Abstract
Power transformers are used to form a connection between distribution, sub-transmission and
transmission power lines in order to allow electric power to flow between networks of
different voltages. Thus, the desired value of transformer reactance value is determined at the
design stage. In most cases, once a transformer is commissioned, its tap changer setting is
fixed at a particular position, and the position is likely to be changed only during
maintenance.
In this dissertation, an investigation into the impact of parameters of high voltage
transmission line interconnecting transformers on power system on the performance of the
power system is being done. The specific transformer parameters that are considered are
reactance and tap changer settings. The performance aspects that are investigated are active
power flow, system losses, and voltage stability.
From the findings of the investigation, it is observed that the reactance value of a transformer
has an influence on power flow, system losses, and voltage stability. Therefore, in networks
where the likelihood of fault current occurrence is low, the reactance of the transformer can
be varied in order to improve the performance of the power system. Moreover, transformer
tap changer positions have a higher influence on power flow, system losses, and voltage
stability.
It is concluded that at the design stage, transformer reactance values need to be carefully
selected for the improvement of power system performance. During the commissioning and
maintenance of transformer units, there is a need for power system planners and operators to
carefully select the tap changer position and fix it in a position that yields better results with
regard to power flow, system losses, and voltage stability of the power system.
M.Ing. (Electrical and Electronic Engineering)