Surface Contamination; Fitting The Test Probes - Textron HDE HI-TEST IT-4 Operating Instructions Manual

SURFACE CONTAMINATION

Most contaminants that collect on the surface of insulators are only conductive in the
presence of moisture. There are only a few wind blown contaminants that are conductive
when dry and their occurrence in any area is generally well known to the utility company.
As a result, these latter types of contaminants generally will not interfere with insulator
testing activities.
For the more common wind blown contaminants, the visible amount of surface contamination
on the insulator is a poor predictor of its surface conductivity for two reasons:
1) the actual visibility of contaminants varies greatly (e.g. concrete dust versus salt spray).
2) most wind blown contaminants are non-conductive until they are moistened - either
by fog, heavy dew, light rainfall or extremely high humidity.
This means that line crews testing insulators for dielectric condition must pay attention to
the moisture at the time they are testing. Since rainfall normally precludes the performance
of live-line work, the surface conductivity of insulators in this circumstance is typically
not a problem in the testing of insulators. It is recommended that the tester not be used
in live-line conditions during rainfall or until after the insulators have fully dried following
a rainfall.
However, early morning dew, fog and extremely high humidity are conditions which will
interfere with insulator testing. To avoid the problem of early morning dew, it is advisable
not to begin testing insulators until the sun has had time to dry the surface of the insulators
to be tested. To avoid the problem of fog, it is advisable not to attempt to test insulators
under foggy weather conditions. To avoid the problem of extremely high humidity, it is
advisable to avoid testing insulators if the relative humidity exceeds 85%.
Finally, if any question arises about the surface conductivity of insulators being tested,
the test crew can measure the surface conductivity of several of the subject insulators
using the test procedures described in the Instructions for Testing Insulators section
beginning on page 8.
OPERATIONAL IMPAIRMENT - If the IT-4 is used in a manner not described in this instruc-
tion manual, the protection and effective operation of this equipment may be impaired.

FITTING THE TEST PROBES

1) The probes can be fitted so that they project from either side of the tester.
2) The couplings on the tester to which the probes are fitted are notched in three locations
on their outer edge to allow the longer probe to be fitted in three (3) configurations (see
Figure Two). The longer probe can be fitted: i) to the top of the tester; ii) to project across
the rear end of the tester; or iii) to project across the bottom of the tester (see Figures
Three, Four, and Five).
The notches on the outside edge of the couplings on the tester are designed to receive a pin
machined on the inside of the couplings on the end of the test probes. In order to fit the probes
correctly to the tester, it may be necessary to rotate the probes slightly as they are being tight-
ened onto the couplings on the tester.This will ensure that the pins fit into the notches.
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