## 2 Overview of Renewable Energy Grid Code Specifications  
The REGCs are a set of technical standards and requirements to be followed when connecting renewable energy sources to the power grid [10; 23; 24].  
Since the voltage level at which the RPPs are integrated into the power grid is significant, we first recap the standard voltage levels. We will then categorize the RPPs at a later stage. It should be noted that standard voltage levels differ depending on the country. For example, one of the Asian articles that categorized the voltage levels at which various WPP categories are integrated also provided some information on the Saudi Arabian standard voltages. This information is presented in Table 2[1].  
However, this article defines voltage levels based on the South African power grid. The National Energy Regulator of South Africa (NERSA) [24] and ESKOM [27] categorizes the grid standard voltage as shown in Table 3.  
RPPs are categorized into three, based on their minimum and maximum apparent power production and the voltage level at which they can be integrated into the power grid. The first category is A (with subcategories A1, A2, and A3), followed by B and C. Table 4 lists the RPP categories and specifies the voltage levels at which the RPP category can be integrated [23].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Category**} & \multicolumn{2}{c}{**Minimum Capacity (kVA)**} & \multicolumn{2}{c}{**Maximum Capacity (kVA)**} & \multicolumn{2}{c}{**Integration Level Voltage**} \\ \hline \multirow{4}{*}{A} & A1 & 0 & 13.8000 & LV \\ \cline{2-5}  & A2 & 13.8000 & 100 & LV \\ \cline{2-5}  & A3 & 100 & 1000 & LV \\ \hline \multirow{4}{*}{A} & B & 0 & 20,000 & MV \\ \cline{2-5}  & C & \textgreater{}20,000 & - & MV/HV \\ \hline \hline \end{tabular}
\end{table}
Table 4: South African renewable power plant categories.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Category**} & \multicolumn{2}{c}{**Wind Power Plant**} & \multirow{2}{*}{**Voltage (kV)**} \\ \cline{3-3} \cline{5-5}  & & **Group** & & 400 \\ \hline \multirow{3}{*}{Transmission} & Normal transmission & Offshore: Group 1 or Group 2 & 220 \\ \cline{2-5}  & Sub-transmission & Onshore & 66 \\ \hline \multirow{3}{*}{Distribution} & Distribution & Small wind turbines & 33 \\ \cline{1-1} \cline{2-5}  & & 11 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Saudi Arabian standard grid voltages at which various types of wind power plants are integrated.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Category**} & \multicolumn{2}{c}{**Voltage (kV)**} & \multicolumn{1}{c}{**Level**} \\ \hline \multirow{3}{*}{Transmission} & \multirow{3}{*}{Normal transmission} & 765 & \multirow{3}{*}{Extra-high} \\ \cline{3-3} \cline{5-5}  & & 275 & \\ \cline{2-5}  & Sub-transmission & 132 & \\ \hline \multirow{6}{*}{Distribution} & \multirow{3}{*}{Distribution} & 66 & \multirow{3}{*}{High} \\ \cline{3-3} \cline{5-5}  & & 50 & \\ \cline{1-1} \cline{2-5}  & & 33 & \\ \cline{1-1} \cline{2-5}  & & 25 & \\ \cline{1-1} \cline{2-5}  & & 22 & \\ \cline{1-1} \cline{2-5}  & & 11 & \\ \hline \hline \end{tabular}
\end{table}
Table 3: South African standard grid voltages.  
WPPs made of squirrel-cage induction generators (SCIGs) may have reactive power support in the power grid since their stator terminals are coupled with capacitor bank exciting circuits. However, this reactive power is minimal [1].  
The work presented in this article mainly focuses on WPPs, whilst the discussions regarding renewable energy grid codes (REGCs) are based entirely on RPPS. Therefore, in this article, for discussions on REGCs, the term RPP instead of WPP is used.