Environmental Engineering Reference
In-Depth Information
computer which applies algorithms to evaluate the rating. This rating is fed to a
control centre energy management system (EMS) to be used in security constrained
dispatch analysis.
An alternative approach when constructing or refurbishing circuits is to use an
embedded fibre-optic filament within the conductor. Attaching suitable equipment
allows the optical phase-shift within the fibre to be used to calculate the tempera-
ture at each meter or so along the conductor. The sources of concern about fibre
optic measurement are:
complexity and skill level for conductor repair
premature aging of the fibre relative to the conductor
unless duplicated in different conductors, the enhanced rating is subject to a
single-mode failure of either the fibre or the terminal electronic equipment
The alternative wind measurements are made at many points and, if needed,
the ratings calculations can be duplicated easily. The fibre method, once calibrated
with real measurements, should however be very accurate.
The above methods clearly provide an enhanced conductor rating (of the order
of 30-50% above existing ratings). Much depends on the statistical level of risk
which an asset owner would assume. Broadly however, asset owners are con-
servative because of the legal and safety consequences of infringing accepted
conductor sag rules.
A benefit from these methods is that not only operators faced with real-time
decisions, but also network planners, can take advantage of the knowledge. If the
wind speed and direction or the appropriate wind farm outputs are also measured
and time-stamped to correlate with the weather and sag information from the
line, utility connection engineers can provide the wind farm developer with a
reliable estimate of network-based curtailment for each level of expenditure on
the circuit. This probabilistic assessment can be conducted using rules and
principles agreed with funding agencies and therefore should be 'bankable' by
the developer.
A further operational benefit of dynamic line rating is that, taken together with
a weather forecast, the system operator now has a micro-scale weather information
map which can provide an accurate output and circuit rating prediction for an hour
or more. The system operator should therefore be in a better position to manage
wind ramping and curtailment and organise mitigation though tertiary reserve
Network power quality management
The issues of concern are likely to be
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