|Electricals & Electronics
|Power Distribution Solutions
18
15.2.
INDOOR BUSDUCT
15.2.1.
Inspect busduct once each year or after any severe electrical short circuit or ground fault.
15.2.2.
Perform an infra-red temperature scan on all electrical connections and busduct enclosure while
busduct is energized and operating under maximum load conditions. A permanent record should be
kept. If readings change with time, deterioration that may be taking place and must be corrected.
15.2.3.
Turn off power to busduct.
15.2.4.
Look for any moisture or signs of previous wetness or dripping onto the busduct or onto connection
boxes from leaky roofs, pipes, sprinklers or other sources moisture. Look for any recent changes in
sprinklers or other plumbing that might now be a source of trouble to busduct.
15.2.5.
Seal off any cracks or openings which have allowed moisture to enter the busduct or its connection
boxes. Eliminate source of any dripping onto the busduct and any other sources of moisture see
SECTION 6 or more details on preventing liquid from getting onto the busduct.
15.2.6.
Replace or thoroughly dry and clean any insulating material which is damp or wet or shows
accumulation of deposited material from previous wettings.
15.2.7.
If there is appreciable accumulation of dust, clean it off by using a brush, vacuum cleaner, or clean
lint-free rags. In order to avoid blowing dust in the busduct joints, circuit breakers, or other equipment,
do not use a blower or compressed air.
15.2.8.
Carefully inspect all visible electrical joints and terminals.
15.2.9.
Visually check connections to be certain that they are clean and secure. Loose and/or contaminated
connections increase electrical resistance which can cause overheating. Such overheating is indicated
by discoloration or flaking of insulation and/or metal parts. Pitting or melting of connecting surfaces is
a sign of arcing due to a loose or otherwise poor connection. Parts which shows evidence of
overheating or looseness should be cleaned or replaced if damaged, contact manufacturer before
opening joint bolts.
15.2.10. Check the insulation resistance prior to re-energizing the busduct. A permanent record should be kept
of resistance readings. If readings decrease appreciably with time, deterioration is taking place and
must be corrected also, refer to section 14.4
Verification of Insulation Resistance (Refer IEC 60439
–
1:1999, page # 72)
For PTTA (Partially Type Tested Assemblies) which have not been subjected to a dielectric test according to
8.2.2 or 8.3.2 (clause numbers 8.2.2 page # 61 or 8.3.2 page# 71 of IEC 60439
–
1), an insulation
measurement using an insulation measuring device at a voltage of at least 500V shall be carried out.
In this case, the test is deemed satisfactory if the insulation resistance between circuits and exposed
conductive parts is at least 1000
𝛀
/V per circuit referred to the nominal voltage to earth of these circuits.
By exception, items which, according to their specific requirements, are current-consuming apparatus (e.g.
windings, measuring instruments) at the application of the test voltage or are not designed for the full test
voltage shall be disconnected as appropriate.