Because of a very thin foil conductor (typically 0.5–2 mm), the most critical is inner low voltage foil winding which can collapse due to radial forces at stresses far below the elastic limit of conductor material. Despite that, winding failure may occur during the short circuit, e.g. A diamond dotted paper with an epoxy coating is used in order to increase the stiffness of the winding.

On the other hand, such windings are more susceptible to radial forces in a short circuit. In the distribution transformers design oval windings are used due to economic advantages. This leads to obtaining precise fault values in all instances. This implies that the developed GA can be further used to determine these ratios for nominal voltages that are not sufficiently accounted for by Standard IEC. The GA results and the IEC values were within an approximate range. The GA was tested on a nominal voltage that is properly catered for by Standard IEC.

During fault computation, the GA was used to stochastically determine R/X and R/Z ratios with regards to the parameters of the power system. In this paper, adjustments were made to the genetic algorithm (GA) with regards to gene replacements and arrangement of scores and expectation. Users often have to approximate these values. These estimates do not cater for every nominal voltage. It estimates voltage factors, resistance to reactance ratios (R/X), resistance to impedance ratios (R/Z) and other scaling factors. However, it uses numerous estimations in its fault evaluation procedures. Standard IEC 60909 provides all the basic information that is used in the evaluation of three-phase short circuit faults. It can serve as a reference document for future research works in the area since the procedures are outlined for calculating the factors of safety through six case studies. The main contribution of the reported work is in highlighting the intricacies associated with the subject of short‐circuit strength of power transformers. The presented overview of the factors of safety can be a useful guide for the practicing transformer engineers.

The work gives pointers for further research at appropriate places while highlighting the challenges involved in the assessment of the short‐circuit strength. These factors are related to the strength and stability aspects of windings. Corresponding factors of safety are defined and calculated for practical transformers. Six major sets of calculations are identified: three each for radial and axial electromagnetic forces. Some of the latest approaches in assessing the strength are elaborated. The purpose of this paper is to give a comprehensive description of various safety factors that need to be determined while assessing the short‐circuit strength of transformers.įactors of safety are divided into two categories: radial and axial.

Vrste spoja transformatora