Introduction  During the planning and design of extra-high and ultra-high voltage power grid, it is necessary to specialized research on electromagnetic transient simulation in order to evaluate the electro-magnetic transient characteristics of the related electrical equipment.

  Method  This paper aims to put forward the key factors affecting the results of simulation. They mainly include the applicability of the simulation software and the completeness and accuracy of power flow and short circuit data of the power system, the physical structure and the electrical parameter information of the transmission lines, the main electrical equipment details of the substation.

  Result  Based on the authority of the electromagnetic transient simulation software, we proposed the main conditions and requirements should be followed and illustrated the corresponding simulation results and application during the simulation of the electromagnetic transient characteristics such as the secondary arc current and recovery voltage, the power frequency over-voltage, operation over-voltage, and the small reactance installed the neutral point of the transformer, and so on.

  Conclusion  The conclusions have been used in the planning of power grid and the design of power transmission and transformation project. And it can meet the electromagnetic transient simulation requirements for the power system.