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Recent developments in electrical networks can increase the probability of out-of-phase switching and dielectric stresses being applied to open circuit-breakers, due to asynchronous systems at both sides. This report presents a systematic study of TRV-stresses associated with generator separation and system separation. TRV peak values are higher than required in the Standards, even for relatively small out-of-phase angles (75º to 90º), and the dielectric stresses are high with respect to the shortduration power frequency withstand voltages across a circuit-breaker open contacts, especially taking into consideration the external insulation under pollution and ageing processes. To the opinion of the authors, the Standards should be revised to give users clear and adequate guidance on the assessment and specification of TRV-values and dielectric withstand requirements under out-of-phase conditions.

Double circuit flashovers may cause very severe system disturbances when taking place on some critical double-circuit lines of an electrical network. Line arresters offer an efficient solution to protect these specific lines against double circuit outages due to lightning. This paper will study, on a double-circuit 400-kV line, the protection provided by line arresters against double circuit outages due to lightning. The efficiency of several configurations of line arresters will be compared. For that purpose, the double-circuit lightning flashover rates of the line with and without line arresters will be calculated using a newly developed software which includes a three-dimensional electro-geometric model and is able to take into account the random nature of lightning. This software automatically launches EMTP-RV (restructured version of EMTP) for analyzing fast front overvoltages impressed on line insulation. The energy stressing the line arresters will also be calculated in order to evaluate the risk of failure of the line arresters due to excess energy absorption. Furthermore, the effects of several other parameters such as the tower footing resistances, the lightning withstand voltages of insulator strings as well as the protective levels of line arresters will also be investigated.

Introduction Urethritis is a common urinary tract infection, in which urethritis due to sexually transmitted infection accounts for a large proportion, especially among sexually active men. The most common causes include gonorrhea and chlamydia. Aim To evaluate the prevalence and combination of gonorrhea and chlamydia in patients with urethritis and treatment outcome. Material and Methods A retrospective study was caried out on all patients with urethritis due to gonorrhea and/or chlamydia at the Center for Andrology and Sexual Medicine (Vietnam-Germany University Hanoi, Vietnam) from January 2021 to March 2021. The patient's urethritis was confirmed by culture and Polymerase Chain Reaction (PCR) testing of fluid from the patient's penis. Patient data were collected and analyzed. Main Outcome Measure The number of urethritis patients were caused by gonorrhea and/or chlamydia were collected during 3 months is 54, the combination of two bacteria was 15% and overall treatment results were good. Results The mean age of patients was 29.56 ± 6.7 (18-54) years old. There were 17/54 (31%) patients with simple gonococcal infection, 29/54 (54%) patients were diagnosed with urethritis solely due to chlamydia, 8/54 (15%) patients had urethritis due to both gonorrhea and chlamydia. Of the 25 patients with gonococcal urethritis (mono and chlamydia co-infection): 18/25 patients (72%) were culture positive, while 7 patients (28%) were positive with gonorrhea by PCR. Antibiogram results of 18 patients diagnosed with gonorrhea showed that 18/18 patients were sensitive to spectinomycin, followed by cefoxitin (15/18 patients - accounting for 83.3%), cefotaxime (12/18 patients - accounting for 66.7%) and ceftriaxone (11 out of 18 patients -61.1%). All patients diagnosed with gonococcal urethritis alone or co-infection with chlamydia recovered after the treatment. One of 29 patients with chlamydial urethritis remained symptomatic after completion of the treatment and was tested positive for chlamydia by PCR; while 28 of 29 patients showed good results. Conclusion The physician should note the presence of gonorrhea and/or chlamydia and their combination in the diagnosis of urethritis. People who are diagnosed with this disease need to be treated early with the right antibiotics for a good outcome. Disclosure Work supported by industry: no.

To examine the sensitivity to geomagnetically induced currents (GIC) of the Hydro-Quebec 735 kV power system, model calculations were made of the GIC produced by uniform electric fields directed northwards (azimuth of 0/spl deg/) and with azimuths increasing in 15/spl deg/ increments. The results show that the maximum GIC was produced in the system for an electric field bearing of 15/spl deg/. In addition the model results allow the variation of GIC amplitude with electric field direction to be examined for individual substations. Maximum GIC occurred at substations at the ends of a long transmission line when the electric field was aligned with the transmission line. >

Double circuit flashovers may cause very severe system disturbances when taking place on some critical double-circuit lines of an electrical network. Line arresters offer an efficient solution to protect these specific lines against double circuit outages due to lightning. This paper will study, on a double-circuit 400-kV line, the protection provided by line arresters against double circuit outages due to lightning. The efficiency of several configurations of line arresters will be compared. For that purpose, the double-circuit lightning flashover rates of the line with and without line arresters will be calculated using a newly developed software which includes a three-dimensional electro-geometric model and is able to take into account the random nature of lightning. This software automatically launches EMTP-RV (restructured version of EMTP) for analyzing fast front overvoltages impressed on line insulation. The energy stressing the line arresters will also be calculated in order to evaluate the risk of failure of the line arresters due to excess energy absorption. Furthermore, the effects of several other parameters such as the tower footing resistances, the lightning withstand voltages of insulator strings as well as the protective levels of line arresters will also be investigated.

Recent developments in electrical networks can increase the probability of out-of-phase switching and dielectric stresses being applied to open circuit-breakers, due to asynchronous systems at both sides. This report presents a systematic study of TRV-stresses associated with generator separation and system separation. TRV peak values are higher than required in the Standards, even for relatively small out-of-phase angles (75º to 90º), and the dielectric stresses are high with respect to the shortduration power frequency withstand voltages across a circuit-breaker open contacts, especially taking into consideration the external insulation under pollution and ageing processes. To the opinion of the authors, the Standards should be revised to give users clear and adequate guidance on the assessment and specification of TRV-values and dielectric withstand requirements under out-of-phase conditions.

An exclusive insulation coordination study has been conducted for the 500 kV DC cables that will be installed in a tunnel under the Saint Lawrence river. These cables will be part of the Radisson-Nicolet section of the Quebec-New England HVDC line. The authors provide an overview of the studies and the phenomena that will cause decisive overvoltage stresses on the cable insulation. The basic assumptions and the simulations of these phenomena with the Electromagnetic Transients Program (EMTP) are also discussed. Finally, the results of the overvoltage studies and the specified insulation levels for the DC cables are presented. >

CIGRE WG A3.13 is studying the impact of changing network conditions and system requirements on the specification of conventional HV equipment within the scope of SC A3. They see three main developments leading to future networks: the strong increase in distributed generation, the increase in the transmission of bulk power over long distance and the increase in the application of power electronics. The impact of each development is described, conclusions are given or studies going on are highlighted