1, protective grounding: protective grounding is in order to prevent damage to the insulation of electrical equipment when the human body suffers from the risk of electric shock, and in the metal casing of electrical equipment or frame and grounding body made between the good connection. Protective grounding applies to the neutral point is not grounded in the low power grid. The use of protective grounding, can only reduce the degree of risk of electric shock, but can not completely guarantee personal safety.
2, protection of zero: to prevent personal electric shock due to damage to the insulation of electrical equipment, the metal casing of electrical equipment connected to the zero line of the grid, known as protection of zero. Protection zero for three-phase four-wire neutral point directly grounded in the low-voltage power system.
Protection of the implementation of the zero, if the electrical equipment equipment charged part of the shell or leakage, constitutes a single-phase short circuit, the short-circuit current is very large, so that the shell phase power supply is automatically cut off (fuse fuse or automatic air switch tripped), then the person touched the shell of the equipment, it will not be electrocuted.
3, work grounding: a point in the power system directly or by special equipment and ground for metal connection, known as work grounding. Work grounding mainly refers to the transformer neutral or neutral grounding. n line must be insulated with copper core wire.
There are auxiliary equipotential terminals in the power distribution, equipotential terminals are generally in the box cabinet. It must be noted that the terminal can not be exposed; can not be mixed with other grounding systems, such as DC grounding, shielding ground, anti-static grounding; also can not be connected to the PE line.
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4, installed leakage protector: the main use of current-activated leakage protector, under normal circumstances, the main circuit of the three-phase current phase and is equal to zero, so the secondary coil of the zero sequence current transformer no voltage output.
But when there is a leakage or electrocution, the main circuit of the three-phase current phase sum is not equal to zero at this time, the transformer has a voltage output, amplified by the F added to the action coil of the debounce device, the debounce device action, will be the main switch to disconnect, cut off the fault circuit. Tested, button QA press test, the whole process is generally within 0.1s, so can effectively play a protective role. Leakage protector principle of action.
5, insulated safety equipment: the use of insulated safety equipment so that people and the ground, or so that people and the metal casing of the tool, including with the connected metal conductor, isolated from each other. This is the current simple and feasible safety measures. Commonly used insulated safety appliances are insulated gloves, insulated boots, insulated shoes, insulated mats and insulated platforms. Insulation safety appliances can be divided into basic safety appliances and auxiliary safety appliances.
Basic safety equipment insulation strength can withstand the working voltage of electrical equipment for a long time, when used, can be in direct contact with the electric part of the electrical equipment. Auxiliary safety gear insulation strength is not enough to withstand the working voltage of electrical equipment, only to strengthen the security role of the basic safety gear, must be used together with the basic safety gear.