Research of the non-sinusoidal loads impact on the operability of tap-changers contacts

Abstract

Purpose. To establish quantitative indicators of the influence of non-sinusoidal loads on the parameters and operability of contacts of voltage control devices of transformers of power-consuming electrical installationsMethodology. In our research, we used the probabilistic-statistical methods to analyze the experimental findings. Experimental studies were carried out applying advanced software-based methods for processing, systematizing and visualizing the findings derived.Findings. The analysis of the accident rate of transformers for power-consuming technological installations showed that adjustable transformers, in particular, on-load tap-changers, are in many cases the cause of failure in the operation of electrical installations. On the example of a switching device of the RNOA-110/1250 type, it was experimentally established that the non-sinusoidality of the current caused by abruptly alternating loads, in combination with an increase in the number of switchings, leads to an increase in the contact resistance, which significantly reduces the reliability and serviceability of contacts.Originality. The dependence of the transient resistance of the contacts of the voltage control device under the load of the transformer on the degree of non-sinusoidality of the load current is obtained.Practical value. The results of the work can be used in the development of new designs of on-load tap-changers for special purpose operation under conditions of load fluctuations. In particular, the work is aimed to increase the reliability of on-load tap changers contact systems, as well as in the study of the operating conditions of network and furnace transformers in power supply systems of energy-intensive technological installations.