A 1472, A1579 Leakage current clamp
3
1
Warnings ........................................................................................... 4
2
Description of leakage current clamp ............................................. 5
2.1
Meaning of symbols .................................................................... 6
3
Maintenance ...................................................................................... 7
3.1
Inspection ................................................................................... 7
3.2
Cleaning ...................................................................................... 7
3.3
Service and calibration ................................................................ 7
4
Leakage current clamp operation .................................................... 8
4.1
Measuring of leakage currents .................................................... 8
4.1.1
Origins of leakage currents...................................................... 8
4.1.2
Leakage currents in normal operation ..................................... 9
4.1.3
Leakage currents in fault conditions ...................................... 10
4.1.4
Problems caused by leakage currents ................................... 11
4.2
Measuring leakage currents with current clamps ....................... 13
4.2.1
Direct method ........................................................................ 13
4.2.2
Differential method ................................................................ 14
4.3
Testing procedures ................................................................... 15
4.3.1
Finding sources of excessive leakage current ....................... 15
4.3.2
Insulation resistance testing .................................................. 17
4.4
Influencing quantities ................................................................ 18
4.4.1
Influence of nearby external magnetic field ........................... 18
4.4.2
Influence of load current in differential leakage current test ... 18
4.4.3
Influence of external electric field .......................................... 19
4.4.4
How to recognize accuracy problems ? ................................. 19
4.4.5
How to minimize the influencing quantities ............................ 19
4.4.6
Consideration of influencing quantities .................................. 20
4.5
Other important current clamp parameters ................................ 21
4.5.1
High measuring range ........................................................... 21
4.5.2
Clamp diameter ..................................................................... 21
4.5.3
Protection category ............................................................... 21
5
Technical specifications ................................................................ 22
