Basler Electric BE1-11m - Manual (Page 95)

9424200996 Rev L 83
Loss of Excitation - Reverse Var Based
(40Q) Protection
The loss of excitation - reverse var based (40Q) element monitors total reactive power (vars).
Element logic connections are made on the BESTlogic
™Plus screen in BESTCOMSPlus® and element
operational settings are configured on the Loss of Excitation - Reverse var Based (40Q) 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, Loss of Excitation - Reverse
var Based (40Q)
HMI Navigation Path: Settings Explorer, Protection, Settings Group x (where x = 0 to 3), Power
Protection, Reverse var 40Q
Element Operation
The loss of excitation element operates on excessive var flow into the machine, indicating abnormally low
field excitation. Operation of synchronous motors drawing reactive power from the system can result in
overheating in parts of the rotor that do not normally carry current. The 40Q pickup response is shown in
Figure 59.
Figure 59. 40Q Pickup Response
Bus CT Configuration
On protection systems equipped with two sets of CTs, the 40Q 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 calculated reactive power increases above or decreases below
the 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).
BE1-11m Loss of Excitation - Reverse Var Based (40Q) Protection