Photovoltaic inverter ground wire fault handling

How does a PV inverter protect against a grid fault?

Protective relay functions are built directly into the PV inverter. A PV inverter does not have any mechanical inertia. During a grid fault condition, the inverter short circuit current is equivalent to its rated current and the inverter disables its operation within one or a few cycles.

Do solar inverters need a ground fault detection & interruption device?

Solar inverters must have a ground fault detection and interruption (GFDI) device to detect and stop ground faults. It can identify the ground fault, generate an error code, and shut down the inverter. The amount of current flowing through the ground fault required to trip the inverter's GFDI varies based on the inverter type.

How does a PV system detect a ground fault?

In PV systems that are equipment-earthed and protected with a system ground (as in most cases), a ground-fault condition is detected by current flow in the grounded conductor and electrode, which results in the circuit being opened and an ground-fault alarm being displayed on the inverter.

Do PV inverters need AC side grounding?

When a PV plant is installed in the distribution feeder, the plant shall meet the IEEE 1547 standard and the interface requirements of the local utility company. Some utility companies require PV inverters to have AC side grounding in order to assure compatibility with their grounding scheme, generally referred to as effective grounding.

How can a DC inverter prevent a ground fault?

DC ground faults can be prevented using transformer-less (non-isolated) inverters, which 1) have sensitive electronics that can sense a fault as low as 300 mA and 2) do not have a grounded conductor, thus reducing the possibility of unintended current to ground.

How much current does an inverter need to trip a GFDI?

The amount of current flowing through the ground fault required to trip the inverter's GFDI varies based on the inverter type. Isolated transformer-based inverters use a fuse as a GFDI. Some ground faults may not have enough current to blow the fuse and shut down the inverter.