A 1472, A1579 Leakage current clamp
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4.1.2 Leakage currents in normal operation
Typical leakage currents in normal operation are:
Leakage currents caused by input filters in electrical equipment
connected between live and earth (filters, monitors). The capacitors
in input filters have a capacitance of ca. 10 nF to 100 nF (see Fig.1).
Leakage currents caused by conductors’ insulation resistance and
their capacitances to earth. Long power cables have a lower
insulation resistance and higher capacitances. The capacitance
between a cable and earth is typically about 150 pF/m (sse Fig. 1).
Leakage currents produced by frequency converters, switch mode
power supplies, different rectifiers and similar equipment. The
shape and frequency of this leakage currents can vary from pure
d.c, pulsed d.c. components up to very high frequency.
In general, leakage currents in normal operation increase with the size of
the electrical installation and the number of connected loads.
Table 1 shows the values of leakage currents for some typical
capacitances and resistances.
Capacitance
Capacitive leakage current
@ 230V/ 50Hz
Note
1 nF
0.072 mA
Typical values of
capacitors in input
cables
10nF
0.72 mA
100nF
7.2 mA
1uF
72 mA
Capacitance of long
power cables
Resistance
Resistive leakage current
@ 230V/ 50Hz
10 kΩ
23 mA
500 kΩ
0.46 mA
1.00 MΩ
0.23 mA
Typical limits for
insulation resistance
2.00 MΩ
0.115 mA
Table 1: Leakage current / capacitance relations
In Table 2 typical values of leakage currents for different types of electrical
equipment are shown.
Equipment
Leakage current
Stationary PC system
1 to 3
Photocopy machine
0.5 to 1.5
Floor heating
1mA / kW
Input EMC filter
1 mA
Printer/ fax
up to 1 mA
Photocopy machine
up tp 1.5 mA
Laundry machine, drying machine
up to 2 mA
Cookers, heaters
1mA / kW
Installed power cable 100 m
1 mA
