Ensuring safe operating conditions for power transformers under thermal effects of short-circuit currents

Introduction. Power transformers are the basic equipment of the industrial power systems. One of the key indicators of determining the service lifetime of the transformer including its performance characteristics is the condition and residual life of its isolation. Aging and f insulation deprecation are directly related to the operating temperature of the transformer in use, as well as to the reliable operation of the cooling system. This research direction is up-to-date, especially when it comes to fully rated power transformers. Materials and Methods. Power transformers of the district substations that feed the industrial and transport enterprises are considered. Modes of power transformers, which are caused by the uneven workload of the phases and short-circuiting, are studied. All these factors lead to the thermal deformation of the power transformer insulation and, as a rule, to the outage of power transformers. Research Results. The forced cooling system of power transformers, which allows increasing their cooling capacity and the cooling fluid volume, is developed by the authors and described in the paper. Thermal calculations of heating design elements of the power transformers are carried out both in the conventional cooling system and the new one. The comparative analysis and calculations have shown the feasibility of the developed cooling system of power transformers, which allows extending the insulation lifetime. The developed cooling system is forced. The authors used a reserve power transformer tank as an additional expander. This design solution can be implemented for transformers operating at low temperatures, as well as under long-term limit loads. Discussion and Conclusions. The developed cooling system eliminates the requirement for purchase costs on extra equipment and maintenance support. It can be used at the enterprise power facilities and in the rail transportation.