Strain Measurement on the Runner of a Hydroelectric Turbineby K. Warren Frizell, (A.M.ASCE), Bureau of Reclamation, Denver, United States,
Abstract: Twelve strain gages were installed on the 10-m-diameter runner of Unit G-23 (700 MW) at Grand Coulee Dam, Third Powerhouse. The gages were located on both the pressure and suction sides of blades 8, 9 and 10 and were positioned in order to measure strains near the trailing edge to crown transition of the runner. This is an area where cracks have previously been discovered on Units G-22 and G-23. Four channels of RF (radio frequency) transmitters were used to record the response of four strain gages at a time while the unit was in various operating conditions. A fixed antenna was placed around the turbine shaft and connected to a receiver. The receiver processed the incoming strain gage signals and they were recorded with a digital audio tape recorder along with the unit speed, wicket gate position and load condition. Strain gage installation techniques are discussed, especially the waterproofing and securing of the lead wires. Each RF transmitter was enclosed within a custom-made box which included a bridge completion circuit, adjustable balancing resistors, and the batteries which powered the transmitter. A sample of the results will be presented for illustrative purposes.
Subject Headings: Strain gages | Turbines | Cracking | Signal processing | Dams | Power plants | Suction
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