Advertisement
INTERPRETATION
1) When the probes are first placed in contact with the insulator one or two yellow lights
may come on briefly and then go off - this is normal and indicates that the tester is in
contact with the insulator being tested.
2) The insulator is good when the probes are in contact with the insulator and the green
LED and/or the first or second yellow LED are lit.
3) The insulator is surface conductive if some but not all red LED's are lit and the buzzer
sounds - see Point 5 below.
4) The insulator is defective or has very high surface conductivity if the complete LED
display is lit and the buzzer sounds - see Point 5 below.
NOTE: Refer to the Leakage Current Measurements Table on page 11 for the measured
leakage current associated with each LED.
5) Readings produced by surface conductivity can be isolated from those produced by
non-visible defects by applying both tester probes directly to the external porcelain
surface of the insulator or one probe to the metal cap and one probe to the external
porcelain surface of the insulator in question (it may be necessary to reposition the
flexible probe 90 degrees from its original position on the tester - see section on
FITTING THE TEST PROBES, page 5). With the probes in contact with the
insulator as described in this step:
a) if the green LED and/or the first or second yellow LED are lit, the insulator is not
surface conductive and the reading produced by Step 3 or 4 above is the result
of a defective insulator. Move the contact point on the porcelain skirt to different
places to rule out a dry banding on the insulator;
b) if the complete LED display is lit and the buzzer sounds, the insulator is surface
conductive. It should be cleaned and dried prior to retesting or be tested at a time
when the relative humidity is lower (see SURFACE CONTAMINATION section, page 5).
NOTE: Test results on strings of insulators will tend to fall into one of two cases.
In the first case, surface conductivity is generally present if EVERY one of the first
several insulators tested indicates defective. If this pattern of defects occurs, the
user should suspect surface conductivity and immediately test for this condition
using the procedure in Point 5 above.
In case two however, if MOST of the insulators tested are found to be good, then
the few which are found to be defective are probably defective. This is because
surface conductivity is not likely to happen on only a few insulators on any partic-
ular string or structure. Therefore, those insulators which indicate they are defec-
tive under these circumstances are almost certain to be defective.
For more information, refer to the SURFACE CONTAMINATION section, page 5.
10
Advertisement
