INFLUENCE RESEARCH OF CHEMICAL COMPOSITION OF HIGH-VOLTAGE CIRCUIT DESIGNS ON THE FIRE BREAK-OUT AT THE LOCOMOTIVES

Abstract

Purpose. The work is aimed at identifying the influence of the incompatibility of chemical composition of the high-voltage circuits designs on the mechanism of fire break-out at the VL-80k locomotive. Methodology. Macro- and microstructural, fractographic, analytical analyses were applied during the research of the samples of contact clamps materials. Findings. Analytical analysis of the parts of electric locomotive made it possible to identify the primary causes of circuit-breaker oil ignition followed by a complete burnout of the locomotive section. It was established that the destroyed contact clamps had a chemical composition that does not meet the requirements of design and technical documentation. The arc formed between the edges of macro-cracks during the destruction of the contact clamps did not lead to the disconnection of the main high-voltage relay, and due to the high power contributed to the ignition of a large amount of circuit-breaker oil, which was located below the contact clamps. Such ignition may also occur as a result of the weakening of the locomotive power circuit caused by the vibration. One can prevent such cases of ignition by identifying critical heating temperatures of the contacts of high-voltage cabinet, contactor and resistor groups to immediately strengthen or replace the connection. Originality. A comprehensive analytical and technical approach was applied in identifying the causes of fire at the VL-80k electric locomotive. A typical fire break-out mechanism and a maximum number of factors that could affect the premature destruction of the contact clamps were investigated. It is shown that a set of factors that negatively affected the performance characteristics of the contact clamps, simultaneously reached the so-called "critical mass" as a result of heating of these defective parts. The introduction of additional signaling factors for supercritical heating of the investigated and other important parts and designs of locomotives will prevent fires at the locomotives. It will help timely to identify the inconsistency of the chemical composition of the parts of the design and technical documentation, as well as to find out the gaps in the electrical connections that were formed either due to the insufficient tightening, or due to the weakening of connections in the process of vibration during the movement of locomotives. Practical value. The proposed additional signaling will contribute not only to the preservation of the locomotive fleet of Ukrzaliznytsia OJSC, but also to the rescue of locomotive brigades.