Solar Lattice

Function

DC ground-fault protection

ID
func:ground-fault-protection
IRI
https://solarlattice.org/kb/func/ground-fault-protection
Status
active
Also known as
GFDI, ground fault detector interrupter, ground fault detection, GFP, ground fault detection and interruption, GFCI
Category
Protection
Function kind
protection

DC ground-fault protection detects current leaking from the PV DC conductors to ground. When it finds a fault, it alarms and stops the inverter or disconnects it from the grid. NEC 690.41(B)(1) requires the device to detect ground faults in PV DC circuit conductors, including functional grounded conductors, and to be listed for PV ground-fault protection. UL 1741 also requires a DC ground fault detection method. CPS and Solectria string inverters use residual current detection to find leakage current. The Solectria PVI 3800-7600TL trips at 300 mA. The Solectria XGI 1500 central inverters have a GFDI circuit with two levels. The DSP trips the breaker at 4.0 A on the 1MW model or 1.0 A on the DCG model, and the ground fault circuit breaker trips by itself at 5 A. On the XGI 1500-1MW, the GFDI only works when the DC input is grounded. The Generac PV Link has an internal GFDI that trips at 240 mA, plus or minus 40 mA. Ground faults are shown on the PWRcell Inverter control panel. The Fronius Galvo uses its GFDI on negatively grounded arrays and uses insulation monitoring on ungrounded arrays. Power Electronics HEM units combine GFDI with an insulation monitoring device. Enphase M-Series and IQ7-based M215 and M250 microinverters have ground fault protection built in. Their DC circuit is isolated from ground, so they need no grounding electrode conductor. The original M215-60-2LL-S22 is the exception and still needs a GEC.

<!-- review notes

Claims

requires

c1 drafted · lead Residual current monitoring

Scope: products CPS SCH200K-T-US-480 / SCH250K-T-US-600, CPS SCH350KTL-DO/US-800, Solectria PVI 3800-7600TL

CPS and Solectria string inverters detect DC ground faults using residual current detection, as the method required by UL 1741.

review note: support check: partial - Residual current detection is stated for CPS/Solectria inverters, but the passages don't name the CHINT products explicitly, and the 'requires' wording is that it's part of the UL 1741 method.

trip_threshold

c2 drafted · lead nominal 240 MilliA

Scope: products Generac PV Link

Conditions: Generac PV Link internal GFDI, PV DC ground current; tolerance plus or minus 40 mA

c3 drafted · lead nominal 4 A

Scope: products Solectria XGI 1500-1MW

Conditions: XGI 1500-1MW: current sensor detection makes the DSP trip the breaker; only works when the DC input is grounded

review note: possible conflict with c4 (same source; check the conditions)

c4 drafted · lead nominal 5 A

Scope: products Solectria XGI 1500-1MW

Conditions: XGI 1500-1MW: second protection level, where the ground fault circuit breaker trips on its own

review note: possible conflict with c3 (same source; check the conditions)

c5 drafted · lead nominal 1 A

Scope: products Solectria XGI 1500-DCG

Conditions: XGI 1500-DCG: current sensor detection makes the DSP trip the breaker

review note: possible conflict with c6 (same source; check the conditions)

c6 drafted · lead nominal 5 A

Scope: products Solectria XGI 1500-DCG

Conditions: XGI 1500-DCG: second protection level, where the ground fault circuit breaker trips on its own

review note: possible conflict with c5 (same source; check the conditions)

c7 drafted · lead nominal 300 MilliA

Scope: products Solectria PVI 3800-7600TL

Conditions: Solectria PVI 3800-7600TL GFDI trip limit

c8 drafted · lead ≤ 1000 MilliA

Scope: products Enphase M215 / M250 Microinverters

Conditions: Original Enphase M215-60-2LL-S22 microinverter, ground fault protection parameter in its datasheet table

review note: support check: partial - Passage gives Max 1000 mA for ground fault protection, but does not state it is a trip threshold or DC-specific; 'up to' fits max.

Referenced by

Data