Custom Search
|
|
|
||
 ELECTRICAL
Switchgear-Continued
n Interior of Compartments, Cubicles and Drawers:
dirty
symptoms of overheating
burns from ground and short circuits
defective insulation
defective operation of locks, doors, and drawers
n Air and Oil Circuit Breakers, Oilless-Type Air Blast Breakers
(Deenergized/50 Amperes and above):
incorrect wipe of main and arcing contacts on opening and closing
overheating
lack of continuity
looseness of connections on all mechanisms
incorrectly placed pins and cotter pins
improper functioning of rods and moving parts and binding occurs
when breaker is operated
n Tests:
Measure operating voltage on electrically-operated breakers
Measure operating voltages in switchgear control circuits
Make liquid dielectric strength tests. Liquid should be changed if
tests under 18,000 volts
Measure insulation resistance and evaluate
minimum value or low limit recommended is 2 megohms
total (after one minute at approximately 25 degrees C.) for
safe operation or before making high-potential tests
make high-potential tests at 65 percent of initial installed
value, or in accordance with manufacturer's recommendation
7.2.24 Wood Poles and Accessories: Comply with all current safety precautions.
Because overhead electric distribution systems are energized almost continuous-ly, in-
spection of such items as poles, hardware, and associated accessories should be made
from the ground using field glasses except during those periods when placed outages of
the various systems will permit a climbing inspection. Ordinarily such climbing inspec-
tions will occur very infrequently and should be performed only when it is certain
7-48
|
 
|
|
|
||
