CBC-8000 capacitor bank control description
12
CBC-8000 capacitor bank control installation and operation instructions
MN916001EN—October 2018
Eaton.com
Figure 14. Neutral current sensor 120 VAC system.
Neutral current verification
The neutral current verification feature provides a method to
verify capacitor bank operation by comparing the
RMS
neutral current measurement to a configurable set point.
Note:
Neutral current sensing must be enabled to use
neutral current readings to verify capacitor bank
operation. To use neutral current sensing, a neutral
current sensor must be connected to the control prior
to enabling this feature.
The neutral current measurement is expected to be above
the configurable set point for a closed capacitor bank and
below this set point for a tripped capacitor bank.
• If the neutral current measurement is not above the set
point for a closed capacitor bank, the control attempts to
close the capacitor bank a configurable number of times
before the operation is considered a failure.
• If the neutral current measurement is not below the set
point for an open capacitor bank, the control attempts to
open the capacitor bank a configurable number of times
before the operation is considered a failure.
Note:
If neutral current fault control is enabled and the
control is in a fault current condition, the control will
not perform any capacitor bank operation.
Neutral current fault control versus neutral current
verification
Neutral Current Fault Control and Neutral Current Verification
are separate features for monitoring the health of the
capacitor bank and associated equipment. Both features
require a neutral current sensor, although each operates on a
different neutral current measurement according to its
requirements.
Neutral current fault control
Neutral current fault control is the most commonly used
feature. It detects when the capacitors on different phases
become imbalanced due to failed equipment (e.g., a blown
fuse or a stuck switch).
A typical setting for the Fault Control Setpoint is 75% of the
current that flows through one phase. When the filtered
60 Hz neutral current is higher than the specified setpoint,
the control will operate the working phases into the opposite
state to balance the capacitor bank's effect on the line, then
the control will lock in that state and set an alarm indicating
that a neutral current lockout has occurred. Note that neutral
current fault control uses the filtered 60 Hz neutral current to
avoid false positives due to harmonic currents which can
often be high through a capacitor bank, but do not indicate
equipment failure.
Neutral current verification
Neutral current verification operates on the principal that
when the capacitor bank is closed a small amount of neutral
current is expected to be present. Neutral current verification
is intended to provide feedback on whether a capacitor bank
operation appeared successful based on the amount of
neutral current.
When the specified current is not seen on a close operation,
or if the unfiltered RMS neutral current does not go to 0
amps on a trip operation, the operation is retried a specified
number of times. If the operation does not appear to be
successful, an alarm point will be set.
Note that if the line is very balanced, the neutral current
verification feature may not see the current it expects and
therefore may give a false positive. Due to the nature of the
distribution system dynamics, careful planning and review of
the data is necessary to reduce the number of false positives
and make this feature effective. Note that this feature uses
the unfiltered RMS neutral current, which allows the
harmonic current to help determine that the capacitor bank
was successfully closed, which in turn reduces the number
of false positives reported by this feature.
Communications loss control
If the control cannot communicate with the master station
for a configurable period of time, the control enters comms
loss mode.
The following automatic control types may be enabled when
the control enters comms loss mode:
• OVUV control
• VAR control
• Time control
• Temperature control
• Sensor Input control
• Current control
Note:
OVUV control uses a secondary set of thresholds
when the control is in comms loss mode.
Note:
If a stand-alone control contains a SelectComm
communications module, you must set the port type
to
unused
; otherwise, the control will go into
Communications Loss operating mode and activate
that alarm. Refer to the
CBC-8000 capacitor bank
control communications user guide (MN916003EN)
for this procedure.
Summary of Contents for COOPER POWER SERIES
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