ABB Relion RES670, Technical Manual

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where:
IA, IB, IC are fundamental frequency phasors of three individual phase currents.
a is so called operator which gives a phase shift of 120 deg, that is, a = 1∠120 deg
a
2
similarly gives a phase shift of 240 deg, that is, a
2
= 1∠240 deg
The phasor magnitude is used within the NS4PTOC (4612) protection to compare it
with the set operation current value of the four steps (
Pickup1 , Pickup2 , Pickup3 or
Pickup4 ). If the negative 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.
8.3.7.2 Internal polarizing facility of the function
GUID-B00FE98B-F269-4F1B-AC03-68250798851B v3
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:
( )
2
1
2
3
V VA a VB a VC
= × + × + ×
ANSIEQUATION00024 V1 EN-US
where:
VA, VB, 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.
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
Section 8
1MRK 511 408-UUS A
Current protection
222 Phasor measurement unit RES670 2.2 ANSI
Technical manual