共查询到20条相似文献，搜索用时 359 毫秒
1.
2.
1 10 kV配电网雷击跳闸原因分析1.1绝缘水平影响绝缘水平低是导致10 kV配电线路遭受雷击时发生跳闸事故的主要原因之一,雷击到线路上或者地面时,过电压超过线路的耐雷水平,就会导致雷击跳闸事故的发生。另一方面,10 kV配电线路通常位于城市郊区,南方地区往往杆塔附近存在着水田、水塘等不利因素,输电线路在遭受雷击时,由于水的导电率远大于周围土壤导电率,这些环境上的不利因素使得感应雷过电压变得更加恶劣,增大了跳闸事故发生的概率。 相似文献
3.
<正>近年来,峰峰矿区供电公司不断加大需求侧用电管理,采取阶梯电价、错峰用电等措施,不断增加电网资金投入,强化管理,综合供电服务水平得到进一步提高。公司为加强配网运行管理,把降低配电线路故障跳闸率作为迎峰度夏期间重点工作之一,有效降低配电线路故障跳闸率,确保了配电线路安全稳定运行。用电宣传筑牢安全防线2013年9月,峰峰矿区供电公司开展了《"你用电,我用心"共同营造农村安全用电和谐环境》安全宣传咨询日活动,公司不断加强用户管理,培养用户安全用电的意识,共发放农 相似文献
4.
我地区属边远地区，农电系统共有１０ｋＶ配电线路７５８２．４ｋｍ，其中两线一地配电线路６６５４．１５ｋｍ，占配电线路总数的８７．７％，担负着我地区农电的主要供电任务。但是，由于两线一地线路自身的技术特性，线路一接地就跳闸、存在着跳闸率高，供电可靠性较差的问题。针对这一问题，我们系统分析了近二年来配电线路跳闸的原因，主要是鸟害对两线一地线路安全运行影响较大，其中，１９９６年全区配电线路跳闸１３１３次，鸟害影响３２５次，占跳闸总数的２４．３％；１９９７年全区配电线路跳闸１２８４次，鸟害影响２９６次，占… 相似文献
5.
为有效治理线路跳闸问题,提高供电可靠性,国网江西崇仁县供电公司开出＂六剂良方＂治疗配电线路＂跳闸病＂。（1）加大改造力度,提高10 k V线路安全运行水平。科学布局10 kV线路,对存在问题的线路进行合理的规划, 相似文献
6.
7.
8.
1配电线路雷击断线的过电压1.1配电线路雷击断线过电压的主要原因根据近几年的统计,雷击过电压造成线路绝缘子闪络、导线烧断,从而引起断路器跳闸的事故较多。雷电过电压引起的断线事故较为严重,抢修费工费时,该类断线十分频繁。其主要原因有:1.1.1配电线路绝缘子老化,耐雷水平低是造成断线事故的重要原因。发生断线的线路大多已运行20余年,线路老化,老式绝缘子绝缘水平低下。为了提高线路耐雷水平,一般来说,10kV钢筋混凝土电杆配电线路应采用瓷横担。如采用铁横担,选择P—20T绝缘子来提高线路耐雷水平,降低雷击过电压跳闸率较为有效。如… 相似文献
9.
配电线路作为电力网的终端,担负着配送电能到千家万户的任务,存在着覆盖面积广、输送线路长、跨越地形复杂、设备数量多、设备质量参差不齐等特点。而随着社会经济的发展,客户对安全可靠的供电提出了越来越高的要求。如何确保配电网安全稳定运行,为客户提供持续可靠的供电是供电企业所关心的问题,因此,分析10kV配电线路跳闸的原因并采取行之有效的措施降低配网线路故障跳闸率,减少非计划停电对客户的影响,从而提高供电可靠性十分必要。本文总结了近几年降低潮州市区10kV线路故障跳闸率的方法和经验,对城网地区和农网地区的配网改造和运行管理都有一定的参考价值。 相似文献
10.
工业化发展不断进,在整个发展中对电能需求有更高的要求。电力市场进步在竞争管理的过程中需要了解实际供电情况,供电系统各种设备的配置有了很大程度的改善,但是依然存在很多问题,考虑到配电线路的稳定性和要求等,必须明确10k V配电线路跳闸的影响因素。本次研究中以10k V配电线路跳闸现状为基础,对降低跳闸率的方法进行分析。 相似文献
11.
Stanley Yokwe 《Agricultural Water Management》2009,96(8):1223-1228
This study investigates the productivity and value of water in two smallholder irrigation schemes (Zanyokwe and Thabina) in South Africa. We apply the residual valuation method (RVM), willingness to pay (WTP) and cost-based approaches (CBA) (i.e. accounting costs of operation and maintenance) to evaluate water productivity and values per crop, per farm, and by scheme. In both schemes, water value estimated by the RVM for vegetables (cabbage, tomatoes and butternuts) is greater than water value for dry maize. At the farm and scheme levels, a comparison was made between gross margin per m3 of water, WTP per m3 and accounting cost per m3 to estimate the relative value of water productivity. The active farmers in the Zanyokwe scheme have lower WTP per m3 (R0.03) than the gross margin of output (R0.69). Also, the accounting cost (R0.084) per m3 of water is less than the gross margin. In the Thabina scheme, active farmers are willing to pay (R0.19) per m3 of water. Hence farmers in Thabina are ready to pay as much as three times the proposed costs of O&M (R0.062) per m3 of water used. Both the accounting cost and willingness to pay are less than the gross margin per m3 of water in the Zanyokwe scheme. Our findings indicate that extension and training may be required to improve the productive use of water for those farmers whose returns are insufficient to cover the cost of supply. 相似文献
12.
Baozhong Zhang Shaozhong Kang Fusheng Li Taisheng Du 《Agricultural Water Management》2010,97(11):1898-797
Grapevines are extensively grown in the arid region of China, but little information is available on the diurnal, seasonal and interannual variability of vineyard evapotranspiration (ET). To address this question, two vineyards in the arid region of northwest China were taken as an example to study the variation of ET using Bowen ratio-energy balance method in 2005-2008. Results indicate that the Bowen ratio method provided accurate estimate of vineyard ET as the instrument was correctly installed. Irrigation and rainfall increased daily ET by 38 and 175%, respectively, but frost decreased it by 32%. Daily ET had a maximum value of 1.6-3.5 mm/d at the berry development stage, and a minimum value of 0.8-1.7 mm/d at the early and later stages. The total ET was 226-399 mm over the growing season. The ratio of transpiration to evapotranspiration was 0.52 and the modified crop coefficient (Kcm) was 0.71-0.88 (except 2005) over the whole growing stage. Larger interannual difference of ET and Kcm mainly resulted from the difference of irrigation and rainfall between different years. 相似文献
13.
Effects of salinity on fruit yield and quality of tomato grown in soil-less culture in greenhouses in Mediterranean climatic conditions 总被引：2，自引：0，他引：2
There is increasing pressure to reduce water use and environmental impact associated with open system, soil-less production in simple, plastic greenhouses on the Mediterranean coast. This may force the adoption of re-circulation of nutrient solutions. In south-eastern Spain, irrigation water is mostly from aquifers and has moderate levels of salinity. The adoption of re-circulation using moderately saline water requires detailed information of crop response to salinity, in order to optimise management. The effect of salinity on fruit yield, yield components and fruit quality of tomato grown in soil-less culture in plastic greenhouses in Mediterranean climate conditions was evaluated. Two spring growing periods (experiments 1 and 2) and one long season, autumn to spring growing period (experiment 3) studies were conducted. Two cultivars, ‘Daniela’ (experiment 1) and ‘Boludo’ (experiments 2 and 3), were used. Seven levels of electrical conductivity (EC) in the nutrient solution were compared in experiment 1 (2.5–8.0 dS m−1) and five levels in experiments 2 and 3 (2.5–8.5 dS m−1). Total and marketable yield decreased linearly with increasing salinity above a threshold EC value (ECt). There were only small effects of climate and cultivar on the ECt value for yield. Average threshold EC values for total and marketable fruit yield were, respectively, 3.2 and 3.3 dS m−1. The linear reductions of total and marketable yield with EC above ECt showed significant differences between experiments, the slope varying from 7.2% (autumn to spring period, ‘Boludo’) to 9.9% (spring period, ‘Boludo’) decreases per dS m−1 increase in EC for total yield, and from 8.1% (spring period, ‘Daniela’) to 11.8% (spring period, ‘Boludo’) for marketable yield. The decrease of fresh fruit yield with salinity was mostly due to a linear decrease of the fruit weight of 6.1% per dS m−1 from an ECt of 3.0 dS m−1 for marketable fruits. Reduction in fruit number with salinity made a smaller relative contribution to reduced yield. Blossom-end rot (BER) increased with increasing salinity. There was a higher incidence of BER with spring grown crops, and ‘Boludo’ was more sensitive than ‘Daniela’. Increasing salinity improved various aspects of fruit quality, such as: (i) proportion of ‘Extra’ fruits (high visual quality), (ii) soluble solids content, and (iii) titratable acidity content. However, salinity decreased fruit size, which is a major determinant of price. An economic analysis indicated that the EC threshold value above which the value of fruit production decreased linearly with increasing salinity was 3.3 dS m−1, which was the same as that for marketable yield. In the economic analysis, the value of increased visual fruit quality was offset by reduced yield and smaller fruit size. 相似文献
14.
Northeast Thailand has a semi-humid tropical climate which is characterized by dry and rainy seasons. In order to stabilize crop production, it may be necessary to develop new water resources, such as soil moisture and groundwater, instead of rainfed resources. This is because rainfed agriculture has already been unsuccessfully tried in many areas of this region. In this study, we investigate the soil water content in rainfed fields in Khon Kaen in Northeast Thailand, where rice and sugarcane were planted, over a 1-year period that contained both dry and rainy seasons, and estimate the actual evapotranspiration (ETa) using micrometeorological data. In addition, we assess the water balance from the results of the soil water content investigation and the actual evapotranspiration. Although the soil water content at depths above 0.6 m in both the lower and the sloping fields gradually decreased during the dry season, the soil water content at a depth of 1.0 m was under almost constant wet conditions. Two-dimensional profiles of the soil water content demonstrated that at the end of the dry season, the soil layers below a depth of 0.4 m showed a soil water content of more than 0.10-0.15 m3 m−3, thus suggesting that water was supplied to the sugarcane from those layers. The range in ETa rates was almost the same as that in the previous study. The average ETa rates were 3.7 mm d−1 for the lower field and 4.2 mm d−1 for the sloping field. In the dry season, an upward water flow of 373 mm (equivalent to a flux of 1.9 mm d−1) was estimated from outside the profile. The source of this upward water flow was the sandy clay (SC) layer below a depth of 1 m. It was this soil water supply from the SC layer that allowed the sugarcane to grow without irrigation. 相似文献
15.
Excess phosphorus (P) in freshwater systems has been associated with eutrophication in agro-ecosystems of the US Midwest and elsewhere. A better understanding of processes regulating both soluble reactive phosphorus (SRP) and total phosphorus (TP) exports to tile-drains is therefore critical to minimize P losses to streams while maintaining crop yield. This paper investigates SRP and TP dynamics at a high temporal resolution during four spring storms in two tile-drains in the US Midwest. Depending on the storm, median concentrations varied between 0.006-0.025 mg/L for SRP and 0.057-0.176 mg/L for TP. For large storms (>6 cm bulk precipitation), for which macropore flow represented between 43 and 50% of total tile-drain flow, SRP transport to tile-drains was primarily regulated by macropore flow. For smaller tile-flow generating events (<3 cm bulk precipitation), for which macropore flow only accounted for 11-17% of total tile-drain flow, SRP transport was primarily regulated by matrix flow. Total P transport to tile-drains was primarily regulated by macropore flow regardless of the storm. Soluble reactive P (0.01-1.83 mg m−2/storm) and TP (0.10-8.64 mg m−2/storm) export rates were extremely variable and positively significantly correlated to both mean discharge and bulk precipitation. Soluble reactive P accounted for 9.9-15.5% of TP fluxes for small tile-flow generating events (<3 cm bulk precipitation) and for 16.2-22.0% of TP fluxes for large precipitation events (>6 cm bulk precipitation). Although significant variations in tile-flow response to precipitation were observed, no significant differences in SRP and TP concentrations were observed between adjacent tile-drains. Results stress the dominance of particulate P and the importance of macropore flow in P transport to tile-drains in the US Midwest. Although only spring storms are investigated, this study brings critical insight into P dynamics in tile-drains at a critical time of the year for water quality management. 相似文献
16.
Grapevines are extensively grown in the semiarid and arid regions, but little information is available on the variability of energy partitioning and resistance parameters for the vineyard. To address this question, an eddy covariance system was applied to measure energy balance over a vineyard in northwest China during 2005-2006. Result indicated that 2-year average Bowen ratio (β) of vineyard was 1.0, canopy resistance (rc) 289.3 s m−1, aerodynamic resistance (ra) 9.7 s m−1 and climatological resistance (ri) 117 s m−1. This implied that the annual energy was split almost equally between sensible heat and latent heat. Compared to the corresponding values in other ecosystems reported by Wilson et al. [Wilson, K.B., Baldocchi, D.D., Aubinet, M., Berbigier, P., Bernhofer, C., Dolman, H., Falge, E., Field, C., Goldstein, A., Granier, A., Grelle, A., Halldor, T., Hollinger, D., Katul, G., Law, B.E., Lindroth, A., Meyers, T., Moncrieff, J., Monson, R., Oechel, W., Tenhunen, J., Valentini, R., Verma, S., Vesala, T., Wofsy, S., 2002. Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites. Water Resource Research 38, 1294-1305.], the vineyard had a higher β, rc and ri than deciduous forests, corn and soybean, and grassland. Such difference was mainly attributed to (1) serious water stress in 2005, which resulted in a greater rc up to 364.4 s m−1; (2) sparse canopy with row spacing of 2.9 m and plant spacing of 1.8 m; (3) warm-dry climate and high attitude (1581 m) along with higher ri and lower psychrometer (54 Pa K−1) in the arid region of northwest China. These characters of vineyard revealed varying process of energy partitioning and surface resistance, and provided a scientific basis in understanding and modeling water and energy balance for the vineyard in the semiarid and arid regions. 相似文献
17.
This paper evaluates the performance of the first drip irrigation scheme in commercial tea production in Tanzania with a view
to making recommendations for improved management and providing data for investment decisions. Uniformity, efficiency and
adequacy of irrigation were calculated and the scheduling of irrigation water was reviewed. Operators were interviewed to
highlight the main benefits and problems of the system. Investment and recurrent costs of drip and overhead sprinkler systems
were quantified and compared. Root development was assessed qualitatively using excavation pits. Irrigation uniformity DU and efficiency ranged between 88 and 95% in the 10 out of 14 irrigation blocks where endline pressures were at least 0.5
bars, and between 77 and 89% in the four blocks were endline pressure was less than 0.5 bars. Scheduling drip irrigation using
tensiometers offered potential water savings of 26% in comparison to a water balance schedule, but these are not currently
realised. Gross marginal income was very sensitive to tea price and yield. Economically optimal fertilizer rates vary in dependence
of tea price and yield and appear to be lower than the current level of 300 kg N ha−1. The higher costs under drip, compared to overhead sprinklers, were mainly for purchase and installation and fertilizer.
The costs of labour for applying water and fertilizer were reduced by nearly 50%. At average 2002 tea prices of 1.31 US$ kg−1, drip irrigation would improve the grower’s gross margin if an additional yield of at least 411 kg ha−1 was achieved. The main threats to drip system performance are discussed. Future research efforts should aim at establishing
the yield response of tea to water and fertilizer under drip irrigation. 相似文献
18.
Talel Stambouli Antonio Martínez-Cob José Maria Faci Terry Howell Nery Zapata 《Irrigation Science》2013,31(5):1075-1089
Gross sprinkler evaporation losses (SELg) can be large and decrease irrigation application efficiency. However, it is not universally established how much of the SELg contributes to decrease the crop evapotranspiration during the sprinkler irrigation and how much are the net sprinkler losses (SELn). The components of SEL were the wind drift and evaporation losses (WDEL) and the water intercepted by the crop (IL). The gross WDEL (WDELg) and evapotranspiration (ET) were measured simultaneously in two alfalfa (Medicago sativa L.) plots, one being irrigated (moist, MT) and the other one not being irrigated (dry, DT). Catch can measurements, mass gains, and losses in the lysimeters and micrometeorological measurements were performed to establish net WDEL (WDELn) during the irrigation and net IL (ILn) after the irrigation as the difference between ETMT and ETDT. Also, equations to estimate ILn and net sprinkler evaporation losses (SELn) were developed. ILn was strongly related to vapor pressure deficit (VPD). SELn were 8.3 % of the total applied water. During daytime irrigations, SELn was 9.8 % of the irrigation water and slightly less than WDELg (10.9 %). During nighttime irrigations, SELn were slightly greater than WDELg (5.4 and 3.7 %, respectively). SELn was mainly a function of wind speed. 相似文献
19.
Applying high rates of nitrogen (N) fertilizer to crops has two major disadvantages: (1) the low N fertilizer use efficiency and (2) the loss of N by leaching, which may cause groundwater nitrate (NO3−) pollution, especially in humid areas.The objectives of this study were to adjust and validate the LEACH-W model simulations with data observed in the field; to quantify nitrate concentrations in the soil solution; to estimate N loss by leaching; and to determine the moments during the year when greatest nitrate transport events occur beyond the rooting profile.A randomized complete block design with four replications was established on a typic Argiudoll. Crop fertilization treatments consisted of three N rates (0, 100, and 200 kg N ha−1) using urea and ammonium nitrate solution (UAN) as the N source. Corn (Zea mays L.) was planted and ceramic soil-water suction samplers were installed to depths of 1, 1.5 and 2 m. Drainage was estimated by the LEACH-W model, which adjusted very well the actual volume of water in the soil profile. Nitrogen losses were statistically analyzed as repeated measure data, using the PROC MIXED procedure.Losses of nitrate-nitrogen (NO3−-N) during the study increased as the rate of N applied increased. At all depths studied, statistically significant higher values were found for 200 N compared to 100 N and 0 N, and for 100 N compared to 0 N (p < 0.001).The greatest NO3−-N losses through leaching occurred during crop growth. Significant differences (p < 0.05) were found between cropping and fallow in the three treatments and depths studied for seasons 4 and 5; these two seasons produced the highest drainage volumes at all depths. 相似文献
20.
《Agricultural Water Management》1998,38(1):45-57
In rainfed rice ecosystem, conservation of rainwater to maximum extent can reduce the supplemental irrigation water requirement of the crop and drainage need of the catchment. The results of 3 years of experimental study on the above stated aspects in diked rice fields with various weir heights (6–30 cm at an interval of 4 cm) revealed that about 56.75% and 99.5% of the rainfall can be stored in 6 and 30 cm weir height plots, respectively. Sediment losses of 347.8 kg/ha and 3.3 kg/ha have been recorded in runoff water coming out of 6 cm and 30 cm weir height plots, respectively in a cropping season. Similarly, total Kjeldahl nitrogen (TKN) loss in runoff water from rice field ranged from 4.23 kg/ha (6 cm weir height plots) to 0.17 kg/ha (26 cm weir height plots) and available potassium loss ranged from 2.20 kg/ha (6 cm weir height plots) to 0.04 kg/ha (30 cm weir height plots). Conservation of rainwater in rice fields with various weir heights could not create any significant impact on grain yield differences, leaf area index and other biometric characters. Irrigation requirement of 18 cm and above weir height plots was found to be half of the requirement of 6 cm weir height plots. Keeping in view the aspects of conserving rainwater, sediment and nutrient and minimizing irrigation requirement, 22–26 cm of dike height is considered to be suitable for rice fields of Bhubaneswar region. 相似文献