Electric Shock: Causes and preventative measures

Electric Shock: Causes and preventative measures

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