# Quantification of the Benefits for Power System of Resilience Boosting Measures
## 5 Case Studies
### Quantifying the Benefits of Passive and Active Measures in Engineering Mode
#### 5.5.2 Effect of Anti-Torsional Devices (EM1-T, EM2-T Cases)  
This subsection describes an application of the engineering mode of RELIEF tool and it simulates a severe storm (S1) and the moderate storm (S2) in the base case of GRID 1, specifically in the Central Italy (a portion of the grid often subject to wet snow events, like the one occurred in 2017), where the anti-torsional devices are applied to the critical lines identified in cases EM1 and EM2. The data related to the anti-torsional devices are derived from current experimentations (mass of each device equal to 10 kg and distances among devices can assume two alternative values, i.e., 50 and 100 m).  
Table 6 shows the critical components when antitorsional devices are installed to the critical lines of cases EM1 and EM2.  
\begin{table}
\begin{tabular}{c c c} \hline
**Severe Storm, Inter-Device Distance = 50 m,** & **Severe Storm, Inter-Device Distance = 100 m,** \\
**EM1-T (50 m)** & **EM1-T (100 m)** \\ \hline Comp ID & Failure prob (/10 min) & Comp ID & Failure prob (/10 min) \\ \hline VLLR11–VLVR111 & \(1.88\times 10^{-2}\) & TRMR411–GSR411 & \(6.90\times 10^{-1}\) \\  & GIUR411–ROSR411 & \(4.53\times 10^{-1}\) \\  & CLTR411–TRMR411 & \(9.20\times 10^{-2}\) \\  & CVDR411–TRWR411 & \(9.05\times 10^{-2}\) \\ \hline
**Moderate Storm, Inter-Device Distance = 50 m,** & **Moderate Storm, Inter-Device Distance = 100 m,** \\
**EM2-T (50 m)** & **EM2-T (100 m)** \\ \hline Comp ID & Failure prob (/10 min) & Comp ID & Failure prob (/10 min) \\ \hline GIUR411–ROSR411 & \(1.60\times 10^{-1}\) & GIUR411–ROSR411 & \(1.60\times 10^{-1}\) \\  & CLTR411–TRMR411 & \(1.28\times 10^{-2}\) \\ \hline \end{tabular}
\end{table}
Table 6: List of critical components for cases EM1-T and EM2-T and two values for inter-device distances.  
Figure 8: Geolocalization of critical components for severe wet snow (**a**) and moderate wet snow storm (**b**).  
\begin{table}
\begin{tabular}{c c c c} \hline
**Case EM1: Severe Wet Snow Storm** & **Case EM2: Moderate Wet Snow Storm** \\ \hline Comp ID & Failure prob (/10 min) & Comp ID & Failure prob (/10 min) \\ \hline ALDR411–GIUR411 & \(>\)0.90 & CLTR411–TRMR411 & 0.768 \\ GIUR411–ROSR411 & \(>\)0.90 & TRMR411–GSR411 & 0.396 \\ TRMR411–IGSR411 & \(>\)0.90 & TRMR411–TRWR411 & 0.199 \\ CVDR411–TRWR411 & \(>\)0.90 & CVDR411–TRWR411 & 0.167 \\ TRMR411–TROSR411 & \(>\)0.90 & & \\ CLTR411–TRMR411 & \(>\)0.90 & & \\ \hline \end{tabular}
\end{table}
Table 5: List of critical components for severe (left) and moderate (right) wet snow storm.  
Figure 9 shows the total LOL risk and its composition on the basis of the contingency category for the base cases EM1 and EM2 and the current cases with inter-device distances of 50 m and 100 m.  
It is worth noticing that a 50 m inter-device distance is sufficient to make the LOL risk negligible also in case of the severe storm of case EM1. A lower number of devices (as for the 100 m inter-device distance case) allows to substantially decrease the total LOL risk and especially the contribution due to N-k common mode branch contingencies. During the current experiments on anti-torsional devices installed on some HV OHLs, the Italian TSO applies an inter-device distance ranging from 30 to 70 m as a function of the span length and conductor diameter: For a 31.5 mm diameter and common span lengths the adopted inter-device distance corresponds to the value of 50 m that the tool has confirmed to be adequate to make the measure effective.