ABB RER620, Technical Manual

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Section 4
Protection functions
RER620 139
Technical Manual
Figure 58: Functional module diagram. I
0
and V
0
represent the zero sequence
current and zero sequence voltage.
Level detector
The measured ground current is compared with the set Pickup value . For directional
operation, the residual voltage (-Uo) also needs to be compared with the set Voltage pickup
value . If both limits are exceeded, the level detector sends an enable-signal to the timer
module. When the Enable voltage limit setting is set to “False”, the Voltage pickup value
has no effect and the level detection is purely based on the ground current. If the
ENA_MULT
input is active, the Pickup value setting is multiplied by the Pickup value Mult
setting.
The pickup value multiplication is normally done when the inrush detection function
(INR) is connected to the
ENA_MULT
input.
Directional calculation
The directional calculation module monitors the angle between the operating current and
polarizing voltage. When the angle is in the operation sector, the module sends the enable
signal to the timer module.
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
current followed by a directional earth-fault current, 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.
0
0