Simplified Logic Diagrams - ABB Relion 670 Series Technical Reference Manual

Section 6
Impedance protection
6.5.2.6
270
The reverse directional characteristic is equal to the forward characteristic rotated by
180 degrees.
The polarizing voltage is available as long as the positive-sequence voltage exceeds
5% of the set base voltage VBase. So the directional element can use it for all
unsymmetrical faults including close-in faults.
For close-in three-phase faults, the V1
sequence voltage, ensures correct directional discrimination.
The memory voltage is used for 100 ms or until the positive sequence voltage is restored.
After 100 ms, the following occurs:
• If the current is still above the set value of the minimum operating current
(between 10 and 30% of the set IED rated current IBase), the condition seals in.
• If the fault has caused tripping, the trip endures.
• If the fault was detected in the reverse direction, the measuring element in
the reverse direction remains in operation.
• If the current decreases below the minimum operating value, the memory resets
until the positive sequence voltage exceeds 10% of its rated value.

Simplified logic diagrams

Distance protection zones
The design of distance protection zone 1 is presented for all measuring: phase-to-
ground loops.
Phase-to-ground related signals are designated by AG, BG and CG.
Fulfillment of two different measuring conditions is necessary to obtain the one logical
signal for each separate measuring loop:
• Zone measuring condition, which follows the operating equations described above.
• Group functional input signal (PHSEL), as presented in figure 136.
The PHSEL input signal represents a connection of six different integer values from
the phase selection function within the IED, which are converted within the zone
measuring function into corresponding boolean expressions for each condition
separately. It is connected to the Phase selection with load enchroachment,
quadrilateral characteristic (FDPSPDIS,21) function output STCNDZ.
The input signal DIRCND is used to give condition for directionality for the distance
measuring zones. The signal contains binary coded information for both forward and
memory voltage, based on the same positive
AM
1MRK505222-UUS C
Technical reference manual