The standard for testing grounding resistance of power supply bureau is 4? The following: Good grounding installation: dig a trench with a length of 15m and a depth of 70cm, lay a triangle iron in the trench with galvanized 1.5m triangle iron, and then weld them all together with galvanized round iron.
To test whether the installation ground wire is qualified, 70Cm galvanized iron sheet should be laid at a distance of 50 meters from the installation ground wire, and the resistance value of the installation ground wire should be measured below 4 with an ohmmeter. If it is qualified, this ground wire can be used as the grounding of the distribution box.
Second, the distribution box grounding requirements:
1. The grounding "bus" (grounding bar and PE bar) in the box is directly connected with the power grounding wire or grounding system;
2. The metal box itself should be processed with "box grounding bolt" (with PE mark), and the bolt must be connected with the grounded PE bus with copper conductor or special flexible cord;
3. The metal conduit connected with the box body must also have reliable electrical connection with the box body (in short, it can be welded with galvanized round steel and flat steel);
4. The part of the electrical components in the cabinet that must be grounded should also be connected to the PE bus;
5. All the ground wires to be distributed in the loop are led out by PE bus.
Proper operation of grounding wire can give full play to the value of grounding wire, which is the basis of safety precautions.
Extended data
Matters needing attention
1. The construction power distribution system is provided with a main distribution box, a distribution box and a switch box, which are arranged in layers in the order of "main-sub-open" to form a "three-level power distribution" mode.
2. The installation position of distribution box and switch box in the construction power distribution system should be reasonable. The main distribution box should be as close as possible to the transformer or external power supply to facilitate the introduction of power supply. The distribution box should be installed in the center of electrical equipment or where the load is relatively concentrated as far as possible to ensure the balance of three-phase load. The installation position of the switch box should be as close as possible to the electrical equipment controlled by it according to the field situation and working conditions.
3. In order to ensure the three-phase load balance of the temporary power distribution system, the power supply and lighting power supply at the construction site should form two power supplies, and the power distribution box and lighting distribution box should be set separately.
4, all the electrical equipment on the construction site must have their own dedicated switch box.
5. The boxes and internal settings of distribution boxes at all levels must comply with safety regulations, and the switch appliances should be marked with the purpose, and the boxes should be numbered uniformly. When stopping using the distribution box, cut off the power supply and lock the door. The fixed distribution box should be fenced to prevent rain and smashing.
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