Basler BE1-CDS220, Инструкция по эксплуатации

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BE1-CDS220 Protection and Control 4-31
An INI (Initiate) logic input is provided to start the breaker
failure timer. When this expression is TRUE and current is
flowing in the assigned input circuit, the breaker failure timer
is started. Supervision of the initiate signal can be designed
in BESTlogic. Once the breaker failure timer is started, the
initiate signal does not have to remain TRUE.
A BESTlogic expression defines how the BLK (Block) input
functions. When this expression is TRUE, the element is
disabled by forcing the outputs to logic 0 and resetting the
timer to zero. For example, this may be an input wired to a
test switch such that breaker failure protection is disabled
when the primary protective elements are being tested to
prevent inadvertent backup tripping during testing.
The breaker failure Timer is stopped by the fast-dropout current detector function. See Section 3, Input
and Output Functions, Input Current, for more details on this function. The fast-dropout current detector is
designed to directly determine when the current in the poles of the breaker has been interrupted without
having to wait for the fault current samples to clear the one-cycle filter time used by the normal current
measurement function. This function has less than one cycle dropout time. The
Timer can also be
stopped by the BLK (Block) logic input being asserted.
The current detector sensitivity is fixed at 10% nominal. A traditional breaker failure relay includes a fault
detector function, which serves two independent purposes: current detector and fault detector. A current
detector is generally included to determine that the current has been successfully interrupted in all poles
of the breaker to stop breaker failure timing. The secondary function of a traditional fault detector is to
provide an independent confirmation that a fault exists on the system to increase security from
misoperation caused by an inadvertent initiate signal. To do this, a fault detector by definition must be set
above load current, reducing its sensitivity as a current detector. Since this breaker failure timer is
included in a multifunction protection system, fault detector supervision is not required.
If you are using external relays to initiate the breaker failure timer, it may be desirable to include fault
detector supervision of the initiate signal using an instantaneous overcurrent function in BESTlogic. For
example, if it is desired that certain initiate signals be supervised by a fault detector, it is possible to AND
them with one of the 50T protective functions using a virtual output expression. In other applications, it
may be desirable to have breaker failure timing with no current detector supervision. In this case, one of
the general-purpose logic timers (device 62) can be used as a breaker failure timer. See Section 8,
Application, Application Tips, for more details on this application.
When the breaker failure timer is picked up, the BFPU logic output is TRUE. This output would typically
be used as a re-trip signal to the protected breaker. This can provide an independent tripping signal to the
breaker that may also open the breaker to prevent backup tripping.
If the current detector remains picked up for the duration of the breaker failure delay time, the BFT output
is asserted. This output would normally be used to trip an 86F lockout relay, which will trip and prevent
closing of adjacent breakers and/or key transfer trip transmitters.
If the target is enabled for the BF function, the target reporting function will record a target when the
protective function trip output is TRUE and the fault recording function trip logic expression is TRUE. See
Section 6,
Reporting and Alarm Functions , Fault Reporting, for more details on the target reporting.
An alarm variable is provided in the programmable alarms function that can be used to indicate an alarm
condition when the breaker failure protection trips. See Section 6,
Reporting and Alarm Functions , Alarms
Function,
for more details on the alarm reporting function.
BESTlogic Settings for Breaker Failure
BESTlogic settings are made from the
BESTlogic Function Element
screen in BESTCOMS. Figure 4-28
illustrates the BESTCOMS screen used to select BESTlogic settings for the breaker failure element. To
open BESTlogic Function Element screen for the breaker failure element, select
Overcurrent from the
Screens pull-down menu. Then select the button labeled BESTlogic. Alternately, settings may be made
using the SL-50BF ASCII command.
D2843-27
07-24-00
INI
Mode =
0-Disable
1-CT ckt 1
2-CT ckt 2
BREAKER
FAILURE
(BF)
BLK
BFPU
BFT
Figure 4-27. Breaker Failure Logic Block