This paper describes the method of improving the interfacial region between the insulation and the semiconducting layer by using an additive. This method provides the diffusion layer of an additive at the interface. Several kinds of nonionic surfactant which were various in molecular weight distribution and HLB value were selected as additives.
The additive concentration in the insulation was measured with FT-IR having micro-beam accessory. To investigate the effect of additives on ac and impulse breakdown strengths were measured and additve content profiles in the insulation were quantitatively analyzed.
The dielectric breakdown strength at 1% Weibull breakdown probability is improved about 2.3 times in AC and about 1.2 times in impulse breakdown strength than that of the conventional materials. An additive which improves the ac breakdown strength also improves the impulse breakdown strength.
The concentration profile is affected by the kind of additive. There exists a close correlation between the weight concentration of additives and the breakdown strengths. Both AC and impulse breakdown strengths increase as the weight concentration of additives diffused in the insulation near the interface increases up to about 1%.

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Electrical breakdown and electrical conduction of ethylene copolymers was studied. It was found that the electric strength of ethylene copolymers containing an optimum content of halogen compounds such as Bromo-phenyl and Fluoro-methyl groups was higher than that of LDPE over a wide temperature range from -196 to 90°C and that their conduction currents were suppressed at high electric fields. X-ray induced TSC revealed that halogen comonomers act as carrier traps whose depth was ca. 0.4eV. It is concluded that the introduction of comonomer containing halogen group into polyethylene supresses the electron acceleration due to an increase of the trapping and scattering of the conduction electrons, leading to an increase of electric strength which is determined by the electron avalanche breakdown.

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The electrical properties of ZnO ceramics were studied from their voltage-current characteristics, thermally stimulated current (TSC), and heat-treatment effects.
ZnO ceramic samples with a few mol% of insulating oxide components were prepared. After sintering at 1, 200°C in air, some of them were heat-treated at various temperatures between 450°C and 900°C in air.
In the voltage-current curves, the current varies as a function of applied DC voltage, according to the relation; I=kV^a, where α is the nonlinear exponent. The nonlinear exponent α decreased with the heat-treatment temperature in the low temperature resion, and it became the lowest around 600-750°C. But they almost recovered at 900°C.
Three TSC peaks (designated by P₁, P₂ and P₃ from low temperature side) were observed in the nonheat-treated sample. The sample heat-treated at 600°C and 750°C showed only the P₁ and P₂ peaks, the P₃ peak increased in magnitude with the increase of the biasing temperature T_b, and it shifted toward high temperature side.
These results suggest that the electrical properties of ZnO ceramics will be associated with the phase transition of the Bi₂O₃-rich intergranular by heat-treatment.

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This paper presents an expert system on insulation diagnosis of medium voltage XLPE cables. Many diagnostic methods have been proposed for the deterioration of XLPE cables. However, most methods can not be used to the insulation diagnosis as live-line methods. The authors built the system whose knowledge base includes a live-line diagnostic method. In the system, fuzzy inference is used as an inference engine to reflect the knowledge and experience of experts for their diagnosis under the conditions, and its rules are formed based on their actual knowledge and heuristic experience. Moreover, residual breakdown voltages can be also estimated by the method of the fuzzy inference in the proposed system. Finally, it is shown that the resultant diagnosis of the system agrees well with that of experts.

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It is reported that electrical properties are decreased by bow-tie type water trees in the insulation of cables. Bow-tie trees originate at nuclei (voids, impurities) and grow approximately parallel to the applied electric field. In order to decrease the number of bow-tie trees, it is important to decrease the number of nuclei. However, the size of nuclei in dry-cured XLPE cables are only about 5-20μm, therefore it is difficult to determine the composition of nuclei with an optical microscope. This paper describes the results of the investigation of nuclei by the SEM-XMA and the micro FT-IR. The SEM photomicrographs showed that nuclei could be divided into three types; X (void), Y (substances found in it), Z (amber) with the ratio of Y being about 84%. The substances in Y-nuclei was analyzed with the XMA and the micro FT-IR. The results show that Y-nuclei can be divided further into two types Y_a (71%) and Y_b (13%), and it is clear that the main substances in Y_b-nuclei are impurities (SiO₂, CaCO₃). From our analysis, we are confident that the main sub-stance in Y_a-nuclei is PE. Also, we hypothesized that Y_a-nuclei were produced at weak points in the insulation during the accelerated test.

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BTA (1, 2, 3-benzotriazole) added oil compared with oil without BTA shows following properties.
(1) Resistivity becomes low value
(2) Dielectric loss tangent, tanδ, becomes low value
(3) Absorption coefficient of absorption current becomes low value
Usually, tanδ of the liquid dielectrics is reversely proportional to the resistivity. That is, properties of (1) and (2) are unnatural physically. The reason is due to property of (3).
From experimental results of BTA content dependence of the absorption current, it was found that the absorption current was related to the mobility of the ionic charge carrier, and that the mobility of BTA added oil was lower than that of the oil without BTA. The reason for the slow mobility is considered on existence of the large ionic charge carrier which consists of BTA and original ion in the insulating oil.
Here reports about chance of the existence of the large ionic charge carrier.

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The electrical conductivity of the multi-layer ceramic capacitor was measured at high temperature, and then the electrical conduction mechanism was investigated.
The measurement carried out under constant voltage. The current was found to increase with time, leading to final breakdown. Two peaks appeared at the current-time cureves. It was considered that the peaks originated from the accumulated space charge. The current density was exponentially proportional with the electrical field. The carrier mobility of the electrical conduction was calculated to be the order of 10^-11-10^-12cm²/V•s.
From the rusults, it was indicated that the, ionic conduction-would be dominant in the multi-layerceramic capacitor at high temperature.

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