Grounding

There is a growing elektrovooruzhennost villager. Pumps, circular saws, compressor sprayers, power tools and other equipment works normally on the four-network 380/220 V. Operation of it outdoors, especially in wet, rainy weather is not safe, requires special conditions and regulations. Observed occasionally dismissive attitude toward the voltage of 220 V - is totally unacceptable. The fact that the magnitude of danger to human life of the current (0,1 A 1) is determined to a considerable degree of resistance to human body contact with the ground. It decreases sharply with increasing humidity. The same effect has and alcohol. Even at 12 V inclement weather and in contact with a large mass of metal can cause death. Thus, in the electrical industry magazine described fatal injuries from contact with the wire with a voltage 10 V! The garden was installed sound burglar alarms, in compliance with all rules of electric safety. On the phenomenon to the wire the higher the voltage was eliminated completely (highly qualified expert committee) and, nevertheless, in wet weather lady garden was killed by touching the wires. There are many cases of fatal injuries in violation of existing simple rules of operation of electrical equipment. The main condition that ensures the safety of people at the right, in accordance with the manufacturer's instructions, maintenance Electrofacilities - reliable and high quality housing of the electric connection with the neutral wire and earth (ground), as well as the installation of two circuit breakers at the entry to the house (in phase and zero). Figure 1 shows the wiring diagram to line 380/220 V power load of individual farms. From the transformer substation through the four-wire distribution line "A" feed entries consumers. Fitted switchgear or fuses "P" placed at the input of electrical connection at home (itself a mask not shown). The zero point of the transformer is earthed via earthing ET, and body electrical users - through individual grounding FROM (individual grounding) (see fig.). "Protective earthing - an intentional connection to the body of the appliance with a grounding device. Earthing conductor (electrode) - a set of interconnected metallic conductors (electrodes) are in touch with the land" ("Electrical Code", 1985). LEGEND: FROM - personal grounding. ET - grounding transformer. Riz-resistance of individual earth. Ret-resistance grounding of the transformer. in-fault current. If the damage is the D in the economy. (See Figure 1, b) - the breakdown of its winding on the case, there is a fault current in flowing through the circuit: The phase "a" through "L" - input - case of this engine - FROM (individual ground) Engine - grounding transformer ET. The main resistance to the current in this circuit is concentrated at the contact earthing Riz and Ret with the ground, because other circuit elements are made of metal, and their electrical resistance is ten times less. Therefore, for large values ??of fault current in Riz may be small, not sufficient for the blown fuse II, and the voltage phase "a" 220 - will be divided between Riz and Ret. If Riz is much larger than Ret (the usual case), almost all the voltage 220 for a long time will be applied between the casing damaged engine and the ground. That is why man (see Fig. 1, b) such a sad face - he came under pressure.