*4.2. Assessment of Individual Risks*

This study first evaluated the influence of the prominent risk factors on the coupled markets when each risk factor functioned independently and the market did not apply a risk response strategy. Given that extreme weather affects both the natural gas and electricity systems, it disrupts the overall systems' performance by influencing demand peaks in natural gas and electricity overload. Moreover, as illustrated by practical conflicts, geopolitical risks often affect the natural gas market via its influence on the risk of import shortages. Hence, we reduced the initial list of risk factors to four tests. Figure 4 exhibits the input value of the risk factors described in the previous section, and Table 2 demonstrates their impacts on the coupled natural gas–electricity market with regard to the reduction in the satisfaction rate.

**Figure 4.** Effects of the experimental risk factors: (**a**) pipeline defects; (**b**) import shortages; (**c**) infrastructural damages; (**d**) extreme weather.


**Table 2.** Market satisfaction losses induced by individual risks.

Regarding pipeline defects, it can be observed that defects such as corrosion and pipeline aging impose long-term and continual disruptions of the efficiency of natural gas transportation, which, in turn, affect the satisfaction of the natural gas market. According to the simulation's results, pipeline defects reduce the natural gas satisfaction rate by 14.69%. However, although it has an effect on the amount of natural gas supply that can be provided to generate electricity, its impact on the electricity market's satisfaction is invisible. This could be because the losses caused by this risk factor are relatively minor. Because only 16% of natural gas is used to generate electricity, and only 3% of the total electricity supply is provided by natural gas generation, such a minor disturbance can be considered negligible in an assessment of the electricity market.

Regarding import shortages, as previously indicated, if import shipments are cut off or an intentional attack is carried out on the key pipelines, this would result in a significant decrease in import supplies. In Figure 4, the natural gas market faces an import shortage starting on day 20, lowering the efficiency of imports to 10% of the initial level. Because of a lack of improvement in the global situation and the difficulty of reconstructing the pipeline, gas imports were still not recoverable within the experimental period (180 days). In light of the fact that natural gas imports constitute a proportion of China's overall natural gas supply, this significant import shortage would result in a loss of 35.52% in the satisfaction rate. Although natural gas supply accounts for a small fraction of the electricity market, the risk is transmitted to the overall markets through interactions as a consequence of the severe supply crisis. This results in a loss of 0.28% in the electricity satisfaction rate, and the loss rate of the coupled markets is around 17.88%.

If we consider damage to the infrastructure, despite the normal electricity transmission loss rate, the transmission infrastructure is frequently exposed to abrupt disruptions owing to exterior damage and other events, resulting in a considerable loss in transmission efficiency. Over a period of time, the infrastructure may be restored and returned to its normal transmission level. In Figure 4, the transmission infrastructure was severely damaged on day 70 and rebuilt on day 120. This reduced the satisfaction rate of the electrical market by 9.06%. However, because we ignored the impact of electricity supply on natural gas production, and the electricity market demand remained constant, the risk of infrastructural damage on the supply side of the electricity market was not propagated to the natural gas market.

In terms of extreme weather, from September to March, the coupled natural gas– electricity market first sees a decrease in temperature, followed by a rebound. In the simulation, the temperature began to oscillate downward after day 40 and stayed excessively low from day 90 to day 130, after which it rose upward to a warm situation. This risk factor increased demand in both the natural gas and electricity markets, which ultimately resulted in a decrease in the satisfaction rate of 8.23% and 9.03%, respectively. Note that in accordance with Table 2, even though in terms of the average loss in the market satisfaction rate of the coupled market, import shortages were ranked as the most significant risk factor because of the severity of their effects, extreme weather could not be ignored, as it influenced both markets.
