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Why is good grounding important?

time:2020/12/22   source:华天电力  reading:255 time

The transient characteristics of lightning and its related rapid rise time and large current mean that good grounding must be specially considered to make lightning protection effective, soil resistivity changes, ease of installation, layout and existing physical characteristics and many other factors It is site-specific and often influences the decision to use the grounding method.


Low impedance is the key to lightning protection. All ground connections should be as short and direct as possible to reduce inductance and reduce the peak voltage induced in the connection. The grounding electrode system must be coupled to the soil to effectively couple the lightning surge to the ground. The resistance to lightning current itself must also be reduced. Only when all these factors are taken into account can the lightning protection effect be achieved.


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Ground impedance


Soil resistivity is an important design consideration. For different soil types, moisture content and temperature, it will change significantly and cause changes in ground impedance.


Short and direct ground connection


The voltage generated by lightning discharge mainly depends on the rise time of the current and the impedance of the ground path (mainly inductance).


Any series inductance caused by long distances, indirect paths or sharp bends in the ground conductor wiring, extremely fast rise times will cause the voltage to rise significantly, which is why short and direct ground connections are important.


Coupling from the electrode system to the ground


The efficiency of the ground electrode system to couple lightning current to the ground depends on many factors, including the geometry of the ground electrode system, the shape of the conductor, and the factors that effectively couple to the soil.


Characteristics of a good grounding system


In short, four characteristics are critical to grounding


1. Good conductivity


2. A conductor that can withstand the available electrical fault current


3. Long service life at least 40 years


4. Low ground resistance and impedance


The basic principle of any grounding device should be to try to increase the surface area of the electrode or conductor and the surrounding soil, which not only helps to reduce the grounding resistance of the grounding system, but also can increase the impedance of the grounding system under lightning impulse conditions.


Equipotential bonding


Equipotential bonding helps to ensure that there are no dangerous potential differences between different input conductors (such as metal water services, power systems, telecommunications systems and local ground), and can also reduce stepping and contact potential.


Good corrosion resistance


The ground electrode system should be corrosion resistant and compatible with other conductors buried in the ground.


So far, copper is a common material used for grounding conductors. Generally, a grounding resistance measuring instrument (or grounding resistance measuring device) maintenance or inspection procedure should be used to ensure the long-term effectiveness of the grounding system.

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