Textron HDE HI-TEST IT-4 Operating Instructions Manual page 9

5) When to test insulators for non-visible defects:
a) immediately prior to installation on the system, thereby ensuring they are not
defective when installed;
b) when insulators are recycled they should all be tested for non-visible defects prior
to being placed in inventory;
c) when troubleshooting RF/TVI and blinking light complaints as non-visible internal
failures in insulators can be a source of such nuisance complaints;
d) as part of a routine maintenance and emergency repair work on transmission circuits -
particularly on dead-end structures - to identify non-visible defective insulators
before they become a safety hazard to line crews. Testing on dead-end structures
is emphasized because evidence from the field indicates that the vast majority of
non-visible insulator failures on transmission circuits occur on dead-ends.
Procedure for Testing Insulators
1) Follow all live line safety procedures when testing insulators energized.
2) When testing in close proximity to dead-end or cutout jumpers, take care to ensure
that the tester probes do not shunt the jumper to the pole or cross arm.
3) When testing energized insulators DO NOT test strings of insulators which are buzzing
abnormally - this is an indication of possible extensive insulator failure. When nominal
voltage of the circuit is 69 kVAC and above, STOP TESTING any string of insulators if
the number of insulators identified as defective reaches the following levels:
69kV Do not test the last insulator if all previous insulators tested defective.
115kV Do not test the last 2 insulators if all previous insulators tested defective.
230kV Do not test the last 3 insulators if all previous insulators tested defective.
345kV Do not test the last 5 insulators if all previous insulators tested defective.
765kV Do not test the last 11 insulators if all previous insulators tested defective.
4) Keep the tester clean - particularly the area between the probes. This will prevent the
possibility of erroneous tester readings due to surface creepage from one probe to the
other across the dirty external surface of the tester. Clean unit with mild soap, rinse and
dry thoroughly before using.
5 IF INSULATORS ARE TO BE TESTED ENERGIZED, attach the tester to a hotstick appro-
priate for the line voltage and raise it to the lineman using a tie assist on the hotstick.
When testing insulators that are energized, the tester should never be used hand held.
IF INSULATORS ARE TO BE TESTED DE ENERGIZED, the tester may be hand held.
6) Apply the tester probes briefly across the metal parts on either side of the insulator or
from metal to concrete bead (depending upon insulator construction - see Section 4c
of IMPORTANT POINTS OF INFORMATION on page 8).
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