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Diagnostics case :

dI-Mess, dI-Meas, Fault Curr Meas

Yellow LED in Blink Code 6 or Permanent Disable Mode (yellow LED continuously illuminated)

The dI-Mess error message indicates that the inverter has detected a leakage current that is too high (> 90 mA) or a sudden change of more than 30 mA in the leakage current.

This error message is usually caused by a problem with the installation of the grounding conductor on the AC side. Other causes could be sudden ground faults or residual currents in the PV module array or a defect in the DI converter in the inverter (i.e. a device fault).

If the disturbance occurs more than 40 times a day, for safety reasons the inverter locks and the yellow LED is continuously illuminated. This lock can only be removed by an electrically qualified person via communication.

Background information about leakage currents:

All PV module arrays are designed in such a way that they have a parasitic capacitance against their environment, and this can rise further in the event of a moist surface (rain, dew). Under specific design or weather conditions, the PV array’s discharge capacity can rise so far that the resulting capacitive leakage current can interfere with the residual current monitoring of the inverter. To ensure that residual currents are always detected, the inverter interrupts feed-in operation as a precautionary measure and then automatically reconnects to the utility grid when normal values have been restored.

Detailed background information about the creation, effect and compensation of capacitive leakage current can be found in the technical information “Capacitive Leakage Currents.” This can be downloaded at https://www.sma.de/en/service/downloads.html.

Corrective measures for PV system operators:

WARNING! Danger to life due to electric shock

Do not touch the PV modules, substructure or frame of the PV array.

• Read out the residual current and insulation resistance via communication (e.g. Sunny Explorer).

The residual current and insulation resistance vary depending on the weather conditions (humidity / moisture on the modules). Therefore, where possible, read out the values directly when the disturbance occurs or during the weather conditions in question.

• Contact your installer immediately. The subsequent steps require the specialist knowledge of an electrically qualified person or installer.

Corrective measures for installers:

Read out the values via communication:

• Read out the residual current and insulation resistance via communication (e.g. Sunny Explorer, USB-Serviceinterface or Sunny WebBox).).

• Check whether there were further error messages.

If the yellow LED is continuously illuminated:

• Reset the Permanent Disable Mode via communication, for the procedure see diagnosis "Permanent Disable Mode"

DANGER! The tasks described below may only be performed by electrically qualified persons:

Check that the grounding conductor (PE) is connected correctly to the inverter and in the subdistribution:

  • Measure the AC voltage between L - N, L - PE and N - PE.
  • There should be no voltage between N - PE. Only in TT grid systems there may be voltage differences between N and PE; these must be kept to a minimum. A maximum of 20 V – 30 V is permitted in TT grid systems.
    Information: Be sure to use a suitable measuring device such as a multimeter. Voltage detectors (e.g. Duspol) are not suitable for these measurements.

Check the PV system for ground faults:

• Check the PV modules by means of voltage measurement +/- to ground, as described in the device type’s service or installation manual.

The voltage measurement can only detect an acute, hard ground fault.

• If the Riso value read out via communication is conspicuously low, measure the insulation resistance, as described in the device type’s service or installation manual.

Information: The Riso value varies depending on the weather conditions (humidity / moisture on the modules). For this reason, take the measurements in the relevant weather conditions.

If, however, the message keeps on appearing, even though the PV system has been checked as described, the subsequent steps must be clarified with SMA Service.

In this case, please contact SMA Service with the following information:

• Device type and serial number of the inverter

• Error message and LED blink code

• How long has the error been present for? Is it sporadic or continuous?

• Are there further error messages?

• Measurement results of the N-PE, L-N, L-PE voltages

• Riso values and residual currents read out via communication

• Measured DC voltages between +/- and PE of all strings

• Measured insulation resistance of all strings

The residual current and insulation resistance can be read out via communication as follows:

Sunny Explorer /Sunny WebBox Bluetooth/ SMA Cluster Controller after the inverter has been selected in the system tree:

Residual current under Spot values/DC Side/Residual current

Insulation resistance under Spot values/DC Side/Insulation monitoring

Sunny WebBox (485) after the inverter has been selected in the system tree:

Residual current under Spot Values/dI

Insulation resistance under Spot Values/Riso

All work on the inverter and the cabling of the PV array must be carried out by an electrically qualified person. SMA accepts no liability for the information and solutions given in the Online Service Center. Additional information can be found in our Online Service Center’s terms and conditions of use.