Basler Electric BE1-11t - Manual (Page 55)

9424200995 Rev H 43
Phase Undervoltage (27P) Protection
Five phase undervoltage (27P) elements monitor the sensing voltage applied to the BE1-11t. An element
can be configured to protect against undervoltage when the phase voltage decreases below a defined
level.
The five, identical phase undervoltage protection elements are designated 27P-1, 27P-2, 27P-3, 27P-4,
and 27P-5. Element logic connections are made on the BESTlogic
™Plus screen in BESTCOMSPlus® and
element operational settings are configured on the Undervoltage 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, Voltage, Undervoltage (27P)
HMI Navigation Path: Settings Explorer, Protection, Settings Group x (where x = 0 to 3), Voltage
Protection, Undervoltage 27P
Element Operation
Phase undervoltage protection can be used to prevent large transformer and equipment damage when an
undervoltage condition exists. For example, an undervoltage condition could occur when a tap changing
control fails.
Modes of Protection
Three modes of protection are available. The One of Three mode activates protection when one of the
three phases of voltage decreases below the Pickup setting. The Two of Three mode activates protection
when any two of the three phases of voltage decrease below the Pickup setting. The Three of Three
mode activates protection when all three phases of voltage decrease below the Pickup setting.
Voltage Response
The phase undervoltage element can be set to monitor VPP or VPN. This is determined by the 27/59
Mode parameter of the phase VT connections found on the System Parameters/Sensing Transformers
settings screen in BESTCOMSPlus. For more information on the VTP setup for PP or PN voltage
response, see the
Configuration chapter.
Timings
The timing mode can be set for definite or inverse. For details on the inverse time curve, refer to the Time
Curve Characteristics chapter.
Pickup and Trip
The Pickup output occurs first, followed by the Trip output.
Pickup
The Pickup output becomes true when the measured voltage decreases below the voltage threshold
established by the Pickup setting. In BESTlogicPlus, the Pickup output can be connected to other logic
elements to annunciate the condition, 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 (definite timing) or Time Dial (inverse timing). A Time Delay or Time Dial
setting of zero (0) makes the 27P element instantaneous with no intentional time delay.
If the pickup condition subsides before the element delay or calculated inverse time expires, the timer and
Pickup output are reset, no corrective action is taken, and the element is rearmed for any other
occurrences of undervoltage.
BE1-11t Phase Undervoltage (27P) Protection