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Breaker failure protection (BFP)
The operating values of the current measuring elements are settable within a wide set-
ting range. The measuring is stabilised against the dc-transient that can cause unwanted
operation at saturated current transformers and correct breaker operation. Time mea-
surement is individual for each phase. Two independent timers are available, t1 for re-
peated tripping of "own" breaker and t2 which operates trip logic for adjacent breakers.
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The parameters for the breaker failure protection function are set via the local HMI or
PST (Parameter Setting Tool). Refer to the Technical reference manual for setting pa-
rameters and path in local HMI.
The breaker-failure protection can be controlled from the human-machine interface
(HMI) by an "Operation" parameter, to be set between alternatives Off/On.
When "Operation" is set to Off, the function becomes inoperative.
The configuration of input and output signals to the function is made with the CAP con-
figuration tool.
The inputs and the outputs to and from the breaker-failure protection are presented in
the signal list.
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Trip pulse, tp
150 ms, fixed
The breaker failure protection shall be set by means of a current limit for detection of a
breaker failure. The current setting shall be chosen in relation to the protection func-
tions, initiating the breaker failure protection. Normally the current setting should be
equal to or lower than the most sensitive setting of a residual overcurrent protection.
If the retrip function is used a time delay before retrip has to be set. In most cases this
time delay can be set to zero.
The time delay of the back-up trip function shall be chosen so that selectivity is main-
tained. Consider the following:
t1: Set retrip time delay
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