Toshikazu Nagata

Estimation on on-load vibration of transformer windings

In this paper the discussions on the on-load vibration of transformer windings are presented. Firstly, the vibration of the windings was investigated on the 6 kVA model coil both experimentally and analytically. On the on-load condition, the axial vibration of conductors was measured by the accelerometers. Numerical analysis was also conducted on the model coil. The electromagnetic force was calculated by a conventional mirror method. The steady state response of the windings was estimated by the finite element analysis. The calculated result showed fairly good agreement with the measurement and the validity of the numerical method was affirmed. Finally, the vibrations of the full-scale transformer windings were estimated with the same calculation method.

Preliminary investigation for application of MEMS acceleration sensor to SF 6 gas circuit breaker

With an aim of applying a MEMS (micro electrical mechanical system) acceleration sensor as a diagnosis tool for a mechanical degradation of a SF6 gas circuit breaker, we investigated the fundamental characteristics. It is confirmed that the MEMS acceleration sensor with a maximum acceleration number of 250 G and a frequency band width up to 400 Hz can be applied to measure an acceleration number of the model GCB, while all tests were carried out under no electromagnetic stresses on the GCB. In addition an optical acceleration sensor by using a photo-reflector was developed to be applied in a severe electromagnetic field. The first model of the optical sensor showed insufficient frequency band width for the purpose.

Research on acceleration phenomena with test equipment of simulating puffer type gas circuit breaker

The diagnosis was investigated by using the acceleration measurement for mechanical failure and degradation of a SF6 gas circuit breaker (GCB). The mechanical model GCB was fabricated to produce similar acceleration characteristics to a real GCB. The MEMS (Micro Electro-Mechanical System) sensor was adopted for the purpose of confirming its applicability with the well-established piezoelectric accelerometer. The acceleration characteristics of the model GCB was generally similar to the real GCB of 300kV class, except the high frequency component. The MEMS sensor application was feasible with some limitations. It was indicated a mechanical failure could be detected by the acceleration measurement.