Contact voltage refers to the potential difference between the hand and foot when a person stands next to a device with a ground short-circuit fault, 0.8 meters horizontally away from the device, and touches the device casing (1.8 meters above the ground). The following is a detailed explanation of contact voltage
1. Definition and generation principle
Definition: Contact voltage is the potential difference formed inside the human body when the human body touches the casing of the electrical equipment and the ground at the same time.
Generation principle: When the insulation of the electrical device is damaged and the shell is short-circuited, the short-circuit current flowing through the grounding electrode will generate a voltage to the ground. At this time, if a person touches the electrical device, since the ground potential of the person is different from the potential of the electrical device casing, a contact voltage will be formed inside the human body.
2. Influencing factors
Grounding resistance: The grounding resistance of the grounding electrode will affect the magnitude of the voltage to the ground, and then affect the contact voltage.
Human body resistance: The magnitude of the human body resistance will also affect the current flowing through the human body and the contact voltage.
Distance between equipment and ground: The horizontal and vertical distances between the ground where the person stands and the electrical equipment will also affect the magnitude of the contact voltage. Usually, the contact voltage is calculated under the condition of standing 0.8 meters horizontally from the electrical device and 1.8 meters vertically from the hand touching the electrical device.
III. Hazards and protective measures
Hazards: The contact voltage may cause electric shock to the human body, causing electric shock injury or even life-threatening.
Protective measures:
The outer edge of the grounding grid should be closed, and the corners of the outer edge should be made into arcs to reduce the generation of contact voltage.
In places where people often pass by the edge of the grounding grid, gravel or asphalt pavement can be laid, or equalizing belts can be laid to reduce the contact voltage.
Regularly inspect and maintain electrical equipment to ensure that its insulation performance is good and prevent ground short circuit faults.
