Study of Reactive Power Consumption for Different Core Material of Distribution Transformers

Abstract

Transformer in the Electrical network is the vital link between Generation, Transmission and Distribution. The magnetic circuit present forms the strategic link between primary and secondary. This link is due to the Electrical steel present in the Magnetic circuit, which is responsible for the flux linkage between the windings in the Transformers. The magnetic material used and its properties affects the efficiency of the Transformer. Due to high cost of Electrical steel, there are certain instances that inferior grade and core material from the dismantled Power Transformers are used in small rating Distribution Transformers affecting the reliability of the Distribution Network. The experimental study was conducted on 3 numbers of 25KVA Distribution transformers of identical designs are made with three different Cold Rolled Grain Oriented (CRGO) core material i.e., Prime CRGO material (New), Used CRGO core material (Removed from transformer after service of 20 years) and Mixed core (placing one new and one used lamination in alternating manner). This paper discusses the study on variation of Reactive Power consumption of different core materials and of the Distribution Transformers made with CRGO cores. And also, the changes in the Magnetizing Reactance in the Transformer. The Epstein results @ 1.5 tesla shows the deterioration in the magnetic properties for used core material as there is increase in reactive power. The transformer open circuit test results at 112% of rated voltages are very predominant in both Mixed and Used core transformer for Active and Reactive power. The results show that these transformers are probable to saturate at small changes in the voltages.