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This page contains answers to a few common
questions regarding turbine generator performance:
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Accurate Turbine evaluations require ASME PTC 6.0 methods which
are not typically provided as part of the OPM systems.
Enthalpy drop tests using high accuracy methods can provide turbine
information with the exception of the LP turbine (with moisture
formation). Unfortunately the LP turbine can produce as much
as 40+% of the total power produced.
This depends on if it is an acceptance test. If it is an
acceptance test, 2 years prior to turbine shipment planning should
commence with the actual test being conducted shortly after the
turbine is put into commercial operation. Some turbine testing
such as enthalpy drop tests can be achieved without flow sections
and therefore the time in preparation for the test can be measured
in terms of weeks.
Commonly the turbine is associated with losses in power and unit
efficiency. The PTC 6.0 turbine testing can establish
precisely the turbine's contribution to power losses and turbine
cycle heat rate losses. The contributions due to leakage,
individual turbine sections, individual heaters, and other major
equipment will normally be determined.
The first step is to work with plant personnel to understand
their concerns and observations and then to summarize this in
writing. The second step is to confirm observed losses and
efficiency with the original data. If the losses are confirmed
then calibrated equipment should be considered with PTC 6.0 being
perhaps the later choice but providing a complete determination.
It would be highly abnormal for units to have the same efficiency
and maximum load capability since this decreases as a function of
time since the last major outage. There are problems
identifying what the load and turbine cycle heat rate is precisely.
The problem becomes one of testing procedures, isolations,
accuracy of data, and flow measurement methods, etc. The full
ASME PTC 6.0 provides an overall uncertainty of
0.25% for turbine cycle heat
rate.
The calibrated flow nozzles and extensive instrumentation
is required for new turbines whereas for the turbine upgrade
existing flow nozzles can be used. However, inspections will
be required. A reduced number of calibrated instruments
is also specified. Corrections can be used to assist in the
evaluations since the reference is made to the pre-upgrade turbine.
Improvements are sometimes measured in Btu/kwhr or Kj/kwhr.
- Who performs, evaluates and reports the
major turbine testing ?
In order to achieve a turbine test
experienced personnel must perform from many areas. In
addition to the plant operating personnel and support staff, there
are many people involved. The responsibilities include the following
areas: test engineers who coordinate and run the tests, electrical technician(s)
who are responsible for measuring power and making instrumentation hookups
- engineers for model and heat balance development, Technicians
who accurately calibrate instruments according to standards, computer /
instrument technicians who install, hookup, and operate the computer aided test
equipment and other qualified
personnel which may get involved in plant acquisition and equipment setup depending on the
requirements.
Finally, the manufacturing craftsman are responsible for building
the flow nozzle which is also specialized work.
In addition the transportation people etc. are needed. The evaluation and reporting
of the test is the responsibility of the performance engineer.
The report
must generally contain a brief summary, detailed heat balances of
the test showing specified and as tested balances, discussion of the tests, specified/as
tested data collections, corrections and generator summaries
for all tests.
Since fuel consumption for power stations over time can amount to
huge sums small differences in equipment performance can
correspondingly have significant costs. Existing plant
monitoring is typically not accurate enough to determine the state
of the turbine in regards to degradation or load impacts.
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