protective

1. REPORT SPECIAL SUBJECT SUPPLY ELECRICAL Topic: Protection against electric shocks SVTH: Dương Văn Trí GVGD: TS_ Võ Viết Cường HCM, Ngày 09 tháng 03 năm 2010 UNIVERSITY OF EDUCATION AND TECHNICAL HO CHI MINH CITY

4. Zones time/current of effects of AC current on human body when passing from left hand to feet

6. 2 - Protection against direct contact  Protection by the insulation of live parts  Protection by means of barriers or enclosures  Particular measures of protection (Safety Extra-Low Voltage)  Partial measures of protection Protection by means of obstacles, or by placing out of arm’s reach

7. Additional measure of protection against direct contact  Lack of proper maintenance  Imprudence, carelessness  Normal (or abnormal) wear and tear of insulation  Accidental contact  Immersion in water, etc Use of residual current operating device Reasons:

8. 3 - Protection against indirect contact 3.1 - Automatic disconnection of the supply  The earthing of all exposed-conductive-parts of electrical equipment in the installation and the constitution of an equipotential bonding network  Automatic disconnection of the supply of the section of the installation concerned Disconnecting-time limits Depends: Illustration of the dangerous touch voltage Uc

9. TT system High sensitivity RCD 3.2 - Automatic disconnection for TT system Maximum operating time of RCD’s (in seconds) RA is the resistance of the earth electrode for the installation IΔn is the rated residual operating current of the RCD

10. 3.3 - Automatic disconnection for TN systems >= Ia Id = the fault current Ia = current equal to the value required to operate the protective device in the time specified Uo = nominal phase to neutral voltage Zs = earth-fault current loop impedance Zc = the faulty-circuit loop impedance The automatic disconnection for TN system is achieved by overcurrent protective devices or RCD’s

11. Protection by means of CB Protection by means of fuses Disconnection by CB for a TN system Disconnection by fuses for a TN system Im < Uo/Zs or 0,8Uo/Zc Ia < Uo/Zs or 0,8Uo/Zc

12. 3.4 - Automatic disconnection on a second fault in an ITsystem First fault situation Second Fault situation

13. Application of RCDs when exposed-conductive-parts are earthed individually or by grroup on IT system Case 2 Case 1 Correspondence between the earth leakage capacitance and the first fault current

14. 3.5 - Protection against direct or indirect contact without automatic disconnection of supply The use of SELV The use of PELV (Protection by Extra Low Voltage) FELV system (Functional Extra-Low Voltage) The electrical separation of circuits Class II equipment

15. Out-of-arm’s reach or interposition of obstacles Earth-free equipotential chambers

16. 4.2 Ground Fault Protection (GFP) “ Residual Sensing” “ Source Ground Return” “ Zero Sequence” 4 - Protection of goods in case of insulation fault 4.1 Measures of protection against fire risk with RCDs

18. THANKS !