ABB REB670 Series Applications Manual page 212

Section 7
Current protection
QOL> = 130% (of SCB MVAr rating); Reactive power level required for pickup. Selected value
gives pickup recommended by international standards.
tQOL = 60s ; Time delay for reactive power overload trip
Harmonic voltage overload feature:
OperationHOL = On ; to enable this feature
Settings for definite time delay step
HOLDTU> = 200% (of SCB voltage rating); Voltage level required for pickup
tHOLDT = 10s ; Definite time delay for harmonic overload trip
Settings for IDMT delay step
HOLIDMTU> = 110% (of SCB voltage rating); Voltage level required for pickup of IDMT stage.
Selected value gives pickup recommended by international standards.
kHOLIDMT = 1.0 ; Time multiplier for IDMT stage. Selected value gives operate time in
accordance with international standards
tMaxHOLIDMT = 2000s ; Maximum time delay for IDMT stage for very low level of harmonic
overload
tMinHOLIDMT = 0.1s ; Minimum time delay for IDMT stage. Selected value gives operate time in
accordance with international standards
7.10.3.1 Restrike detection
Opening of SCBs can be quite problematic for certain types of circuit breakers (CBs). Typically
such problems are manifested as CB restrikes.
In simple words this means that the CB is not breaking the current at the first zero crossing
after separation of the CB contacts. Instead current is re-ignited and only braked at
consecutive current zero crossings. This condition is manifested as high current pulses at the
moment of current re-ignition.
To detect this CB condition, the built in overcurrent feature can be used. Simply, any start of
the overcurrent feature during breaker normal opening means a restrike. Therefore simple
logic can be created in the Application Configuration tool to detect such CB behavior. Such CB
condition can be just alarmed, and if required, the built in disturbance recorder can also be
triggered.
To create this logic, a binary signal that the CB is going to be opened (but not trip command)
shall be made available to the IED.
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1MRK 505 370-UEN D
GUID-114747A5-0F7C-4F48-A32D-0C13BFF6ADCE v1
Busbar protection REB670
Application manual