Underimpedance detection
The operating characteristic is an origin-centric circle on the impedance plane. The origin-
centric circular characteristic is defined using the Polar reach setting. If the calculated
impedance value enters the circle in the impedance plane, the module sends an enabling
signal to start the Timer.
GUID-87BF61EC-937C-4C2C-928E-984CA26D23DE V1 EN
Figure 352: Origin-centric circular operating characteristics
More than one impedance value is available when Impedance Meas mode
is set to "3Phase-phase", and the function considers the lowest impedance
value for picking up and tripping.
Timer
Once activated, the Timer activates PICKUP output. The time characteristic is according
to DT. When the duration of the underimpedance condition exceeds the set definite Trip
delay time, the TRIP output is activated. If the impedance locus moves out of circular
operating characteristics before the module operates, the reset timer is activated. If the
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 709
Technical Manual
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