ABB Relion 650 Series Technical Manual page 181

1MRK 506 326-UUS B
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2. calculated from three-phase current input within the IED (when the fourth analog input into
the pre-processing block connected to EF4PTOC (51N/67N) function Analog Input I3P is not
connected to a dedicated CT input of the IED in PCM600). In such case the pre-processing
block will calculate 3I
following formula:
= ×
I 3 Io
op
EQUATION2011-ANSI V1 EN-US
where:
IA, IB, IC
The residual current is pre-processed by a discrete Fourier filter. Thus the phasor of the
fundamental frequency component of the residual current is derived. The phasor magnitude is
used within the EF4PTOC (51N/67N) protection to compare it with the set operation current value
of the four steps (
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 will, without delay, activate the output signal PUSTx (x=step
1-4) for this step and a common PICKUP signal.
6.6.7.2 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 the residual voltage -3V
quantity V3P. This 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
following formula:
Line distance protection REL650
Technical manual
parallel connection of current instrument transformers in all three phases (Holm-Green
connection).
one single core balance, current instrument transformer (cable CT).
one single current instrument transformer located between power system WYE point
and ground (that is, current transformer located in the neutral grounding of a WYE
connected transformer winding).
one single current instrument transformer located between two parts of a protected
object (that is, current transformer located between two WYE points of double WYE
shunt capacitor bank).
from the first three inputs into the pre-processing block by using the
0
= + +
IA IB IC
are fundamental frequency phasors of three individual phase currents.
Pickup1 , Pickup2 , Pickup3 or Pickup4 ). If the residual current is larger than the
from the first three inputs into the pre-processing block by using the
0
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Section 6
Current protection
(Equation 29)
M13941-82 v6
as polarizing
0
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