Principles of Charge Estimation Methods Using High-Frequency Current Transformer Sensors in Partial Discharge Measurements

This paper describes a simplified model and a generic model of high-frequency current transformer (HFCT) sensors. By analyzing the models, a universal charge estimation method based on the double time integral of the measured voltage is inferred. The method is demonstrated to be valid irrespective of HFCT sensor, assuming that its transfer function can be modelled as a combination of real zeros and poles. This paper describes the mathematical foundation of the method and its particularities when applied to measure nanosecond current pulses. In practice, the applicability of the method is subjected to the characteristics and frequency response of the sensor and the current pulse duration. Therefore, a proposal to use the double time integral or the simple time integral of the measured voltage is described depending upon the sensor response. The procedures used to obtain the respective calibration constants based on the frequency response of the HFCT sensors are explained. Two examples, one using a HFCT sensor with a broadband flat frequency response and another using a HFCT sensor with a non-flat frequency response, are presented.

The Acoustics of Kabuki Theaters

The study presents a room acoustical investigation of a representative sample of eight Kabuki theaters as the most important public performance venues of pre-modern Japan. Room acoustical parameters according to ISO 3382 were measured for the unoccupied and simulated for the occupied condition. In comparison with European proscenium stage theaters, they have lower room heights in the auditorium, with usually only one upper tier, and no high stage house for movable scenery. The lower volume per seat results in lower reverberation times, The wooden construction and the audience seating arrangement on wooden straw mats on the floor instead of upholstered seats leads to a mostly flat frequency response up to 4 kHz, resulting in an excellent speech intelligibility, as documented by values for definition (D50) and the speech intelligibility index (STI). The acoustical conditions support the dynamic acting space created by pathways extending the stage from the front through the audience to the rear of the auditorium. They allow great contrasts in the perceived acoustical proximity depending on the selected acting position, and support a high degree of immersion of the audience into the dramatic action.