<p><span>This paper presents a study about electrical performance of ceramic and polymeric insulators bio-contaminated with alga <span><em>Chlorella </em><span><em>vulgaris</em><span>. The performed tests involve ANSI 55-2 and ANSI 52-1 ceramic insulators and ANSI DS-15 polymeric insulators, all of them <span>used in distribution systems of Colombia. Biological contamination of insulators is realized using a controlled environment chamber <span>that adjusts the temperature, humidity and light radiation. The laboratory tests include measurements of flashover voltages and leakage currents and they were performed to determine how insulators are affected by biological contamination. After a series of laboratory tests, it was concluded that the presence of <span><em>Chlorella vulgaris </em><span>on the contaminated ceramic insulators reduces the wet flashover <span>voltage up to 12% and increases their leakage currents up to 80%. On the other hand, for polymeric insulators the effect of algae <span>growth on flashover voltages was not to strong, although the leakage currents increase up to 60%.</span></span></span></span></span><br /><br class="Apple-interchange-newline" /></span></span></span></span></span></p>