Grid connection requirements for rooftop solar System
Small amounts of electricity generated by residential PV systems can be easily fed into the local utility grid. Transformer capacity, appropriate grounding and system protection are obligatory, as otherwise the grid itself would be affected. The situation changes if the solar PV-generated electricity is beyond the limit of what an already designed system can support. In this case, the existing system equipment and protection must be adapted for safe integration of the PV system.
Due to the variable nature of solar PV-generated electricity, high grid availability with reserve capacity to compensate unavailability of PV systems might be required. Reactive power compensation also might be required to support the grid. This would be necessary when PV systems reduce the use of conventional power plants and their supply of reactive power, as was the case in Germany when PV became such a success.
However, since the capacities of SHS and PPS systems are typically very small compared to the overall grid capacity, the inverters must comply with the grid code and respective standards. Typical requirements, particularly concerning solar PV inverters, are grid-supporting functions such as the supply of both active and reactive power for voltage stability.
Furthermore, the addition of PV-generated electricity might introduce voltage harmonics and flicker, which could harm equipment at downstream loads. The equipment manufacturer therefore must test the interconnection for harmonics and unintentional islanding in line with the local grid code and technical standards. If necessary, countermeasures to avoid grid instability must be put in place.