GUID-0C80D68A-9D22-47C6-8AAA-8E0D639764D9-ANSI V2 EN
Figure 308: Functional module diagram
Level detector
The fundamental frequency component of the measured three-phase voltages are
compared phase-wise to the set value of the Pickup value setting. If the measured value is
higher than the set value of the Pickup value setting, the level detector enables the phase
selection logic module. The Relative hysteresis setting can be used for preventing
unnecessary oscillations if the input signal slightly differs from the Pickup value setting.
After leaving the hysteresis area, the pickup condition has to be fulfilled again and it is not
sufficient for the signal to only return to the hysteresis area.
The Voltage selection setting is used for selecting phase-to-ground or phase-to-phase
voltages for protection.
For the voltage IDMT operation mode, the used IDMT curve equations contain
discontinuity characteristics. The Curve Sat relative setting is used for preventing
undesired operation.
For a more detailed description of the IDMT curves and the use of the
Curve Sat Relative setting, see the IDMT curve saturation of the over
voltage protection section in this manual.
Phase selection logic
If the fault criteria are fulfilled in the level detector, the phase selection logic detects the
phase or phases in which the fault level is detected. If the number of faulty phases match
with the set Num of pickup phases, the phase selection logic activates the Timer.
Timer
Once activated, the Timer activates the PICKUP output. Depending on the value of the set
Operating curve type, the time characteristics are selected according to DT or IDMT.
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 611
Technical Manual
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