## 2 PV Systems and LV Network Context in Europe  
### Legislation in Europe  
In order to make a connection between the simulation work and the real world, a literature review was carried out on the main SPPS in the European Union. The market for residential systems is active in all Member States (MS). In most of the countries, it appears that the sector is mature and with high penetration levels, fast procedures, and no major barriers (such as in Belgium or Portugal). However, in others, despite demonstration projects and some increase in investment, there is still a low contribution in residential PV penetration, as is the case of Romania and Hungary; hence, the levels of power that are typically installed is unclear. From the literature review, a limitation of single-phase systems connection is not taken as a threat to the network. This is possibly due to the variety of network configurations, levels of penetration, or market designs; the limits for residential PV power are quite diverse. The results of the legislation and literature review of the 28 MS can be seen in Table 1, which is divided into the limits of single-phase connection limits, i.e., the power levels available for consumers when signing a power contract with a DSO. Equation (1) provides the ratio of PV installed power (\(P_{PV}\)), divided by the total contracted power (\(P_{C}\)) in the considered low-voltage network or consumer. This ratio can be found in some European Member States' legislation or DSO technical recommendations. \[\%PV_{kWp/kVA}=\frac{P_{PV}}{P_{C}}\times 100\% \tag{1}\]  
Other limitations for power injection exist apart from defined ratios of PV peak power over the consumer's contracted power. Many MS limit the injection of power as a certain number of hours or energy injected per year (as is the case of Portugal). Another case is in Bulgaria, where the electricity system operator (ESO) orders a limitation of the generation from renewable energy sources (RES) to work with no more than 40% of their capacity, usually for the hours from 10 h to 17 h [24]. In many MS, a three-phase contract for households is typical, even though at least one option of single phase is available. The differences from country to country are due to the use of specific appliances, cooling needs, or heating needs. This implies that the cabling of the distribution networks can widely differ between MS, as recognised as well by the RN report [22]. In three-phase connection options, it was found that many DSOs refer to an unbalance limit of 4.6 kW between phases. \begin{table}
\begin{tabular}{c c c} \hline
**EU Member State** & **SPPS Connection Limit (kWp)** & **Single-Phase Contracted Power (kVA) Levels** \\ \hline Austria & 3.68 & 2.3, 3.68, 4.83, 5.75, 7.36, 9.2, 11.5 \\ Belgium & 5 & 3.68, 4.6, 5.75, 7.36, 9.2, 11.5, 14.49 \\ Bulgaria & 5 & 6, 7-15 \\ Croatia & 5 & 4.6, 5.75, 7.36, 9.2, 11.5 \\ Cyprus & 4 & 9.2 \\ Czech Rep. & 3.68 & 5.75 \\ Denmark & 3.68 & 5.75 \\ Estonia & 3.68 & 1.38, 2.3, 3.68, 4.6, 5.75 \\ Finland & 3.68 & 5.75 \\ France & 6 & 3, 6, 9, 12, 15, 18 \\ Germany & 4.6 & 4.6 \\ Greece & 5 & 8, 12 \\ Hungary & 5 & 1.38, 2.3, 3.68, 4.6, 5.75, 7.36, 9.2, 11.5, 14.49, 18.4 \\ Ireland & 5.75 & 12, 16 \\ Italy & 6 & 1.5, 3, 4.5, 6 \\ Latvia & 3.68 & 3.68, 4.6, 5.75 \\ Lithuania & \textless{}10 & 3, 4, 5, 6, 7, 8, 9, 10 \\ Luxembourg & \textless{}30 (3\textgreater{}) & 9.2, 11.5, 14.49, 18.4 (3\textgreater{}) \\ Malta & 3.68 & 9.2 \\ Netherlands & 5 & 1.38, 2.3, 5.75, 8.05, 9.2 \\ Poland & 4.6 & 1.38, 2.3, 3.68, 4.6, 5.75, 7.36, 9.2, 11.5 \\ Portugal & 5.75 & 1.15, 2.3, 3.45, 4.6, 5.75, 6.9, 10.35, 13.8 \\ Romania & 10 (3\textgreater{}) & \textless{}3-3-6, 5 \\ Slovakia & 4.6 & 5.75 \\ Slovenia & 4.6 & 3, 6, 8 \\ Spain & 5 & 1.73, 2.3, 3.45, 4.6, 5.75, 6.9, 8.05, 9.2, 10.35, 11.5, 14.49 \\ Sweden & 2 and 4 & 3.68, 4.6, 5.75, 8.05, 11.5, 14.49 \\ Great Britain & 3.68, 17 & 5.75, 13.8, 15, 18.4, 23 \\ \hline \end{tabular}
\end{table} 
Table 1: Limits of single-phase power connections on residential segment in Europe [23].