6.9.2.6 Simplified logic diagrams
Distance protection zones
The design of the distance protection zones are presented for all measuring loops: phase-
to-ground as well as phase-to-phase.
Phase-to-ground related signals are designated by AG, BG and CG.. The phase-to-
phase signals are designated by AB, BC and CA.
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 80.
The PHSEL input signal represents a connection of six different integer values from
Phase selection with load encroachment, quadrilateral characteristic function
FRPSPDIS (21) within the IED, which are converted within the zone measuring
function into corresponding boolean expressions for each condition separately. Input
signal PHSEL is connected to FRPSPDIS (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
reverse direction. The zone measurement function filter out the relevant signals
depending on the setting of the parameter OperationDir. It must be configured to the
STDIRCND output on directional function ZDRDIR (21D) function.
Section 6 1MRK505222-UUS C
Impedance protection
316
Technical reference manual
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