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Electrical energy can change in an instant from a silent assistant at work and provider of well-being and comfort into a mortal danger, and it is a change that is occurring with alarming frequency.
Instalações elétricas – Helio Creder – Google Books
In order to perform satisfactorily and be sufficiently protected against the hazard of fatal accidents, every electrical installation needs to have an adequately dimensioned grounding system.
To characterize such systems at high-rise worksites in Pernambuco, Brazil, the research was performed at 66 sites sampled randomly among 47 construction firms between May and Aprilanalyzing the conditions and compliance with current norms of their electrical installations and grounding systems.
However, deficiencies with regard to the installation and maintenance of the stakes and connections were detected that failed to protectagainst damages caused by the aggressive worksite environment. The research results showed that while companies, especially those of larger size, are investing in electrical installations and adequate protection systems, there are still grave problems in the manner of installation and utilization of such systems and in the availability of required documentation.
This proves that it is necessary to invest more in education and awareness for civil construction workers and management, not only about the equipment they must acquire, but on the manner in which it must be installed, documented and utilized.
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It is impossible to imagine the present world without the electrical system, it is displayed in all the branches of professional activities but electrical energy has also as characteristic the potentiality of causing accidents.
Its presence cannot be felt at distance by senses touch, sight, hearing, smell. These non-controlled risks can cause accidents which vary from superficial injuries to fatal accidents.
Therefore, for understanding the steps and safe procedures needed to the use of energy and the handling of electrical installations requires the comprehension of electrical risks . The civil construction industry displays a multiplicity of factors whichpredispose the instalaoss to accidental risks such as: Albeit this ratio has diminished, the death of construction workers still would correspond to a ratio four times bigger than that of all industries put together, what justifies a corrective action to the problem.
Inserted on this problem, electrical risks arising out of unfitted installations must be extricated or at least minimized at work sites. The Brazilian norms predict specific protection systems to electricalinstallations, on what refers to the safety of eletrias worker one can quote the Regulatory Norm n. The NBR norm  establishes the guidelines to the dimensioning and installation of the equipotentialization systems.
In addition to this norm recently came into force the law n. In the year of one would find registered in this sector of civil construction, 1, employees in all Brazilian territory, being According to Cadick et al  electric shock is the physical manifestation that occurs when an electrical current flows through the human body.
The symptoms may include from a slight sensation of tingling, to violent muscular contractions, cardiac Arrhythmia or damage to the eletriacs. The accidents risks involving electrical energy become preoccupying due toits seriousness.
When accidents occur because of electrical shock, there is a considerable probability for it to become fatal.
This will depend eletdicas on the intensity of the intensity, frequency, time of duration and on the passage of the current instalaes human body .
When approaching the subject Protection against Electric Shock, such norm establishes two fundamental principles which are key-ring for the understanding of the rules, procedures and norms and, consequently, to the effectuation of the hazards control inherent to the handling, operation and intervention in electrical webs. Thus, the protection against electric shocks, still in accordance with NBR understands two lines of defense or two types of protection: In this way, NBR establishes as general rule for protection against electric shocks that the declared principles are assured at the very least, for the joint provisions of basic protection and supplementary protection.
In the places or situations where the provisions of these last ones integrally does not assure the basic principles previously cited, the set will be added to the additional protection. This measure of protection is destined to prevent that a contact tension of maintaining for a time which can result in risk of dangerous physiological effect for people or animals and, it is based on the performance of a device of automatic cut that detaches the defective installation when it will be able to circulate dangerous intensities through people or animals.
According to NBR , the prescriptions that translate the basic principles of the applied equi-potentialization to the protection against electric shocks are the following ones: According to Mamede Filho [ 6 ], in order to function with a performance satisfactory enough and to be insured against risk of fatal accidents, all high- voltage instalaoex installation and of low tension must adequately possess a system of dimensioned grounding helii the conditions of each project.
Soon, a grounding system aims at: The objective of the groundings is to assure without risk of danger the draining of currents of lack and escape for land, satisfying the necessities of security of the people and employees of the installations. It can also be spoken ingrounding of work or provisorywhose objective epetricas to make it possible, without risk of danger, action of maintenance on parts of the installation normally under tension, placed outside of service for this end.
Instalações eletricas helio creder
The election and installation of the grounding components must be such that: Grounding basically possesses four components: In a grounding system, it is considered as land resistance the effect of three resistances, knowing: The bigger the length of the rod the less resistance of grounding, this because the bigger the connecting rod the bigger the surface the current passage, thus diminishing the resistance.
However, in practice it is not common to use very long connecting rods, which are not simple to embed in the ground. The most used are of 2 and 3 m. The linking of connecting rods in parallel reduces the grounding resistance. In this in case, so that the possibility of dispersion of the connecting rod is used fully is necessary helioo nail it outside the zone of dispersion of the other, or either, in the region of null potential.
It is common to use the removal between connecting rods equal instapaoes superior to the length of the 8 connecting rod [ 8 ]. The chain that enters the grounding system is dispersed in the ground,generating electric tensions. These tensions if applied to the human being, they provoke electric shocks being able to cause ventricular fibrillation.
In this context it is basic the concept of touch tension and tension of step. The touch tension is the existing electric tension between the superior and inferior limbs of an individual, due to an imperfection in the equipment, while the step tension can be understood in the following way, considering an electrode of vertical grounding nailed into a homogeneous land, and its area of radial dispersion of until a meter one has a limited parcel of tension which a close person can be submitted to a tension called step.
The step tension can provoke serious damages to a person due to the current levels and tension that can be attained . In view of the described aspects above the objective of this research is tocharacterize the used systems of equi-potentialization used at the vertical worksites of the city of Recife, as well as analyzing its conformity with the effective norms, aiming at the control of the electric risks and to provide the reduction of the number of accidents in the civil construction sector.
One has had the concern about distributing the workmanships amongst the diverse quarters of instalqoes region. Figure 1 presents a space vision of the distribution of the used mistral space in the research. For identification of the electric risks at the work sites, a specific protocol, based in previous studies was elaborated and the current law NR jnstalaoes, NR 18 and NBR This instrument had as greater objective the identification of relative non-conformity to the electric installations that could generate danger to the user, the proper installation and the patrimony, especially as for the systems of protection against electric shocks.
The collection of data in the work sites was carried through between May of the April of Special care was taken so that the visits were made with the presence of the electrician, engineer or technician of security of the workmanship, credwr order to preserve the security of the scholarship holder, as well as, also of obtaining refined information.
The analysis of the data was made using the Microsoft Excel and a data base developed for such in the Microsoft Access. The eletricax of the visited workmanships was found in the phase of structure and finishing, as it shows Table 1, as the provisory electric installations are installed in the beginning of the activities in the work site, there were realized that the constructors do not carry through a periodic maintenance in the installations, they are only modified in agreement with the necessities without the existence of a project adjusted for the respective adaptations.
Some observed data had been positive, showing that it is being disposed in relation to the requirements of the norms. These numbers, however, are on this side of what is expected to find exactly in the considered companies of great transport and demonstrates that the great majority of the enterprises possesses the equipment filled with earth with the elements electrodes, connections and conductors adjusted but they display imperfections in other important items of the norm many times credfr to knowledge or efficient fiscalization.
The study of the raised data demonstrated that the systems of equi- potentialization of the provisory electric installations of the work sites still present significant shunting lines in relation to the fulfillment of the lapsing established for norms NBR and NR 10, what demonstrates the necessity of consequently increasing the knowledge in relation to the systems of protection of the electrical installations, in order to manage them in efficient way taking the reduction in the number of accidents and diminishing the costs direct and indirect and with thesame ones, increasing the productivity at the work sites.
These campaigns can reverse these indices found in the research, with spreading of the norms, and mainly the part related to the protection against electric shocks, besides informing and enabling the workers of the civil construction, in relation to the procedures of assembly, operation and maintenance of the provisory electric installations of the work sites.
It must therefore be evidenced, as much for the public in general, as for instalsoes entrepreneurs of the industry of the civil construction, the importance of the use, adequate sizing and installation of the equi-potentialization systems so that they guarantee its effectiveness in the prevention of when requested the electric shocks.
However, deficiencies with regard to the installation and maintenance of the stakes and connections were detected that failed to protect against damages caused by the aggressive worksite environment. Protection system against electric shock Protections against electric shock According to Cadick et al  electric shock is the physical manifestation that occurs when an electrical current flows through the human body.
Equi-potentialization of xreder electrical installations. Basic specifications for eletricax grounding system. ANALISYS OF THE RESULTS The majority of the visited workmanships was found in the phase of structure and finishing, as it shows Table 1, as the provisory electric installations are installed in the beginning of the activities in the work site, there were realized that the constructors do not carry through a periodic maintenance in the installations, they are only modified in agreement with the necessities without the existence of a project adjusted for the respective adaptations.
Field research Table 1 — Work phases Some observed data had been positive, showing that it is being disposed in relation to the requirements of the norms. Field research Table 2 — Grounding of gears, Length of the grounding electrode and grounding resistance. Congresso Brasileiro de Ergonomia, crerer A vida por um fio: Rio de Janeiro,