ABB RELION 670 Series Technical Manual page 505

1MRK 502 066-UUS B
where:
IA, IB, IC
a
2
a
The phasor magnitude is used within the NS4PTOC (4612) protection to compare it with the set
operation current value of the four steps (
sequence current is larger than the set operation current and the step is used in non-directional
mode a signal from the comparator for this step is set to true. This signal, without delay, activates
the output signal PU_STx (x=1 - 4) for this step and a common PICKUP signal.
8.5.7.2 Internal polarizing facility of the function
A polarizing quantity is used within the protection to determine the direction to the fault
(Forward/Reverse).
Four step negative sequence overcurrent protection NS4PTOC (4612) function uses the voltage
polarizing method.
NS4PTOC (4612) uses the negative sequence voltage -V2 as polarizing quantity V3P. This voltage is
calculated from three phase voltage input within the IED. The pre-processing block calculates -V2
from the first three inputs into the pre-processing block by using the following formula:
1
(
= ×
V 2
3
ANSIEQUATION00024 V1 EN-US
where:
VA, VB, VC
This phasor is used together with the phasor of the operating current, in order to determine the
direction to the fault (Forward/Reverse).To enable voltage polarizing the magnitude of polarizing
voltage must be bigger than a minimum level defined by setting
Note that –V2 is used to determine the location of the fault. This ensures the required inversion of
the polarizing voltage within the function.
8.5.7.3 External polarizing for negative sequence function
Technical manual
are fundamental frequency phasors of three individual phase currents.
is so called operator which gives a phase shift of 120 deg, that is, a = 1∠120
deg
similarly gives a phase shift of 240 deg, that is, a
)
+ × + ×
2
VA a VB a VC
are fundamental frequency phasors of three individual phase voltages.
To use this all three phase-to-ground voltages must be connected to three IED VT
inputs.
2
= 1∠240 deg
Pickup1 , Pickup2 , Pickup3 or Pickup4 ). If the negative
VpolMin .
Section 8
Current protection
GUID-B00FE98B-F269-4F1B-AC03-68250798851B v3
GUID-21930E81-1B40-4BA4-B1D8-3B365327AEF6 v1
499