ABB RELION 650 SERIES, Technical Manual

Page: 218 / 942

( )
2
1
2 1 2 3
3
I IL a IL a IL
= × + × + ×
EQUATION2266 V2 EN-US
(Equation 29)
where:
IL1, IL2 and IL3 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 protection to compare it with
the set operation current value of the four steps (
I1> , I2> , I3> or I4> ). 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 STx (x=1 - 4) for this
step and a common START signal.
7.5.7.2 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 function uses the
voltage polarizing method.
NS4PTOC uses the negative sequence voltage -U2 as polarizing quantity U3P.
This voltage is calculated from three phase voltage input within the IED. The pre-
processing block calculates -U2 from the first three inputs into the pre-processing
block by using the following formula:
( )
2
2
1
1 2 3
3
UPol U
UL a UL a UL
= - = -
× + × + ×
EQUATION2267 V2 EN-US
where:
UL1, UL2 and UL3 are fundamental frequency phasors of three individual phase voltages.
To use this all three phase-to-earth 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
Section 7
1MRK 506 382-UEN A
Current protection
212 Line distance protection REL650 2.2 IEC
Technical manual