19
20
Fault localization and trouble shooting
Measurement
Item
Normal
measurement
result
Fault
measurement
result
Possible
cause
Trouble
shooting
Conductor
impedance
for
live line
and
zero line
The
impedance
is
too high
Redistribute
the
circuit load.
The circuit
is overloaded.
Check the
wire diameter
and
rearrange
the wire
accordingly.
High
impedance
point exists in
the circuit
or
switchboard.
Locate the
high
impedance
and repair
or replace
the parts
The wire
diameter is
too small
for the power
transmission
length.
Check
the wire
diameter and
rearrange
the wire
accordingly.
Locate
the high
impedance
and repair
or replace
the parts
The wire
diameter is
too small
for the power
transmission
length.
High
impedance
point exists
in the circuit
or
switchboard.
The
impedance
is
too high
Conductor
impedance
for
earth line
For
personnel
safety
<1Ω
For
equipment
safety
<0.25Ω
No. 14 line
(2.0mm )
<0.15Ω/m
No. 12 line
(3.3mm )
<0.1Ω/m
No. 10 line
(5.2mm )
<0.03Ω/m
Residual current device (RCD) test
During the RCD test, the analyzer will generate a
low current between live line and earth line by
means of a fixed resistance, which will affect the
current balance between live line and zero line.
According to UL, this current trigger shall be less
than 30mA. The RCD shall response to the current
imbalance by cutting off the power. The analyzer
will display the value of the current triggered (mA)
and response time (ms).
The word “TEST” will be displayed when the button
“ ” is pressed, which means the test is in the
process. RCD shall be triggered within the specified
index to cut off the power of the circuit under test.
If the RCD fails to be triggered, the analyzer will
stop testing automatically after 6.5 seconds.
Analysis on RCD shall be made according to the
test result to see if it goes wrong, is installed
properly or protects the circuit effectively.
Notes:
1. Check the circuit to see if there is heavy load over
the circuit before testing and, if necessary, turn
off the load to avoid wrong test result.
2. Earth connection is required when the RCD is
tested in the 2-wire system (without earth line). .
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