Computation of Arrester Thermal Stability Zhong Zheng; Boggs, Steven A; Imai, Toshiya ...
IEEE transactions on power delivery,
07/2010, Volume:
25, Issue:
3
Journal Article
Peer reviewed
Full-scale thermal stability type tests on substation class metal oxide arresters are not practical. As a result, standards such as IEC 60099-4 specify the use of a reduced-scale model and define ...test methods which are intended to assure that the reduced-scale model is conservative relative to the full-scale arrester. The authors succeeded in computing the thermal stability of full-scale arresters based on the operating duty arrester type test specified in IEC60099-4 and ANSI in a few hours using transient nonlinear finite element software customized for the purpose. Based on these computations, the cooling mechanism of a polymer arrester and the effect of arrester structure on thermal stability could be evaluated. The authors are continuing this approach with the expectation of achieving more accurate prediction of full-scale arrester stability computationally than can be achieved using reduced-scale models. The present paper contributes to the understanding of appropriate reduced-scale models, their relationship to the thermal stability of full-scale arresters, and how to define the thermal stability of a full-scale arrester.
The Kii-Channel HVDC Link under construction in Japan is equipped with metallic return transfer breakers (MRTBs) in one converter station. A new MRTB for an interrupting current of 3500 A d.c. was ...developed. To interrupt a d.c. current, a method that produces a current zero point by superimposing a self-excited oscillatory current on a d.c. arc current was employed. For this purpose, a LC circuit was coupled in parallel to a SF6 gas circuit breaker. Developing a SF6 gas circuit breaker that has a large arc voltage drop gradient against currents permitted a large oscillatory current to be generated. A modified Mayr-type dynamic arc equation was newly presented. The d.c. interruption limits calculated using this equation agreed with the measured values.
This paper describes the technologies for developing a compact and highly reliable dead-tank gas circuit breaker (GCB) on the basis of extensive data on the behavior of hot gas flow and the ...mechanisms of ground fault under highly inhomogeneous thermal conditions. When predicting the dielectric capability of a GCB during a large current interruption, the temperature and gas density distributions caused by the hot gas must be taken into account in addition to the electrical field imposed across the gas. Hot gas behavior was investigated quantitatively and qualitatively, to provide a basis for determining optimum exhaust tube dimensions which minimize overall circuit breaker dimensions while avoiding ground faults.
We measured transient recovery voltage (TRV) in a 1500 MVA-525 kV/276 kV/63 kV transformer of the three-phase-in-one-tank type. We proved that TRV can be measured by interrupting the current ...generated by discharging a capacitor of low voltage through the transformer. The current was interrupted at its zero point by a diode at a low voltage. To calculate TRV via a computation, we developed a transformer equivalent model composed of a L-C multi-mesh circuit. The TRV waveform computed using the transformer equivalent model we developed agreed well with the measured TRV waveform.
A 52-year-old man admitted for palpitation and exertional dyspnea was found by our internal medicine department to have anemia and sigmoid colon carcinoma. The patient had situs inversus (Kartagener ...syndrome), and preoperative diagnosis of complicated anomalies were right-sided heart, two-lobe lung, multiple spleens, IVC defect and intestinal malrotation. Surgical findings were left-sided liver, right-sided stomach, total situs inversus, and nonrotational intestinal malrotation in which the cecum was on the median. Since sigmoid colon carcinoma inveded the cecum we conducted sigmoidectomy with ileocecal resection. The man was discharged on postoperative day 18. Situs inversus is a rare congenital disease and often has several complicated anomalies. Although this case involved sigmoid colon carcinoma with some complicated anomalies, no severe problems occurred during surgery.
To suppress reignition overvoltages caused when a 500-kV shunt reactor current is interrupted by a 550-kV one-break circuit breaker (CB), a study was carried out on controlled switching. Using a ...full-scale test circuit, reactor current interruption tests were carried out to obtain the relation between opening phase angle and generation of reignition. The results showed that even with the dispersion of CB operations taken into account, there were contact separation points free from high reignition overvoltages. It was also proved that no voltage escalations were caused by reignition and high-frequency arc extinction, and that overvoltages due to current chopping were at a safe level in terms of equipment insulation.
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