Based on China’s resource endowment and coal mine disaster statistics, it has been found that there are many deficiencies in the management of disasters and risks in mining areas in China. Therefore, to scientifically and effectively manage mining areas, based on the theory of internal control, this paper systematically analyzes the risks of mining areas in the context of various factors and relevant suggestions. From the occurrence of mine risk to the occurrence of damage, the importance of risk management is highlighted. In accordance with the five selection principles of evaluation indicators (goal principle, comprehensiveness principle, scientificity principle, timeliness principle and focus principle) as well as the five elements of internal control (control environment, risk assessment, control activities, information and communication and supervision), a mining area risk managementframework of human-machine-environment-management – disturbance is constructed, and twentyseven secondary risk indicators are divided. The criteria for determining the risk level and the risk response process have been established, and a more systematic and accurate mine risk management system under the theory of internal control has been formed. Finally, based on four key technologies, a dual prevention and control mechanism is formed around the system risk and job risk management system. This provides new methods and ideas for the prevention and control of coal mine safety risks and the containment of disasters and accidents.

The single-phase voltage loss is a common fault. Once the voltage-loss failure occurs, the amount of electrical energy will not be measured, but it is to be calculated so as to protect the interest of the power supplier. Two automatic calculation methods, the power substitution and the voltage substitution, are introduced in this paper. Considering the lack of quantitative analysis of the calculation error of the voltage substitution method, the grid traversal method and MATLAB tool are applied to solve the problem. The theoretical analysis indicates that the calculation error is closely related to the voltage unbalance factor and the power factor, and the maximum calculation error is about 6% when the power system operates normally. To verify the theoretical analysis, two three-phase electrical energy metering devices have been developed, and verification tests have been carried out in both the lab and field conditions. The lab testing results are consistent with the theoretical ones, and the field testing results show that the calculation errors are generally below 0.2%, that is correct in most cases.