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LiMa (De-)Ice

 

The measurements of the conductor temperature and the catenary angle (inclination) are used to detect conductor elongation caused by ice. The model considers the mechanical properties and physical characteristics of the conductor as well as its own conductor mass, length, and the length of the span between two towers. The parameters of the catenary curve at the temperature of the freezing rain represent the initial state of the activation of the ICE-ALARM computer algorithm.

 

If an angle significantly increases in the meteorologically favourable conditions (humidity and ambient temperature) considering the temperature inversion and if the calculated angle significantly differs from the angle measured by inclinometer, the application informs the operator that ice has built on the conductor.

OTLM sensor can detect ice higher than 5 mm (additional field measurements are required).

OTLM de-icing:

De-icing is combining knowledge about icing, sag and temperature measurement. To calculate the current necessary to remove the ice build-up, Joule heating – convective heat transfer and melting of ice must be considered. Since Joule heating represents the dominant mechanism, convection and radiation are neglected. Specific thermal capacity is considered for each separate material. The necessary temperature that is needed to heat the conductor and the ice build-up from – 5 °C to 0 °C and to transform ice into liquid water is obtained by calculating the mass of the steel core conductor, Al-stripes and ice. If the ice build-up stopped at the time of a current increase, the time needed for the ice to melt is presented in figure 7. The red line shows the result for the maximum current that is allowed by the HV equipment in the overhead power field (e.g. disconnector, break-switch, measuring transformers), i.e. 800 A. This line shows the shortest possible time for the removal of the ice from the conductor by increasing the current.

 

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