46 Program features
Grounding
As default, the MGND-01 board is configured for DC- grounding but this can be changed
during commissioning of the inverter. Option code F282 selects DC+ grounding instead of
DC- grounding. Option code F314 selects Floating DC (no grounding).
For details of the MGND-01 board, refer to the Hardware manual.
Software control for grounding is identical regardless of grounding types. The following
descriptions and parameters are valid for all types of grounding.
Grounding modes
The grounding mode can be selected through parameter 210.01 Grounding mode.
Grounding at low insulation resistance
If the insulation resistance reading is low due to, for example, high ambient moisture,
grounding can still be activated with parameter 210.04 Ignore insulation resistance.
Note: Grounding is automatically removed if the MGND-01 unit discovers high
grounding currents or voltages.
Ungrounded operation
When insulation resistance is sufficiently high and the solar panel array is allowed to
operate without grounding, ungrounded operation can be enabled with parameter 210.05
Ungrounded operation.
Grounding events
Whenever the grounding unit detects an abnormal condition, such as high grounding
currents, high grounding voltages or sudden change in the resistive grounding current, the
inverter triggers a warning or a fault. The action of how the inverter should react can be
selected with parameters:
• 210.12 Grounding circuit voltage fail action
• 210.16 Grounding current fault action
• 210.18 Sudden change current fault action
Note: The action in parameter 210.18 can also be set to value "No", which
disables the sudden change in grounding current feature.
Mode Description
Off Grounding feature and grounding unit are disabled.
Forced Forced activation of grounding without first checking the insulation resistance.
If, during forced grounding, high ground current (through the grounding resistor) or high
grounding voltage (across the series-connected grounding resistor and fuse) is mea-
sured by the internal measurement circuitry, then the MGND-01 unit will enter the “Failed
forcing state” and at the same time will remove the grounding action and triggers a warn-
ing or a fault. The MGND-01 unit will remain in the Failed forcing state until the mode is
changed to Off or the fault is reset.
If the MGND-01 unit is configured to only trigger a warning then the grounding mode
must be changed to Off to restore normal operation of the MGND-01 unit.
Note: Forced mode is intended for tests only.
Automatic Automatic or autonomous mode. In this mode, grounding is automatically enabled and
the behaviour is defined with parameters 210.03...210.09.
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