ABB REG650 ANSI, Technical Manual

Page: 198 / 728

1. I3P, input used for “Operating Quantity”.
2. U3P, input used for “Voltage Polarizing Quantity”.
3. I3PPOL, input used for “Current Polarizing Quantity”.
4. I3PDIR, input used for “Operating Directional Quantity”.
These inputs are connected from the corresponding pre-processing function blocks in
the Configuration Tool within PCM600.
8.2.7.1 Operating quantity within the function
If the function is set to measure zero sequence, it 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 same
SMAI AI3P connected to I3PDIR input (same SMAI AI3P connected to I3P
input)):
If zero sequence current is selected,
Iop 3I IL1 IL2 IL3
0
= = + +
EQUATION1874 V2 EN
(Equation 47)
where:
IL1, IL2 and IL3 are fundamental frequency phasors of three individual phase currents.
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 protection to compare it with the set operation
current value of the four steps (
IN1> , IN2> , IN3> or IN4> ). If the residual current is
Section 8
1MRK 502 048-UEN A
Current protection
192
Technical manual