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67976 2010 年 07 月 24 日 00:53 Reading (loading. ..) Comments (0) Category: Project
Safety is extremely heavy, in addition to management, the technical measures is also an important link. Security lines, the safe operation of equipment, direct and effective protection of technical measures is well grounded. According to technical design, construction management experience, current methods adopted are the following:
1 Replace the soil
this approach is the use of low resistivity of the soil (such as: clay, black soil and sandy clay, etc.) to replace the original high resistivity soil, displacement range of around 0.5m in the grounding and grounding within the 1 / 3. However, this approach borrow replacement cost of manpower and working hours are larger.
2 artificial soil (soil chemical treatment)
the soil around the grounding to add chemicals, such as salt, charcoal, ash,
la gear, nitrogen residue, slag, lime, and improve the soil around the grounding of the electrical conductivity. Use of salt, the effect of different soil is different, such as sandy clay with salt treatment, the soil resistivity can be reduced 1 / 3 to 1 / 2 sand decreases the resistivity of 3 / 5 3 / 4 sand decreases the resistivity of 7 / 9 7 / 8; the rocky soil, impregnated with 1% salt solution,
la gears, its conductivity increased 70%. This method, although a lower project cost and the effect is obvious, but the soil by artificial treatment, will reduce the thermal stability of the ground to accelerate the corrosion of grounding, grounding to reduce the use of life. Therefore, in general,
la gear shoes, may not be in the million, only under the conditions recommended.
3 deep grounding
local soil or water under the deep low resistivity, can be taken to reduce the deep earth grounding resistance. This method is most effective on the sand soil. According to historical records, 3m deep in the soil resistivity is 100%, 4m deep as 75%, 5m deep as 60%, 6m deep as 60%, 6.5m deep as 50%, 9m deep as 20%, this method can not consider freezing and drying of the soil resistivity increases, but construction difficulties, earthwork volume, high cost, in the rocky terrain even greater difficulties.
4 multivessel-type grounding device for introduced
such as conducting a good grounding device near the ice-free rivers and lakes,
la gear sneakers, this method can be used. However, in the design, installation, grounding connections must take into account its own Route impact resistance, therefore, outside the lead-type ground electrode length should not exceed 100m.
5 by grounding resistance reduction agent
laying around in the grounding of the reduction agent, you can play a larger ground electrode dimensions,
la gear police, lower the surrounding land from the contact resistance between the media, and thus can to some extent reduce the grounding resistance of grounding . The concentration of reducing agent used for small area ground, small grounding, its more significant reduction in resistance.
reduction agent from the preparation of several substances from the chemical reduction agent, is a good strength and conductivity of electrolytes and water. These strong colloidal electrolyte and water surrounded by mesh, mesh colloid space and is partially hydrolyzed gel filled, it Buzhi Yu lost with the ground water and rain water, which can effect long-term good electrical conductivity. This is currently used in a more active promotion of new and popular method.
6 contacts using water and water dispersed medium as a reinforced concrete body
full use of hydraulic structures (wells, ponds, etc.) and other contact with water within the concrete as a natural grounding metal body can be reinforced concrete structures under water within the bang tied into many of the steel mesh, select point to a number of vertical and horizontal cross-welding, connecting with the grounding.
When used as a natural grounding of hydraulic structures can not meet the requirements, or the use of hydraulic structures as a natural grounding difficulties, priority should be in the nearest water (river water, water, etc.) lay outside the lead (artificial ) grounding device (underwater grounding), the grounding device shall be laid in the water flow is not in place or still water, and filling some big rocks to be fixed.
7 to elongation of the level of grounding
practical engineering application, after analysis, results show that the level of grounding length increases, the inductance increases, so that the impact factor increases,
la gear womens shoes, when the earth reaches a certain length of the body, and then increase its length , impulse grounding resistance is no longer declining. In general, the level of grounding should not be greater than the effective length. The effective length of grounding resistance determined according to the soil as shown in Table 1.
Table 1, soil resistivity at different levels under the effective length of grounding
soil resistivity (Ωm) 500 1000 2000
effective length of the level of grounding (m) 30 ~ 40 45 ~ 55 60 ~ 80
8 to take water into
grounding in order to reduce the resistivity of the surrounding soil can lead to the laying of sewage at the grounding. Grounding steel pipe, steel pipe at intervals of 20cm in diameter and 5mm drill a small hole, so water to seep into the soil.
9 to deep ground
deep ground conditions can be used Shihai. With the rig drilling (exploration and drilling can also be used), the ground electrode into the well bore tube to the infusion tube wells within and mud.
in determining the reduction of high soil resistivity areas of specific measures earth resistance should be based on local original operating experience, weather conditions, terrain features and the level of soil resistivity conditions such as a comprehensive, integrated analysis, through the technical and economic compared to determine, according to local conditions to select appropriate methods. This can protect the lines, equipment, normal operation of the project investment and avoid excessive grounding happening.
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