Governor Time And Surge Tanks

In pumped storage plants, the time specified for the governor servomotors to move the wicket gates through a complete stroke is generally not less than 30 s. The reasons for this are that (1) about 30 s is the minimum practicable time for penstock valve operation if the valve operating machinery is not to be made unduly complicated by the incorporation of dashpots and accessories and (2) one of the primary purposes of massive EHV connection is to carry loads from emergency outages for 30 to 60 s or more until the local pumped storage units take over. In the lengths of waterways that are permissible economically, penstock and tunnel velocities may usually be accelerated to full load in a much shorter time

FIGURE 9 Pump-turbine with motor generator. Starting motor is located on top, above the motor-generator. The pump-turbine runner—surrounded by adjustable vanes, stay vanes, and spiral case—is located above the conical draft tube that has a minimum throat diameter at the runner eye of 2823 mm (111.1 in). In the turbine mode, flow is downward and out of the draft tube, and power generated is 210 MW at a head of 250 m (820 ft). In the pumping mode, the flow direction is reversed, and the motor input power is 198.1 MW at a head of 260 m (853 ft). Speed is 272.7 rpm in both modes (Voith Siemens Hydro)

FIGURE 9 Pump-turbine with motor generator. Starting motor is located on top, above the motor-generator. The pump-turbine runner—surrounded by adjustable vanes, stay vanes, and spiral case—is located above the conical draft tube that has a minimum throat diameter at the runner eye of 2823 mm (111.1 in). In the turbine mode, flow is downward and out of the draft tube, and power generated is 210 MW at a head of 250 m (820 ft). In the pumping mode, the flow direction is reversed, and the motor input power is 198.1 MW at a head of 260 m (853 ft). Speed is 272.7 rpm in both modes (Voith Siemens Hydro)

without excessive positive or negative waterhammer, so surge tanks are not necessary. However, in the exceptional case of a long tailrace tunnel flowing as a closed conduit, under the relatively low head of tailwater, even a 30-s closure could be sufficient to produce negative waterhammer great enough to cause separation of the water column and damage to the unit. For such cases, a surge tank1 at the downstream face of the power station is required. In a dual-purpose project for municipal water supply and by-product power, the length of the tunnel is dictated by water supply economics and may be as great as 40 to 50 miles (64 to 80.5 km). In such cases, a surge tank on the upstream side of the power station may be indicated.

FIGURE 10 Arithmetic integration, full load rejection (1 hp = 0.746 kW; 1 ft = 0.3048 m; 1 ft/s = 0.3048 m/s; 1 ft3/s = 0.0283 m3/s) versus time in seconds.
Survival Treasure

Survival Treasure

This is a collection of 3 guides all about survival. Within this collection you find the following titles: Outdoor Survival Skills, Survival Basics and The Wilderness Survival Guide.

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