9424200996 18-1
BE1-11m Power Factor (55) Protection
18 • Power Factor (55) Protection
The power factor (55) element provides synchronous motor pull-out or loss of synchronism protection.
Loss of synchronism can occur when there is an increase in load with no increase in field excitation.
Continuing to operate a synchronous motor after a loss of synchronism will result in increased line current
and additional heating in the motor.
Element logic connections are made on the BESTlogic™Plus screen in BESTCOMSPlus® and element
operational settings are configured on the Power Factor (55) settings screen in BESTCOMSPlus. A
summary of the logic inputs and outputs and operational settings appears at the end of this chapter.
BESTCOMSPlus Navigation Path: Settings Explorer, Protection, Power, Power Factor (55)
HMI Navigation Path: Settings Explorer, Protection, Settings Group x (where x = 0 to 3), Power
Protection, Power Factor 55
Element Operation
The power factor element monitors the power factor and protects a synchronous motor from consuming
excessive reactive power (vars) from the power system. The power factor element can also prevent a
synchronous condenser from exporting excessive vars to the power system. A mode setting enables the
power factor element.
Bus CT Configuration
On protection systems equipped with two sets of CTs, the power factor element can monitor CT circuit 1
or CT circuit 2. The CT source is selected on the Sensing Transformers settings screen in
BESTCOMSPlus.
Pickup and Trip
The Pickup output occurs first, followed by the Trip output.
Pickup
The Pickup output becomes true when the measured power factor decreases below the lagging or
leading threshold established by the Leading Pickup or Lagging Pickup setting. A specific trip region can
be disabled by setting its Pickup setting to zero (0). In BESTlogicPlus, the Pickup output can be
connected to other logic elements to annunciate the condition (act as an alarm), to control other elements
in logic, and start the fault recorder (logic element FAULTTRIG).
Assertion of the Pickup output initiates a timer that begins timing to a trip. The duration of the timer is
established by the Time Delay setting. A Time Delay setting of zero (0) makes the 55 element
instantaneous with no intentional time delay.
If the pickup condition subsides before the element delay expires, the timer and Pickup output are reset
and the element is rearmed for any other fault occurrences.
Trip
The Trip output becomes true if a leading or lagging pickup condition exists for the duration of the
element Time Delay. In BESTlogicPlus, the Trip output can be connected to other logic elements and to a
physical relay output to annunciate the condition (act as an alarm) and to initiate corrective action. If a
target is enabled for the element, the BE1-11m will record a target when the Trip output becomes true.
See the Fault Reporting chapter for more information about target reporting.
Element Blocking
Fuse Loss
The fuse loss (60FL) element of the BE1-11m can be used to block 55 protection when fuse loss or loss
of potential is detected in a three-phase system.
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