Uprating of overhead lines

This thesis establishes a rigorous procedure for overhead line uprating with guidance for calculating the increase in voltage rating that may be achieved for given configurations. It initially investigates different technical issues and conventional methods of voltage uprating of overhead transmission lines. Various issues such as clearance, insulation, pollution, transient overvoltages, surge arresters and its combinations were studied for optimised insulation coordination of voltage uprated transmission systems with reference to international standard IEC 60071 and British standard BSEN 50341. It then considers a case of existing 275kV line in 'L3' structures to analyse these issues and propose appropriate process for its possible uprating to 400kV system. In this investigation, overhead line uprating techniques used by different utilities around the world, as published in the literature were analysed. It was found that, the decision to uprate overhead lines is influenced by technical, institutional and financial issues. In this thesis, issues such as conductor air clearance, insulation electrical strength and overvoltages are investigated and taken into account to develop an appropriate methodology. For uprating overhead lines, an exemplar case study of uprating an L3, 275kV line to 400kV was used, introducing minimum structural changes to the tower. The selection of the L3 tower is made on the basis that it is not readily upratable to 400kV due to restricted air clearances it offers. This work has demonstrated that the voltage uprating of overhead transmission lines is possible with minimal modification to the existing line. In this case, the phase-to-earth clearance was found to be the critical factor which determines the level to which the voltage level of the line can be increased. Computations of overvoltages due to switching and lightning phenomena were conducted to estimate overvoltage levels and optimise the protection scheme required to minimise the required minimum electrical clearances. Employing gapless metal-oxide line surge arresters were proposed to be the most effective solution to control the overvoltages, thereby reducing the minimum phase-to-earth clearance requirements. This solution is preferred to modifying the tower structure in order to achieve the required clearance for 400kV system. The study of lightning and switching surge performances along the line under different arrester configurations was carried out so that the appropriate surge arrester configuration could be selected to maintain overvoltage levels within the targeted withstand level for the line. The extensive transient simulations performed in this work identified that, for a double circuit overhead transmission line as used on the UK system, the top-most phase conductors are prone to shielding failure lightning strikes whilst the bottom-most phase conductors are likely to be subjected to backflashover surges for the case of high tower footing resistance. The assessment of electric and magnetic field profiles of a 275kV line uprated to 400kV was computed. It showed that, the field intensities of voltage uprated lines are within the limits adopted by national and international standards and requires no additional wayleave for uprating.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Uprating of overhead lines

This thesis establishes a rigorous procedure for overhead line uprating with guidance for calculating the increase in voltage rating that may be achieved for given configurations. It initially investigates different technical issues and conventional methods of voltage uprating of overhead transmission lines. Various issues such as clearance, insulation, pollution, transient overvoltages, surge arresters and its combinations were studied for optimised insulation coordination of voltage uprated transmission systems with reference to international standard IEC 60071 and British standard BSEN 50341. It then considers a case of existing 275kV line in 'L3' structures to analyse these issues and propose appropriate process for its possible uprating to 400kV system. In this investigation, overhead line uprating techniques used by different utilities around the world, as published in the literature were analysed. It was found that, the decision to uprate overhead lines is influenced by technical, institutional and financial issues. In this thesis, issues such as conductor air clearance, insulation electrical strength and overvoltages are investigated and taken into account to develop an appropriate methodology. For uprating overhead lines, an exemplar case study of uprating an L3, 275kV line to 400kV was used, introducing minimum structural changes to the tower. The selection of the L3 tower is made on the basis that it is not readily upratable to 400kV due to restricted air clearances it offers. This work has demonstrated that the voltage uprating of overhead transmission lines is possible with minimal modification to the existing line. In this case, the phase-to-earth clearance was found to be the critical factor which determines the level to which the voltage level of the line can be increased. Computations of overvoltages due to switching and lightning phenomena were conducted to estimate overvoltage levels and optimise the protection scheme required to minimise the required minimum electrical clearances. Employing gapless metal-oxide line surge arresters were proposed to be the most effective solution to control the overvoltages, thereby reducing the minimum phase-to-earth clearance requirements. This solution is preferred to modifying the tower structure in order to achieve the required clearance for 400kV system. The study of lightning and switching surge performances along the line under different arrester configurations was carried out so that the appropriate surge arrester configuration could be selected to maintain overvoltage levels within the targeted withstand level for the line. The extensive transient simulations performed in this work identified that, for a double circuit overhead transmission line as used on the UK system, the top-most phase conductors are prone to shielding failure lightning strikes whilst the bottom-most phase conductors are likely to be subjected to backflashover surges for the case of high tower footing resistance. The assessment of electric and magnetic field profiles of a 275kV line uprated to 400kV was computed. It showed that, the field intensities of voltage uprated lines are within the limits adopted by national and international standards and requires no additional wayleave for uprating

Effects of different combinations of poultry manure and urea on growth, yield and economics of garlic (Allium sativum L.)

A field experiment was carried out in garlic (Allium sativum L.) in Randomized Complete Block Design (RCBD) with four replications and five treatments in horticulture farm of Agriculture and Forestry University, Chitwan, Nepal to find out the efficacy of different combination of poultry manure and Urea as nitrogen fertilizers in its yield and yield attributes. The five treatments used for experiment were designed altering the recommended nitrogen dose through different sources i.e. (T1) 100% Urea, (T2) 7% Urea and 25% poultry manure, (T3) 50% Urea and 50% poultry manure, (T4) 25% Urea and 75% poultry manure and (T5) 100% poultry manure. The data regarding to the plant height, number of cloves, diameter of bulbs and fresh bulb weight were taken. In case of plant height, non-significant result was found between various treatments. The number of cloves was found highest in T5 (24.69±1.30), the diameter of bulb was found highest in T2 (3.93±0.39 cm), fresh bulb weight was found highest in T2 (14.32±0.39 gm) and total bulb yield was found highest in T2 (7.16±0.19 t/ha) which were significant at 5 % level of significance. The total bulb yield was found positively correlated (r=0.53) with diameter of bulb at 1 % level of significance. The benefit cost (B/C) ratio was found highest in T2 (1.54) and lowest in T3 (1.28). So 75% Urea and 25 % Poultry Manure stood one of the best combinations of nitrogen fertilizers providing higher economic yields

A Comprehensive Assessment of Apple Production in Jumla District, Nepal: Status, Economics, Marketing and Challenges

Apple production is a vital sector of agriculture in Nepal, significantly impacting local livelihoods and the regional economy. This study, conducted in Jumla District, Nepal, from January to July 2022, aims to comprehensively assess apple production, including its existing conditions, economic implications, marketing and challenges. The research hypothesizes that while apple production in Jumla District contributes significantly to the local economy, it faces challenges related to pest and disease management, marketing, and adoption of modern practices. Using Statistical Package for Social Science (SPSS), descriptive statistics were computed based on data collected from a sample of 80 respondents selected through simple random sampling. The result revealed that agriculture constituted the primary source of income for 73.75% of the population, with an average landholding size of 0.3428 ha and an apple-growing land area of 0.3164 ha. Income from apple production, along with vegetables and fruits, was a major income source. The average annual sales of apple production were 7.291 t/ha. Labor costs accounted for 45.67% of the total cost of apple production, with an average total production cost of NPR 238,097.2 and average gross returns of NPR 485,500. Apple productivity was 9.71 t/ha, demonstrating its economic viability with net returns of NPR 247,402.80 per ha and benefit cost ratio of 2.039. However, the study found that farm produce only sufficed for 6-9 months, with pest and disease incidence and marketing issues as major challenges. Interventions should address pest and disease management, marketing strategies, and modern practices adoption to enhance sustainable and profitable apple production in Jumla. Efforts to extend farm produce sufficiency should also be explored, highlighting apple production's potential and the need for targeted support to overcome challenges and foster sector development

Detection of Methicillin Resistant Staphylococcus aureus and Determination of Minimum Inhibitory Concentration of Vancomycin for Staphylococcus aureus Isolated from Pus/Wound Swab Samples of the Patients Attending a Tertiary Care Hospital in Kathmandu, Ne

The present study was conducted to evaluate the performance of cefoxitin disc diffusion method and oxacillin broth microdilution method for detection of methicillin resistant S. aureus (MRSA), taking presence of mecA gene as reference. In addition, inducible clindamycin resistance and beta-lactamase production were studied and minimum inhibitory concentration (MIC) of vancomycin for S. aureus isolates was determined. A total of 711 nonrepeated pus/wound swab samples from different anatomic locations were included in the study. The Staphylococcus aureus was identified on the basis of colony morphology, Gram's stain, and biochemical tests. A total of 110 (15.47%) S. aureus isolates were recovered, of which 39 (35.50%) isolates were identified as MRSA by cefoxitin disc diffusion method. By oxacillin broth microdilution method, 31.82% of the Staphylococcus aureus isolates were found to be MRSA. However, mecA gene was present in only 29.1% of the isolates. Further, beta-lactamase production was observed in 71.82% of the isolates, while inducible clindamycin resistance was found in 10% of S. aureus isolates. The MIC value of vancomycin for S. aureus ranged from 0.016 g/mL to 1 g/mL. On the basis of the absolute sensitivity (100%), both phenotypic methods could be employed for routine diagnosis of MRSA in clinical microbiology laboratory; however cefoxitin disc diffusion could be preferred over MIC method considering time and labour factor

Визначення деяких закономірностей функціонування гідроенергетичних компонентів для правильної експлуатації ГЕС Хамелія в Непалі

The main objective of the research study is to identify the status and analyze the problems in Chameliya hydropower plants in Nepal. In this paper, the hydropower has been studied to identify some regularities of hydropower components on proper operation and generation through primary and secondary data. Further, it been analyzed by bottlenecking through mechanical components testing for the detail study to find the actual problems. Hydropower contributes about 86 % of total internal generation to available energy in Nepal with 93 % of people having access to electricity through the national grid. Small hydropower plants (less than 30 MW) are 90 % of the installed plants contributing the major electricity demands of nearly 50 % in the country. Though hydropower is one of the major export commodities in the past few years, it still has deficits in the dry season. Chameliya hydropower plant, 30 MW situated in the far-western part of Nepal, generates 670 MWh of energy in the wet season and which declines to 384 MWh in the dry season. Even though the plant does not have the problem of much erosion and has a sufficient flow in the dry season, the generation value is still below the design. The issue of variation in shaft speed, misalignment of shaft bearing integrity and ultimately friction due to vibration, rises the temperature beyond the limit in the bearing Babbitt material result for failure in the plant with problematic shutdown. Thus, this research primarily focuses on the problem analysis in hydropower plants, concluding with the result that the developing countries need to have more focus on regular preventive maintenance and also schedule large maintenance on mechanical components like shafts, bearings, turbine etc. to avoid bigger damage in the long run. Hence, the study also suggests that mechanical failure in a hydropower is mostly common and therefore, a robust mechanical structure along with high safety factor components need to be encouraged where the possibilities of regular maintenance and smooth operation are reduced.Основна мета дослідження полягає в тому, щоб визначити стан і проаналізувати проблеми гідроелектростанцій Chameliya в Непалі. У цьому документі наведено результати досліджень, спрямованих на виявлення деяких закономірностей компонентів гідроенергетики щодо належної роботи та виробництва за допомогою первинних і вторинних даних. Крім того, проаналізовано функціонування шляхом тестування механічних компонентів для детального вивчення для виявлення фактичних проблем. Гідроенергетика забезпечує близько 86 % загальної внутрішньої генерації наявної енергії в Непалі, при цьому 93 % людей мають доступ до електроенергії через національну мережу. Малі гідроелектростанції (потужністю менше 30 МВт) складають 90 % встановлених станцій, що забезпечують майже 50 % основних потреб країни в електроенергії. Хоча гідроенергетика є одним із основних експортних товарів за останні кілька років, вона все ще має дефіцит у сухий сезон. ГЕС Chameliya потужністю 30 МВт, розташована в крайньо-західній частині Непалу, виробляє 670 МВт-год енергії в сезон дощів і знижується до 384 МВт-год в сухий сезон. Незважаючи на те, що станція не має проблеми значної ерозії та має достатній потік у сухий сезон, значення генерації все ще нижче за проектне. Проблема зміни швидкості валу, порушення цілісності підшипника валу та, зрештою, тертя через вібрацію, підвищує температуру понад лімітовану у бабітовому матеріалі підшипника, що призводить до поломки установки з проблемною зупинкою. Таким чином, це дослідження в першу чергу зосереджено на аналізі проблем на гідроелектростанціях, в результаті чого країни, що розвиваються, повинні приділяти більше уваги регулярному профілактичному технічному обслуговуванню, а також планувати масштабне технічне обслуговування механічних компонентів, таких як вали, підшипники, турбіна тощо, щоб уникнути більшого пошкодження в довгостроковій перспективі. Таким чином, дослідження також припускає, що механічні збої в гідроелектростанціях є здебільшого поширеним явищем, і тому необхідно заохочувати надійну механічну конструкцію разом із компонентами з високим коефіцієнтом безпеки, де можливості регулярного технічного обслуговування та безперебійної роботи зменшуютьс

Effect of different fermentation containers on the quality of gundruk

Gundruk, a typical indigenous vegetable product of Nepal was prepared from leaves of mustard (Brassica juncea) and cabbage (Brassica oleracea capitata) in different fermentation containers viz. glass jar, wooden box, earthenware pots and plastic jars which were evaluated sensorially and analyzed chemically. Sensory analysis revealed higher acceptability for gundruk prepared in glass jar compared to others. The moisture content, crude fiber, ash, calcium and iron contents on dry basis were found to be 7.92%, 14.65 g/100g, 0.68 g/100g, 2253 mg/100g and 86.4 mg/100g respectively for gundruk prepared in glass container. The optimum acidity and pH for gundruk prepared in glass was found to be 1.0% (as lactic acid) and 3.9 respectively on 9th day of fermentation

Prediction of Difficult Airway Among Patients Requiring Endotracheal Intubation in a Tertiary Care Hospital in Eastern Nepal

Introduction: Unanticipated difficult intubation is an undesirable situation. Various bedside screening tests are routinely performed for predicting difficult airway. Although considered a surrogate indicator, difficult laryngoscopy is not the exact measure of intubation difficulty. We aimed to determine the best screening test for predicting difficult laryngoscopy and the association between difficult laryngoscopic view and difficult intubation. Methods: This prospective, observational study involved 314, ASA I/II adult patients requiring endotracheal intubation for various routine surgical procedures. Sternomental distance 3 attempts for insertion of the tracheal tube was defined as ‘difficult intubation’. The association between difficult laryngoscopic view and difficult intubation was determined. Results: The sensitivity of the modified Mallampati class for predicting difficult laryngoscopy was highest (83%). Twelve (3.8%) patients had grade III laryngoscopic view and none had a grade of IV. Intubation was difficult in seven (2.2%) patients. Majority of patients (4 of 7) with difficult intubation had difficult laryngoscopic view (p<0.001). Conclusions: Modified Mallampati test was better for predicting difficult laryngoscopy compared to other bedside screeing tests. Difficult laryngoscopy could significantly predict difficult intubation in our patients.   Keywords: Airway evaluation; difficult intubation; difficult laryngoscopy; modified Mallampati class; Nepalese patients; sensitivity