| Supported by National Natural Science Foundation of China under grant No. 50077006, the numerical methods to predict the transient electromagnetic environments when the circuit breakers and disconnect switches are operated in air-insulated substations and gas insulated substations are researched in this paper. The main contributions are as follows: 1. The finite difference-time domain method for the multi-conductor transmission lines connected by arbitrary load network or with many branches is proposed, and the iterative equations of the connection points are derived. 2. The method to treat the frequency-dependent parameters of MTLs over lossy soil in time domain is proposed, and then the finite difference-time domain iterative equations for overhead transmission lines are obtained. 3. Based on a generalized Sommerfeld identity and the generalized pencil-of-function method, the electromagnetic field generated by a dipole can be easily calculated, which is quite robust and less noise sensitive 4. Based on multi-conductor transmission lines and dipole method, a numerical method to predict the transient electromagnetic environments due to the operation of switches in air-insulated substation is proposed. After a model of busbars in a 500kV substation is set up, the transient electromag~etic field is predicted. 5. Based on transmission line model and the method of moment, a suit of software to predict the transient electromagnetic environments in gas-insulated substations is developed. A 125kV substation is analyzed, and the validity of the software is testified by contrasting the results of calculation with the results of measurement. The analysis results are useful when the control and protection devices are placed in the high-voltage yard.
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