A 1472, A1579 Leakage current clamp
20
Fig. 11: Minimizing influencing quantities, correct placement of conductors
Fig. 12: Minimizing influencing quantities, avoiding external magnetic and
electric fields
4.4.6 Consideration of influencing quantities
Only high quality current clamp can accurately measure in range of mA in
presence of external fields and high load currents. The given resolution or
basic accuracy are not telling a lot about the real quality of the current
clamp. The immunity of the current clamp against influencing quantities is
much more representative.
The IEC (International Electrotechnical Commission) is preparing a new
international standard
IEC 61557-13 Hand-held and hand-manipulated
current clamps and sensors for measurement of leakage currents in
electrical distribution systems
that will cover the aspect of influencing
quantities and will be launched in 2010. One of its main objectives is to
define rules how to consider the immunity of influencing quantities in scope
of the accuracy of leakage current clamps. This will enable the user to
make a relevant comparison when deciding between different current
clamp models.
