou r wire systems can
rea d both line-to-neutral and line-to-line voltage d isplay
for each phase. The smallest resolution of the voltage
display is one volt (e.g. 2 77V, or 276V).
•
Energy:
The energy display indicates the a mount of real
power that has passed through the breaker. The display
has three-digit resolution, and automatically scales the
display from kWh to MWh to GWh. Normal power flow can
be selected as either load-line or line-load in the setup
mode. Once normal flow is configures, energy values will
accumulate in the positive direction. For certai n applica
tions where power may flow i n either direction, such as tie
breakers, energy may d isplay a negative value.
•
Rea l power:
Real power in units of kW or MW can be
shown on command on the LCD display.
•
Volt-amperes (or tota l power):
"Total power" or volt-am
peres in units of kVA o r MVA can be viewed on command
on the LCD display.
Table
21.1
Trip Unit Metering Display Accuracy
Value
Breaker Full Scale
System Full Scale
AccuracyCD
Accuracy@
Current. rms -A, kA
±2.5%
±2.5%
Voltage, rms -V
N/A
± 1.5%
Phase-Phase, Phase-Neutral
Energy -kWh, MWh, GWh
N/A
±4 0%
Demand - kW. MW
N/A
±4.0%
Peak Demand- kW. MW
N/A
±4 0%
Real Power - kW, MW
N/A
±4.0%
Total Power - kVA, MVA
N/A
±4.0%
Frequency
N/A
± 1 Hz
Time Delay
N/A
±1 sec
CD
Includes trip unit. breaker. current sensors and rating plug. Accuracy is based on
loading range of 20% to 100% of breaker current sensor rating.
@
Includes trip unit. breaker. current sensors. rating plug. plus Voltage Module [poten
tial transformers. control power voltage conditioner[. Accuracy is based an loading
range of 20 % to 100 % of breaker current sensor rating.
•
Demand:
Demand in units of kW or MW can be displayed.
The monitoring time period can be varied from 5 to 60
minutes, in increments of 5 minutes. The display provides a
rolling average of power over the scheduled time interval.
•
Pea k demand:
Peak demands in units of kW or MW can be
displayed. This value indicates the highest power demand
reached since the start of demand measurements, or since
reset. The peak demand value can be reset to the present
demand via the keypad.
Protective Relaying
When protective relaying functions are selected, a ny combi
nation of the following protective relays can be enabled. All
relay functions combine both an adjustable setpoint and a n
adjustable d iscrete (not inverse) time delay. A l l t i m e delays
a re adjustable from 1 to 15 seconds in increments of 1 sec
ond. All tripping is performed through the trip unit. The user
can configure the trip unit to activate the bell alarm only, the
bell alarm with lockout, or neither, in response to a protective
relay (or overcurrent/ground-fault) trip.
•
Undervoltage:
U ndervoltage protection may be set from
50% to 90% of the true rms nominal voltage in increments
of 1%.
•
Overvoltage:
Overvoltage protection may be set from
1 10% to 150% of the true rms nominal voltage in incre
ments of 1%.
•
Voltage unbalance:
Voltage-unbalance protection com
pares the lowest or highest p hase voltage with the other
two, and initiates a trip if the difference exceeds the
setpoint. True rms voltages a re computed for each phase.
The range of trip settings varies from 10% to 50% in incre
ments of 1%.
•
Cu rrent unbalance:
Current-unbalance protection com
pares the true rms current in either the highest or lowest
phase with the true rms current in the other two phases. A
tri p is initiated if the d ifference exceeds the setpoint. The
range of trip settings varies from 10% to 50% in incre
ments of 1%.
•
Power reversal:
The Power Break® II breaker may be set
so that "positive" power flow can be in either direction (i.e.,
from line to load, or vice versa). Reverse power protection
is set in units of kW. Reverse power setpoints vary from
10kW to 990kW in i ncrements of 10kW.
•
Ena ble/disa ble relays:
To disable any of the protective
relay functions, set the time delay for that function to OFF.
Setting the time delay to any discrete value enables the
relay.
21
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