Non-Limiting Operation of The On-Load Tap Changing Transformer, and Its Effect on Voltage Stability, with Regards to The Nineveh Electrical Grid

The achievement of voltage stability is among the most prominent challenges faced by grid operators. In the past, generator excitation regulation was the only method available, for restoring the voltage to its rated values. However, rapid developments in the areas of power grids and power stations, has led to the need of a new technique, for controlling the voltage level, and maintaining the system in the voltage stability band. On-load tap changing (OLTC) is currently among the most widely employed methods, for improving the stability of the power system voltage. OLTC restores the voltage value, whether the disturbance occurs on its primary or secondary side. While a minor disturbance is easily overcome by OLTC, its capacity for restoring the voltage level, during a significant disturbance, is dependent on its ratings and setting values. The failure of the OLTC transformer, to restore the voltage value within a short period, may result in a collapse of the voltage system, when the transformer proceeds with reverse action. A simulation model in MATLAB Simulink shows the effect of OLTC on the Nineveh power grid.