The grounding wire behind the withstand voltage tester is to be connected to the protective earth in the workshop. If not connected to the person will be subjected to electric shock, equipment and lines will be damaged, can not guarantee the normal operation of the power system.
Protective grounding is to prevent the equipment due to insulation damage charged and endangered personal safety set up by the grounding, such as the metal casing of power equipment, reinforced concrete poles and metal towers. Protective grounding is only in the case of equipment insulation damage to the current flow, the value can be varied within a wide range.
Current flow through the above three grounding electrode will cause the grounding electrode potential increases, affecting the safety of people and equipment. For this reason, the grounding electrode potential rise must be limited, or take appropriate safety measures to ensure equipment and personal safety.
Expanded:
The role of grounding
1, to prevent the person suffers from electric shock
The electrical equipment under normal circumstances is not charged metal parts and grounding electrode for a good connection between the metal to protect the human body's safety.
For electrical equipment with grounding device, when the insulation is damaged, the shell charged, the ground current will flow along the grounding pole and the human body two paths. The value of the current flowing through each path will be inversely proportional to the size of its resistance, the smaller the resistance of the grounding electrode, the smaller the current flowing through the human body.
When the grounding resistance is very small, the current flowing through the human body tends to be close to zero, the human body to avoid the risk of electric shock. Therefore, no matter what the situation, should ensure that the grounding resistance is not greater than the design or specification of the grounding resistance value.
2, to ensure the normal operation of the electrical system
Power system grounding is generally neutral ground, so the neutral point and the potential between the ground close to zero. When the phase line touching the shell or ground, the other two phase-to-ground voltage, in the neutral point insulation system will be raised to the phase voltage times.
In the neutral grounded system is close to the phase voltage. Because of the neutral grounding line, can ensure the reliability of relay protection. DC power supply in the communication system is generally used positive grounding, can prevent the noise tampering and ensure the normal operation of communication equipment.
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