Comutador eletrônico de taps aplicado a um transformador de distribuição monofásico

Abstract

Voltage regulation still is a problem faced by power utilities currently. In addition to the series impedance and the significant load variation of the distribution grids, the main causes of voltage regulation problems, the requirements for the enhancement of power quality by the electricity regulatory agencies, increasing energy consumption, the inclusion of distributed generation and the development of the smart grids tends to increase the complexity of the distribution systems. One of the most used methods for voltage regulation in alternating current systems is the employment of tap changer on transformers, this method allows voltage regulation by varying the transformation ratio, modifying the value of the secondary voltage. The application of these devices is primarily performed by manual commutation mechanical devices in distribution systems, and by automatic electromechanical on load tap changers in substations. In the case of manual devices, operating costs and the impossibility of automatic voltage regulation are limiting factors, while in the case of electromechanical devices the limitations are mainly related to the costs of employment and maintenance. Currently, the increase of voltage and current operating levels of semiconductor devices has allowed envision the application of semiconductor switches instead of the mechanical switches employed nowadays. However, due to the operating characteristics of these devices, a detailed analysis of the commutation process is necessary, in order to allow the proper design of the devices involved in the commutation and protection process of the electronic tap changer. In this context, this work presents the analysis, design and implementation of an electronic on load tap changer applied to a single-phase distribution transformer, proposed as an alternative to the existing mechanical and electromechanical tap changers. Such a system enables the automatic voltage regulation, avoiding the insulation oil degradation, resulting from the commutation process, and also the elimination of movable parts, the main cause of defects in current automatic commutation devices. In addition to allowing steady state voltage regulation, the system allows the regulation for momentary voltage sags, since they occur in the transformer operating range. The analysis of the commutation process is presented, allowing the design of the electronic switches, as well as the protection system to be employed. Experimental results show the correct voltage regulation for different kinds of load, demonstrating the potential application of electronic on load tap changers in the current distribution systems and in future smart grids.