In this paper, 100% stator ground fault protection by application of low frequency (20 Hz) injection for 6.6/132 KV alternators have been investigated. Here, different types of faults of alternators and possible protections by conventional means have been discussed. It is shown why conventional method by differential relay protection is not adequate. Modern approach of alternator fault protection is reviewed and effective methods of 100% stator ground fault protection of alternators have been applied. In this work, it is focused protection of alternators based on sub-harmonic injection method using low frequency band pass filter. The design of stator ground fault protection consists of 20 Hz signal generator, band pass filter, 20 Hz current relay and protection system model includes alternator, total capacitance to ground of stator winding, grounding transformer turns ratio, and neutral resistor. PSPICE simulation of the protection scheme is performed and analyzed.

Resumen: La enfermedad periodontal inflamatoria ocasiona la destrucción de los tejidos que protegen y soportan al diente; es por eso de gran importancia el papel que pueden desempeñar las enzimas que sean capaces de degradar la matriz del tejido conectivo, como las ...

This work contributes to the monitoring of Agricultural soil pollution in Katsina State, North western Nigeria by assessing the degree of heavy metal pollution in Agricultural soil samples. The study was conducted in the year 2017 within some catchment areas located within the 3 senatorial zones that constitute to make up the state (Katsina senatorial zone: Birchi, Dutsinma and Katsina; Daura senatorial zone: Daura, Ingawa and Zango; Funtua senatorial zone: Dabai, Funtua, Kafur, Malunfashi and Matazu). Analysis for the concentration of these heavy metals; Cr, Cd, Fe, Ni, Mn, Pb and Zn was conducted by the use of AAS (by Atomic Absorption Spectrophotometry) method. . Several indices were used to assess the metal contamination levels in the Agricultural soil samples, namely; Geo-accumulation Index (Igeo), Enrichment Factor (EF), Contamination Factor (CF), Degree of Contamination (Cd) and Pollution Load Index (PLI). The result of this study has shown that generally among the heavy met...

The article draws attention to the importance of documentation in the daily professional interventions and focuses on the recording of professional actions in the field diary. It is assumed that documentation is crucial in the process of data gathering and analysis, since it makes it possible to systematize the intervention developed by social workers and social work students both in order to investigate social reality, the people involved and the process of professional intervention and to find orientation for their actions when they are articulated in different intervention processes. Nonetheless, one sees that documentation as an instrument that improves the quality of professional actions is little explored by social workers. This applies particularly to the field diary, which is usually restricted to descriptions, occasional observations and mere scheduling of daily tasks. Hence the article’s insistence on the importance of analyses and/or diagnoses of the social reality and th...