Once the integrator gets below the previous lowest value, it begins to roll back the output power
to lower the individual cell power. This will proceed until an equilibrium power point is reached
between actual cell power and the rated cell power.
The rated cell maximum power is based upon the transformer secondary winding rating derived
from the parameter "Rated Secondary Power" (2022), the harmonic load factor, cell voltage and
current rating, and cell conguration (installed number of cells).
Figure 7-18 Transformer Secondary Current Protection
Parameters
• Transformer Secondary power rating – "Rated Secondary Power" (ID 2022) – in kVA
• Harmonic loading factor – "Harmonic Load Factor" (ID 2024)
• Excessive secondary power loading rollback enable – "Power Rollback Enable" (ID 7114) –
turns o the rollback and relies on alarm and fault instead (default is "Enable")
• Cell Overload Level (7112) - Sets the upper limit of the integrator (to not interfere with this
feature)
• Full load current (1050) - motor rated current (to calculate cell PU rated power)
• Cell voltage (2550) - cell voltage (to calculate cell PU rated power)
SOP ags (as part of fault word 4)
• Trans2ndAlarm_I bit 30 Alarm if transformer secondary power too high
• Trans2ndFault_I bit 31 Fault if transformer secondary power too high
Alarm / Fault Messages
• "Xfrm Secondary Alarm"
• "Xfrm Secondary Fault"
Operating the Control
7.9 Input Side Monitoring and Protection
NXGPro+ Control Manual
Operating Manual, A5E50491925A 207
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