In this paper,the calculation methods of the deterministic model and the stochastic model are discussed on the basis of the voltage and current function when power system is in trouble.

• 根据电力系统故障时的电压电流函数，从算法原理上重点分析了微机保护中随机函数模型的算法，并讨论了确定性函数模型算法的特点和应用范围。