4.1.3 Earthing
4.1.3.1 Overview
Earthing is an electrically conductive connection to the earth. Earthing helps to cope with electromagnetic
interference (EMI) and should always be considered.
A differentiation can be made between functional earthing (FE) and protective earthing (PE), which is
additionally related to electrical safety.
Note
In Extra-Low-Voltage devices such as SOMANET Drives, protective earthing is not required but
functional earthing is essential to cope with EMI issues.
4.1.3.1.1 What is earthing or grounding in an electrical system?
An earthing system (UK and IEC) or grounding system (US) is a common and standardized way to keep the
potential of a system to the same level.
Earthing or grounding is the process of transferring the immediate discharge of electricity directly to the
earthing plate with low resistance electrical cables or wires. It facilitates a physical connection between the
ground and the electrical equipment and ensures the same voltage potential.
4.1.3.1.2 Hazards of electricity
Electricity has two hazards which occur when an electric current passes through a person: thermal and shock
risk.
Electrical current can be life-threatening above 25 mA in AC and 50 mA in DC. The resistance of the human
body is generally between 1 kΩ - 5 kΩ. Assuming a human body has a resistance of 2 kΩ, the dangerous
voltage can be calculated as 50 V or 120 V .
AC
DC
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