Potential equalization of the earth
When the potential of the earth of each equipment is greatly different because of lightning etc. , an electronic equipment might be destroyed by this potential difference. To prevent this, all the potential of the earth in the building is made the same. This is called the potential equalization of the earth, and it does by bonding and one point earth (integrated earth), etc. methods.
Method of past, individual earth and the problem
Usual industrial method in earth of telecommunications equipment and equipment in building so far to ground alone respectivelyIt was usual that the earth resistance was also different respectively according to each equipment.
For instance, telecommunications equipment is five ohms the lightning rod, 30 ohms the earth of the switchboard, 50 ohms, has the washing machine like 80 ohms etc. in case of all asunder, and there are several kinds when it is the same.
In this case, a large current (hundreds of-ampere or several thousand amperes etc.) might flow under the soil when there is lightning in ,for instance, the lightning rod or another nearby building, and the potential of each equipment of the earth become asunder high potential. As a result, various equipment might be destroyed.
If the current of several thousand amperes flows between those when assuming that the resistance between earths is one ohm as the example, the voltage of several thousand volts is generated between earths. If resistance is large, it becomes a bigger voltage.
Potential equalization of recent grounding procedure and earth
When the potential of the earth of each equipment is different because of lightning etc. , each equipment might be destroyed by this potential difference. For instance, the telephone drop of the phone wire is an arrester for the telecommunications equipment such as the telephones It is grounded by (arrestor). And, telecommunications equipment is assumed to be done another earth. Then, a very big potential difference is generated when striking it and the equipment is damaged between the phone wire, the housing interval, the phone wire, and AC100V.
To prevent this, all the potential of the earth in the building is made the same. This is called a potential equalization in the building, and it does by bonding and one point earth (integrated earth), etc. methods.
The potential bonding is like the method.
The potential bonding is the done one because of the stability of the prevention of a fire, destruction, and the noise and operation as for each telecommunications equipment, an electric equipment, and the electric installation. The potential bonding connects between earths of each equipment with a direct conductor or is a method of the connection with the serge protection device (arrestor and arrester).
The ground each other might be connected with a serge protection device (arrestor and arrester) because there is a possibility that the occurrence of an unforeseen trouble and an uncertain noise happens when the earth between different equipment is connected directly with the conductor.
Method of connecting between earths directly with conductor
Because all earths become parallel as for the potential bonding as the earth of each equipment connects between the earths directly with the conductor by separately setting it up, the ground resistance can be lowered further. In this case, the electric wire used for the bonding should use the electric wire of the maximum thickness used with the earth system.
When some trouble (problem of the unforeseen trouble and the noise) happens, this method cannot be used when the earth is connected mutually.
The method in an individual equipment with a thunder measures equipment (arrestor,etc.).
The serge protection device (arrestor, arrester, surge protector, and SPD:Surge Protective Device) is individually installed in each telecommunications equipment, an electric equipment, and the electric installation, and those earths'(earth) methods of defending each equipment from a fire and destruction together (integrated earth). In this case, common ..the earth.. is most important. The earth of each equipment is not so effective separately.
Method of connecting between earths with serge protection device etc.
It is a method of connecting each telecommunications equipment, an electric equipment, and the earth of the electric installation (earth) mutually with the serge protection device (arrestor and arrester, etc.) of earth balancer. As for the ground resistance, each equipment comes not to become a potential difference more than the operation voltage of the arrestor so far.
There is no possibility that the occurrence of an unforeseen trouble and an uncertain noise happens because this method doesn't connect the earth directly mutually.