接地零保护(国外英文资料).doc

接地零保护(国外英文资料) Zero access protection An electric safety measure to connect the metal casing of an electric appliance with the zero line of a power grid to protect personal safety. In the zero to zero power line with voltage below 1000 volts, if the electrical equipment is charged by the insulation damage or accident, a single-phase short circuit of the phase line to the neutral line is formed, and the protection is zero The protection device (automatic switch or fuse) on the line can act quickly and cut off the power supply, so that the metal part of the equipment does not have a dangerous voltage for a long time, thus ensuring personal safety. In the polyphase AC power system, the neutral point of the winding connected by the star is directly grounded so that the equipotential potential of the winding is zero. The wire drawn from the neutral point of the earth is called a zero line. In the same power supply of the electrical equipment, does not allow part of the equipment using protective zero connection, and the other part of the device using protective grounding (see ground). Because when the live shell grounding protection device, if the grounding resistance of R D is large, ID is not sufficient to make the fault current protection device, due to working resistance rD, the neutral line has been voltage U0 = IDrD, the shell zero protection equipments long time storage in voltage U0 dangerous, endanger personal safety. Protective zero connection is the direct connection of wires with the system under the normal condition that the metal parts are not charged. The protective zero connection mode is adopted to ensure personal safety and prevent electric shock. Edit this paragraph to protect the difference between zero and protective ground Work is more than the ground - electricity generated in the work, in order to let more people get electric shock, it can make more than electricity into the earth body, called grounding; protective zero line - in fact is the ground