“INSULATORS 101”
PRESENTED BY ANDY SCHWALM
PRESIDENT – VICTOR INSULATORS, INC.
IEEE LIFE MEMBER
PRESENTED TO: SWEDE
MAY 8, 2014- SAN ANTONIO, TX
WHO DEVELOPED INSULATORS 101?
 INSULATOR WORKING GROUP 15.09.09 OF THE (THEN) L&I
SUBCOMMITTEE – NOW OHL SUBCOMMITTEE
• TONY BAKER – VICE PRESIDENT – TECHNOLOGY – K-LINE
INSULATORS USA
• AL BERNSTORF – PRINCIPAL ENGINEER – INSULATORS –
HUBBELL POWER SYSTEMS
• TOM GRISHAM – CONSULTANT – GRISCUT LTD
• ANDY SCHWALM – PRESIDENT – VICTOR INSULATORS,
INC.
WHAT IS AN INSULATOR? WHAT DOES
IT DO
?
 AN INSULATOR IS A “DAM***” POOR
 MAINTAINS AN AIR GAP
CONDUCTOR!
AND MORE, TECHNICALLY SPEAKING!
 AN INSULATOR IS A MECHANICAL
SUPPORT!
 PRIMARY FUNCTION - SUPPORT
THE “LINE” MECHANICALLY
 SECONDARY FUNCTION–
ELECTRICAL
 AIR IS THE INSULATOR
 OUTER SHELLS/SURFACES
ARE DESIGNED TO INCREASE
LEAKAGE DISTANCE AND
STRIKE DISTANCE
 SEPARATES LINE FROM GROUND
 LENGTH OF AIR GAP
DEPENDS PRIMARILY ON
SYSTEM VOLTAGE, MODIFIED
BY DESIRED SAFETY MARGIN,
CONTAMINATION, ETC.
 RESISTS MECHANICAL STRESSES
 “EVERYDAY” LOADS, EXTREME
LOADS
 RESISTS ELECTRICAL STRESSES
 SYSTEM VOLTAGE/FIELDS,
OVERVOLTAGES
 RESISTS ENVIRONMENTAL STRESSES
 HEAT, COLD, UV,
CONTAMINATION, ETC.
HISTORY
• WHERE DID INSULATORS COME FROM?
BASICALLY GREW OUT OF THE NEEDS OF THE TELEGRAPH INDUSTRY –
STARTING IN THE LATE 1700S, EARLY 1800S
• HISTORY FROM APPROX. 1840 TO PRESENT
GLASS PLATES USED TO INSULATE TELEGRAPH LINE DC TO BALTIMORE
• TYPES OF INSULATORS
DISTRIBUTION, TRANSMISSION, SUBSTATION, PORCELAIN, GLASS, NCI,
CYCLOALIPHATIC, HDPE ETC.
• COMPARISON OF TYPES (MATERIALS)
THE “PLUS AND MINUS” OF THE MULTITUDE OF DESIGNS AND MATERIALS
IN USE TODAY
INSULATOR TYPES - COMPARISONS
• CERAMIC
• PORCELAIN OR TOUGHENED
GLASS
• METAL COMPONENTS FIXED WITH
CEMENT
• ANSI STANDARDS C29.1
THROUGH C29.10
• NON CERAMIC
• TYPICALLY FIBERGLASS ROD
WITH RUBBER (EPDM OR
SILICONE) SHEATH AND WEATHER
SHEDS
• HDPE LINE INSULATOR
APPLICATIONS
• CYCLOALIPHATIC (EPOXIES)
STATION APPLICATIONS, SOME
LINE APPLICATIONS
• METAL COMPONENTS NORMALLY
CRIMPED
• ANSI STANDARDS C29.11 –
C29.19
INSULATOR TYPES - COMPARISONS
• CERAMIC
• NON CERAMIC
• MATERIALS VERY RESISTANT TO UV,
CONTAMINANT DEGRADATION,
ELECTRIC FIELD DEGRADATION
• HYDROPHOBIC MATERIALS
IMPROVE CONTAMINATION
PERFORMANCE
• MATERIALS STRONG IN
COMPRESSION, WEAKER IN
TENSION
• STRONG IN TENSION, WEAKER IN
COMPRESSION
• HIGH MODULUS OF ELASTICITY STIFF
• BRITTLE, REQUIRE MORE CAREFUL
HANDLING
• HEAVIER THAN NCIS
• DEFLECTION UNDER LOAD CAN BE
AN ISSUE
• LIGHTER – EASIER TO HANDLE
• ELECTRIC FIELD STRESSES MUST BE
CONSIDERED
INSULATOR TYPES - COMPARISONS
• CERAMIC
• GENERALLY DESIGNS ARE
“MATURE”
• NON CERAMIC
• “MATERIAL PROPERTIES HAVE
• LIMITED FLEXIBILITY OF
DIMENSIONS
•
• PROCESS LIMITATIONS ON SIZES
AND SHAPES
•
• APPLICATIONS/HANDLING
METHODS GENERALLY WELL
UNDERSTOOD
•
•
BEEN IMPROVED – UV RESISTANCE
MUCH IMPROVED FOR EXAMPLE
STANDARDIZED PRODUCT LINES
NOW EXIST
BALANCING ACT - LEAKAGE
DISTANCE/FIELD STRESS – TAKE
ADVANTAGE OF
HYDROPHOBICITY
APPLICATION PARAMETERS STILL
BEING DEVELOPED
LINE DESIGN IMPLICATIONS
(LIGHTER WEIGHT, IMPROVED
SHOCK RESISTANCE)
DESIGN CRITERIA - MECHANICAL
•
AN INSULATOR IS A MECHANICAL SUPPORT!
ITS PRIMARY FUNCTION IS TO SUPPORT THE LINE
MECHANICALLY
ELECTRICAL CHARACTERISTICS ARE AN AFTERTHOUGHT
WILL THE INSULATOR SUPPORT YOUR LINE?
DETERMINE THE MAXIMUM LOAD THE INSULATOR WILL
EVER SEE - INCLUDING NESC OVERLOAD FACTORS.
DESIGN CRITERIA - MECHANICAL
• LINE POST INSULATORS
• PORCELAIN
• CANTILEVER RATING
• REPRESENTS THE AVERAGE ULTIMATE STRENGTH IN CANTILEVER
– WHEN NEW.
• MINIMUM ULTIMATE CANTILEVER OF A SINGLE UNIT MAY BE AS
LOW AS 85%.
• NEVER EXCEED 40% OF THE CANTILEVER RATING – PROOF TEST
LOAD
• NCIS (POLYMER INSULATORS)
• S.C.L. (SPECIFIED CANTILEVER LOAD)
• NOT BASED UPON LOT TESTING
• BASED UPON MANUFACTURER TESTING
• R.C.L. (REFERENCE CANTILEVER LOAD) OR MDC OR MDCL (MAXIMUM
DESIGN CANTILEVER LOAD) OR MCWL OR WCL (WORKING
CANTILEVER LOAD)
• NEVER EXCEED RCL OR MDC OR MDCL OR MCWL OR WCL
• S.T.L. (SPECIFIED TENSILE LOAD)
• TENSILE PROOF TEST=(STL/2)
DESIGN CRITERIA - MECHANICAL
• SUSPENSION INSULATORS
• PORCELAIN
• M&E (MECHANICAL & ELECTRICAL) RATING
• REPRESENTS A MECHANICAL TEST OF THE UNIT WHILE
ENERGIZED.
• WHEN THE PORCELAIN BEGINS TO CRACK, IT ELECTRICALLY
PUNCTURES.
• AVERAGE ULTIMATE STRENGTH WILL EXCEED THE M&E RATING
WHEN NEW.
• NEVER EXCEED 50% OF THE M&E RATING
• NCIS (POLYMER INSULATORS)
• S.M.L. – SPECIFIED MECHANICAL LOAD
• GUARANTEED MINIMUM ULTIMATE STRENGTH WHEN NEW.
• R.T.L. – ROUTINE TEST LOAD – PROOF TEST APPLIED TO EACH
NCI.
• NEVER LOAD BEYOND THE R.T.L.
DESIGN CRITERIA - ELECTRICAL
•
DESIGN CRITERIA - ELECTRICAL
FOCUS ON THE IMPORTANCE OF STRIKE DISTANCE AS THE PRIMARY
CHARACTERISTIC FOR DETERMINING ELECTRICAL PROPERTIES, WITH
CONSIDERATION GIVEN TO LEAKAGE (CREEPAGE)
•
STRIKE AND LEAKAGE
•
DRY 60 HZ F/O AND IMPULSE F/O – BASED ON STRIKE DISTANCE.
•
WET 60 HZ F/O - SOME WOULD ARGUE LEAKAGE DISTANCE AS A
PRINCIPAL FACTOR. AT THE EXTREMES THAT ARGUMENT FAILS –
ALTHOUGH IT DOES PLAY A ROLE.
•
LEAKAGE DISTANCE HELPS TO MAINTAIN THE SURFACE RESISTANCE
OF THE STRIKE DISTANCE.
DESIGN CRITERIA – ELECTRICAL
WHAT’S AN APPROPRIATE LEAKAGE DISTANCE?
“Application Guide for Insulators in a
Contaminated Environment” by K. C.
Holte et al – F77 639-8
ESDD
(mg/cm2)
0 – 0.03
0.03 – 0.06
0.06 – 0.1
>0.1
Site
Severity
Very Light
Light
Moderate
Heavy
Leakage
Distance
I-string/Vstring
(“/kV l-g)
IEC 60815 Standards
ESDD
(mg/cm2)
Site
Severity
Leakage
Distance
(“/kV l-g)
<0.01
Very Light
0.87
0.01 – 0.04
Light
1.09
0.04 – 0.15
Medium
1.37
0.15 – 0.40
Heavy
1.70
>0.40
Very Heavy
2.11
0.94/0.8
1.18/0.97
1.34/1.05
1.59/1.19
DESIGN CRITERIA – ELECTRICAL
WHAT’S AN APPROPRIATE LEAKAGE DISTANCE?
Flashover Vs ESDD
300
Leakage Distance Recommendations
250
2.5
2
IEEE I
1.5
IEC
Poly. (IEC)
1
Poly. (IEEE V)
Poly. (IEEE I)
200
Flashover Voltage
Leak ("/kV l-g)
IEEE V
Porcelain
New EPDM
150
Aged EPDM
New SR
Aged SR
100
0.5
CEA 280 T 621
SR units - leakage equal to porcelain
EPDM Units - leakage 1.3 X Porcelain
0
50
0
0.1
0.2
0.3
0.4
0.5
ESDD (mg/cm^2)
0
0.01
0.1
ESDD (mg/cm^2)
DESIGN CRITERIA - ELECTRICAL
• IMPULSE WITHSTAND
IF ONLY CRITICAL IMPULSE FLASHOVER IS AVAILABLE –
ASSUME 90%
(TAKE POSITIVE OR NEGATIVE POLARITY, WHICHEVER IS
LOWER
SAFE ESTIMATE FOR WITHSTAND)
•
IMPORTANCE OF CORONA (GRADING) RINGS
INSULATOR ELECTRICAL
RATINGS
Dry 60 Hz Flashover Data
1400
1200
Suspension Insulator
Flashover (kV)
1000
800
Station Post and Line Post
600
400
200
0
0
20
40
60
80
100
Dry Arcing Distance (inches)
120
140
160
STANDARDS
•
FOCUS ON ANSI STANDARDS
•
REVIEW OF MECHANICAL AND ELECTRICAL RATINGS
•
ANALYSIS OF RATINGS VS. DESIGN FOR IN SERVICE LOAD
REQUIREMENTS
STANDARDS
C29
ANSI C29 Insulator Standards (available on-line at nema.org)
.1
Insulator Test Methods
.2
Wet-process Porcelain & Toughened Glass - Suspensions
.3
Wet-process Porcelain Insulators - Spool Type
.4
“
- Strain Type
.5
“
- Low & Medium Voltage Pin Type
.6
“
- High Voltage Pin Type
.7
“
- High Voltage Line Post Type
.8
“
- Apparatus, Cap & Pin Type
.9
“
- Apparatus, Post Type
.10
“
- Indoor Apparatus Type
.11
Composite Insulators – Test Methods
.12
“
- Suspension Type
.13
“
- Distribution Deadend Type
.17
“
- Line Post Type
.18
“
- Distribution Line Post Type
.19
“
- Station Post Type (under development)
STANDARDS
•
ANSI STANDARDS APPLY TO NEW INSULATORS AND
COVER:
•
DEFINITIONS
•
MATERIALS
•
DIMENSIONS & MARKING (INTERCHANGEABILITY)
•
TESTS
1. PROTOTYPE & DESIGN, USUALLY PERFORMED ONCE FOR A GIVEN
DESIGN.
(DESIGN, MATERIALS, MANUFACTURING PROCESS, AND TECHNOLOGY).
2. SAMPLE, PERFORMED ON RANDOM SAMPLES FROM LOT OFFERED FOR
ACCEPTANCE.
3. ROUTINE, PERFORMED ON EACH INSULATOR TO ELIMINATE DEFECTS
FROM LOT.
STANDARDS
STD. No.
C 29.2
Insulator Type
Ceramic Suspension
Sample test
Routine test
M&E
Tension
C29.3,
C29.4
Ceramic Spools and
Strains
Tension
None
C29.5
Pin Type
Puncture
Electrical
C29.6
“
Pin Type
Cantilever
Electrical
C29.7
“
Line Post
Cantilever
4 quad. cantilever
C29.8
“
Cap & Pin
Cantilever, T, To
Tension
Station Post
Cantilever, T
Cantilever, T or BM
C29.9
“
C29.10
Indoor Apparatus
Cantilever
Electrical
C29.12
Composite Suspension
SML
Tension
C29.13
“
Deadend
SML
Tension
C29.17
“
Line Post
Cantilever, T
Tension
C29.18
“ Dist. Line Post
Cantilever
Tension
STANDARDS – NEW C29.2
C29.2A AND C29.2B
• FOR TRANSMISSION CLASSES (C29.2B) NOW TWO RATINGS CLASS
FOR EACH “LEVEL”
• E.G. PREVIOUSLY ONLY CLASS 52-3
• NOW: 52-3L AND 52-3H
STANDARDS – NEW C29.2
Dimensional Values
ANSI
Class
52-3-L
52-3-H
Connection
type
Leakage
distance,
inches
(mm)
Spacing,
inches
(mm)
Shell
diameter,
inches
(mm)
M&E
strength,
pounds
(kN)
B&S
Type B
B&S
Type B
11-1/2
(292)
11-1/2
(292)
11-1/2
(292)
11-1/2
(292)
11
(279)
11
(279)
11
(279)
11
(279)
11
(279)
11
(279)
11
(279)
11
(279)
15
(381)
15
(381)
5-3/4
(146)
5-3/4
(146)
5-3/4
(146)
5-3/4
(146)
5-3/4
(146)
5-3/4
(146)
5-3/4
(146)
5-3/4
(146)
5-3/4
(146)
5-3/4
(146)
6-1/2
(165)
6-1/2
(165)
6-1/8
(155.5)
7
(178)
10-3/4
(273)
10-3/4
(273)
10-3/4
(273)
10-3/4
(273)
10-3/4
(273)
10-3/4
(273)
10-3/4
(273)
10-3/4
(273)
11-3/4
(298)
11-3/4
(298)
11-3/4
(298)
11-3/4
(298)
12-1/4
(311)
12-1/4
(311)
15,000
(67)
20,000
(89)
15,000
(67)
20,000
(89)
25,000
(111)
30,000
(133)
25,000
(111)
30,000
(133)
36,000
(160)
40,000
(178)
36,000
(160)
40,000
(178)
50,000
(222)
50,000
(222)
52-4-L
Clevis
52-4-H
Clevis
52-5-L
52-5H
B&S
Type J
B&S
Type J
52-6-L
Clevis
52-6-H
Clevis
52-8-L
52-8-H
Mechanical Values
B&S
Type K
B&S
Type K
52-10-L
Clevis
52-10-H
Clevis
52-11
B&S
Type K
52-12
Clevis
Impact
strength,
inchpounds
(N-m)
55 (6.0)
55 (6.0)
55 (6.0)
55 (6.0)
60 (7.0)
60 (7.0)
60 (7.0)
60 (7.0)
90 (10)
90 (10)
90 (10)
90 (10)
90 (10)
90 (10)
Tension
proof,
pounds
(kN)
7,500
(33.5)
10,000
(44.5)
7,500
(33.5)
10,000
(44.5)
12,500
(55.5)
15,000
(66.5)
12,500
(55.5)
15,000
(66.5)
18,000
(80)
20,000
(89)
18,000
(80)
20,000
(89)
25,000
(111)
25,000
(111)
Radio-influence
Voltage
Electrical Values
Lowfrequency
dry
flashover,
kV
Lowfrequency
wet
flashover,
kV
Critical
impulse
flashover,
positive,
kV
Critical
impulse
flashover,
negative,
kV
Lowfrequency
puncture
voltage,
kV
Lowfrequency
test
voltage,
kV
Maximu
m RIV at
1,000
kHz, µV
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
125
130
110
10
50
80
50
140
140
125
10
50
80
50
140
140
125
10
50
STANDARDS – NEW C29.2
COMBINED MECHANICAL AND ELECTRICAL-STRENGTH TEST
TEN ASSEMBLED INSULATORS SHALL BE SELECTED AT RANDOM FROM THE LOT AND TESTED IN ACCORDANCE WITH 5.2 OF ANSI
C29.1. THE CRITERIA FOR DETERMINING CONFORMANCE WITH THE STANDARD ARE AS FOLLOWS:
ALL INSULATORS SUBJECTED TO THE COMBINED MECHANICAL AND ELECTRICAL-STRENGTH TEST SHALL EQUAL OR EXCEED THE
RATED COMBINED MECHANICAL AND ELECTRICAL STRENGTHS AS GIVEN IN TABLE 2 OF THIS STANDARD.
STANDARDS – IMPLICATIONS
EXAMPLE C29.2 M&E TEST
Coefficient
of variation, vR
Strength value
at -3σ
5%
90% of M&E rating
10%
79% of M&E rating
15%
67% of M&E rating
STANDARDS – IMPLICATIONS
EXAMPLE C29.7, 8, 9 CANTILEVER TEST
Coefficient
of variation, vR
Strength value
at -3 σ
5%
85% of Cantilever rating
10%
70% of Cantilever rating
15%
55% of Cantilever rating
NESC ANSI C2 TABLE 277-1
ALLOWED PERCENTAGES OF STRENGTH RATINGS
Insulator Type
Strength Rating2
Ref. ANSI Std.
C29.2
-1992
C29.7
-1996
40%
50%
40%
50%
Combined
mechanical & electrical strength (M&E)
Cantilever strength
Tension/compression
Strength
Cantilever strength
Tension/compression/torsion strength
Cantilever strength
Tension/compression/torsion strength
C29.9
-1983
C29.8
-1985
50%
Specified mechanical load
(SML)
C29.12-1997
C29.13-2000
50%
50%
Specified cantilever load (SCL) or
specified tension load (STL)
All strength ratings
C29.17-2002
C29.18-2003
%
Ceramic3
Suspension
Line Post
Station Post4
Station
Cap & Pin4
Nonceramic5
Suspension
Line Post
Station Post
50%
40%
50%
----------
STRENGTHS – MORE IN DEPTH
DISCUSSION
2 NEW IEEE PAPERS
• IEEE TF ON INSULATOR LOADING, “HIGH VOLTAGE INSULATORS
MECHANICAL LOAD LIMITS –PART I: OVERHEAD LINE LOAD AND
STRENGTH REQUIREMENTS,” IEEE TRANSACTIONS ON POWER DELIVERY,
VOL. 27, NO. 3, JULY 2012
• IEEE TF ON INSULATOR LOADING, “HIGH VOLTAGE INSULATORS
MECHANICAL LOAD LIMITS –PART II: STANDARDS AND
RECOMMENDATIONS,” IEEE TRANSACTIONS ON POWER DELIVERY, VOL.
27, NO. 4, OCTOBER 2012.
INSPECTION & EVALUATION –
HAVE THE INSULATORS DETERIORATED IN SERVICE?
ANSI C29.2 – 1971 Quality Control(Lot) Tests – M&E Tests
Select random sample from lot: n=10
Determine Average M&E Strength & Standard Deviation s:
Requirements for Average&
Standard Deviation: L ≥ M&E Rating + 1.2
s ≤ 1.72 , where = historical standard deviation
Assuming s ≈
the above requirements can be re-stated as
XL = M&E Rating + 1.2 s
Sample
Mean
= L
= M&E + 2 s
X
M&E
L
1.2 š
-1 s
Minimum standard
-2 s
Typical – good mfg
-1 s
Possible % of
M&E Strengths
Less Than Rating
11.4 %
2.2 %
INSPECTION & EVALUATION –
HAVE THE INSULATORS DETERIORATED IN SERVICE?
SOURCES
DOMESTIC MANUFACTURING
• TRANSMISSION
 PORCELAIN, GLASS – NONE
• DISTRIBUTION
 PORCELAIN – ONLY 1 PLANT LEFT
 NCIS – FULL LINES
 NCIS- FULL LINES (CHANGING)
 GLASS – NONE
• SUBSTATION
• PORCELAIN:
 PORCELAIN – FULL LINES (FOR
NOW)
 NCIS- FULL LINES (CHANGING)
 SPOOLS, STRAINS – NONE
 CUT OUT PORCELAIN – NONE
 LINE POSTS – MIXED
 PIN TYPES – 1 PLANT
MARKET SIZE
DATE
TOTAL
LVPOST
HVPOST
LVSUSP
HV SUSP
STATION
SALES
SALES
SALES
SALES
SALES
SALES
2005
$162,659,854
$9,175,541
$50,689,720
$21,321,445
$37,249,650
$44,223,498
2006
$186,134,838
$8,764,774
$56,879,248
$21,326,689
$42,944,457
$54,341,020
2007
$178,871,136
$8,148,902
$54,370,706
$19,123,333
$41,294,116
$55,934,079
2008
$184,703,067
$9,033,449
$55,328,125
$20,249,198
$45,963,460
$54,128,835
2009
$199,346,541
$7,212,093
$55,796,547
$16,462,470
$64,840,398
$50,381,412
2010
$204,434,456
$5,631,635
$57,686,263
$19,853,611
$57,254,895
$64,008,052
2011
$265,809,282
$8,490,867
$82,247,066
$21,663,012
$78,483,176
$74,925,161
2012
$275,534,244
$8,761,597
$81,904,852
$21,427,918
$91,549,038
$71,890,839
MARKET DISTRIBUTIONS
• DISTRIBUTION – STILL MAINLY PORCELAIN BELOW 35 KV, EXCEPT FOR
DEAD ENDS – 90% NCI, GROWING USE OF HDPE
• TRANSMISSION – MAINLY NCI BELOW 345 KV, >50% CERAMIC
ABOVE THAT
ECONOMICS
• TRANSMISSION LINES – INSULATORS TYPICALLY <3% TOTAL COST OF
LINE
• DISTRIBUTION LINES – INSULATORS TYPICALLY 1% - 3% OF COST OF
LINE
INSPECTION & EVALUATION –
INSPECTION TECHNIQUES AND EVALUATION OF RESULTS
• VISUAL INSPECTION• INDIVIDUAL INSULATORS FROM A
BUCKET TRUCK OR HELICOPTER
• BINOCULAR ASSIST
• VIDEO IMAGING• DAYTIME (DAYCOR)
• NIGHT TIME (THERMAL IMAGING)
• EVALUATING CORONA ACTIVITY
• RIV MEASUREMENTS
• ESTABLISHED BASIS OF GOOD
AND BAD
• REPLACEMENT OF INSULATORS• DO NOT “HOT” WORK ANY LINE
WITH KNOWN FAILURES.
• PROCEDURES TO WORK “HOT”
LINES IS NO DIFFERENT FOR
CERAMIC OR NCI’S.
• UNCERTAIN IF WE SHOULD
REPLACE INSULATORS IN THE
“HOT” MODE!
• SELECT A RANDOM SAMPLE, N= 30.
• SUBJECT TO M&E TEST AND
DETERMINE 30 & S
• WOULD LIKE (
30
– KS) ≥ M&E RATING
• USE STUDENT’S T STATISTIC
• FOR Α = .05 (95% CONFIDENCE),
WANT T≥ 1.699.
k
Want
30
≥
1
M&E + 1.31 s
2
M&E + 2.31 s
3
M&E + 3.31 s