## 5 Model Application
Thus, these input data are connected with uncertainties). The sequence of initial events (shown in black) and their consequences (shown in orange and red) are summarized in Figures 6 and 7 for scenario 1 and scenario 2, respectively. It can be seen from the figures, that when a minimum pressure violation for a GFPP is detected in the gas model, the failure of the corresponding power plant is applied after 45 (min) due to the required shut-down time. Figures 8-10 show the difference in gas supply to the system through the CBI station, the production field and the LNG terminal. There is a big difference in inflows to the system through these supply points in scenario 0 and scenario 1, where the difference is more than 20 (Msm\({}^{3}\)/d) (Million standard cubic meter per day, where the reference pressure is 1.0135 (bar) and the reference temperature is 0 (\({}^{\circ}\)C)). The impact of this observation can be seen in Figures 8-12. Figure 11 shows that the disruptions introduced in scenario 1 have the highest impact on the gas network, since the flow balance, which is the sum of inflow minus sum of outflow, is always negative; the system is not able to supply enough gas to balance the demand. In fact, the flow balance is quite negative throughout the time, peaking down to equivalent daily flows of \(-\)32 (Msm\({}^{3}\)/d). As a result, the quantity of gas stored in the pipeline (i.e., the line pack) reduces significantly as time passes. The flow balance can be viewed as the time derivative of the line pack, thus, if the flow balance is negative the line pack decreases and if positive the line pack increases. A zero flow balance corresponds to no change in line pack. Latter is the assumption made in steady state gas models, which cannot capture the changes in line pack, and therefore, the real behavior of the gas system appropriately. Moreover, Figure 11 shows a decrease in line pack from ca. 85 to 67 (Msm\({}^{3}\)/d) for scenario 1 (approx. 18 (Msm\({}^{3}\)/d) lost along the day in the pipelines). In contrast, in scenario 0 only approx. 1.5 (Msm\({}^{3}\)/d) of line pack is extracted. This produces a steady decrease of pressure in the CBI station, the production field and the LNG facility causing the pressure to reduce to approx. 39, 42 and 31 (bar-g), respectively (see Figures 8-10). An important observation is the pressure drop to approximately 31 (bar-g) at the LNG terminal, which is the main gas supplier for some of the GFPPs in the hydraulic region. This value is slightly above the 30 (bar-g) minimum delivery pressure threshold required by the GFPPs. When gas supplies are scarce, the only way to keep maintain sufficient pressure and to allow the network to continue operating is to reduce consumption, either through curtailment or fuel switching, if there is the chance to do this with some power plants. In scenario 1, gas curtailment at GFPPs is implemented, presuming that replacement fuel is not available in any of the investigated GFPPs. Figure 12 shows the behavior of the UGS facility, the only supply node able to increase gas supply to satisfy the increased demand in scenario 1. The UGS facility is able to maintain its pressure set point till the end of the simulation (see Figure 12). The disconnection of four GFPPs from the gas network at 14:15, 15:45 and 16:30, respectively, allows the gas system to continue running (see Figures 6 and 13). The pressure and load profiles for failed GFPPs are given in Figures 13 and 14. This curtailment was sufficient to cope with the pressure drop in the network. Therefore, there was no need of gas curtailment at CGSs, where protected customers (e.g., households, public services) are supplied with gas. Figure 6: Timing of initial (**black**) and cascading (**orange**, **red**) events for Scenario 1. Abbreviation PNS stands for power not supplied, while GNS stands for gas not supplied, value in brackets refers to the fraction of not supplied power/gas with respect to total power/gas loads.