Dangerous voltages
The following voltages can be dangerous:
A.C. voltage with a peak value of 42.4 V and higher
D.C. voltage of 60 V and higher.
Causes
If a person touches a component that is under dangerous voltage, it can cause electric shock. This contact is divided into two categories:
Type of contact |
Definition |
|---|---|
Direct contact |
Contact with components that are supplied with a voltage in undisturbed operation |
Indirect contact |
Contact with components that are supplied with a voltage caused by a fault |
Preventative measures against direct contact
If components carry dangerous voltage, people must be prevented from coming into direct contact and therefore risking injury.
The following measures considered:
Secure separation between circuits
Housing or cover
Insulating active components
Energy restrictions (capacitor loads, protective impedance)
Voltage restriction
Additional fault current protective circuits
Preventative measures for indirect contact
A fault could also occur, in which case preventing people from getting an electric shock (by indirect contact) is also necessary.
The following measures can be considered:
Doubled/reinforced insulation
Basic insulation and protective grounding
Additional fault current protective circuits
Respective standards
Regulations for protective measures against electric shock are covered in the following standards:
Safety regulation standard:
IEC 61140: Protection against electric shock. Common requirements for systems and electrical equipment (safety standards)
Safety group standards:
IEC 60364-4-41: Electrical Installations of Buildings - Part 4: Protection for Safety, Chapter 41: Protection against electrical shock
For systems:
IEC 62103 and EN 50178: Electronic equipment for use in power installations
For machines:
IEC 60204: Safety of machines - electrical equipment of machines