ABB REF615 Applications Manual page 79

1MRS756378 D
REF615
Application Manual
A071352 V4 EN
Figure 35: Phase discontinuity, thermal overload and circuit breaker failure
protection
The phase discontinuity protection (PDNSPTOC1) provides protection for
interruptions in the normal three-phase load supply, for example, in downed
conductor situations. The thermal overload protection (T1PTTR1) provides
indication on overload situations. The operate signal of the phase discontinuity
protection is connected to the Master Trip and also to the alarm LEDs. LED 4 is used
for the phase discontinuity protection operate indication, the same as for negative
sequence overcurrent protection operate indication, and LED 5 is used for the thermal
overload protection alarm indication.
The breaker failure protection (CCBRBRF1) is initiated via the start input by a
number of different protection stages in the IED. The breaker failure protection
function offers different operating modes associated with the circuit breaker position
and the measured phase and residual currents. The breaker failure protection has two
operating outputs: TRRET and TRBU. The TRRET operate output is used for re-
tripping its own breaker through the Master Trip 2. The TRBU output is used to give
a back-up trip to the breaker feeding upstream. For this purpose, the TRBU operate
output signal is connected to the output PO2 (X100: 8-9). LED 6 is used for back-up
(TRBU) operate indication.
Section 3
REF615 variants
73