Post on 30-Mar-2023
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
by
ENHANCING GRID RELIABILITY
WITH
GEN-4 RTV SILICONE COATINGS
NEELESH ARORA
1
EPSILON
neelesh.arora@epsilonasia.com
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
3
1. Contamination Flashovers vs. Grid Reliability
• Insulators are a fraction of the cost of Transmission Grids yet
heavily impact grid reliability.
• In some coastal locations, up to 32.5% of all outage faults are
attibuted to pollution
• Contamination flashovers are still a global problem
• Robustness of Insulators across varying service conditions needed
• Ultimate target: To bring insulator monitoring/maintenance to ‘near
zero’ levels in all service conditions
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
4
2. Pollution Conditions
• Much research has gone into pollution
types, severities and the impact on AC
and DC insulators
• As per IEC60815:
– ESDD of 10μg/cm2 is considered ‘light’
– ESDD > 400μg/cm2 considered ‘very heavy’
• This presentation is concerned with
“Fourth Generation RTV Silicone
Rubber Insulator Coatings in medium
to very heavy level of contamination”
• This paper is valid for global conditions;
however, since colloquium venue is India,
most examples/references are local
400kV Switchyard, Udupi Power Corp. Ltd., Udupi, India
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
5
3. Common Methods to Eliminate Pollution Flashovers
• Insulator Washing in Live-line and Offline state
• Silicone Greases
• Anti-fog insulators
• Contamination Source Reduction
• Use of Non-ceramic Insulators
• Insulator Modification: RTV Insulator Coatings
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
Washing: High risk; Recurring Silicone Grease: Short-term efficacy
6
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
Anti-Fog Insulators: Nonceramic Insulators
7
Multiple failures Reported
PSTCL, Ludhiana
• Generally Encouraging except:
• Arid/Semi-arid conditions
• Where mechnical strength is critical
• Coastal locations (Peru, Colombia, etc.)
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
8
Composite Silicone Rubber Insulators (SRIs)
• Generally positive feedback
• Exceptions:
– Arid/Semi-arid Conditions: Long
rod Insulators with RTV Coating
preferred in most of the Middle
East
• In VH pollution conditions,
failures reported [*]
– Red de Energia del Perú S.A.
– ISA Colombia (Interconexión
Eléctrica S.A.
[*] INMR Q1/2011, Utility Practice and Experience”, ISA Colombia (Interconexión Eléctrica S.A. E.S.P and REP (Red de
Energia del Perú S.A.)
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
9
Excerpts: INMR: “Utility Practice and Experience”[*]
SRI Experience, South America
“Prevailing wisdom is that SRIs offer the best performance when it comes to
reducing or even eliminating service problems triggered by pollution
flashovers.
Based on this premise, Colombia’s Interconexión Eléctrica and Red de
Energia del Perú began incorporating SRI Technology in the late 1990s
mainly for lines running near a desert coastal plain dominated by subtropical
climate, high humidity and low rainfall.
In both cases, results were not as had been expected and a considerable
number of failures occured.
This eventually forced both utilities to replace the composite insulators.
[*] INMR Q1/2011, Utility Practice and Experience”, ISA Colombia (Interconexión Eléctrica S.A. E.S.P and REP (Red de
Energia del Perú S.A.)
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
10
Colombia’s ISA: Experience with SRIs[*]
Fault Rate of SRIs: up to 3 faults per 100 circuit km/year
2003: SRIs replaced with Porcelain in high-failure sections
No failures reported since
Other Challenges:
Ease of Access for Maintenance Personnel while inspecting conductors,
fittings & spacers. Typically, workers crawl out on SRIs which can deform or
break with a corresponding loss in insulation properties
SRIs are typically custom-designed therefore cost of spares is higher
[*] INMR Q1/2011, Utility Practice and Experience”, ISA Colombia (Interconexión Eléctrica S.A. E.S.P and REP (Red de
Energia del Perú S.A.)
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
11
Peru RED: Experience with SRIs[*]
Experience: 12,000 SRIs (220kV) installed in coastal area up to 2009
Failures between 2004 – 2011: 17, all due to mechanical failure caused
by high pollution, high humidity and electrical stress
Average Insulator Life:
Ceramic Insulator: 30 years
Glass Insulator: 34 years
SRI: 6-7 years. Even less when close to the sea
“Future Installation of SRI’s thrown into doubt’
[*] INMR Q1/2011, Utility Practice and Experience”, ISA Colombia (Interconexión Eléctrica S.A. E.S.P and REP (Red de
Energia del Perú S.A.)
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
12
SRI: Critical Maintenance Limitations
No established protocol for Live-Line Work (LLW) on SRIs unlike for ceramic
insulators
LLW by maintenance workers on SRIs is not encouraged
For critical lines, (system stability and revenue producing lines), this is a
major deterrent
Lines must be taken out of service for maintenance and this defeats the aim
of ‘uninterrupted performance’
Therefore, many utilities have banned the use of non-ceramic insulators on
critical lines
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
13
4. What is an RTV Insulator Coating?
• Room temperature Vulcanizing (RTV) Insulator Coatings are one-
part hydrophobic, UV-resistant coatings
• Use: Enhancement of an insulator's surface properties to prevent
the formation of a conductive layer in all service conditions
• RTV Insulator coatings also be referred to as:
– “High Voltage Insulator Coatings (HVICs), or
– “Anti-Tracking Coatings”
– RTV Silicone Insulator Rubber (SIR) Coatings
• For AC and DC systems
• For equipment up to 1200kV class
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
5. About RTV Insulator Coatings
14
• Usually Spray Coated in the
field, or pre-coated in
factories
• Eliminates flashovers in
pollution conditions without
compromising physical
integrity of equipment
• Maintenance-Free
• Tried, tested and evolved
technology
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
6. Advancement in RTV Coatings:
15
RTV Core Characteristics
Gen-1 • Used in the early 1970s with Trichloroethane as a solvent
Gen-2 • Contain Alumina Trihydrate (ATH). • Focus on Inclined Plane Tracking and Erosion Tests as opposed to
Hydrophobicity
Gen-3 • Use variations of ATH in different sizes. • Solvent changed from Trichloroethane to Naphtha
Gen-4 • Primarily silica-based• Display improved thermal characteristics. • Silica extends thermal resistance of the coating to above 350°C • Display better Hydrophobicity Recovery Characteristics• Unlike older coatings, are not prone to acid depolymerization• Not Prone to Peeling like some GEN-3 Coatings
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
6a. Gen-4 RTV: Improved Hydrophobicity Recovery
16
Gen-3 RTV Coating: Recovery
“Between HC2 & HC3” [1]
• HC3 Spec:
– 20° < θr <80° for majority of droplets
– Usually droplets are no longer
round at HC3
Gen-4 RTV Coating: Recovery
“to HC2” [1]
• HC2 Spec:
– 50° <θr < 80° for the majority of
droplets
– Droplets are Round
[1] Hydrophobicity Recovery Tests REC 76/2206 as
conducted by the Central Power Research Institute, India
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
6b. Dr. Cherney: The Argument for Gen-4 Coatings
Dr. Edward Cherney
Chairman, IEEE DEIS Outdoor Service Environment Committee
Contributing Participant, IEEE 1523-2002 Standard entitled “Guide for the Application,
Maintenance, and Evaluation of RTV Silicone Rubber Coatings for Outdoor Ceramic Insulators”
Co-Editor-in-Chief of the IEEE Electrical Insulation Magazine
Professor of High Voltage Studies at the University of Waterloo, Canada
17
“ATH is very sensitive to moisture uptake and this causes problems in the manufacture of a coating as a ‘wet ATH’
leads to gels in the coating.
Secondly, there is no physical or chemical mechanism for bonding of ATH particles to the silicone rubber backbone,
and this leads to porosity, a bad thing for a coating as moisture uptake can lead to:
(1) Hydrolysis of a coating
(2) Higher dissipation factor or dielectric loss, and
(3) Higher relative permittivity
On the other hand, silica is not sensitive to moisture uptake, so none of the mentioned problems occur. In addition,
because of the chemically similar structure, silica actually forms chemical bonds with the host matrix thereby
improving strength, reduces porosity, and further improves adhesion to substrates.
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
7. Gen-4 RTV HVIC: 100% Success in Switchyards
18
• 40+ Projects in just India alone
• 100% Flashover Elimination
• Only RTV coating with 0% Peeling and
Failure Rate
• TATA Power 4,000 MW UMPP (CGPL)
authored paper about success
• NTPC Kawas Gas Plant presented a
paper on their successful experience
with Gen-4 RTV Coating at “NTPC
Technogalaxy 2015”
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
19
Success in Extreme Pollution
Environments
Pollution Source
Insulator yard
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
20
8a. Case Overview: Tata Power CGPL 4,000 MW TPP
• 400kV Yard in Mundra,
coastal India
• 33mm/kV Creepage design
• 31 discs per 400kV string
• Multiple Flashovers Annually
• Existing Methods to Eliminate
Flashovers Unsuccessful
• Daily Live-line Washing cycle
through the year
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
21
8b. Tata Power CGPL 4,000 MW TPP, Mundra
Tata Power Authored Paper for CPRI
Conference: Excerpts:
• All Flashovers Eliminated
• “The Gen-4 RTV Silicone coated
insulators are completely maintenance
free.”
• Additional advantages like reduction in
leakage current, saving due to reduction
in maintenance cost, etc. can be
considered as an additional gain”
Tata Power CGPL paper “Experiences with Gen-4 RTV Coating” can be provided upon request. Please contact the speaker at +91.98715.16222 or neelesh.arora@epsilonasia.com
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
22
9. Transmission Lines: Field testing in India
Year Location Details
2008 Delhi Transco,Mandola 220kV
Fully Flashed-over strings, coated with Gen-4 RTV HVIC and installed on Flashover Prone part of Line
2009 PGCIL, 400kV Hisasar-Bawana line
Fully Flashed-over string, coated and installed on flashover prone part of line, near brick kilns
2010 Punjab Transco, 220kV & 66kV
Coating on failed anti-fog insulators in highly flashover-prone area near dye factories
2010 PGCIL WRTS-2/Kawas Haldarwa220kV
500 Field Aged insulators (15 years old) coated and installed in flashover-prone Kawas-Haldarwa CKT-1.
2011 Indian Railways, 132kV: Pilot Project
4,500 discs on highly flashover prone line in North India
All field trials have been successful.
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
9a. Field Trials on Field-Aged & Flashed Over Insulators
23
PGCIL: Field Tests on Flashed Over and Aged Insulators Delhi Transco: Field Tests on Flashed Insulators
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
24
10. Comparing Corona on Uncoated & Gen-4 Coated Insulators (UV Cam)
View Video Online
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
25
11. Northern Grid Collapse: Jan 2010
Incident Description:
• Line tripping during dense winter fog (DEC-FEB) is a common feature in Northern region
• Northern Grid partially collapsed in 2007 due to pollution flashover
• On 02 JAN 2010, Northern Region (NR) experienced a grid disturbance in which power supply in
Punjab, North Haryana, HP, J&K & Chandigarh sub-system was affected.
• The incident was initiated to fog related tripping/ flashovers. [2]
If Gen-4 RTV Coatings had been Deployed…
• Considering no known failures of GEN-4 RTV Coating have been reported despite widespread
global deployment even in coastal conditions where weekly flashovers reported pre-coating, it is
near-certain that even dense fog would not result in pollution flashovers.
• NORTHERN GRID would not have collapsed had Gen-4 RTV Coating been applied
[2] CEA Report Of The Inquiry Committee On Grid Disturbance In Northern Region On 2nd January 2010, published June 2010
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
26
11 a. Northern Grid Collapse: CEA Recommendations [3]
Recommended Remedial Measure Impact of Gen-4 RTV Coating
Replacement of Insulators Not Required
Routine Cleaning of Insulators Not Required
Shutdown of lines in order to facilitate insulators replacing/cleaning Not Required
Effective and experienced personnel should be made available particularly at important stations during foggy nights
Unrealistic, not required
Real-time Monitoring of Humidity & Temperature of Different Locations Not Required
Deployment of Additional manpower during night shifts Not Required
Classification of Pollution Levels Not Required, RTV Robust enough to handle extreme pollution
Banning brick kilns, industrial units or biomass/diesel based power plant with < 30 meter chimney to be set up within 0.5 km of the 220 kV + line
Method would further complicate ROW challenges. Not Required
Ensure availability of O&M and senior officers at all strategic locations if forecasted RH > 85-90% and temperature likely to fall below 15-17°C
Unrealistic, not required
[3] The Central Electricity Authority vide order no. CEA/5-41 (07)/Secy-2009 dated 08-01-2010 (Annexure-1/III) constituted a Committee to inquireinto the grid incident and ascertain the cause of grid disturbance and suggest remedial measures to avoid recurrence of such incidents.Recommendations u/s 9.4 were stated as are listed above
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
27
12. RTV on HVDC: Operational Experience
• “Application of RTV hydrophobic coatings has contributed to the
achievement of the low pollution flashover rate.
• Insulation strength, after application of coatings has improved”
800KVDC: EXTERNAL INSULATION, INSULATION COORDINATION, TEST Levels, D. Wu, U. Åström, V. F Lescale, ABB
Power Systems, HVDC Ludvika, Sweden as presented at IEC/CIGRE UHV Symposium Beijing 2007-07-23
• In Italy, more than 2,000 RTV pre-coated toughened glass insulators have
been installed on HVDC lines after more than 4 years showing satisfying
performance
• Refurbishment of existing DC lines and future upcoming DC interties could
rely on RTV pre-coating technology
• RTV pre-coating could be the right answer to very polluted environments
DC-toughened glass insulators pre-coated with RTV silicone rubber – field returns from aged samples installed on HVDC lines;
M. Marzinotto, G. Lavecchia, M.R. Guarniere, A. Posati, M. Rebolini, Terna Rete Italia – TERNA Group, J-M. George, S. Prat,
SEDIVER
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
28
13. RTV Coatings on Air Core Reactors
• A combination of light pollution and
moisture causes:
– Discharges between the windings/coils
– Tracking of the fibreglass support structure
short circuiting the windings
– inductance to be ineffective
• Under polluted operating environments
– Tracking could occur on the surface of an AC
stressed reactor winding
– Anti-tracking coating is applied on the winding
surface
– TRENCH, Installation & Maintenance Manual for Dry-Type Reactors
• “Reactors shall be finished with a uniform
RTV coating on its exposed surfaces”: – ESKOM Specification for Air Core Reactors
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
29
14. Long Term Performance of RTV Coatings
UV Resistant therefore long outdoor life
Proven record with Pacific Gas & Electric, USA having 25+ years of
using RTV coating on 500kV bushings and insulators.
(These bushings were in a highly polluted area that previously
required routine washing)
Expected life: At least 20 years in most service conditions
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
30
15. Silicones for Corrosion Prevention
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
31
15. Silicones for Corrosion Prevention
April 8th - 9th, 2015, Pragati Maidan, New Delhi, India
International Colloquium on Overhead Lines in association with CIGRE SC B2
32
16. Conclusion
• RTV Coatings are tried and tested in switchyards with a 100%
performance record, even in H-VH pollution levels
• Considering line outages are not required for maintenance of RTV
Coated insulators unlike for SRIs, true uptime and TCO is more
favorable for RTV Coated insulators vis-à-vis SRIs
• RTV Coating is therefore a realistic and viable option for insulators
all Overhead Lines, up to 1200kV
• Methods for in-situ application (off line) on up to 400kV lines are
being developed which could further reduce downtime