13
14
Fault localization and trouble shooting for voltage
problems
Measurement
Item
Normal
measurement
result
Fault
measurement
result
Possible
cause
Trouble
shooting
Phase voltage
108-132V
(120V)
198-242V
(220V)
The voltage
is
too high
or
too low.
The circuit is
overloaded.
Redistribute
the circuit load.
High
impedance
points are
found in
switchboard
or circuit.
Locate the
high impedance
and repair
or replace
relevant parts.
The supply
voltage
is
too high
or
too low.
Consult the
power supply
department
Voltage to
earth
of zero line
<2V
>2V
Leakage
current
Find the
current source:
Is there any
multipoint
ground?
Does the
equipment
or
device
leak current?
Three-phase
imbalance
Check and
redistribute
the load
>2V
<2V
Voltage to
earth
of zero line
Harmonic
interference
Increase neutral
line conductor,
install electrical
filter or use
other methods
to reduce the
harmonic
interference
The supply
voltage
is
too high
or
too low
Consult the
power supply
department
The electron
device in
the circuit
results in the
electric wave
distortion
Revaluate
and
relocate
(if necessary)
the electronic
device
in the circuit
The voltage
is
too high
or
too low.
153-185V
(120V)
280-342V
(220V)
Peak voltage
The supply
frequency
is
too high
or
too low.
Consult
the electricity
department
The frequency
is
too high
or
too low.
60Hz
(50Hz)
Frequency
