On the possibilities of dynamic evaluation of contact surface temperature under impulse-current loads

Abstract

This paper considers monitoring of the condition of electric-power-plant contact busbar connections. Stationary temperature measurements of operating buses do not provide adequate accuracy of the contact-connection control, for example, measurement of transient resistance, due to the high thermal conductivity of the busbar material, which leads to a substantial equalization of the temperature field along the busbar. It is proposed to use dynamic measurements of the plant temperature conditions, arising in particular in short-circuit clearing, electric-motor starting, etc. Temperature fields near a contact connection arising in heavy short-time currents differ from stationary fields in having a substantially greater contrast, which significantly increases the possibilities of diagnostics. The maximum temperature value of the busbar contact surfaces, which is outside the reach of direct measurements, is of greatest interest. The quality factors of f lat busbar contact connections and a contact-connection temperature algorithm, which are determined from the time–temperature dependence, detected on the outer busbar surface near the contact in the short circuit clearing, are considered. To analyze nonstationary fields of current density and a contact area temperature, numerical simulation methods and known analytical results of the heat transfer theory are used.