Electrical Installation Safety Trainer
AD 1 - MI 3399
29
TABLE OF CONTENTS
1
Basic theory about LV Electrical Installations Safety and Measurements ......... 34
1.1
TN system ............................................................................................................34
1.1.1
TN-S system ................................................................................................................................... 34
1.1.2
TN-C system................................................................................................................................... 35
1.1.3
TN-C-S system ............................................................................................................................... 35
1.2
TT system ............................................................................................................36
1.3
IT system .............................................................................................................37
1.4
Ensurance of Safety ............................................................................................38
1.4.1
Line impedance ............................................................................................................................. 38
1.4.2
Fault Loop impedance ................................................................................................................... 39
1.4.3
Comparison Line and Fault Loop impedances ............................................................................... 40
1.4.4
RCD ................................................................................................................................................ 41
1.4.4.1
RCD trip-out time test .......................................................................................................... 42
1.4.4.2
RCD trip-out current test ..................................................................................................... 42
1.4.4.3
RCD trip-out contact voltage test ........................................................................................ 42
1.4.5
Earth Resistance and Contact Voltage .......................................................................................... 43
1.4.6
Insulation ....................................................................................................................................... 44
1.4.7
Continuity ...................................................................................................................................... 44
2
Measurements on electrical installations in practice .......................................... 45
2.1
Instrument’s general settings ............................................................................45
2.2
Line impedance measurement ...........................................................................47
2.2.1
Background of measurements ...................................................................................................... 48
2.2.2
Line impedance ............................................................................................................................. 49
2.2.2.1
Short circuit line – neutral impedance and prospective short circuit current ..................... 49
2.2.2.2
Short circuit line – line impedance and prospective short circuit current ........................... 50
2.2.2.3
Voltage drop ........................................................................................................................ 51
2.2.3
Exercises ........................................................................................................................................ 52
2.2.3.1
Exercise No. 2.2-1: dU, Z
L-N
and I
PSC
measurement on the supply side ................................ 52
Measuring connection topology ........................................................................................................ 52
Measuring procedure ......................................................................................................................... 52
Expected results ................................................................................................................................. 53
Expected results with a simulated error ............................................................................................ 54
2.2.3.2
Exercise No. 2.2-2: dU, Z
L-N
and I
PSC
measurement on the socket side ................................ 55
Measuring connection topology ........................................................................................................ 55
Measuring procedure ......................................................................................................................... 55
Expected results ................................................................................................................................. 56
Expected results with a simulated error ............................................................................................ 57
2.2.3.3
Exercise No. 2.2-3: dU, Z
L-N
and I
PSC
measurement on the socket side in an IT earthing
system
58
Measuring procedure ......................................................................................................................... 59
Expected results ................................................................................................................................. 60
Expected results with a simulated error ............................................................................................ 61
2.3
Fault loop impedance measurement .................................................................62
2.3.1
Background of measurements ...................................................................................................... 63
2.3.1.1
Fault loop, fault impedance and prospective fault current in TN systems .......................... 63
2.3.1.2
Fault loop, fault impedance and prospective fault current in TT systems........................... 64
Summary of Contents for MI 3399
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