ABB Relion REG670, Техническое руководство

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8.4.7 Operation principle
This function has the following three “Analog Inputs” on its function block in the
configuration tool:
1. I3P, input used for “Operating Quantity”. Supply the zero-sequence magnitude
measuring functionality.
2. U3P, input used for “Voltage Polarizing Quantity”. Supply either zero or
negative sequence voltage to the directional functionality
3. I3PPOL, input used for “Current Polarizing Quantity”. Provide 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”. Supply either zero or negative
sequence current to the directional functionality.
These inputs are connected from the corresponding pre-processing function blocks in
the Configuration Tool within PCM600.
8.4.7.1 Operating quantity within the function
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 (that is, 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 (that is, 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 into 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
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 I2 from SMAI
AI3P connected to I3PDIR input which was connected to I3P input also):
If zero sequence current is selected,
Iop 3I IL1 IL2 IL3
0
= = + +
EQUATION1874 V2 EN
(Equation 63)
Section 8
1MRK502052-UEN B
Current protection
362
Technical manual