Internal Polarizing - ABB REL650 series Technical Manual

Section 7
Current protection
7.6.7.2
222

Internal polarizing

A polarizing quantity is used within the protection in order to determine the direction to
the ground fault (Forward/Reverse).
The function can be set to use voltage polarizing, current polarizing or dual polarizing.
Voltage polarizing
When voltage polarizing is selected the protection will use either the residual voltage 3V
or the negative sequence voltage V
The residual voltage can be:
1. directly measured (when a dedicated VT input of the IED is connected in PCM600 to
the fourth analog input of the pre-processing block connected to EF4PTOC (51N/
67N) function input V3P). This dedicated IED VT input shall be then connected to
open delta winding of a three phase main VT.
2. calculated from three phase voltage input within the IED (when the fourth analog
input into the pre-processing block connected to EF4PTOC (51N/67N) analog
function input V3P is NOT connected to a dedicated VT input of the IED in
PCM600). In such case the pre-processing block will calculate 3V
three inputs into the pre-processing block by using the following formula:
VPol=3V0=(VA +VB +VC)
ANSIEQUATION2407 V1 EN
where:
VA, VB, VC
In order to use this, all three phase-to-ground voltages must be connected to three IED VT
inputs.
The residual voltage is pre-processed by a discrete fourier filter. Thus, the phasor of the
fundamental frequency component of the residual voltage is derived.
The negative sequence voltage is calculated from the three-phase voltage input within the
IED by using the pre-processing block. The preprocessing block will calculate the
negative sequence voltage from the three inputs into the pre-processing block by using the
following formula:
= + × + ×
VPol ( VA alpha VB alpha VC
GUID-F09A69D7-A8A6-4354-B0B8-F4EC7BBE603F V2 EN
as polarizing quantity V3P.
2
are fundamental frequency phasors of three individual phase voltages.
)/3
1MRK 506 335-UUS A
0
from the first
0
(Equation 49)
(Equation 50)
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