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Decision:: A% a; ~. e2 A/ @% c! g
Measuring the protective earth connection has in fact two reasons. It is to determine impedance
" a# _, K2 B0 M8 R* y7 m/ @& oand cross-sectional area of protective earth connections. For a measuring current of 25 A both+ V5 `/ T2 m. L7 J) F1 y
can be done with one measurement. Requiring a measuring current of more than 25 A it shall be- B% _2 ?+ C( R/ l! ]) m
splitted up into two measurements. In this case, the impedance shall be determined first, using a5 T+ v2 W: F7 ?% o) y
voltage not exceeding 6 V.
* |8 A1 F2 _; |- b" ~8 o' T0 A" C" uIf cross-sectional area of the protective earth connections cannot be determined as equal to the
: t5 Z) n+ Z3 I4 q* A1 B# {one for the phase by measurement of the area, then measurement with current shall be from a
7 m- K3 U R. A2 k: ]source with a higher voltage than 6 V.
/ z, t: y" k/ s1 r8 iExplanatory notes:; X" K3 S- W" Q4 ~
A circuit to the PROTECTIVE EARTH TERMINAL may have zones of higher impedance, for
' n, y2 Z; h$ g6 G B, [' jexample due to oxidation of materials. Voltages higher than 6 V prevent detection of such zones
( t, d2 _- [+ e8 tbecause of their ability to flash through. In this case, the impedance shall be determined first,
: C2 ?1 ~& n9 j3 a: l1 _: busing a voltage not exceeding 6 V.
3 c( B0 i G. F% e7 FUsing low voltages and low currents has a great impact on the accuracy of the measurement of- S. N& {( V( I' W& G
low impedances. Impedances in the range of 0.1 W and 0.2 W then require a sophisticated, [9 b4 d! G- e4 A4 s0 H
measuring device.
; [6 i* {4 p, i2 QThe relation between rated current of the EQUIPMENT and measuring current is because to2 x0 F0 [1 c6 y
check cross-sectional areas of protective earth connections. If parts of the construction or printed( w- Y" T# w& j( I1 T! C( I
circuit boards are used for protective earth connections the cross-sectional areas and the ability) ~. |' n6 a& E6 L% y+ ~3 _! G
of carrying short circuit c urrents are in doubt. |
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