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What is the soft grounding in chemical ground electrode?


Soft grounding: Make the object connect to the earth through a high enough impedance so that the current can be limited under the personal safety current in case of electric shock.


Related knowledge:

1) Hard grounding: Make the object connect to the earth directly or through a low impedance.


2) Direct grounding: A grounding type in which the metal conductor is electrically connected to the ground so that the potential of the metal conductor is close to the ground potential.


3) Indirect grounding: In order to make the electrostatic conductor and electrostatic subconductor outside the metal conductor electrostatically ground, all or part of its surface is tightly connected with the grounded metal conductor, and the metal is used as a grounding-type of grounding electrode.


4) Jumper grounding: A kind of chemical ground electrode that the structure of metal objects is fixed by mechanical or chemical methods, so as to make two or more mutually insulatied metal conductors electrically connect to establish a low impedance path for power supply flow, and then grounding.


Chemical ground electrode grounding refers to that the neutral point of the power system and electrical device, the exposed conductive part of electrical equipment and the external conductive part of the device are connected with the earth through a conductor.


Types of grounding

It can be divided into working grounding, lightning protection grounding, and protective grounding. 


Working grounding is set by the power system operation needs (such as neutral grounding). Therefore under normal conditions, there will be a long-term current flowing through the ground electrode, but only a few amperes to dozens of amperes of unbalanced current. In the case of grounding fault in the system, thousands of amperes of working current will flow through the chemical grounding electrode. However, the current will be cut off by the relay protection device within 0.05 ~ 0.1s. Even if it is backup protection, the action is generally within 1s. 


Lightning protection grounding will only flow under the impact of lightning.The amplitude of the lightning current flowing through the lightning protection grounding electrode can reach tens to hundreds of thousands of amperes, but the duration is very short. 


Protective grounding is designed to prevent equipment from endangering personal safety due to insulation damage and electrification, such as the metal shell of power equipment, reinforced concrete pole and metal tower.