1 - Alaska Energy Data Inventory

3.05 PRESSURE AND SPEED REGULATION.Since the size of the generator and thus its polar moment of inertia(WR2) is already limited by powerhouse size and hoist capacity, overs peedanalysis is based on a constant WR 2 of 1,075,000 lb-ft 2 as establ ishedby HEDB. The synchronous speed of the turbine is set at 600 r/min andmaximum overs peed is limited to 900 r/min or 50 pct increase. The wicketgate closing pattern was suggested by HEDB. For the "5" s closure forexample, the closing pattern is nearly a straight line from 100 pct openingat 0 s to 13 pct opening at 4.3 s; slow closure is initiated at 4.3 sandthe gates do not fully close until 9.0 s. Figure 11 in Hydraulic AppendixB2 illustrates the gate closing pattern.The "WHAMO" computer program was used to determine overspeed for variousgate closure times and various net heads at a turbine output ofapproximately 47,190 hp (blocked output, 1.0 power factor). Maximumovers peed was found to occur at the lowest net head at which the turbinecould produce 47,190 hp, i.e., 100 pct gate opening. The "5" s gateclosure time will produce an approximate 50 pct overs peed (901.5 r/min) ata net head of 846 ft starting from the 100 pct open wicket gate position. and turbine output of 47,116.8 hp, and moving to the fully closed wicketgate position and turbine output of 0 hp.Water hammer pressures are also based onrates for the wicket gates."5" s opening and closureB3-15