combined with their rugged construction, make them
durable and reliable instruments.
The maintenance and cleaning of these
instruments are easy. Maintenance consists of periodic
cleaning, battery replacement, fuse replacement, and
recalibration. Calibration on these meters should be
performed every year. The exterior of the instrument
can be cleaned with a soft, clean cloth to remove any
oil, grease, or grime from the exterior of the
instrument. Never use liquid solvents or detergents. If
the instrument gets wet for any reason, dry the
instrument using low-pressure clean air at less than
25 psi. Use care and caution while drying around the
display protector and areas where water or air could
enter the interior of the instrument.
All resistance measurements should be taken
on de-energized circuits ONLY!
When using compressed air for cleaning, wear
chemical splash goggles. Do not direct the air
toward eyes or skin.
MAINTENANCE OF DISTRIBUTION
The elements, accidents, and willful vandalism are
the cause of most damage to power distribution
equipment. To repair these damages, the lineman
requires experience, a total commitment to safety, and
the knowledge to accomplish repairs to the system as
quickly and economically as possible.
The maintenance required on the poles, timbers,
and crossarms in a power distribution system is
minimal. Normally, this equipment lasts for a period of
20 years or more. However, the following problems
may occur and create a need for maintenance action:
A pole can settle and require straightening.
Wood can shrink and cause all hardware to
become loose and require tightening.
Over time, guys stretch and require re-
Insulators get dirty and require cleaning,
especially around sea water where there is salt in
Connections become loose with age and must be
re-torqued to prevent hot spots.
In time, conductors stretch and require re-
Another important area of maintenance is noise
interference elimination in the power distribution
Power lines may be a source of interference with
radio communications. Conductors, insulators, and
hardware contribute their share by means of spark
discharges, localized corona discharge, and cross
Spark discharges occur when localized excessive
voltage stress exists. A conductor may become
partially insulated by corrosion products or an
insulator partially conductive because of cracks. A
third source of stress occurs when a conductor is
separated from another metallic part on a pole only by a
small air gap.
Corona is defined as the luminous discharge due
to ionization of the air in the vicinity of a conductor
when the voltage gradient exceeds a certain critical
Cross modulation (often the result of a corroded
connection that causes nonlinear rectification of
currents) may occur when splices are made by twisting
the conductors, rather than using a tighter mechanical
splice. Additionally, when conductors of dissimilar
metals are joined, corrosion occurs unless special
connectors designed for the specific combination of
metals are used.
Remedies for conductor, insulator, and hardware
interference are relatively simple. Remember, the
condition for hardware interference is set up whenever
two pieces of hardware are not securely bonded to each
other or are permanently separated by too short an air