GE Industrial Solutions EntelliGuard TU Trip Units - Manual (Page 46)

EntelliGuard TU Trip Units: UL/ANSI Models DEH-4567B
Metering Screens
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SECTION 4. METERING SCREENS
Metering values are dependent on the accuracy of the
current sensors in the breaker, see table below. Current
sensors in breakers are designed to be more accurate at
85% of current and greater than 100%, seeing their
purpose is protection. If you see negative or non-
directionally correct values check your power direction or
your voltage configuration. The frequency is determined
from the current. Current sensors are designed to be more
accurate/linear at full load current and above (where the
protection needs to be). The table below shows the
accuracy of the reading based on the percentage of the
sensor. This is consistent across all breaker types.
Table 4-1: GTU Nomenclature
% of Sensor (A) Accuracy - % of Reading
20% - 50% ± 10.0%
50% – 85% ± 5.0%
85% - 100% ± 2.0%
CURRENT METERING DISPLAY
What this shows:
The level of current flowing in each breaker phase.
Phase current metering is a standard feature of every GTU.
Neutral current display is optional and depends on the
configuration of the circuit breaker.
With 24V external power, metering data will be displayed
down to 8% of the installed sensor rating.
Without 24V external Power, the primary current flow
needs to cross the self-power operating threshold which
occurs between 10% and 15% of sensor before any
metering activity occurs. If metering is required below this
level, an external means of powering the trip unit will need
to be provided, because the breaker CTs are not capable of
generating enough energy to operate the trip unit below
this threshold.
Tip: When using Modbus serial communications, do not
leave this window displayed. Modbus response time will
increase due to the higher computing overhead to
continually update metering values.
EXTERNAL CT CURRENT METERING DISPLAY
(ENTELLIGUARD G ONLY)
What this shows:
The level of current flowing in the
external CT channel.
This display is only enabled when the
trip unit has Earth Fault or CT Ground
Fault protection options installed, and
the Monitoring advanced feature
enabled.
VOLTAGE METERING DISPLAY
What this shows:
The system voltage.
This display is accessible only if the optional Monitoring
Function is installed.
When the PT Connection setpoint is PH-N, the voltage
display is configured for Phase to Neutral voltage.
When the PT connection setpoint is PH-PH, the phase to
phase voltage is displayed.