ABB RER620 Technical Manual page 90

Section 4
Protection functions
84
The single-phase non-directional overcurrent protection function is used as one-phase and
three-phase overcurrent and short circuit protection. The phase-tripping mode is selected
with the Configuration setting Recloser type.
The operation in either tripping mode can be described by using a module diagram (see
Figure 35). Some modules have different functionality depending on whether the function
is in one-phase or three-phase tripping mode. All the blocks in the diagram are explained
in the next sections.
I_A
Level
I_B
detector
I_C
ENA_MULT
BLOCK
Figure 35: Functional module diagram. I_A, I_B and I_C represent phase currents.
Level detector
The measured phase currents are compared phase-wise with the set Pickup value.and, if
enabled, the Pickup block value. If the measured value exceeds the set Pickup value, and
is less than the Pickup block value, the level detector reports the pickup to the phase
selection logic. If the ENA_MULT input is active, the Pickup value setting is multiplied by
the Pickup value Mult setting.
Do not set the multiplier setting Pickup value Mult higher than necessary.
If the value is too high, the function may not trip at all during an inrush
followed by a fault, no matter how severe the fault is.
The relay does not accept the Pickup value or Pickup value Mult setting if
the product of these settings exceeds the Pickup value setting range.
Timer
t
t
Timer
t
t
Phase
selection
Timer
logic
t
Blocking t
logic
1MAC309294-MB F
TRIP_A
PICKUP_A
TRIP_B
PICKUP_B
TRIP_C
PICKUP_C
RER620
Technical Manual