SMA SC 500HE-US - Manual (Page 51)

SMA America, LLC 9 Grid Monitoring
Operating Manual SC500HEUS-eng-BE-BUS120320 51
9 Grid Monitoring
9.1 How Grid Monitoring Works
The Sunny Central has an integrated grid monitoring function. This means that the Sunny Central
monitors the power distribution grid to ensure that it remains within a definable range of limiting
values. If the configured limiting values for the line voltage or the power frequency are exceeded or
are not met for a specific time, the Sunny Central disconnects from the power distribution grid.
9.2 Monitoring the Line Voltage
For the line voltage monitoring, two limiting values in percent are defined for the minimum and the
maximum line voltage respectively, in accordance with IEEE 1547. The percentage is based on the
nominal voltage of the inverter.
If the line voltage falls below the value defined in the parameter "VCtllLim" or "VCtlllLim", the
Sunny Central waits for the period defined in the parameter "VCtllLimTm" or "VCtlllLimTm" and
disconnects from the power distribution grid.
If the line voltage increases above the value defined in the parameter "VCtlhLim" or "VCtlhhLim", the
Sunny Central waits for the period defined in the parameter "VCtlhLimTm" or "VCtlhhLimTm" and
disconnects from the power distribution grid.
Loss of UL certification
The limiting values for the line voltage and the power frequency are configured in accordance
with IEEE 1547. Changes to the factory-configured limiting values result in the loss of UL
certification.
• If the UL certification is the deciding factor for the operation permission of the inverter, do
not make any changes to the factory-configured limiting values for the grid monitoring
parameters.
Example: Behavior of the inverter in the event of undervoltage
The first limiting value for the undervoltage is defined in the parameter "VCtllLim" and is 88% of the
nominal voltage of the inverter. The associated period is set to 2 000 ms in the parameter
"VCtllLimTm". The second limiting value for the undervoltage is defined in the parameter "VCtlllLim"
and is 50% of the nominal voltage of the inverter. The associated period is set to 160 ms in the
parameter "VCtlllLimTm".
The line voltage falls to 85% of the nominal voltage and has therefore fallen below the first limiting
value of the undervoltage. The inverter waits 2 000 ms. If the line voltage does not increase above
the first limiting value within this period, the inverter disconnects from the power distribution grid. If
the line voltage falls below the second limiting value, the Sunny Central switches off after 160 ms.