ABB RELION 620 Series Technical Manual page 629

1MAC504801-IB E
6.7.4
620 series ANSI
Technical Manual
The phase discontinuity protection function provides individual counter values for the
number of times a self-clearing fault is observed in each phase. The phase discontinuity
protection function also determines whether the self-clearing fault is observed in all three
phases or not.
This phase discontinuity protection contains a blocking functionality. It is possible to
block the function outputs or the function itself if desired.
Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of the phase discontinuity protection function can be described with a
module diagram. All the modules in the diagram are explained in the next sections.
GUID-3318EF60-5E36-4872-B257-B44C54BC252F-ANSI V1 EN
Figure 318: Functional module diagram.
SCFD analysis
The self-clearing fault detection SCFD analysis module detects the self-clearing fault in
each phase by comparing the corresponding phase current magnitude to the set value
PhPu.
If the phase current I_A magnitude goes above double the set value PhPu, the module
calculates the time duration for which the current I_A continuously stays above double the
set value PhPu. If the calculated time duration is greater than 1/4 cycles and less than the
number of cycles set by CyMulit, it regards that the self-clearing fault is observed in phase
A and DetectfaultPhA in the monitored data is set to "True". If the time duration
criterion fails, PickUpNoTripA in the monitored data is set to "True". Once the self-
clearing fault is detected in phase A, function increments the count SCA in the monitored
data, which keeps record of the number of times the fault has been detected.
Self-clearing faults in phase B and phase C are detected similarly as explained for phase
A, that is, by comparing I_B and I_C magnitudes to the set value PhPu and by checking
the time duration. If the fault is detected in phase B or phase C, DetectfaultPhB or
respectively DetectfaultPhC in the monitored data is set to "True". If the time
duration criterion fails for phase B or phase C, the corresponding PickUpNoTripB or
Section 6
Supervision functions
623