La Felicidad

12-E-HVS-747

Performance Investigation of HV Insulators Coated
by Silicon Rubber
Ali Naderian1,2, Majid Sanaye-Pasand1, Hosein Mohseni1,
Saleh Moonesan 1, Ayman H. El-Hag3 , Edward Cherney2,
Shesha Jayaram2, Gholamreza Jalali 4

2

1
Electrical and Computer Engineering , Faculty of Engineering, University of Tehran
High Voltage Lab, Faculty of Engineering, University of Waterloo,Ontario, Canada, anaderia@uwaterloo.ca
3
Electrical Department, American University of Sharjah, Sharjah, UAE
4
Alvand Pooya Niroo Co., Tehran, Tel: 66925272, 66595371

Keywords : Insulator, RTV coating, silicone rubber, filler, pollution

1. Introduction
Insulator contamination has been a problem
since the birth of electrical power distribution.
Natural pollution likes salt spray anddesert
sand and industrial pollutants can lead to
costly power interruptions due to arcing and
flashover. Wet atmospheric conditions give
rise to water filming and, in the presence of
contaminants, an uncontrolled leakage current
develops and results in flashover. This type of
disruption can be very costly. Application of
Room temperature vulcanized (RTV) silicone
rubber coating has beeninvestigated as an
effective solution to make a hydrophobic
surface spraying over the bushing of
transformers, stand of circuit breakers and
post insulators and even cap and pin
insulators of new overhead lines[1,2,3,4].
Application of RTV silicone rubber coating is
recommended for insulator of existing
substations in highly polluted areas [1,2,3].
Fig 1 shows different type of application ofAbstract :
This paper discusses important parameters for
evaluating room temperature vulcanized
(RTV) silicone rubber coatings for high
voltage insulators of substations and overhead
lines. It presents the results of conducted tests
for 3 different commercial RTVs which are
used by utilities nowadays. Tracking and
erosion resistance, loss of hydrophobicity,
mechanical strength,thermo-gravimetric
analysis, and scanning electron microscopy,
have been employed to evaluate these
coatings in laboratory. As a final conclusion,
RTV-C, which has both ATH and silica fillers
with the filler size about 1 µm , shows the best
electrical,
mechanical
and
chemical
performance among available insulators. It is
recommended for applying to ceramic
insulators in the field.

953Performance Investigation of HV Insulators Coated by Silicon Rubber
21th International Power System Conference

this coatings on the insulators of substations
and overhead lines[1,2,5].

Fig.2. Suppression of leakage current on a coated
insulator during slat fog test, the first generation[1]

The anticipated life of present coatings is
estimated to be about 10 to 20 years [3].
IEEEguideline suggested using standard tests
like dielectric strength, dissipation factor, arc
resistance, insulation resistance and erosion
and tracking resistance for the evaluation of
RTV coatings [4]. Also, salt fog test and
tracking wheel test is recommended as nonstandard methods of evaluation. However
commercial RTVs usually have acceptable
specifications according to the recommendedstandard tests, evaluation of aging of them
and prediction of lifetime is the most
important problem which is not clear in the
standard.
There are some literature on RTV coatings
[3,4,5,6], however, in all of this work the main
emphasis has been on the degree at which the
various fillers are capable of reducing the
degree of mass loss during dry band arcing. Of
course this assumes that thetemporary loss of
hydrophobicity inevitably leads to the
development of leakage current and dry band
arcing on insulators in the field. After many
years of HVIC use, this observation has yet to
be reported. What has been observed by users
is a loss of hydrophobicity but only on the
unprotected parts of the leakage path., for
example on the upper surfaces of insulators as
evident in Fig. 3....