P12x/EN T/Eb6 - Schneider - error

Application GuideP12x/EN AP/Eb6MiCOM P120/P121/P122/P123 Page 65/78• If there is a current signal going out in opposite way compared to the first one, therelay considers that the pole of the CB is not yet open. The « CB pole closed » internalsignal is maintained.Once the t BF time delay has elapsed, the relay checks the internal state of each pole of thecircuit breaker. If one or several internal poles are not opened, the relay then declares thatthe CB has failed. The “CB FAIL” message is displayed.Note that it is possible to initiate the CB fail detection function by a digital input withouthaving any trip order being given by the relay. In this case, the tBF timer starts its countdownwhen receiving this digital input signal. If the CB is not opened (by an another protectionrelay) once the tBF has elapsed, the relay declares that the CB has failed.The user can associate the digital input to the "CB Fail detection" under the AUTOMAT.CTRL/Inputs menu.Figure 17 hereafter shows the start of the CB Fail detection after a trip order was sent:Trip order20 samplest BF timer20 samples 20 samples 20 samples 20 samples 20 samplesI< thresholdI< threshold20 samples20 samples 20 samples 20 samples 20 samples20 samplesP0033ENaFIGURE 17: CB FAIL DETECTION PRINCIPLEFigure 18 hereafter shows the normal opening of the CB before tBF has elapsed. In thiscase, no CB fail alarm is given.« CB pole closed » internal signalTrip ordert BF timer20 samples 20 samples 20 samplesCB pole openeddetectionI< thresholdI< threshold20 samples20 samples 20 samples 20 samplesP0034ENaFIGURE 18: CB OPEN BEFORE tBF EXPIRED