Breaker Failure (50Bf) Protection; Element Operation - Basler BE1-11g Instruction Manual

9424200994 Rev U 101

Breaker Failure (50BF) Protection

The breaker failure (50BF) element provides protection and security for the power system against the
monitored breaker failing to open.
Element logic connections are made on the BESTlogic™Plus screen in BESTCOMSPlus® and element
operational settings are configured on the Breaker Fail (50BF) 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, Current, Breaker Fail (50BF)
HMI Navigation Path: Settings Explorer, Protection, Settings Group x (where x = 0 to 3), Current
Protection, Breaker Fail 50BF

Element Operation

The 50BF element uses two methods to determine when the breaker has failed to open. The first method
uses the breaker status (52a or 52b input) to determine if the breaker has successfully opened. The
second method uses the monitored current to detect if the breaker has successfully opened.
In the first method, the breaker is closed when the Breaker Status (BRKSTAT) logic element is true. The
52BFI logic input is used to signal the breaker to open. When the BRKSTAT logic element and the 52BFI
logic input are true, a delay timer is initiated to allow time for the breaker to transition. If the time delay
expires and the BRKSTAT logic element and the 52BFI logic input are still true, the Trip output becomes
true, signaling that the breaker has failed to trip.
In the second method, monitored current is used to determine if the breaker is closed. The 50BFI logic
input of the Breaker Failure logic block is used to signal the breaker to open. When current is present and
the 50BFI logic input is true, a timer is initiated to allow time for the fault to clear. If the time delay expires
and current is still present, the Trip output becomes true, signaling that the breaker has failed to open. A
control timer specifies the duration the breaker can remain closed before a Breaker Fail alarm will occur.
In both methods above, a Breaker Fail Retrip (BFRT) will be true while the delay timer is true. A breaker
fail trip indicates a failed breaker. The Trip signal can be used to trip the next set of breakers upstream in
the power system. Breaker failure protection may be applied to any portion of the power system where
failure of a circuit breaker to operate properly could result in severe system damage or instability.
Contact Sensing
Before any relay output can occur, there must first be an initiating signal to the Breaker Failure logic
element. There are two possible initiating signals. The 52 Breaker Fail Initiate (52BFI) signal is the
initiation signal when breaker status is used to determine a breaker failure. The 50 Breaker Fail Initiate
(50BFI) is the initiation signal when current is used to determine a breaker failure. These initiate inputs
can be driven by other relays through BE1-11g contact inputs or GOOSE over IEC 61850. Alternately,
they can come from trip signals from other protective elements within the BE1-11g. Breaker status input is
provided by the BRKSTAT logic element.
Information on setting up the breaker status logic can be found in the Breaker Monitoring chapter.
Control Timer
The control timer provides a window of opportunity for a breaker failure Trip output when the 50BFI logic
input is used to signal the breaker to open. It improves dependability by sealing in the initiate request to
prevent stopping of a breaker failure timing if the tripping relay drops out prematurely. The control timer is
initiated by a 50BFI signal. Upon sensing the 50BFI transition from a 0 to 1 state, the control timer seals
in the 50BFI signal for the duration of the Control Timer setting. If the control timer expires and the 50BFI
signal is still present, an alarm signal occurs. A control timer setting of zero (0) disables the control timer
seal-in function allowing the control timer to follow the 50BFI input.
BE1-11g Breaker Failure (50BF) Protection