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The harmonic or three-phase unbalance current injection into
the Taiwan Power (Taipower) system due to customer''s nonlinear
load can cause the voltage distortion at Taipower''s substation.
This voltage distortion also varies with the system impedance
of Taipower.For example,during the base-load duration, because
the system impedance is high (or the three-phase short-circuit
current,abbreviated by 3-φ SCC, is low),the injection current
can cause a higher voltage distortion than that caused by the
same current during the peak-load duration. As the system
impedance (or 3-φ SCC)is variational,the power utility has to
specify the minimum 3-φ SCC based on which to regulate the
harmonic or 3-φ unbalance current injected into the utility
system. Presently,Taipower adopts a rule-based approach to
specify the yearly minimum 3-φ SCC.For a theoretical
soundness, Tsing-Hua University has proposed a statistical
approach to the same specification. Our research comprises of
two major parts.In the first part,we simulate the traction load
of Taiwan high-speed railway (HSR) system which is now under
planning.With the load evaluated,we then estimate the maximum
3-φ voltage unbalance factor at each HSR substation on basis
of the station''s minimum 3-φ SCC specified by the Taipower''s
rule-based and the Tsing-Hua''s statistical approaches
respectively. In the second part,we simulate the load of Taipei
mass rapid transit (MRT) system,and estimate the harmonic
distortion limits to be imposed on each MRT substation .In this
estimation,we also uses the minimum 3-φ SCC specified by the
Taipower''s and the Tsing-Hua''s approaches respectively,and
compare the impact of these two approaches on the MRT harmonic
distortion limits.
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