# The Impact of Distributed Energy Storage on Distribution and Transmission Networks' Power Quality
## 3 Data Analysis  
### Power Quality Performance of Benchmark Network  
The NEPLAN load flow analysis was used to determine the power quality performance of the benchmark network and its variants. According to the findings, the ratio of observed voltage magnitude to the rated node voltage of thirteen nodes in the benchmark network (Table 2) was outside the 5% rated node voltage electricity system compliance tolerance limit. \begin{table}
\begin{tabular}{c c c c} \hline
**Variant Name** & **ESS Integration Architecture** & **Energy Storage Technology** &
\begin{tabular}{c} **ESS Integration Node** \\ **Location (Topology)** \\ \end{tabular} \\ \hline DN-C\_CAR & Centralized & BESS & 66 kV DL-GAR \\ DN-C\_ASO & Centralized & BESS & 66 kV DL-ASO \\ DN-C\_KAT & Centralized & BESS & 66 kV DL-KAT \\ DN-C\_WUY & Centralized & BESS & 66 kV DL-WUY \\ DN-C\_STH & Centralized & BESS & 66 kV DL-STH \\ TN-C\_EST & Centralized & PHS & 132 kV TN-EST \\ TN-C\_STH & Centralized & PHS & 132 kV TN-STH \\ TN-C\_WST & Centralized & PHS & 132 kV TN-WST \\ \hline DN-D\_LVN & Distributed & BESS & 0.24 kV DL-RC1\_F1 \\  & & & 0.24 kV DL-RC2\_F1 \\  & & & 0.24 kV DL-RC3\_F1 \\  & & & 0.24 kV DL-RC4\_F1 \\ \hline DN-D\_All & Distributed & BESS & 06 kV DL-GAR \\  & & & 66 kV DL-ASO \\  & & & 66 kV DL-KAT \\  & & & 66 kV DL-WUY \\ DN-D\_All & Distributed & BESS & 11 kV DL-IBD \\  & & & 11 kV DL-CBD \\  & & & 0.24 kV DL-CC1 \\  & & & 0.24 kV DL-RC1\_F1 \\  & & & 0.24 kV DL-RC2\_F1 \\  & & & 0.24 kV DL-RC2\_F1 \\  & & & 0.24 kV DL-RC3\_F1 \\  & & & 0.24 kV DL-RC4\_F1 \\ \hline TN-D\_All & Distributed & PHS & 132 kV TN-EST \\  & & & 132 kV TN-STH \\  & & & 132 kV TN-STH \\  & & & 132 kV TN-STH \\  & & & 132 kV TN-WST \\  & & & 66 kV DL-GAR \\  & & & 66 kV DL-ASO \\ TN\&DN-D\_All & Distributed & PHS \& BESS \\  & & & 66 kV DL-WUY \\  & & & 11 kV DL-IBD \\  & & & 11 kV DL-BD \\  & & & 0.24 kV DL-CC1 \\  & & & 0.24 kV DL-RC1\_F1 \\  & & & 0.24 kV DL-RC2\_F1 \\  & & & 0.24 kV DL-RC3\_F1 \\  & & & 0.24 kV DL-RC4\_F1 \\ \hline \end{tabular}
\end{table} 
Table 1: Characteristics of Benchmark ESS Variants. In this study, we considered the worst-case scenario where the On Load Tap Changers (OLTC) have reached the highest possible position and there is not any other tap changer adjustment for improving the voltage profile of the transformers. This could be a real case scenario of a transmission system where the system's load is greater than the predicted load, and therefore, there is undervoltage with the OLTC having reached its highest position for improving the voltage. This is a real scenario that happens very often not only due to the mismatch of the system's load but also due to production problems (trips of power units or lack of fuels, e.g., natural gas, etc.). Therefore, the impact of distributed energy storage devices such as BESS needs further investigation. Power Quality Performance Comparison between Benchmark Network and Centralized ESS Integrated Variants  
Following the identification of the benchmark network nodes with poor power quality under steady-state conditions, the individual performance of the centralized ESS integrated variants, as shown in Table 1, was obtained to determine the compensatory effect of the ESS integration on improving the node voltage magnitude deficit. Figure 2 shows the benchmark network's performance versus the DN-C GAR variant, which represents a single centralized BESS integrated at the 66 kV DL-GAR node. This variant improves power quality performance by 1.44 percent average voltage magnitude compensation and 0.7 degrees average voltage angle compensation. With the exception of the 66 kV DL-ASO node in Figure 2a, most nodes in the benchmark network that were previously outside the 5% of rated voltage compliance requirement are now compliant. Figure 2b shows a small improvement in voltage angle correction; however, the unity angle deviation is only obtained at node TL-KAT.