6.4.7
Operation principle
IP12992-1 v2
M13941-51 v7
This function has the following four analog inputs on its function block in the
configuration tool:
1. I3P, input used for the operating quantity. Supplies the zero-sequence
magnitude measuring functionality.
2. U3P, input used for the voltage polarizing quantity. Supplies either the zero or
the negative sequence voltage to the directional functionality
3. I3PPOL, input used for the current polarizing quantity. Provides polarizing
current to the directional functionality. This current is normally taken from the
grounding of a power transformer.
4. I3PDIR, input used for directional detection. Supplies either the zero or the
negative sequence current to the directional functionality.
These inputs are connected from the corresponding pre-processing function blocks
in the configuration tool in PCM600.
6.4.7.1
Operating quantity within the function
M13941-58 v9
The function always uses residual current (3I
0
) for its operating quantity. The
residual current can be:
1. directly measured (when a dedicated CT input of the IED is connected in
PCM600 to the fourth analog input of the pre-processing block connected to
EF4PTOC function input I3P). This dedicated IED CT input can be, for
example, connected to:
•
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
star point and earth (current transformer located in the star point of a star
connected transformer winding).
•
one single current instrument transformer located between two parts of a
protected object (current transformer located between two star points of
double star shunt capacitor bank).
2. calculated from three-phase current input within the IED (when the fourth
analog input of the pre-processing block, connected to EF4PTOC function
Analog Input I3P, is not connected to a dedicated CT input of the IED in
PCM600). In such a case, the pre-processing block will calculate 3I
0
from the
first three inputs into the pre-processing block by using the following formula
(will take 3I
0
from SMAI AI3P and will be connected to I3PDIR and I3P
inputs.
If the zero sequence current is selected,
Iop 3I
IL1 IL2 IL3
0
=
=
+
+
EQUATION1874 V2 EN-US
(Equation 7)
1MRK 505 384-UEN A
Section 6
Current protection
Breaker protection REQ650 2.2 IEC
113
Technical manual
Summary of Contents for impreza 2017
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