Control of Ice Jams at Barrett Chute G.S.

During severe winter months, ice jams form in the canal of a Canadian hydroelectric peaking plant following the initial loading sequence. The ice cover that forms on the surface of the canal during relatively long shutdown periods (weekends, etc.) disintegrates under the severe surge action that accompanies the rapid loading sequence, and the strong surface currents above the intake structures forcefully compact the fragments into temporary ice jams in the forebay area. Eventually the fragments are drawn into the penstocks and discharged through the plant. Three tests are described, their purpose being: (1) to investigate the effects of discharging ice through the plant on the performance of same; and (2) to ascertain the most suitable loading sequence (of the units) which would produce a minimum degree of blockage in the forebay area and consequently result in a rapid clearance of ice in the canal. The results indicate that the plant can successfully discharge the ice without suffering significant reductions in performance, or damage to the units, and an efficient loading sequence was obtained.