基于综合相量的电力系统振荡频率实时测量

提出了一种基于综合相量幅值和相位变化规律实时测量电力系统振荡中振荡频率及瞬时频率的算法,利用三相电流经相应变换获得综合相量。算法经过严格的数学推导,没有近似处理。理想情况下只需要两个采样间隔即可以完成频率测量。仿真计算结果表明,频率测量结果有较高精度。算法对于改善保护及电力系统安全自动装置在振荡中的性能具有实用性。

三相电磁量的综合相量在abc和dq0坐标系的表示

介绍了三相电磁量的综合相量在abc和dq0坐标系的公式 ,分析了各公式的使用条件 。

35 kV线路单相断线故障实例分析及实用判据

针对一起35 kV线路单相断线故障实例,利用对称分量法和综合相量法,对电源端35 kV母线及连接Yd11型变压器的负荷端的35 kV、10 kV母线电压异常变化情况进行理论分析,分析结果与现场实际情况一致。提出一种基于电压异常变化特征和SCADA系统接地信号的实用性判据,有助于调控运行人员对类似故障进行分析判断。

Age-related symptom and life quality changes in women with irritable bowel syndrome

AIM:To explore age-related changes in symptoms and quality of life(QoL) of women with irritable bowel syndrome(IBS).METHODS:Two-hundred and fifty-four female adult outpatients with IBS attending the Department of Gastroenterology at the First Affiliated Hospital of Nanjing Medical University between January,2008 and October,2008 were approached.Patients with a history of abdominal surgery,mental illness or those who had recently taken psychotropic drugs were excluded.A physician obtained demographic and abdominal symptom data.All patients were asked to complete the Zung Self-Rated Anxiety and Depression Scale(SDS/SAS) and the IBS-specific QoL questionnaire.The patients were divided into six groups according to age,in 10-year increments:18-27 years,28-37 years,38-47 years,48-57 years,58-67 years and 68-75 years(maximum 75 years).Age-related differences of abdominal pain or discomfort were analyzed using ranksum tests.Differences in SDS/SAS and IBS-QoL scores between age groups were analyzed using one-way analysis of variance.Pearson's correlations evaluated potential associations between IBS symptoms,psychological factors and QoL in each age group.RESULTS:There were no differences in the distribution of IBS subtypes between age groups(χ2 = 20.516,P = 0.153).Differences in the severity of abdominal pain/discomfort with age were statistically significant(χ2 = 25.638,P < 0.001);patients aged 48-57 years,58-67 years or 68-75 years had milder abdominal pain/discomfort than those in the younger age groups.The severity of anxiety or depressive symptoms did not differ between age groups(SDS,χ2 = 390.845,P = 0.110;SAS,χ 2 = 360.071,P = 0.220).Differences of IBSQoL scores were statistically significant between age groups(χ2 = 1098.458,P = 0.011).The scores of patients in the 48-57-year group were lower than those in the 18-27-year and 28-37-year groups(48-57-year group vs 18-27-year group,74.88 ± 8.76 vs 79.76 ± 8.63,P = 0.021;48-57-year group vs 28-37-year group,74.88 ± 8.76 vs 79.04 ± 8.32,P = 0.014).The scores in the 68-75-year group were lower than those in the 18-27-year,28-37-year and 38-47-year groups(68-75-year group vs 18-27-year group,71.98 ± 9.83 vs 79.76 ± 8.63,P = 0.003;68-75-year group vs 28-37-year group,71.98 ± 9.83 vs 79.04 ± 8.32,P = 0.002;68-75-year group vs 38-47-year group,71.98 ± 9.83 vs 76.44 ± 8.15,P = 0.039).Anxiety and depression were negatively correlated with QoL in all age groups(SDS and QoL:18-27-year group,r =-0.562,P = 0.005;28-37-year group,r =-0.540,P < 0.001;38-47-year group,r =-0.775,P < 0.001;48-57-year group,r =-0.445,P = 0.001;58-67-year group,r =-0.692,P < 0.001;68-75-year group,r =-0.732,P < 0.001.SAS and QoL:18-27-year group,r =-0.600,P = 0.002;28-37-year group,r =-0.511,P < 0.001;38-47-year group,r =-0.675,P < 0.001;48-57-year group,r =-0.558,58-67-year group,P = 0.001;r =-0.588,P < 0.001;68-75-year group,r =-0.811,P < 0.001).A negative correlation between abdominal pain severity and QoL was found in patients aged more than 58 years(58-67-year group,r =-0.366,P = 0.017;68-75-year group,r =-0.448,P = 0.048),but not in younger patients(18-27-year group,r = 0.080,P = 0.716;28-37-year group,r =-0.063,P = 0.679;38-47-year group,r =-0.029,P = 0.812;48-57-year group,r =-0.022,P = 0.876).CONCLUSION:Factors affecting QoL should always be treated in IBS,especially emotional problems in young adults.Even mild abdominal pain should be controlled in elderly patients.