Eaton Digitrip RMS Series, Instructional Leaflet

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Figure 7 BYZ Zero-Sequence Current Sensor
As the breaker opens, the left pole unit lever pin strikes
the spring finger attached to the reset lever; this furnishes
the assistance required to move the disc so as to close the
air gap between it and the permanent magnet against the
spring force.
The device is reset when the disc is in contact with the
magnet. If the gap is not fully reset, the trip shaft lever will
hold the breaker mechanism in the trip-free condition and
the breaker cannot be re-closed.
The trip actuator must be replaced, if it will not stay reset,
when the plunger has been moved to the top of its travel.
5.4 Ground Fault Protection
When the Digitrip Trip Assembly includes ground fault pro-
tection, the distribution system characteristics, i.e., system
grounding, number of sources, number and location of
ground points, etc. must be considered as well as the man-
ner and location in which the circuit breaker is connected to
the system.
If the system neutral is grounded but the neutral is not car-
ried with the phase conductors, the Digitrip Trip Assembly
includes all of the equipment necessary for ground fault pro-
tection. The basic mode of ground fault sensing employs a
residual sensing scheme which vectorially sums the outputs
of the individual phase current sensors. As long as the vecto-
rial sum is zero, then no ground fault exists.
If the system neutral is grounded and a neutral conductor
is carried with the phase conductors, it is necessary to use
an additional sensor for the purpose of canceling out any
residual current in the phase conductors. This sensor must
be mounted separately and must be located on the neutral
conductor at the point where the neutral conductor connects
to the neutral bus. These sensors are duplicates of those
supplied on the breaker except for the 2400A and 3200A rat-
ings where a modified neutral sensor is required.
The adjustment of the ground fault functional settings is
illustrated in the applicable Digitrip RMS and Digitrip OPTIM
Trip Unit instruction leaflets referenced in Section 7.1 of this
instruction book. Either flat response or I
2
t response settings
may be selected. The effect of these settings is illustrated in
the ground fault time-current curve referenced in Section 8.2
of this instruction book. Applicable residual ground fault set-
tings are given in Table 3 and on the time-current curve.
Effective July 2010
Instructional Leaflet
IL8700C39-04
7.88
9.90
6.12
3.06
3.06
6.12
4.75
.530 Dia. 4-Total
9.12
Dimensions (in Inches)
Current Style
Ratio
100/5 592C102G03
50/5 592C102G01
13
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