Ανάπτυξη συστήματος προστασίας των εργαζομένων από ηλεκτροπληξία

Abstract

Occupational accidents still happens besides the technical development and theprogress of science. The experience of being harmed at work can be devastating, withprofound consequences for the employees, their families, friends, and work colleagues.Although many accidents involve not considerable harm for the workers, the number of fatalor seriously injured person cannot be ignored. In 2012, there were just under 2.5 million nonfatalaccidents that resulted in at least four calendar days of absence from work and 3515fatal accidents in EU. The consequences are unable to be measured directly such as theamount of pain suffered. The impact of workplace accidents involves mainly the worker’sfamily. The initial reaction to an injury, is shock and fear. For the family and friends of theinjured, one of the most considerable consequence is separation, both physical andemotional. Family relationships are also affected, mostly negatively. The domestic and familyresponsibilities are altered. The changes are temporary or permanent depending on theseverity of the injury. The family suffers also financial. More often the severally injuredvictims are the only one working person in the family and males. In the same time, thefamily’s expenses are increased (for medical care and drugs, transportation, domesticassistance, rehabilitation etc.). The importance of occupational health to both Ministers ofHealth and Ministers of Labor is illustrated by the long tradition of collaboration between theInternational Labor Organization (ILO) and World Health Organization (WHO). It is difficult, however, to convince employers and decision-makers to improve working conditions. Anoften effective way is to make financial or economic estimations. Accidents at work andoccupational injuries represent a considerable economic burden to employers, employees andto society as a whole. Some of these costs, like lost workdays or lost income, are clearlyvisible and can readily be expressed in monetary value. According to economic evaluationscarried out with the state members of the European Union, the cost of occupational diseasesand injuries that occurred at work varies from 1-3% of gross national product (GNP).This thesis instills awareness of occupational accidents due to electricity. Hundreds ofworkers have suffered injuries while installing, maintaining or servicing machinery andequipment. Some electrical injuries are electrocution, electric shock and burns. The thesis has3 chapters. The statistics concerning electrical accidents is presented in the first chapter. Inthe same chapter the pathophysiological effects of electric current taking into considerationthe international standards are also developed. The electrical accidents are classified incategories in the second chapter and technical measures for workers protection are proposed.In the third chapter are presented three devices that can be used for preventing electricshocks.Taking into consideration accidents that happened, due to suddenly reenergization ofpower lines, of step voltage hazards, and due to the discontinuities of neutral or groundconductors, three devices for injuries prevention are proposed. Therefore, the first device canprotect in cases of suddenly reenergization of power lines. When a power supply isreconnected inadvertently or by mistake, electricians are vulnerable to electrical hazardsincluding electric shock and flashover. The electricians were unaware of the electrical hazarduntil an injury occurred, suggesting that these injuries could be prevented by an alarmsystem. The operating principle of the proposed device is based on this idea. Alarm systemsare widely used to prevent injury and death. The device is placed on distribution board anduses also a motion detector system to detect a possible human approach or movement nearthe distribution board.The second device can be used for protection of step voltage hazards. Uncontrolledflow of electrical current in the earth may have a range of effects, from barely perceptible todangerous electrical shocks, or unintended electrical heating resulting in fires. It is brieflydescribing the root causes of voltage in the ground and it is proven that the values of groundpotential may be above permissible limits even though a 220 V ac voltage is applied into the ground. It is confirmed experimentally that the step voltage hazards depend on the distanceof the fault as well as from the step length. Ground resistivity also affects ground-potentialrise. Finally, a wearable device is proposed for avoiding such injuries. The device must beworn on human body and its sensors should be as close as possible to the soles of the feet.The device measures the current and alerts the user of step voltage hazards by LED segmentdrivers. It is operated during the standing phase of gait only, since the step voltage hazardsexist when both humans’ feet are in contact with the ground. It can be used by the generalpopulation or by workers, and its operation is independent of the mechanism creation ofground-potential rise.Any discontinuity in power cords of electrical devices, can lead to electric shock,injuries, or even deaths. The third suggested device measures the electric and magnetic fieldnear electric hand tools. It is proved by an experiment that if the grounding conductor ofelectrical tools having metal enclosure is broken, the electric field around them is increased.In a same way, when the neutral conductor is broken, the magnetic field becomes higher. Anelectric and magnetic field meter placed on the tool with display segment leds, may protectworkers in case of abnormal high electric and magnetic fields. After the warning sigh, the tooluser should not use it before its maintenance.

Παρά την ανάπτυξη τεχνικών προστασίας από ηλεκτροπληξία, την πρόοδο της επιστήμης, τη βελτίωση του νομοθετικού πλαισίου στη Χώρα μας, σημειώνονται θάνατοι και τραυματισμοί εργαζομένων από ηλεκτροπληξία. Η παρούσα διατριβή περιλαμβάνει 3 κεφάλαια.Στο 1ο κεφάλαιο αναφέρονται στατιστικά στοιχεία για τα εργατικά ατυχήματα και οι παθοφυσιολογικές συνέπειες της ηλεκτροπληξίας στον άνθρωπο όπως περιγράφονται σε διεθνείς προδιαγραφές και σε διεθνή περιοδικά (θεωρητικό υπόβαθρο).Στο 2ο κεφάλαιο τα εργατικά ατυχήματα κατατάσσονται σε ομάδες και προτείνονται τα εξειδικευμένα μέτρα τα οποία θα μπορούσαν να είχαν ληφθεί για την αποφυγή τους.Στο 3ο κεφάλαιο αναφέρονται οι διατάξεις και οι κατασκευές που προτάθηκαν για την προστασία από ηλεκτροπληξία.