In order to ensure that the conductor length of multiple parallel coils of power transformer is consistent and the current density is balanced, the structure transposition is usually carried out in the winding process. The actual operation shows that the insulation at the conductor transposition is easy to damage and leads to inter-turn short circuit fault. Aiming at the problems that the fault point is difficult to set and the electrical quantity cannot be directly detected in the actual test, this paper uses the 'field-circuit' coupling principle to take the distribution transformer with the model of S13-M-200/10, the low voltage winding is wound by two flat copper wires and the transposition point is in the middle of the winding as an example. Based on the finite element simulation software, the simulation analysis model with the same size as the physical structure is established. Through the comparison of the actual test value and the simulation analysis value of the performance parameters, on the basis of verifying the correctness of the model, the electrical characteristics and electrodynamics of the low voltage winding of the power transformer are studied when the single inter-turn short circuit occurs at the conductor transposition. The results show that when a single inter-turn short circuit occurs in the low voltage winding of the transformer, the loop current of dozens of times the rated current flows inside the short circuit ring, the fault phase current decreases slightly, and the active power loss increases sharply. Conductor transposition causes uneven distribution of axial force and radial force of the coil, and the winding is prone to instability and deformation. It is necessary to take mechanical and insulation strengthening measures at the conductor transposition.

After a high proportion of new energy is connected to the grid, the grid security and stability are significantly increased by multiple uncertainties. In order to quickly form a power adjustment plan to maintain the source-gridload dynamic balance under the scenario of power gap caused by large fluctuations of new energy, it is urgent to quantitatively evaluate the maximum power supply capacity of the grid. In this paper, the maximum power supply capacity and the minimum section margin of important sections are taken as the optimization objective functions, and the maximum power supply capacity assessment scenario of provincial power grids is modeled with power balance, slice reserve capacity, and section margin as the constraints, and the multi-stage constrained multi-objective evolution (CMOEA-MS) algorithm and the fast non-dominated ranking genetic algorithm NSGA-Ⅱ with elite strategy are used to solve the model, respectively. The quality of the solution sets of the two algorithms is evaluated in term of three indexes of convergence, uniformity and extensiveness of the solution sets. The simulation results of example show that the CMOEA-MS model has larger super volume values and better performance in solving the model, and can effectively improve the maximum power supply capacity of the provincial grid.

Based on the SRTM digital elevation DEM model, using the hourly precipitation data of Chongqing from May to September 2017 to 2021, this paper analyzed the temporal and spatial distribution characteristics of short-term heavy precipitation under different terrains in Chongqing, and discussed the relationship between the frequency and intensity of short-term heavy precipitation and topographic factors. The results show that the spatial distribution of short-term heavy precipitation in Chongqing is uneven. The overall average frequency high value area of the previous year and stations ≥ 60mm/h are mainly located near Huaying Mountain in Northwest Chongqing, Daba Mountain in Northeast Chongqing and Wuling Mountain in Southeast Chongqing; For the station average frequency of short-term heavy precipitation in Chongqing, the monthly variation shows a significant single peak type, and the frequency is the most in July; The diurnal variation is bimodal, with the main peak occurring most frequently at 03:00-05:00 and the secondary peak occurring more frequently at 16:00-19:00. The frequencies of the north and west slopes are slightly more than those of the other slopes. The frequency of flat slope and gentle slope is more than that of other slopes. The frequency of 500-1 000 m and > 1500 m is more than that of other altitudes; The fluctuation ≤30 m and 30-200 m are more frequent than other fluctuations; When slope ≤15°, altitude ≤1 000 m, and undulation ≤200 m, stations with precipitation intensity ≥100 mm/h appear, indicating that appropriate mountain topography is conducive to the increase of short-time heavy rainfall intensity. The research results can provide reference for near early warning, disaster prevention and reduction of short-term heavy precipitation in Chongqing.

In order to explore the temporal and spatial variation of annual precipitation and the type of precipitation field in Heilongjiang Province, this paper analyzed the precipitation of Heilongjiang Province from 1980 to 2020 using the Mann-Kendall test method, EOF decomposition method, Morlet wavelet analysis and other methods commonly used in modern climate statistical diagnosis. The results show that the precipitation tendency rate in Heilongjiang Province from 1980 to 2020 is 15.52 mm/10 a, that is, the precipitation has a significant upward trend. The precipitation in summer accounts for about 65% of the whole year, and only 3% in winter; Under the influence of topography and climate, precipitation in Heilongjiang Province showed significant spatial differences. As a whole, the south and central regions have higher precipitation, followed by the east, and the west and north regions have lower precipitation. According to the EOF decomposition, the precipitation in Heilongjiang Province can be divided into three modes and six precipitation fields: the first mode indicates that the precipitation in Heilongjiang province is more or less; The second mode showed that the central and northeastern parts of the province had more precipitation, while the southwest and Greater Khingan Mountains had less or opposite precipitation. The third mode showed that the precipitation was higher in the southwest of the province, and less or opposite in the southeast and Greater Khingan Mountains. There were two scale variation cycles of precipitation in Heilongjiang Province, 11-30 a and 3-7 a, with 28 a as the first main cycle.

Drought index is crucial to the study of drought. With the influence of climate change and human activities, the frequency distribution of hydrological time series changes with time, so the nonstationary of drought index needs to be considered. The standardized precipitation index (S_SPI) considers that the precipitation obeys the Gamma distribution, the corresponding distribution function parameters are usually stationary and invariable. The actual distribution function parameters have a certain correlation with the time series. Therefore, based on the GAMLSS model, the nonstationary Gamma distribution model of precipitation series was constructed with time series as covariate. The nonstationary standardized precipitation index N_NSPI was calculated. Taking Yunnan Province as an example, the monthly N_NSPI and S_SPI during 1960 to 2019 were calculated respectively. Comparing the two indices, it is found that the overall trend of drought recognition results of the two indices is similar. However, in 1960~1985, the number and grade of droughts identified by N_NSPI were stronger than those identified by S_SPI, and the two were similar in 1986~2005. In 2006~2019, the number and grade of droughts identified by S_SPI gradually exceeded those identified by S_SPI. Further analysis shows that the N_NSPI with considering the time-varying distribution function parameters can more accurately reflect the actual drought situation.

In recent years, it causes disasters increasingly by too much or too little precipitation. Therefore, accurate prediction of precipitation is of great significance and practical application value to human life and social development. Based on the monthly precipitation data of Zhengzhou from 1990 to 2019, monthly precipitation was forecasted from 2020 to 2021 by utilizing SARIMA, Prophet and LSTM model, respectively. In order to improve the prediction accuracy of the model for monthly precipitation, two combined models of the SARIMA-EMD-LSTM and Prophet-EMD-LSTM were proposed. Empirical analysis shows that the proposed two combined models have higher prediction accuracy and decrease the root mean square error significantly. Furthermore, Prophet-EMD-LSTM model has comparatively better prediction effect. The monthly precipitations in Zhengzhou from April to December, 2022 were forecasted with higher precision.

Based on the monitoring data of 36 meteorological stations in Jiangxi Province from 1960 to 2018, the characteristics of drought change and the correlation between SPEI index and M-K trend test. The results show that the SPEI-12 index showed a slight downward trend, and drought and flood alternated from year to year. The annual drought mainly distributed in the northeast, west and southeast of Jiangxi Province, and most of the drought was global and regional, and the regional drought was more significant after 2000. The seasonal drought occurred in summer and autumn, especially in autumn. The drought degree in spring and winter was light and more frequent in the southern part of Ganzhou. However, after 2001, spring showed an aridity trend, and the SPEI index in summer, autumn and winter showed an upward trend, even easy to cover the province's serious autumn drought. Crop to the affected area and summer and autumn were significantly correlated with SPEI index and summer drought influence on Jiangxi crops than autumn drought. The results can provide reference for drought control and drought resistance in Jiangxi Province.

In order to explore the impact of landfall typhoons in China's coastal areas, based on the typhoon data and socioeconomic data from 1949 to 2020, M-K trend analysis, R/S analysis, wind and rain analysis, and disaster quantification and other research methods were used to comprehensively analyze the temporal and spatial changes, wind and rain characteristics and disaster situation of landfall typhoons in China. The research results show that the number of typhoons landing in China is decreasing, and the duration is prolonged. In terms of intensity, there is a situation of "weak decrease and strong increase", and the landfall sites are shifted to the east and north. Both the wind speed and precipitation of the landfall typhoon showed an upward trend. Considering the maximum value, it was found that the wind speed and precipitation showed a significant increase trend. The impact of typhoon has gradually evolved into a disaster pattern that has shifted from the secondary industry to the primary and tertiary industries. The research results can provide data support and scientific basis for reducing the economic losses of typhoon disasters.

The precipitation and ice melt water supply in Huma River Basin have a great impact on the runoff changes of the main stream of Heilongjiang Province. Climate change is an important factor affecting the precipitation and ice melt water of the Huma River. By collecting the data of Huma, Xinlin, Tahe, Huzhong meteorological stations and Humaqiao hydrological stations in the basin, combined with the DEM data, land use data and soil data, a SWAT runoff model suitable for the basin was constructed to simulate the monthly runoff. At the same time, the response of runoff to climate change in the basin was studied by setting temperature and precipitation gradients through the weather generator. The results show that the SWAT model has good adaptability in the basin, and the R² and N_NSE in the calibration and validation periods have reached the evaluation standard of the model. The runoff of Huma River Basin is much more sensitive to precipitation changes than temperature, and precipitation is the main control factor of runoff changes in the basin.

It is of great practical significance for flood control and drought relief in the basin to accurately identify the variation characteristics of the extreme value of "hydrological consistency" caused by changing environment. Therefore, this paper took the Yellow River basin with significantly reduced runoff as an example. Firstly, The Mann-Kendall test method and univariate linear regression method were used to accurately identify the abrupt and trend characteristics of runoff at important hydrological stations in the main stream of the Yellow River. Secondly, 13 hydrological characteristic indexes were used to reveal the temporal and spatial variation law of hydrological characteristics of the basin under the condition of inconsistency. The results show that the annual runoff of Tangnaihai, Toudaoguai, Huayuankou and Lijin stations decreases year by year at the rate of 27.46, 105.75, 172.20 and 141.37 m³/(s·10a) respectively, and the abrupt change years are 1989, 1992, 1992 and 1984 respectively. Before and after runoff variation, 13 hydrological characteristic values vary in time and space scale, and the change degree in the middle reaches is large, and the source area is small. The research results provide important theoretical support for determining the development and utilization mode of water resources in the basin.