This failure happens when an inverter is connected to a grid earthing system or grid configuration that the model does not support, such as an IT grid on a model without IT support, or a delta grid other than the one specified. Support depends on the model. Some hybrid models do not support IT networks and are not recommended for TN-C, while some commercial and utility models support all major earthing systems. On a TN-C system with a large load imbalance, a touch voltage can appear on the inverter enclosure. Connecting to an unsupported delta grid can damage the inverter. Before installing, verify the site earthing system and confirm it is compatible with the inverter model, using the manufacturer compatibility table and the installation manual. If TN-C cannot be avoided, keep the unbalanced output function disabled. Where possible, convert the installation to TN-C-S before connecting the inverter. Balance loads across the phases, and do not use a neutral terminal for loads when there is no neutral conductor. For non-standard topologies, contact the manufacturer and the utility. Never change earthing arrangements without approval from the electrical authority or a qualified engineer.
<!-- review notes
affectsEach inverter model supports only certain grid earthing systems or grid configurations; for example some hybrid models do not support IT grids, and TN-C is not recommended for them.
tbl=1 h=24362010cc2fsec=h11 h=638e47cbf091sec=h87 h=1a9a178d6ef0presents_asc2 drafted · lead Touch voltage on enclosure proposed
On TN-C systems, a large load imbalance can put a touch voltage on the inverter enclosure under some operating conditions.
sec=h11 h=638e47cbf091caused_byc3 drafted · lead Installation error
Connecting the inverter to a grid topology or earthing system the model does not support. On one product line, delta grids other than the supported one may damage the inverter and void the warranty.
sec=h14 h=a99e703fbd5dsec=h87 h=1a9a178d6ef0review note: support check: partial - The delta-grid damage and warranty caution is stated, but nothing explicitly names installation error as the cause. Only best practices that imply it are given.
c4 drafted · lead Recurring line-to-ground faults proposed
On a 480 V delta service, co-located loads that cause recurring line-to-ground faults effectively turn it into a corner-grounded delta grid, which exposes the inverters to excessive line-to-ground voltage.
sec=h110 h=347cabe51550review note: support check: partial - u25 describes recurring line-to-ground faults on 480 V delta giving an effective corner-grounded delta and excessive line-to-ground voltage. It does not say this is an earthing incompatibility, and it prescribes isolating the PV system from the fault source.
mitigated_byc5 drafted · lead Earthing system verification proposed
Check the site earthing system and confirm it is compatible with the inverter model before installing.
sec=h14 h=a99e703fbd5dc6 drafted · lead TN-C-S conversion proposed
Where possible, convert a TN-C installation to TN-C-S before connecting the inverter.
sec=h11 h=638e47cbf091c7 drafted · lead Inverter settings review
If a TN-C connection cannot be avoided, the unbalanced output function must stay disabled.
sec=h11 h=638e47cbf091c8 drafted · lead Balanced phase loading proposed
On three-phase systems, balance loads across all phases. If there is no neutral conductor, do not connect loads to a neutral terminal.
sec=h13 h=10802b4ec3aec9 drafted · lead Contact manufacturer service
Contact the manufacturer when the site topology or transformer configuration is outside the supported standard configurations.
sec=h14 h=a99e703fbd5dsec=h37 h=a2433cb3d772sec=h29 h=853ef8d607e3c10 drafted · lead Utility company consultation
Get the exact connection specifications from the electric utility; local regulations and distribution system operator requirements take priority.
sec=h35 h=14372b068de8sec=h2 h=bf11df3c0f94c11 drafted · lead Proper installation
A qualified electrician should do the work, following local regulations and the model-specific installation manual. Earthing arrangements should never be changed without approval.
sec=h14 h=a99e703fbd5dsec=h2 h=bf11df3c0f94sec=h11 h=638e47cbf091