Utilization of the voltage rate to localization of harmonic sources in a power system
The paper proposes the new approach to determine which side, the utility or the customer is dominant harmonic source in a power system. At the beginning, review of existing approaches to localization of harmonic sources is given. Then, the theoretical background of the new approach is presented. The used criterion of localization of harmonic sources in a power system is based on examining the voltage ratio, which is defined in the paper. The results of investigation of sensibility of this ratio to the errors burdening quantities used for its calculation are analyzed. The practical conclusions are given. It is underlined that the presented approach has better properties than existing ones.
A generalized approach to localization of sources of harmonics in a power system
Finding an answer to the question who is responsible for the generation of harmonics in power system is an essential problem especially in the conditions of the energy market. In the paper, the method which unlike other methods is reliable and does not require exact knowledge on parameters of equivalent circuit representing the utility and customer sides, is considered. This method utilizes the specially-defined rate, being generalization of the so-called voltage and current rates. Using the generalized localization rate, the localization of sources generating harmonics in voltage differs from the localization of sources generating harmonics in current by other definition of areas of possible changes of variables from which the mentioned rate depends. In the paper, the relatively-simple way of performance of required calculation is also described. As the result of the presented consideration is standardization and simplification of localization of sources of harmonics in voltage or current in a power system.
Development of an Analytical Method for Explosive Residues in Soil
Abstract : An analytical method was developed to determine the concentrations of HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT in soil. The method involves extracting a 2-g sample with 50 mL of acetonitrile using an ultrasonic bath procedure for 18 hr. A 10-mL portion of the extract is diluted with 10 mL of water, filtered through a 0.45-micrometer Millex SR filter, and analyzed by RP-HPLC using a fixed 254-nm UV detector. Separations were obtained on an LC-18 column eluted with 50:50 water-methanol. Retention times were 2.55, 3.82, 5.16, 6.25, 7.04, 8.47 and 10.15 min for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT, respectively. Confirmation of analyte identities is recommended by RP-HPLC on an LC-CN column using 50:50 water-methanol. Kinetic studies using naturally contaminated soil indicated that equilibrium was achieved within 24 hr for the majority of soils and analytes studied. The method provides linear calibration curves over a wide range of concentrations. Reporting limits were conservatively estimated at 1.6, 1.8, 1.5, 0.5, 5.5, 0.8 and 0.8 micro grams/g for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT. Analytical precision was estimated at + or - 0.44, 0.51, 0.43, 0.13, 1.24, 0.27 and 0.20 micro grams/g, respectively, in the range of homogeneous variance near the detection limits. At higher concentrations the relative standard deviation was constant at 2% for HMX, RDX, DNB and TNB, 3% for TNT and 2,4-DNT, and 6% for Tetryl.