METREL MI 3399, Инструкция с упражнениями

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Electrical Installation Safety Trainer AD 1 - MI 3399
117
2.8.2 Exercises
2.8.2.1 Exercise No. 2.8-1: Earth Resistance Measurement
– three wire
method
Measuring procedure
1 To measure the earth resistance select first the 3W (three wire) function in the Earth
section.
2 Set the maximum allowed earth resistance by clicking in the bottom left dark grey
corner.
When setting the limits the following thresholds should be considered:
o
2
Ω
above ground,
o
10
Ω
for the complete system,
o
20
Ω
for a single wire or
o
8% of the specific earth resistance.
3 During this type of measurement cables in combination with earth probes are to be
used. Plug the neutral cable to the PE conductor or the earthing rod. Connect the
phase cable to one probe and the PE cable to the other probe. After the measurement
is completed reverse the cables connected to both rods in order to exclude any funnel
overlap. If the measured resistances are equal (20% to 30% difference is acceptable),
funnel overlap is not present.