― 15 ―
Max value of Zs for this example is 2.1Ω (16A gG fuse, 0.4s) the loop tester
reads 1.14Ω (or 202 A on Fault current range) it means that the condition
Zs
＜
Uo/Ia
is respected.
In fact the Zs of 1.14Ω is less than 2.1Ω (or the Fault current of 202 A is
more than Ia of 110A).
6.2 Measurement of "OLD-TT System"
OLD-TT system is a TT system with phase to phase voltage of 220 V
(instead of 400 V) and phase to earth of 127 V (instead of 230V) and
normally the neutral conductor is not used.
Connecting the loop testers to this system, all three wiring check LEDs
should be lit and the display reads a value of 127 V.
Only if
all
these conditions are respected the test can be carry out.
Fig.10
WARNING
● This instrument is intended only for use in single phase operation
at 230V +10% -15% AC phase to earth or for use in OLD-TT
system phase to neutral.
● If the overheat symbol appears in the display (
) disconnect the
instrument from the mains supply and allow to cool down.
L1
L2
L3
PE
R
R
O
RCD 30mA
220V
220V
220V
