Eiichi Haginomori

High frequency short-circuit inductance for model transformer

AbstractCurrently, the International Electrotechnical Commission (IEC) standard (IEC62271-100) requires that the transformer limited fault (TLF) interruption shall be verified in the test duty T10, the amplitude factor of which is defined as 1.7 for the transient recovery voltage (TRV). But, the TRV measurements for the TLF at various transformers show that the factor is mostly lower than 1.7. The reason for the low values is considered to be that the short-circuit inductance of transformer at the TRV frequency region is lower than that at the power frequency, and consequently the factor is lower than the standard value 1.7. But, the frequency-dependence of the short-circuit inductance of transformer has not been clarified yet. We measured the short-circuit inductances of model transformer with and without the iron core. The short-circuit inductance with the iron core becomes small and equals to one without the iron core at the TRV frequency region. We concluded that this is the reason for the phenomena o...

Investigation on frequency response analysis measurement method for power transformer impedance

The frequency response analysis of transformer has been expected to be a good method for diagnosing the transformer condition. As the transformer impedance is affected by the configuration, the change of the impedance will be a good indicator for the change of the transformer configuration. The method which has been recognized cannot achieve the measurement of current flowing through the stray capacitance to the earth. The measured impedance was not correct at the high frequency range where an influence of the capacitance becomes large. In this paper, the new method was proposed in which the resistor for the current measurement is connected to the terminal of the power application and its value is adjusted. It is shown that the correct measurement can be achieved by the proposed one document.

Consideration of uncertainty for current measurement and development of test data generator for TRV measurment

The uncertainty in the measurement at the high power testing was discussed. The uncertainty of current measurement was analyzed in detail. The test data generator for the transient recovery voltage was developed. Two processes are essential in the high power testing who needs to comply with the processes.

University research approach to switchgear technology//// circuit switching phenomena

The calculation of transient recovery voltage (TRV) was investigated. The current injection principle was used to simplify the calculation. The source side impedance and ramped injection current gives the TRV. The TRV is expressed by the 4 parameter in the standard. The standard TRV is modified by switching circuit conditions. The synthetic short-circuit testing needs to know the TRV modification beforehand. The Laplace transformation is applied to express the 4 parameter TRV by segmenting the straight line. It was shown that the TRV modification by an arrester can be calculated easily by the proposed method.