How to dynamically model & analyze generator stability during step loading using ETAP software

This study simulates the impact of step loading on the transient stability of a 2 x 25 MW GTG-based captive power plant at one of the Chemical Fertilizer Plants located at Trombay, India. The variation of electrical frequency and terminal voltage of the generator during the most conservative step loading of one generator unit is studied. The loads divided in steps are switched at certain time intervals to determine whether the frequency profile of the system is within the acceptable limit of ±5%. Load Flow and Short Circuit Studies are performed on the entire power plant distribution network of the fertilizer plant in advance to check the adequacy of equipment ratings during normal and short circuit conditions with all verified input data. The step load response study is carried out with only one GTG unit running in isolation, feeding only the critical emergency loads. Transient behavior of the GTG unit is simulated with IEEE transfer function dynamic models, viz. AC8B model of excitation system (AVR) and IEEE GGOV1 model for turbine governing system using the in-built standard library in ETAP software version 16.1.0. Various parameters of the generator like speed, active and reactive power, bus voltage, and frequency are plotted for determining the transient performance of the GTG unit.