ABB RELION 620 Series Technical Manual page 206

Section 4
Protection functions
200
0
0
A070438-ANSI V1 EN
Figure 88: Functional module diagram. I
current and zero sequence voltage.
Level detector
The measured ground current is compared to the set Pickup value. The zero sequence
voltage (-Vo) also needs to be compared to 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.
If the Enable voltage limit setting is set to "True", the magnitude of the
polarizing quantity is checked even if the Directional mode was set to
"Non-directional" or Allow Non Dir to "True". The protection relay does
not accept the Pickup value or Pickup value Mult setting if the product of
these settings exceeds the Pickup value setting range.
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 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. When the angle is in the operation sector, the module sends the
enabling signal to the timer module.
and V represent the zero sequence
0 0
1MAC504801-IB E
620 series ANSI
Technical Manual