1. Experience in the Evaluation ofExperience in the Evaluation of
Polymeric Insulators for
Distribution Systems in
Medium Voltage through aed u o age oug a
Natural Laboratory
Author: Augusto Abreu
VenezuelaVenezuela
São Paulo, November 2010

2. Content
Introduction.
E l ti M th d lEvaluation Methodology.
Results.
Conclusions and Recommendations.

3. IntroductionIntroduction
Therefore, this research develops a
Natural Lab.
“Caño Sagua”
Therefore, this research develops a
methodology to evaluate different designs
of polymeric insulators (silicone rubber)
suspension type with galvanized steelsuspension type with galvanized steel
hardware, aluminum and polymer coated
in a natural environment.
For this, a specific area was available
where environmental conditions are the
most severe on the west coast of Zuliamost severe on the west coast of Zulia
State, located north of the Venezuela
Guajira, and establishing it as a Natural
LaboratoryLaboratory.
Salt
Contamination
Corrosion
Sand
Blasting+ +Contamination Blasting

4. Evaluation MethodologyEvaluation Methodology
“Natural Lab”

5. Evaluation Methodology (Cont )Evaluation Methodology (Cont…)
“Polymer and Hardware Visual Inspection”

6. Evaluation Methodology (Cont )Evaluation Methodology (Cont…)

7. Results
Model “A”
The insulators used were
model DS-28 established inmodel DS-28 established in
standard ANSI C29.13, with
leak distances from 550 mm to
660 mm and with galvanized660 mm and with galvanized
steel hardware with a minimum
of 95 microns thick.
In the case of insulators with
exposures of 4 years, hardware
were found in an advanced
state of deterioration.
With regard to polymeric material, it did not present any type
f d d ti d b i i l diti I l tof degradation and being in regular condition. In general terms,
with the results obtained with this model of insulator, it can be
concluded that in the northern zone of Zulia this insulator would
have a useful life of approximately 5 years of hardwarehave a useful life of approximately 5 years of hardware
degradation due to corrosion.

8. Results (Cont…)( )
Model “B” After 18 months installed, a visual
inspection found a number of deep cracks,
breakage and wear of polymeric materialbreakage and wear of polymeric material.
Of the cuts made it was detected that the
leakage current circulates between the
fiberglass bar and the polymer coat (B-2, B-
3 and B-5).
Based on the gathered evidences theBased on the gathered evidences, the
best hypothesis raised for this crack is that
because of the mechanical strains the
present seal brakes between the galvanized
steel buttonhole and the polymeric cover,
causing the entry of moisture and causing
partial discharges between the polymeric
layer and the fiberglass barlayer and the fiberglass bar.
Additionally, when the insulator was
sectioned is was found an asymmetry in the
injection of the polymeric cover (B-4).

9. Resultados (Cont…)( )
Model “B” (Cont…)
B-1 Galvanized Hardware.
B-2 Stainless Steel Hardware.

10. Resultados (Cont…)( )
Model “C”
The exposure time of this
insulator was 4 years. It was
utilized an insulator model with
a leak distance of 950 mm. The
intention of testing this designintention of testing this design
was to subject the aluminum
alloy hardware to the actual
conditions of the area.
With respect to the
polymeric material present a
poor condition as was
observed erosion andobserved erosion and
polymer separation between
the cover and hardware. For
this reason it is not convenient
to use insulators with hardware
partially covered.

11. Conclusions and Recommendations (Cont…)
For the case evaluated and depending on the results
obtained, it was decided to reduce the leak distance of 863.60
mm used with two ceramic bells to 550 mm with a polymeric
insulator without the need to do preventive maintenance (wash).
The use of insulators with galvanized steel hardware with 95
microns thick for the entire northwestern region of Venezuela,
except for the region of La Guajira, where it is recommended theexcept for the region of La Guajira, where it is recommended the
use of polymeric insulators with aluminum alloy hardware
because of the high levels of corrosion.

12. Conclusions and Recommendations (Cont…)Conclusions and Recommendations (Cont…)
Model “A” Model “B” Model “C”
    
It is recommend the application of the methodology developed in
this work in regions of the world where environmental conditions
such as environmental pollution, corrosion and sand blasting are
present in an extreme way, and it is required to implement new
designs for polymeric insulators, in order to detect faults andg p y
improvement points before mass implementation.

13. ThanksThanks forfor youryour
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