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The paper describes the development of insulation structure and enhancement of insulation reliability of 500 kV dc GIS. Considering problems of metallic particles and charge accumulation on spacers, the developed insulation structure of GIS consisted of three regions, i.e. the spacer, particle scavenging and non-levitating regions. Particles could be efficiently scavenged, and the developed GIS withstood all insulation specifications with sufficient margins under the clean and particle-contaminated condition. Now, a long-term site test for one year of the 500 kV dc GIS has been continued since October in 1995.

On-site winding of two helical coils of LHD started at the beginning of 1995, using a numerically controlled winding machine. They are large-scale pool-cooled superconducting coils which are designed to satisfy fully stabilized criterion. The conductor consists of Nb-Ti/Cu strands with a pure aluminium stabilizer and copper sheath. The main demanded values for winding the coils are 2.0 mm and 65 [[micro]meter] for the accuracy of coil and the average gap between layers, respectively. A winding method was established by trial of winding.

A thyristor controlled ground fault current limiting system (TGCL) was proposed to prevent one-line ground fault current rises due to increased capacitance to ground. Basic components of the TGCL are a main ground fault current limiter, which rapidly adjusts a compensating reactor level for the capacitance to ground, and the TGCL's controller. Control is ensured by an in-phase control method for zero-phase sequence voltage and current. The method determines the direction of ground faults and the compensating reactor level. The fast control which can be realized shows the TGCL is a valuable protecting system for high ground fault current distribution systems. Keywords: Current Limiter, Ground Fault, Thyristor Control, Fault Protection, Distribution System.

A fault current limiter with series compensation, which is composed of a compensation capacitor and a limiting reactor in series, is proposed. A solid-state switch connected in parallel with the capacitor controls either the ordinal series compensation or fault current limitation. A feasibility study of the current limiter by simulation analysis is presented and the effectiveness of the current limiter is evaluated from the viewpoints of transient stability improvement and device capacity. The current limiter is a useful protection device for large, high power transmission systems. Keywords: Current Limiter, Series Compensation, Thyristor Control, Fault Protection, System Stability.

To prevent voltage decrease of distribution systems, the principle and fundamental characteristics of a solid-state current limiter using GTO thyristors were investigated. Basic components of the apparatus were a fast solid-state switch and a current limiting impedance of low resistance in parallel with the switch. Experimental results of the test current limiter showed the fault current was limited successfully, regardless of DC component size. The time from detection of fault occurrence to interruption of the fault current by the solid-state switch was 40 microseconds. This time was very short in comparison with that before the fault current reached a large value. Thermal rise of the solid-state switch for conduction was solved by a self-cooling apparatus using a non-combustible cooling liquid. The results indicated that the solid-state current limiter was a valuable protecting device for high fault current distribution systems.

A preventive maintenance system for gas-insulated switchgear (GIS) has been developed, which detects signs of trouble and prevents breakdowns in service. The system constantly monitors UHF signals, which are generated by partial discharges (PDs) and propagate in the GIS, by using couplers built into the apparatus. The PDs are detected at high sensitivity (5pC) and located according to the attenuation of the signals. Then the system injects a different gas into the section where PDs are occurring and improves the dielectric strength. This prevents faults in service and allows remedial actions to be taken with less urgency. By injecting a small quantity (5-10%) of c-C4F8 into the GIS, dielectric strength is raised more than 20%. A preventive maintenance system with a facility to inject a different gas was constructed for a full-scale GIS model. The system detected and located PDs, and automatically injected the different gas to improve the dielectric strength.

Voltage-time characteristics of spacer surfaces for steep-front impulse waves are investigated under a particle-contaminated condition in [SF.sub.6] gas. The characteristics are measured as a function of particle length, particle position and spacer shapes. Flashover voltages monotonically increase in the submicrosecond region as time to flashover is shorter, and are a minimum in the 1 us region. Applicability of the equal voltage-time area criterion for estimating voltage-time characteristics is discussed and the technical meaning of the two parameters used in the estimation is clarified. Moreover, it is demonstrated that an optimized spacer with ribs remarkably improves flashover voltages in the submicrosecond region as well as in the 1 us and power frequency region.

The article presents a study which investigates the antidotal effect of cyclodextrin dimer and ferric porphyrins, which can be used as treatment for cyanide poisoning. The study used trypan blue dye exclusion (TBDE) assay for cell variability determination. Sevoflurane has been used to anesthetize the mice and keep it under spontaneous respiration. Results show that cyclodextrin dimer is more effective to be used as pretreatment for cyanide poisoning compared to hydroxocobalamin (OHCbI).

Traumatic retropharyngeal hematoma is a rare condition and may be lethal in some cases. In patients with this condition, the absence of a vertebral fracture or a major vascular injury is extremely rare. We present the case of a 92-year-old man who hit his forehead by slipping on the floor in his house. He had no symptoms at the time; however, he experienced throat pain and dyspnea at 6 hours after the injury. On arrival, he complained of severe dyspnea; therefore, an emergency endotracheal intubation was performed. A lateral neck roentgenogram after intubation showed dilatation of the retropharyngeal and retrotracheal space and no evidence of a cervical vertebral fracture. Cervical computed tomography (CT) with contrast medium revealed a massive hematoma extending from the retropharyngeal to the superior mediastinal space but no evidence of contrast medium extravasation or a vertebral fracture. However, sagittal magnetic resonance imaging (MRI) revealed an anterior longitudinal ligament (C4-5 levels) injury. We determined that the cause of the hematoma was an anterior longitudinal ligament injury and a minor vascular injury around the injured ligament. Therefore, we recommend that patients with retropharyngeal hematoma undergo sagittal cervical MRI when roentgenography and CT reveal no evidence of injury. [ABSTRACT FROM AUTHOR]