Operating Quantity Within The Function - ABB RES670 Technical Manual

1MRK 511 408-UUS A
8.2.7.1
Phasor measurement unit RES670 2.2 ANSI
Technical manual

Operating quantity within the function

The function always uses residual current (3I
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 (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 (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 of 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 a case, the pre-processing block will calculate 3I
three inputs into the pre-processing block by using the following formula (will
take 3I from SMAI AI3P and will be connected to I3PDIR and I3P inputs.
0
If the zero sequence current is selected,
= × = + +
I 3 Io IA IB IC
op
EQUATION2011-ANSI V1 EN-US
where:
IA, IB, IC 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 larger than the 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 STINx (x=step 1-4) for this step
and a common START signal.
Current protection
) for its operating quantity. The residual
0
Section 8
M13941-58 v9
from the first
0
(Equation 14)
199