According to the recent development of electric insulation materials, there has been an increase in demand for an sensitive megohmmeter To meet the above demand, we have developed an electronic megohmmeter (Type RM-211) which, by impressing 1000V DC on an unknown resistor, can directly read its insulation resitance from 5×10⁷Ω up to 2×10¹³Ω with better accuracy, more stability and for simpler operation than any coventional galvanometer device can provied. In this paper, the description has been made on how to stabilize DC Amp. and DC high voltage source as well as how to get an extremely high input impedance of said DC amplifier. Also the upper sensitivity limit of this method has been discussed.

抄録全体を表示

Nowadays in Japan we have several methods to measure insulation resistance of a photovoltaic module string against the earth, i.e., “Short-circuit” method, “Open-circuit” method and “Self-Bias” method. These methods are commonly used but theoretical differences among them are not understood well so far. Therefore, in this report, the methods are reviewed from a theoretical viewpoint by using a simple equivalent circuit model and compared based on outdoor experiment. In, addition, the author introduces estimation equations which enable to obtain the insulation resistance from two different value measured by the “Open-circuit” method.

抄録全体を表示

The adhesive strength of insulation films for fusion reactor is important from the view point in which the durability is improved. In the present study, the adhesive strength of a plasma sprayed alumina insulation film coated on the stainless steel substrate was investigated by using a repeated impact test. The impact tests were performed at 3 kinds of mean impact pressure, 3, 5 and 12 times as large as the yield strength of the substrate, about 200MPa, in 2 surface materials combinations of alumina/alumina and alumina/bear stainless steel. In the alumina/alumina combination, the durability of the alumina films were over 30, 000 cycles at the mean impact pressures of 3 and 5 times, and we confirmed sufficiently high adhesive strength of the alumina film. And the alumina/stainless combination improved the durability of the alumina film by a factor of 2.7. While at the mean impact pressure of 12 times, because the stainless steel substrate gave rise to a plastic strain being 2 orders higher than the allowable strain of the alumina films, the alumina film was fractured by the propagation of cracks.

抄録全体を表示

For safe operation of a photovoltaic generating system, an insulation monitoring function, which can immediately detect deterioration of insulation between photovoltaic module strings and the earth, is indispensable. This function requires accurate measurement, low leakage current and suppression of rising voltage against the earth. In this paper, a new insulation monitoring method of photovoltaic module strings is proposed by the improved existing self-biased method that has an inevitable voltage rise under measurement. In this new method, both terminals of photovoltaic module strings are always connected to the ground with appropriate resistors. Theoretical discussion and experiments for this new method showed precise measurement, and acceptable leakage current under various outdoor conditions. In addition, it was confirmed that this method could sufficiently decrease in the voltage rise compared with the existing self-biased method.

抄録全体を表示

In this paper, aiming at active discussion on electrical shock caused by PV module string/array, several basic measurements concerning this accident were carried out by using actual PV module string/array. As result, following information were obtained: (1) human body current might be affected by not insulation resistance measured by insulation tester but some unknown lower resistance component, (2) human body current is in proportion to the square of series number of PV module, and (3) blocking diode is ineffective for protection of electrical shock.

抄録全体を表示

Regarding the self-bias method which is well known as measuring the insulation resistance of photovoltaic module strings, that measurement circuit may make the voltage against the earth rise to the generating voltage. We considered them using the equivalent circuit model between a photovoltaic module string and the earth from safety in case of constant monitoring the insulation resistance, and experimented. In this paper, we propose an improvement of the measurement method for the development of the insulation monitoring device.

抄録全体を表示

Ferroelectric PZT thick films were deposited on Ni coated SiO/Si substrates by jet printing method. Material powder was commercially used PZT fine particles which had mean diameter of 1.2μm. The shape of deposited films is 5.5mm in width and its thickness can be controlled in the range of several to several tenth um. After heat treatment of maximum temperature of 873K for 1.8ks in air, dielectric constant of 740 and dielectric loss tangent of 0.024 at 1kHz, and dielectric strength of 5MV/m were measured. The defect-free structure of the cross section of thick films was observed by SEM, and the polycrystallized PZT pattern of the surface was characterized by X-ray diffraction. Aerosol jet printing system is expected to utilize as deposition of dielectric thick films.

抄録全体を表示