Development of a new adaptive LQG system generator for high‐speed damping control techniques of power system oscillation

With the advent of interconnection of large‐scale electric power systems, many new dynamics power system problems have emerged, which include low‐frequency intersystem oscillations and many others. To date, most major generators in trunk electric power systems in Japan are equipped with supplementary excitation control, commonly referred to as the conventional single and two input PSS. However, low‐frequency oscillations still occur. It is difficult for these conventional PSS to improve the additional damping of power system oscillation, because of the hardware and design of fixed PSS control constants from a one‐machine infinite‐bus model. It has therefore become necessary to develop a new adaptive LQG system generator. This paper explains the development of the new adaptive LQG system and the simulation of low‐frequency and local mode oscillation for this new adaptive LQG system. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(3): 30–40, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10109     

Calcium disodium ethylenediaminetetraacetate-chelated lead as a predictor for subclinical lead neurotoxicity: follow-up study on gun-metal foundry workers

OBJECTIVES: To examine if chelated lead was a more predictive indicator of the subclinical effect of lead on conduction velocities of faster or slower nerve fibers as compared with blood lead (BPb). METHODS: Distribution of conduction velocities (DCV) in large myelinated fibers of the sensory median nerve was measured twice at a 1-year interval in 17 male gun-metal foundry workers with BPb concentrations of 22-59 (mean 40.2) microg/dl and a mobilization yield of lead into urine (MPb) by calcium disodium ethylenediaminetetraacetate of 0.15-2.09 (mean 1.19) mg/24 h for the 1st year and in 20 healthy males (controls). RESULTS: Yearly changes in the conduction velocities of faster fibers were significantly correlated with the corresponding change in MPb (P < 0.05) but not with that in BPb (P > 0.05). In ten workers showing an increase in MPb during the 1-year period (0.44 mg/24 h on average) the conduction velocities of faster fibers were decreased significantly, resulting in the values being significantly lower in all the workers combined than in the controls (P < 0.05). On the other hand, in the remaining workers, who showed a lesser extent of reduction in MPb (0.08 mg/24 h on average), the DCV did not change (P > 0.05). CONCLUSION: Chelated lead might be a more predictive indicator of the effect of lead on the conduction velocities of faster fibers than blood lead.     

Mitogen-activated protein kinase cascade is activated in glomeruli of diabetic rats and glomerular mesangial cells cultured under high glucose conditions

The activation of protein kinase C (PKC) found in diabetic glomeruli and glomerular mesangial cells cultured under high glucose conditions has been proposed to contribute to the development of diabetic nephropathy. However, the abnormalities distal to PKC have not been fully elucidated yet. Herein, we provide the evidence that mitogen-activated protein kinase (MAPK) cascade, an important kinase cascade downstream to PKC and an activator of cytosolic phospholipase A2 (cPLA2) by direct phosphorylation, is activated in glomeruli isolated from streptozotocin-induced diabetic rats. MAPK cascade was also activated in glomerular mesangial cells cultured under high glucose (27.8 mmol/l) conditions for 5 days, and the activation of MAPK cascade was inhibited by treating the cells with calphostin C, an inhibitor of PKC. Furthermore, the activities of cPLA2 also increased in cells cultured under the same conditions and this activation was inhibited by both calphostin C and PD 098059, an inhibitor of MEK (MAPK or extracellular signal-regulated kinase [ERK] kinase). These results indicate that MAPK cascade is activated in glomeruli and mesangial cells under the diabetic state possibly through the activation of PKC. Activated MAPK, in turn, may induce various functional changes of mesangial cells at least through the activation of cPLA2 and contribute to the development of diabetic nephropathy.     

Age-independent constancy of mineral contents in human vertebra and auditory ossicle

To elucidate age-related changes of mineral contents in human bones, element contents of human vertebrae and auditory ossicles were determined by inductively coupled plasma atomic-emission spectrometry. The cervical, thoracic, and lumbar vertebrae were removed from 12 vertebral columns. The mallei of auditory ossicle were removed from 27 cadavers. It was found that average relative contents (RCs) of calcium and phosphorus in cervical, thoracic, and lumbar vertebrae remained almost constant within ages ranging from 46 to 99 y. In addition, it was found that the RCs of calcium and phosphorus in men's and women's mallei remained constant within ages ranging from 40 to 98 yr. These results support the view that there is no significant age-dependent change of mineral contents in human bones.     

Improvement of thermal interruption capability in self‐blast interrupting chamber for new 245‐kV 50‐kA GCB

Current zero measurements are performed for 245 kV‐50 kA‐60 Hz short line fault (L90) interruption tests with a self‐blast interrupting chamber (double‐volume system) which has the interrupting capability up to 245 kV‐50 kA‐50 Hz L90. Lower L90 interruption capability is observed for longer arcing time although very high pressure rise is obtained. It may be caused by higher blowing temperature and lower blowing density for longer arcing time. Interruption criteria and an optimization method of the chamber design are discussed to improve L90 interruption capability with it. The new chambers are designed at 245 kV‐50 kA‐60 Hz to improve gas density in thermal volume for long arcing time. 245 kV‐50 kA‐60 Hz L90 interruptions are performed with the new chamber. The suggested optimization method is an efficient tool for the self‐blast interrupting chamber design although study of computing methods is required to calculate arc conductance around current zero as a direct criterion for L90 interruption capability with higher accuracy. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 9–17, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20743     

Autonomous decentralized voltage profile control of super‐distributed energy system using multi‐agent technology

A super‐distributed energy system is a future energy system in which a large part of its demand is fed by a huge number of distributed generators. At one time some nodes in the super‐distributed energy system behave as load, whereas at other times they behave as generator—the characteristic of each node depends on the customers' decision. In such situation, it is very difficult to regulate the voltage profile over the system due to the complexity of power flows. This paper proposes a novel control method of distributed generators that can achieve autonomous decentralized voltage profile regulation by using multi‐agent technology. The proposed multi‐agent system employs two types of agent: a control agent and a mobile agent. Control agents generate or consume reactive power to regulate the voltage profile of neighboring nodes and mobile agents transmit the information necessary for VQ‐control among the control agents. The proposed control method is tested through numerical simulations. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(4): 43–52, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20484     

Durability of polymeric encapsulation materials in a PMMA/glass concentrator photovoltaic system

The durability of polymeric encapsulation materials was examined using outdoor exposure at the nominal geometric concentration of 500 suns. The results for 36‐month cumulative field deployment are presented for materials including: poly(ethylene‐co‐vinyl acetate), (EVA); polyvinyl butyral (PVB); ionomer; polyethylene/polyoctene copolymer (PO); thermoplastic polyurethane (TPU); poly(dimethylsiloxane) (PDMS); poly(diphenyl dimethyl siloxane) (PDPDMS); and poly(phenyl‐methyl siloxane) (PPMS). Measurements of the field conditions including ambient temperature and ultraviolet (UV) dose were recorded at the test site during the experiment. Measurements for the experiment included optical transmittance (with subsequent analysis of solar‐weighted transmittance, UV cut‐off wavelength, and yellowness index), mass, visual photography, photoelastic imaging, and fluorescence spectroscopy. While the results to date for EVA are presented and discussed, examination here focuses more on the siloxane materials. A specimen recently observed to fail by thermal decomposition is discussed in terms of the implementation of the experiment as well as its fluorescence signature, which was observed to become more pronounced with age. Modulated thermogravimetry (allowing determination of the activation energy of thermal decomposition) was performed on a subset of the siloxanes to quantify the propensity for decomposition at elevated temperatures. Supplemental, Pt‐catalyst‐ and primer‐solutions as well as peroxide‐cured PDMS specimens were examined to assess the source of the luminescence. The results of the study including the change in optical transmittance, observed failure modes, and subsequent analyses of the failure modes are described in the conclusions. Copyright © 2016 John Wiley & Sons, Ltd.