ABB Relion 670 series - Principle of operation; Operating quantity within the function

Directional operation can be combined together with corresponding communication
logic in permissive or blocking teleprotection scheme. Current reversal and weak-end
infeed functionality are available as well.
EF4PTOC (51N/67N) can be configured to measure the residual current from the three-
phase current inputs or the current from a separate current input.
7.4.2 Principle of operation
This function has the following three “Analog Inputs” on its function block in the
configuration tool:
1. I3P, input used for “Operating Quantity”.
2. V3P, input used for “Voltage Polarizing Quantity”.
3. I3PPOL, input used for “Current Polarizing Quantity”.
These inputs are connected from the corresponding pre-processing function blocks in
the Configuration Tool within PCM600.
7.4.2.1 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 (51N/
67N) 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
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).
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
0
from the first
three inputs into the pre-processing block by using the following formula (will
Section 7 1MRK505222-UUS C
Current protection
400
Technical reference manual