Field reference for utility scale solar technicians. 20 entries, taken from the FieldWatt app.
Reference notes from FieldWatt, the offline field toolkit for utility scale solar commissioning and O&M technicians. It works with no cell signal, because the sites do not have any.
Get FieldWatt on the App StoreEvery central inverter measures insulation resistance (often shown as Riso) between the PV array and ground before and during operation. A trip in this family means current is leaking to ground somewhere in the DC field: damaged module, chafed or rodent damaged cable, water in a connector or combiner, or a failed surge protective device. The faulted conductor can energize racking and enclosures.
Stop work. Treat the array and racking as energized. Do not reset and restart to see if it clears. A qualified person locates the fault with DC rated PPE using ground referenced voltage measurements and an insulation resistance test.
Verify trip levels and reset behavior against the current manufacturer manual and the site operating procedures.
DC overvoltage usually appears on cold clear mornings when string open circuit voltage rises above the inverter maximum input. It can indicate a string sizing error against the record low temperature. DC undervoltage during daylight points to open strings, blown combiner fuses, or a contactor that did not close.
Log ambient temperature and time of the trip. If overvoltage recurs on cold mornings, escalate for a string sizing review before further operation. Repeated resets can damage the DC input stage.
Verify voltage windows against the current manufacturer manual.
Inverters must disconnect when grid voltage or frequency leaves the protection window, per IEEE 1547 and the interconnection agreement. A plant wide burst of grid faults at the same timestamp usually means a real utility event, a substation switching operation, or a plant controller setpoint excursion rather than an inverter problem. A single unit tripping alone points at its own AC connection, breaker, or measurement.
Compare timestamps across the block before touching anything. If the whole plant tripped together, check with the control room and the utility before restarting units.
Ride through settings are site specific. Verify against the interconnection agreement and protection settings file.
Central inverters derate and then trip on internal temperature. Common causes are blocked or dirty air filters, failed cooling fans or pumps, blocked heat exchanger fins, and door filters caked with dust after mowing season. Repeated thermal derating on hot afternoons costs real energy even when no hard fault is logged.
Inspect and replace filters and confirm fan operation on the next maintenance visit. Persistent trips with clean cooling need manufacturer support.
Verify derating curves and filter intervals against the current manufacturer manual.
A communication fault means the inverter lost its link to SCADA or the plant controller. The unit may still be producing normally. Before rolling a truck, check whether production telemetry from neighboring devices on the same switch, gateway, or fiber run dropped at the same time. Loss of comms to many devices at once is a network problem, not an inverter problem.
Confirm production locally at the unit display before assuming an outage. Never reset power electronics just to clear a comms alarm.
Verify port, protocol, and timeout settings against the site network drawings.
The insulation monitoring on the inverter bridge measured insulation resistance below the trip threshold. Indicates a ground fault or severe insulation degradation in the connected DC field or within the inverter DC section. Moisture intrusion after rain, damaged string cabling, and failed surge protective devices are frequent causes. A fault that appears in early morning damp conditions and clears by midday still requires investigation.
Stop work. Treat the DC field and racking as energized. Qualified person only, with DC rated PPE. Locate the fault with ground referenced voltage checks and insulation resistance testing before any restart.
Verify against the current SMA Sunny Central manual for the installed firmware.
A ground fault was detected and then cleared on its own. Typical of moisture related leakage: dew, rain intrusion into a connector, conduit, or combiner, or a cable with damaged insulation lying against grounded steel that dries out during the day. Temporary faults reliably become permanent faults; find the cause while it is still intermittent.
Treat as a real ground fault, not a nuisance alarm. Schedule insulation resistance testing of the associated DC field. Qualified person with DC rated PPE.
Verify against the current SMA Sunny Central manual for the installed firmware.
A sustained ground fault is present in the DC field or inverter DC section and the unit will not operate. The faulted circuit can place hazardous voltage on racking, enclosures, and conductors that are normally at ground potential, and the fault current path may not blow any fuse.
Stop work. Do not reset. Isolate per the site LOTO procedure, then locate the fault: measure positive to ground and negative to ground voltage at the DC input, compare against expected values, and section the array with insulation resistance tests until the faulted string or feeder is found. Qualified person only, DC rated PPE.
Verify against the current SMA Sunny Central manual for the installed firmware.
Instantaneous DC input voltage exceeded the permitted operating limit while running. On 1500 volt plants this most often appears near record low ambient temperatures, when string open circuit voltage rises above design assumptions. Can also follow a sudden load rejection.
Record ambient temperature and time. If trips cluster on cold mornings, escalate for a string sizing review against NEC 690.7 before continuing normal operation.
Verify limits against the current SMA Sunny Central manual for the installed firmware.
Measured array open circuit voltage before connection exceeded the maximum permitted DC input voltage, so the inverter refuses to connect. Points directly at string sizing versus the record low temperature, or at a metering fault. The unit is protecting its DC stage from damage.
Do not bypass or repeatedly force reconnection. Measure string Voc with a DC rated meter, compare to the temperature corrected expected value, and escalate for design review if the array really is over voltage.
Verify limits against the current SMA Sunny Central manual for the installed firmware.
Array insulation resistance to ground measured below the trip threshold at startup. Part of the Sungrow insulation and leakage fault family (see also 039, 041, 056). Morning dew and water intrusion are common causes, along with damaged DC cabling and failed surge protective devices.
Stop work. Treat the DC field as energized and faulted. Qualified person locates the fault with DC rated PPE and an insulation resistance tester. Never bridge or lower the trip threshold to force a start.
Sungrow code numbering varies by model line and firmware. Verify against the manual for the installed model.
Residual or leakage current to ground exceeded the permitted level during operation. Same underlying causes as the insulation family: a ground fault path somewhere in the DC field, moisture, or damaged cabling. Distinct from a metering artifact only after the measurement chain is verified.
Treat as a live ground fault until proven otherwise. Qualified person, DC rated PPE, insulation resistance testing to localize.
Sungrow code numbering varies by model line and firmware. Verify against the manual for the installed model.
The insulation monitoring circuit itself raised an alarm: either degraded array insulation near the threshold or a problem in the monitoring path. Frequently precedes a hard insulation trip by days or weeks as moisture damage develops.
Investigate promptly rather than waiting for the hard trip. Schedule insulation resistance testing of the associated array section. Qualified person, DC rated PPE.
Sungrow code numbering varies by model line and firmware. Verify against the manual for the installed model.
The ground fault protective function operated and locked the unit out. On large Sungrow central inverters this family latches and requires investigation; the fault path may energize racking and enclosures in the affected subarray.
Stop work. Do not reset to test. Isolate per site LOTO, localize with ground referenced voltage measurements and insulation resistance tests, repair, retest, and only then restore.
Sungrow code numbering varies by model line and firmware. Verify against the manual for the installed model.
AC grid voltage rose above the protection window, so the unit disconnected per its grid code settings. Plant wide occurrences point to a utility event or a plant controller reactive power or voltage setpoint problem. A single unit alone points to its AC connection or local measurement.
Compare timestamps across units and check plant controller voltage setpoints before restarting. Coordinate with the control room.
Sungrow code numbering varies by model line and firmware. Verify against the manual for the installed model.
AC grid voltage fell below the protection window. During real grid disturbances the ride through function should carry the unit through short sags; a disconnect means the sag exceeded the configured ride through envelope, or ride through settings are wrong for the site.
Check whether neighboring units logged the same event. Review ride through settings against the interconnection agreement if trips seem too sensitive.
Sungrow code numbering varies by model line and firmware. Verify against the manual for the installed model.
Grid frequency rose above the permitted band. Overfrequency events are system wide by nature: if one unit logs it, every unit and the substation relays should have seen it too. A lone unit reporting frequency trips has a measurement or settings problem.
Correlate with substation relay records and the plant controller event log before treating the inverter as faulty.
Sungrow code numbering varies by model line and firmware. Verify against the manual for the installed model.
Grid frequency fell below the permitted band, indicating generation loss somewhere on the system. Units should ride through per the site grid code settings and may be asked for frequency response by the plant controller.
Correlate across the plant and with the utility. Verify frequency ride through and response settings if units disconnect during events they should ride through.
Sungrow code numbering varies by model line and firmware. Verify against the manual for the installed model.
TMEIC PVS central inverters communicate through a gateway that introduces roughly 200 milliseconds of response latency. SCADA masters and plant controllers polling with a default timeout near 50 milliseconds will flag the units offline or log communication faults even though the inverters are healthy and producing. The classic symptom is a plant full of intermittent comms alarms with zero production impact.
Configure the Modbus master with an inter frame delay and response timeout of at least 250 milliseconds for TMEIC devices before treating any comms alarm as real. Never restart producing inverters to chase comms alarms.
Verify gateway model and recommended timing against the current TMEIC documentation for the installed units.
TMEIC PVS units group faults the same way as other central inverters: insulation and ground fault, DC over and under voltage, grid voltage and frequency, over temperature, and communications. Treat insulation and ground faults as safety critical lockouts requiring a qualified person. Communications alarms on TMEIC deserve extra skepticism because of the gateway latency issue.
Apply the per family posture from this library and always confirm at the unit before resetting anything.
Verify exact code lists against the current TMEIC manual for the installed model and firmware.
Reference notes from FieldWatt, the offline field toolkit for utility scale solar commissioning and O&M technicians. It works with no cell signal, because the sites do not have any.
Get FieldWatt on the App StoreThese notes are a field aid, not a substitute for the governing codes, the stamped drawings, the authority having jurisdiction, or manufacturer manuals. Verify against the current documentation for your installed equipment.