TITLE:
Influence of Phase Compensation Method on Magnetizing Inrush Identification
AUTHORS:
Xiangfei Sun, Jianping Zhou
KEYWORDS:
Transformer; Differential Protection; Magnetizing Inrush; Second Harmonic; Phase Compensation
JOURNAL NAME:
Energy and Power Engineering,
Vol.5 No.4B,
November
13,
2013
ABSTRACT:
The effect of different phase compensation methods on
second harmonic ratio of magnetizing inrush is investigated. The flux linkage
expression of switching on an unload transformer is deduced and influence
factors of inrush current are analyzed firstly. Then the difference of two
kinds of phase compensation methods, from star to delta and from delta to star
connection, is compared. The second harmonic ratio of symmetric inrush is
analyzed specially. Using inrush waveform of a real transformer, second
harmonic ratio of phase inrush and that of differential current under two kinds
of phase compensation methods are calculated respectively. Furthermore, based
on the calculation results, the effect of two kinds of phase compensation
methods on the inrush current identification is proved. The analysis
and calculation results show that the second harmonic ratio of symmetric inrush
caused by phase compensation method, from star to delta, is not low. Moreover,
the split-phase blocking scheme should not be adopted for differential
protection of from delta to star compensation. Using the phase current without
compensation to calculate the ratio of second harmonic is inadvisable too.