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I.
Cutout Design & Function
1.
2.
3.
Function
a.
Purpose
b.
System construction
Terminology
a. Common terms
b. Cutout components
History
II.
Cutout Standards
1.
2.
3.
2
Current standards
a. IEEE / ANSI
b. CSA
c.
IEC
Evolution of standards
a. NEETRAC
b. IEEE / ANSI
c. Considerations
Design tests
a. Standard tests
b. MPS tests
c.
NEETRAC proposed
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III. Advantages of Polymer
1.
2.
3.
IV. MPS Cutouts
Design
a. Material
b. Insulation
c. Thermal cycling
Installation
a. Durability
b. Weight
c. Handling
Maintenance & operation
a. Core strength
b. Safety
c. Lifecycle & replacement
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1.
2.
Design advantages
a. Transmission experience
b. Silicone vs. EPDM
c. Core
d. Shed pattern
e. Fittings
f. Hardware
Service advantages
a. Domestic factory
b. Storm capabilities
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I. Cutout Design &
Function
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a.
Purpose
• Over-current protection
- System demand
- Short circuits
- Various fault types
b.
System construction
• Overhead distribution
• All distribution kV classes
• Commonly applied in front of transformers
• Applied prior to beginning underground line
http://www.youtube.com/watch?v=zAxGBHZtUM0&feature=youtu.be
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a. Common terms
• Interrupt Rating
- Maximum short-circuit current the cutout device can interrupt, extinguish, and clear
under standard test conditions
• Basic Insulation Level (BIL)
- Measure of withstand for surge voltages such as lightning or system switching
• Dry Arc
- Distance of the shortest path from line voltage to ground
• Leakage
- Distance from line voltage to ground when the current path is along the insulation
surface
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b.
Components
Parallel-groove clamp
Sleet shield
Fuse support / body
Upper contact spring
Center bracket
Upper contact
Lower contacts
Arcing horns / guide
hooks
Hook stick ring / eye
Lower hinge
Fuse holder / tube /
door
Trunnion
Fuse tube ferrules
Flipper
(under trunnion)
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• Fuse holder
- Current interrupt rating specific
- Filament wound tube to support fuse link
- Reusable, but liner must be inspected after interruption
- Arc energy used to convert synthetic liner to di-electric gas
• Fuse link
- Selected by current rating and system coordination
- Replaced after every over-current incident
- Time / Current characteristics control melt speed
Flipper
spring
Arc-shortening rod
Cap
Arc-extinguishing
liner
Fuse link
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• General
- Cutout patents date back to 1930
- Up to mid 1990’s each manufacture had unique fuse holder dimensions
• Fuse tube
- Bone fiber or fish paper
- Problems with moisture absorption and swelling
- Durability
- S&C fuse tube design patented 1980 with synthetic lining
- Current tubes are constructed from fiberglass
• Insulator
- Porcelain devices
- S&C silicone insulator patent filed 2002
- MPS silicone cutouts 2010
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II. Cutout Standards
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a. IEEE / ANSI
• Institute of Electrical and Electronics Engineers Power & Energy Society
-Shares developments in the electric power industry, creates standards
for the development and construction of equipment and systems, and
educates industry and the general public
-Switchgear subcommittee is the controlling body for cutouts standards
• ANSI / IEEE C37.41-2008 Standard Design Tests
-Power Frequency Dry Withstand
-Power Frequency Wet Withstand
-Impulse
-Interrupting Test Series 1 – 5
-Radio Influence
-Temperature Rise
-Manual Operation
-Thermal Cycle
-Bolt Torque
• ANSI / IEEE C37.42-2009 Standard Specifications
-Tables specify test values for design tests listed above
-Currently under revision with long term goal to roll C37.42 into C37.41
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b.
CSA – Canadian Standards Association
• C310-09 Distribution Class Polymeric Cutouts
- References C37.41 & C37.42
- Additional tests for polymer fuse supports, based on distribution insulators
- Additional mechanical tests
- Interchangeability clause
- Bolt torque
• Concerns with C310-09 Specifications
- Tracking & erosion test is at fixed 35V/mm leakage, not system voltage,
penalizing high-leakage designs
- Interrupt interchangeability of fuse tubes has no standard - annex A.5.4
suggests customers to inquire with manufactures
c.
IEC
• Used internationally in European, African, and many Latin American and Asian
countries
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a. NEETRAC
• School of Electrical and Computer Engineering at Georgia Tech
• Self-supporting, membership based testing & research center
b. ANSI / IEEE
•
C37.41 – porcelain cutout standard evolving to cover polymer cutouts
- Currently under revision
- Incorporating sections of C37.42
- NEETRAC polymer working group has proposed recommendations to IEEE
committee to include tracking & erosion, mechanical tests on fuse support
and interruption at temperature extremes
•
C37.42 – phasing `out
-Currently under revision
-Many sections being moved to C37.41
-Next revision most likely to be the last change
c.
CSA
•
CSA 310-09
-Test parameters should be reconsidered
-MPS has not participated in this committee
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a.
Standards Tests
•ANSI / IEEE C37.41-2008 Standard Design Tests
- Power Frequency Dry Withstand
Tests insulator design and construction by holding a specified voltage for a
period of time
-Power Frequency Wet Withstand
Same as above but in a simulated high humidity or rainfall environment
- Impulse (BIL):
Tests insulation level to protect against surge voltages such as lightning or
system switching
-Radio Influence Voltage (RIV)
Tests to ensure the design does not create electrical noise
- Interrupting Test Series 1 – 5
Tests the entire cutout system to interrupt different over-current conditions
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a.
Standards Tests cont.
•ANSI / IEEE C37.41-2008 Standard Design Tests cont.
- Temperature Rise
Tests resistance factors (i.e. contact pressures, material selection and design)
- Manual Operation
Tests ability to function properly after 200 open and close operations
- Thermal Cycle
Tests design integrity during thermal expansion/contraction
- Bolt Torque
Tests hardware up to at 125% of nominal manufacturer-specified torque values
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b.
MPS Tests
• 3 point bend – Test glass core rigidity
• Water Diffusion
–Tests fiberglass core integrity and silicone bond to core
• Dye penetration
– Tests fiberglass core integrity & end fitting seal
• Torque
– Tests crimp joint integrity and fiberglass core strength
• Tensile test – Tests fiberglass core and end-fitting strength
• Loadbuster – Tests mechanical operation using S&C Loadbuster device
c.
NEETRAC proposed testing
• Insulation Test (42 hr boiling water / steep front impulse / withstand)
• Water Diffusion Tests (CSA 7.4)
• Interruption Test Series 1 at +50 °C and -50 °C
• Tracking & Erosion
• Weathering - UV Aging
• Long Term Deformation
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III. Advantages of
Polymer
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a.
Material
•
Polymer types
PTFE – Polytetrofluoro ethylene
EPR – Ethylene propylene rubber
EPDM – Ethylene propylene diene methylene
SIR – Silicone rubber
•
Inherent resistance to pollution & are hydrophobic
•
Pliable material vs. brittle porcelain material
•
Weight differential (1:10)
•
Engineered material – easy to mfg.
b.
Insulation1
•
Increased leakage
•
Greater dry-arc distances lead to higher kV flashover levels
•
Better performance in polluted environments 2-4
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c.
Installation
•
Durability & Handling
No possibility of chipping
Higher impact resistance
Cutout/arrester combo units save new install time
•
•
Weight
Freight savings
Easier warehouse handling
Chipped Porcelain
Safety
Ergonomics – low extended weight when installing
No potential sharp edges
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a.
Strength of fiberglass core over repeated interruptions and
closures
b.
Safety
•
No sharp edges due to damage (hail/ice)
•
No possibility of cracking or shrapnel dispersion under
catastrophic events
c.
Lifecycle & replacement
•
Longer lifecycles in polluted environments
•
No possibility of cracking due to thermal cycling
•
Reduced vandalism threat
•
Easier & cheaper disposal due to lighter weight
Cracked Porcelain
Fractured Porcelain
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IV. MPS Polymer
Cutouts
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a.
MPS is an experienced leader in insulator design
•
25+ Years and 29 million years of installed service life
•
Designs up to 500kV
•
All environments
•
This experience is designed into our cutouts
b.
Advantages of Silicone vs. EPDM 5-10
•
Superior flashover performance
•
“Recovery” of hydrophobic properties 11-13
•
Superior UV & aging performance 14
•
Chemically inert – unaffected by pollutants
eJournal of New World Sciences Academy, 2007 V2, N4, A0038
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c.
Core
•
Boron-free/corrosion resistant E-glass core15
•
High-strength to withstand dynamic loads during interruption & fuse replacement
•
3-point bend sampling tests
d.
Alternating Shed Pattern
•
Meets IEC 60815-1, 3 for polymer selection & dimensioning in polluted conditions
s/p well above major competitors
Sufficient C (distance between sheds)
Lower l/d (leakage distance vs. clearance) than major competitors
Lower l/A (leakage over arching distance) value
•
Superior pollution performance (including ice)16
s/p
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l/d
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e.
Fittings
•
Crimped on fittings
Prevents rotation and alignment issues
Provides mechanical barrier against moisture ingress
•
Over-molded rubber design provides additional barrier against
moisture ingress
f.
Hardware
•
Thicker sleet-shield prevents deformation and upper contact
pressure issues
•
Thicker top contacts prevent deformation after interruption or
mishandling
•
“Floating” top contact design provides sufficient pressure should a
non-MPS fuse holder be installed
•
Dimpled top contact prevents over-closures
•
Gentle top contact angle allows for easier closing
•
Eyebolts & parallel groove clamp connector options
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a.
Domestic Factory
•
Polymer cutout assembly in York SC
•
Domestic stocking of components
•
Short lead times & disaster recovery
b.
Storm Capabilities
•
Cross-trained operators allow capacity-flexing in emergencies
•
Capabilities for 3 shifts 7 days a week
•
York location is out of typical disaster areas, yet in 1-2 days proximity to
major shipping lanes & destinations
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1. James, F.H., (1993). History and Bibliography of Polymeric
Insulators for Outdoor Applications. IEEE Transactions on Power
Delivery, Volume:8, No:1, pp:376-385.
2. Jahromi, A.N., El-Hag, A.H., Jayaram, S.H., Cherney, E.A., SanayePasand, M., and Mohseni, H., (2006). A Neural Network Based Method
for Leakage Current Prediction of Polymeric Insulators. IEEE
Trans. on Power Delivery, Volume:21, No:1, pp
Application guide for Composite Suspension Insulators, SEDIVER,
Paris, 1993.
3. Houlgate, R.G., and Swift, D.A., (1990). Composite Rod Insulators
for AC Power Lines: Electrical Performance of Various Designs at a
Coastal Testing Station", IEEE Transaction on Power Delivery,
Volume:5, No:4, pp:1944-1955.
4. Houlgate, R.G., Swift, D.A., Cimador, A., Poubaix, F., Marront,
G., and Nicolini, P., (1986). Field Experience and Laboratory
Research in Composite Insulators for Overhead lines. International
Conference on Large Electric High Tension Systems (CIGRE),
Paper:15-12.:506–507.
5. Van Der Huir, R., and Karner, H.C., (1989). Evaluation of
Polymeric Insulating Materials for HV Outdoor Applications.
Proceedings of 6th ISH, 30.02.
6. Pilling, J., Chrzan, K., Hofmann, J., and Baersch, R., (1993).
Artificial Aging of Polymer Insulation Surface in a Clean Fog
Chamber and its Evaluation. Proceedings of 6th ISH, Volume:2,
pp:165-188.
7. Fourmigue, J., Noel, M., and Riguel, G., (1995). Aging of
Polymeric Housings for HV Insulators- Comparison Between Natural
and Artificial Testing. Annual Report of CEIDP, pp:404-407.
8. Otsubo, M., Shimono, Y., Hikami, T., and Honda, C., (1996).
lnfluence of the Humidity on Leakage Current under Accelerated
Aging of Polymer Insulating Materials. Conference Record of ISEI,
pp:267-270.
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9. Zhao, T. and Sakich, J., (1996). Salt Fog Aging on Non-Ceramic
Insulators and Fog Chamber Data Acquisition System. Annual Report
of CEIDP, pp:377-380.
10. Gorur, R.S., De la, O.A., El-Kishky, H., Chowdhary, M., Mukherjee,
H., Sundaram, R., and Burnham, J.T., (1997). Sudden Flashover of
Nonceramic Insulators in Artificial Contamination Tests. IEEE Transaction on
Dielectrics and Electrical Insulation, Volume:4,
No:1, pp:79-87.
11. Kim, S.H., Cherney, E.A., and Hackam, R., (1990). The Loss and
Recovery of Hydrophobicity of RTV Silicone Rubber Insulator
Coatings, IEEE Transactions on Power Delivery, Volume:5, No:3,
pp:1491-1499.
12. De Decker, D. and Wright, S., (1993). Recovery and Hydrophobicity
Transfer in Silicone, SEE Symposium on Composite Polymer
Insulators.
13. Chang, J.W. and Gorur, R.S., (1994). Surface Recovery of Silicone
Rubber Used for HV Outdoor Insulation. IEEE Transactions on
Dielectrics and Electrical Insulation, Volume:1, No:6, pp:10391046.
14. Sherif, E.M., (1987). Performance and Aging of HVAC and HVDC
Overhead Line Insulators, Ph. D Thesis, Chalmers Institute of
Technology, Sweden.
15. Kumosa, M., Kumosa, L., and Armentrout, D., (2001). Failure
Analyses of Nonceramic Insulators Part 1: Brittle Fracture
Characteristics. IEEE Electrical Insulation Magazine, Volume:21,
No:3, pp:14-27.
16. Matsuoka, R., Ito, S., Tanaka, K., and Kondo, K., (1997).
Contamination Withstand Voltage Characteristics of Polymer
Insulators. ISH97 Montreal, pp:81-84.
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