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Chapter 3
CGCM-DLR Unit Operation
64
When the ripple current at one of these frequencies exceeds the applicable user
specified threshold, a timer is started. Once the time delay is exceeded, a rotating
diode fault occurs. If the ripple current falls below the threshold (configured as
percent of measured excitation current) before the timer expires, the timer is
reset. If this fault occurs, tag RotDiodeFlt = 1 in the Scheduled Read table.
The Rotating Diode fault is inhibited if the field current is less than
1.5 A DC or if the generator frequency is outside the range of 45...70 Hz.
Phase Rotation Fault (47)
The CGCM-DLR unit calculates the negative sequence voltage of the 3-phase
generator voltage sensing input. When the generator phase rotation is opposite to
the wiring rotation you configured, the level of the generator negative sequence
voltage increases to approximately 100%. The pickup value for this function is
fixed at 66%. When the pickup value is exceeded, timing is started. After a
1 second delay, a phase rotation fault is indicated. A phase rotation fault is also
indicated when a phase loss condition occurs. If this fault occurs, tag
PhRotFlt = 1 in the Scheduled Read table.
Generator Over-current (51/51V)
A generator over-current fault occurs when generator current exceeds the
generator over-current function setpoint. You configure over-current protection
by selecting a time characteristic curve, an over-current setpoint, a time dial
setting, and a voltage restraint setpoint. The over-current function meets
ANSI/IEEE C37.112.
See
Appendix A
for a list of available curves and more detail.
If this fault occurs, tag Ovr_I_Flt = 1 in the Scheduled Read table.
Synchronizing
The CGCM-DLR unit monitors the generator and bus voltage sensing inputs to
provide synchronization between the generator and either of two buses. The
CGCM-DLR unit provides voltage, phase and frequency error parameters, and a
breaker close permissive signal, to its host Logix controller. These parameters and
signal let the controller control the prime mover, achieve phase synchronization,
and voltage matching.
The CGCM-DLR unit can also provide synchronization between two busses by
measuring appropriate synchronization parameters. For synchronizing between
two busses, substitute the term second bus for generator in the discussions that
follow.
Rockwell Automation Publication 1407-UM002B-EN-P - February 2019
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