Environmental Engineering Reference
In-Depth Information
there has not yet been a detailed assessment of the reactive power requirements of
the whole system to ensure accurate voltage performance and voltage stability.
Account needs to be taken of how much static (slow acting) and dynamic (fast
response) reactive power is needed on a particular power system. A further question
is: what is the most economic approach to making the requirement available?
Before discussing the analysis approach, it should be noted that there are two basic
philosophies applied by energy market makers. The first is that all generators should
be required to conform to the same standards. The second recognises technological
difference and the fact that it may be more expensive overall to force certain tech-
nologies to comply with a common standard. This more flexible approach therefore
sets compliance rules for technology bands. The sample grid code in Appendix 2
follows this technology specific route. The North American Electric Reliability
Corporation Report IVGTF Task Force 1-3 (NERC, 2012) serves to promote align-
ment of the American and European models by stating: 'Applicability: generator
interconnection requirement for reactive power should be clearly established for all
generator technologies. NERC should consider giving transmission planners some
discretion to establish variance based on the characteristics of their transmission
system and the size of the generator.'
The power system reactive power requirement problem analysis steps are:
Determination, from load flow calculations, of the reactive power require-
ments of an intact maximum loaded system in normal configuration.
●
Determination of the additional requirements for worst case secured generation
and circuit outages under maximum load conditions.
●
Determination of how this changes with maximum expected penetration of
wind energy (and other future changes to the system).
●
Determination, from load flows, of the reactive power requirements of an
intact minimum loaded system in normal configuration.
●
Determination, from load flows, of the reactive power requirements of a
minimum loaded system with maximum foreseen maintenance.
●
Determination, from load flows, of the reactive power requirements of a
minimum loaded system with maximum foreseen maintenance and worst case
generation and circuit outages.
●
Examination of these cases should indicate the requirement for static and
dynamic reactive compensation throughout the year. More refinement can be
achieved by repeating the steps for a number of intermediate loads. Dynamic
compensation is required to take account of unexpected occurrences. The limits
applied in assessing the dynamic requirements throughout the studies are the
maximum and minimum network voltage for normal and secured outage situations
and the associated allowable step changes. Studies on small systems tend to indi-
cate that the static and dynamic requirements are approximately equal, but network
topology and the ratio of loading to capacity will have a bearing on the result.
The above analysis is a starting point for reactive power studies. More accurate
studies need to model the system performance in a dynamic rather than a steady-
state condition. Various factors are important. Load behaviour following a system
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