Further improvements to a phase-domain ARMA line model in terms of convolution, steady-state initialization, and stability

This paper presents further improvements to a phase-domain ARMA (Auto-Regressive Moving Average) line model that is implemented in the ATP version of EMTP. According to the improvement to convolution, each ARMA model, which reproduces the phase-domain frequency dependence of a transmission line, uses its own economical time step considering the frequency characteristic. Linear interpolation is used to allow a different time step for each ARMA model, and this new convolution strategy makes transient calculations more efficient. A steady-state initialization method of the line model is developed, and fault-surge calculations requiring the initialization are demonstrated. Convenient stability criteria of the line model are also presented.