ETL 1110-2-550
30 May 97
C-3. Problems include turbine runner cracking,
Appendix C
Example Problem Description
severe cavitation damage, generator coil degrada-
tion, and deterioration of the generator step-up
transformers. Over the past 10 years, the turbine
runners have exhibited increased cracking. On three
separate occasions, pieces of the buckets have
analysis, the hydroelectric power benefits analysis,
broken off. An enhanced maintenance program was
and the economic modeling process, a brief
instituted. This program, which includes more
overview of an example rehabilitation project is
frequent inspections and welding repair, has
warranted.
prevented further breakage. However, cracking and
cavitation damage continue to increase at an
accelerated rate. Deterioration of coil insulation has
C-2. The "Chapman Hydroelectric Power Project"
caused coil failures in three of the four generators in
consists of a single powerhouse with four Francis
the last two years. Spare generator coils are not
turbines that were placed into service beginning in
available, and there is no spare transformer.
1947. The total rated capacity is 200 megawatts
Unsatisfactory performance of either the generator
(MW). There are two three-phase generator step-up
or turbine runner will cause a unit outage.
transformers, each serving two generating units.
Unsatisfactory performance of a transformer will
The plant is a storage project located in the
cause an outage of two units. Field testing has
southeast portion of the United States. There is a
shown that the units have experienced an efficiency
relatively small variation in lake elevation due to
loss from their original condition. Average unit
seasonal flows and the need for flood protection.
availability has also deteriorated from 95 percent
The storage in the lake is very large in relation to
10 years ago, to 93 percent 5 years ago, and to
the flow in the river. Therefore, all of the flow into
88 percent this year.
the lake either evaporates or passes through the
turbines for power production. The plant factor is
25 percent.
C-1
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