Basler Electric BE1-11m - Manual (Page 61)

9424200996 Rev L 49
Frequency (81) Protection
Four frequency (81) elements monitor the frequency of the sensing voltage applied to the BE1-11m. An
element can be configured to protect against underfrequency, overfrequency, or the rate of frequency
change.
The four, identical frequency protection elements are designated 81-1, 81-2, 81-3, and 81-4. Element
logic connections are made on the BESTlogic
™Plus screen in BESTCOMSPlus® and element operational
settings are configured on the Frequency settings screen in BESTCOMSPlus. A summary of the logic
inputs and outputs and operational settings appears at the end of this chapter.
Note
BE1-11m protection systems enabled for IEC-61850 communication
(style Mxxxx5xxxxxxxx) have their frequency protection elements fixed
at two underfrequency elements and two overfrequency elements.
BESTCOMSPlus Navigation Path: Settings Explorer, Protection, Frequency, Frequency (81)
HMI Navigation Path: Settings Explorer, Protection, Settings Group x (where x = 0 to 3), Frequency
Protection 81
Frequency Measurement
For four-wire or single-phase sensing connections, the power system frequency is measured through the
BE1-11m A-phase sensing voltage input. For a three-wire connection, the power system frequency is
measured through the A- and B-phase sensing voltage connections. Refer to the
Typical Connections
chapter for information on voltage connections.
To measure frequency, the voltage sensed by the BE1-11m must be greater than 10 Vac. The measured
frequency is the average of two cycles of voltage measurement.
Underfrequency and Overfrequency Protection
Underfrequency and overfrequency protection can be useful for detecting load shedding or islanding. For
example, when a source of distributed generation (DG) is suddenly separated or isolated from the electric
utility, the frequency will change quickly from the nominal value (except for the improbable case of a
perfect load-to-generation match). This makes frequency measurement an excellent method for detecting
an island condition.
Any of the four 81 elements can be configured for underfrequency or overfrequency protection.
Mode
Underfrequency or overfrequency protection is selected through the Mode setting. A setting of Under
selects underfrequency protection and a setting of Over selects overfrequency protection.
Pickup and Trip
The Pickup output occurs first, followed by the Trip output.
Pickup
The Pickup output becomes true when the measured frequency decreases below (underfrequency
protection) or increases above (overfrequency protection) the frequency threshold established by the
Pickup setting for three consecutive sensing voltage cycles. 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 Frequency (81) Protection