MEA – Springfield, IL – May 2015
David M. Geibel, Tecnical Director
ABB Alamo
Dry (Oil-less) bushings
Tutorial
© ABB Group
May 18, 2015 | Slide 1
Introduction - Transformer
Spark Plugs
Big Gray
Box
We have been “bushings” for a long time
ABB Alamo: World Leader - OIP Condenser Bushings
Standards: IEEE and CSA
25 kV through 550 kV
400 A through 21,500 A
© ABB Group
May 18, 2015 | Slide 4
Bushings!
IS
WHO
WE
ARE!!!
Why Dry? Why Silicon? Why RIS?
 No
oil to leak
 No
oil to contaminate
 No
oil to burn
 No
pressure vessel to rupture
 High
seismic performance
 Long
life
 Easy
Storage
 100,000+
© ABB Group
May 18, 2015 | Slide 10
dry bushings produced
Dry Bushings


Advantages

Reduced risk of fire

Oil leakage is eliminated

Mechanically rigid design and no need for
oil supervision

Seals the transformer and reduces
the down-time in the event of major
TFO failures

Lightweight and compact, less than 50% of
OIP

Transported, stored and installed at
any angle

Can be energized immediately
after installation
Important

Needs to be stored properly long-term
Dry Bushings intentional fault testing (63kA X 0.5Sec)
Voltage Distribution
No
Capacitive
Grading (bulk
bushing)
Uncontrolled
field
follows the laws of
nature unequally
stressing porcelain,
oil, epoxy and/or
paper insulation
system
75%
50%
25%
Capacitive
Grading (condenser
bushing)
75%
Field
50%
25%
controlled
by capacitive
grading follows
controlled
contours making
effective use of
all insulation
Function of High Voltage Bushing
Uncontrolled
(natural)
electrical field
Capacity-controlled
electrical
field
100%
voltage
0%
voltage
Electric Field Distribution in and around Bushings
Grounded
flange
Condenser Core Types

Oil Impregnated Paper (OIP)

15 kV to 800 kV

Plain paper condenser body

Core impregnated with hot oil under vacuum

Aluminum foil or ink print gradients

Partial discharge 10 pc at 1.5 times line to ground

Power factor requirements – less than .50%

Resin Bonded Paper (RBP)

Cast Epoxy

Resin Impregnated Paper (RIP)

Resin Impregnated Synthetic (RIS)
Condenser Core Types

Oil Impregnated Paper (OIP)

Resin Bonded Paper (RBP)

15 kV to 230 kV

Resin treated plain paper condenser body

Dry processed with varnish dipped core

Aluminum foil gradients

Partial discharge 100 pc at 1.5 times line to ground

Power factor requirements – less than 2.0%

Cast Epoxy

Resin Impregnated Paper (RIP)

Resin Impregnated Synthetic (RIS)
Condenser Core Types

Oil Impregnated Paper (OIP)

Resin Bonded Paper (RBP)

Westinghouse type S and OS

Cast Epoxy

Resin Impregnated Paper (RIP)

Resin Impregnated Synthetic
(RIS)
Condenser Core Types

Oil Impregnated Paper (OIP)

Resin Bonded Paper (RBP)

Cast Epoxy

15 kV – 138 kV

Metal screen mesh graded

Epoxy resin condenser body

Partial discharge 25 pc at 1.5 times line to ground

Power factor requirements – less than 1.0%

Resin Impregnated Paper (RIP)

Resin Impregnated Synthetic (RIS)
Condenser Core Types

Oil Impregnated Paper (OIP)

Resin Bonded Paper (RBP)

Cast Epoxy

Resin Impregnated Paper (RIP)


15 kV to 800 kV

Crepe paper condenser body

Resin impregnated core under vacuum

Aluminum foil gradients

Partial discharge free although guideline of 10 pc

Power factor requirements – less than .85%
Resin Impregnated Synthetic (RIS)
Condenser Core Types

Resin Impregnated Paper (RIP)
Condenser Core Types

Oil Impregnated Paper (OIP)

Resin Bonded Paper (RBP)

Cast Epoxy

Resin Impregnated Paper (RIP)

Resin Impregnated Synthetic (RIS)

25 kV to 161 kV

Synthetic mesh condenser body

Encapsulated with resin under vacuum

Aluminum foil gradients

Partial discharge free although guideline of 10 pc

Power factor requirements – less than .85%
Condenser Core Types





Oil Impregnated Paper (OIP)
Resin Bonded Paper (RBP)
Cast Epoxy
Resin Impregnated Paper (RIP)
Resin Impregnated Synthetic (RIS)
 Molded design condenser body
RIP vs. OIP technology
RIP Technology
tube
main
/ conductor
insulation
RIP
body with
fine
grading
R
esin
I
mpregnated
P
aper
dry
filling
Micagel
porcelain
or
composite
flange
insulator
test
tap
air
side
oil
side
RIP Technology
Tube
/ conductor
Main
insulation
RIP
body with
fine
grading
Dry
filling
Micagel
Porcelain
composite
insulator
Flange
or
Modern Bushings Production
3D-Construction
Dielectric
Thermic
Mechanics
Modern RIP Bushings Production
Conductor:
-
Al, Cu,
-
solid, tube
Special
crepe paper
Aluminium
foils
Modern Bushings Production
Paper -Drying
 Winding-Process
Resin-Impregnating
 Curing Process
RIP Bushings Technical Facts

Low dielectric losses (Power Factor < 0,4%)

PD “free“up to double service voltage

Excellent mechanical strength

Excellent Siemic withstand capablity

Fire resistant (oil free)

High thermal strength (class E, 120°C )

No oil to leak out, contaminate, degrade

High design flexiblity for custom mechanical fit
SeismicRIP® Bushings
SeismicRIP® Bushings
 New line of SeismicRIP® Oil/Air
Bushings
 Satisfing the highest requests as per
IEEE Standard 693
 Nominal voltages from 69 up to
550kV
 RIP technology with composite
insulator
 Delivered to Californian utilities
Transformer Bushings
Oil – Air application
High Voltage Bushings
 24-550
 up
kV
to 5,000 A
 with
 porcelain
 silicone
or
composite insulator
SeismicRIP ® Bushings
 69-550
 up
kV
to 5,000 A
 only
with silicone composite insulator
Transformer Bushings
Oil – Oil bushings

for cable box

72.5 – 550 kV

up to 4000 A

with double flange available
Transformer Bushings
Oil – SF 6 application

For GIS connection

72.5 – 550 kV

Up to 4000 A
GSU Transformer Bushings
Oil – Air high current

17,5 – 52 kV

Up to 40kA

With

Porcelain

Silicone composite
insulators
Three Gorges Project – China
Micafil supplied:

SF6/Air bushings
550 kV, 4000 A

Transformer high current
bushings
24 kV, 35,000 A
ABB Alamo: O Plus Dry™
Standards: IEEE

2015
25 kV through 138 kV
400 A through 1,200 A

By late 2015
25 kV through 138 kV
2000 & 3000 Ampere

Coming soon:
230kV (800 – 5,000 Amp)
© ABB Group
May 18, 2015 | Slide 37
69kV
400/1200A
Same condenser theory
C
L
Effect of Capacitive Grading
V
1
V/6
5/6 V
2
V/6
4/6 V
3
V/6
3/6 V
4
V/6
2/6 V
5
V/6
1/6 V
6
V/6
6/6 V
1 2 3 4 5 6
1 2
3
4 5
6
1 2 3 4 5 6
Capacitive Layer
EasyDry Bushing Construction
Synthetic mesh fabric

Used in winding
condenser

Provides structure &
supports foils that form
condenser

Open structure allows
easy impregnation

Synthetic material
does not absorb
moisture
EasyDry Bushing Construction
Isolation of conductor
EasyDry Bushing Construction
Synthetic mesh fabric winding
EasyDry Bushing Construction
Foil “Equalizers”
New Condenser
Type O Plus Dry™
Windings

Conductor

Isolator

Synthetic Mesh

Equalizer Foils

Winding
Condenser
Tap connections
Condenser



© ABB Group
May 18, 2015 | Slide 43
Winding
Filled Epoxy
No Machining
EasyDry Bushing Construction
Critical Resin Curing
EasyDry Bushing Construction
Epoxy “factory”
New Condenser
Type O Plus Dry™
Windings

Conductor

Isolator

Synthetic Mesh

Equalizer Foils

Winding
Condenser
Tap connections
Condenser



© ABB Group
May 18, 2015 | Slide 46
Winding
Filled Epoxy
No Machining
EasyDry Bushing Construction
Flange Installation
EasyDry Bushing Construction
Condenser Preparation
New Manufacturing Practices
Type O Plus Dry™
Weather shed extruder
World class silicon


High Temperature Vulcanized

Modern shed profile


© ABB Group
May 18, 2015 | Slide 49
Infinitely variable
Reduced lead time
New Weather Sheds
Type O Plus DryTM
© ABB Group
May 18, 2015 | Slide 50

HTV Silicon

Extruded

Helical

Directly
Applied
New Weather Sheds
Type O Plus DryTM
“Homogeneous”
turn-to-turn joint
(Undetectable
joint)
© ABB Group
May 18, 2015 | Slide 51
EasyDry Bushing Construction
Final Assembly
Resin Impregnated Synthetic
Composite Insulator Aplication through 1200kV
AC/DC
Circuit
Breakers
Instrument
Transformers
Cable
Terminations
Bushings
Surge
Arresters
Just ABB Service experience
World
wide in > 60 countries and >80 000 composite
insulators
Composite insulators
One-piece design
Glass fiber reinforced
epoxy resin tube
Silicone rubber sheds
Aluminum end fitting
Glass fiber composite tube
One-piece design

Glass fiber reinforced epoxy resin tube using wet filament winding technique

Tailored mechanical and electrical performance

Continuous one-piece tube design for length >15 m (no gluing of tube segments)

Conical and cylindrical design available in length >15 m
Silicone Insulators

Reduced maintenance
 Hydrophobic surface



Reduced leakage currents
Longer cleaning intervals
compared to porcelain
Improved safety
 Non shattering



Non flammable
Increased seismic withstand
Self extinguishing when exposed
to open fire
Hydrophobicity

Silicone is by nature more
hydrophobic than porcelain or
other polymers

Constant diffusion of silicones to
the surface

Water on a hydrophobic surface
stays as water droplets and does
not form a continuous film

Automatic hydrophobicity recovery
after possible temporary reduction
under constant heavy pollution

No ageing effect on hydrophobicity

Gives excellent pollution
performance with minimum
maintenance
Maintenance of HTV shed bushings
 Self-Cleaning(Hydrophobic
Good
Degrees
= self cleaning)
Bad
of hydrophobic performance
Advantages with Silicone Rubber Sheds
Flashover resistant
 Insulator surface hydrophobic
 Water stays as droplets
 The leakage currents are suppressed
 Tracking resistant
Ageing withstand
 Less discharge activity in case of severe
pollution
UV stability
 Max. absorption below wavelength
of natural UV-light
Mechanical strength
 Elastic and stable over a wide
temperature range
Composite insulators
Manufacturing processes
Silicone rubber housing
Seamless helical extrusion process

One continuous seamless outer
silicone housing for length >15 m

Manufacturing in one step without
parting lines/ mold lines or joints

Flexible production method for
different diameters, lengths, shapes
and creepage distances
Silicone rubber housing
Optimized shed profiles

Shed tip with large radius and
“drip edge” to minimize the
electrical field and the risk of
flashover

Inclined bottom surface gives
high protective creepage
distance and lowest possible
leakage currents

Special shed profile fulfilling
requirements for 800 kV UHVDC
Silicone rubber housing
Optimized shed profiles
Injection molding
Low protective creepage distance
Helical extrusion
High protective creepage distance
Silicone rubber housing
Optimized shed profiles
Injection
molding
Helical
extrusion
High electrical field
Mold lines
Low electrical field
Shed profile ≠ Shed profile
No mold lines
Experience
Well verified design




Quality and -50°C performance approved by Hydro Quebec
Pressure cycling test ANSI C37.09
 10 000 cycles 0 to MSP at -40°C
 90 000 cycles 0 to MSP at +100°C
Performed on several insulators, including the most severely
loaded tube and joint in pressure
Tube surge arresters qualified for -60°C IEC60099-4
 Performed on the most severely loaded joint in bending
Long term performance verified in field and test stations
 Dungeness, UK
 Guangzhou, CN
 Ludvika (800 kV DC), SE
 Koeberg (KIPTS), ZA
Silicone rubber material
HTV for reliable performance

Silicone rubber usually discussed in 3
general classes

RTV - Room temperature
vulcanizing

LSR - Liquid silicone rubber

HTV - High temperature vulcanizing

Lower quality Insulator after 1 year KIPTS test
Silicone Rubber ≠ Silicone
Rubber

ABB HTV Insulator after 1 year KIPTS test
Koeberg Insulator Pollution Test Station (KIPTS)
ESKOM, ZA

Severe test station for pollution and
ageing performance of insulators

Very harsh environment for
insulators:

Salt fog

Strong UV light

Sand

Industrial pollution

Pollution level up to 6 times “very
heavy” from IEC 60815

12 month test cycle
Severe service experience
Long term test at KIPTS
Composite
Insulators tested
successfully at
Koeberg Insulator
Pollution Test
Station (KIPTS)
Silicone rubber material
High-temperature vulcanized (HTV) silicone


High-temperature vulcanized (HTV)
silicone from well known sub-suppliers

Highest durability of sheds

Superior performance in sandstorm areas

Minimization of damages during transportation and
handling
High amount of Aluminum Trihydrate
(ATH)

Improved tracking and erosion performance

Increased fire resistance capability

Outstanding long term performance
Severe service experience
Long term test at Dungeress, UK

Bushing after 4 years at coastal testing station

(IEC pollution level IV - Very Heavy)
ABB
Composite Insulator Training
Handling,
cleaning, repair
Handling

Put slings around flanges, never on silicone

Be careful with sealing surfaces and silicone

Protect sheds during assembly, construction and
maintenance
Picture courtesy of CIGRE WG3.21
Maintenance of HTV shed bushings
 Cleaning

Hydrophobic and self cleaning

The right Alcohol!!

Denatured Alcohol is poisoned ethanol (poisoned with
what???)

Methanol is not recommended

Use Isopropyl Alcohol contaminated/diluted only with
water.

Water with or without mild detergent is ok if rinsed.
 Repair?
On site repairable damage types
Type A. Cut or crack at shed tip
Type B. Closed cut or crack
in shed
Type C. Piece of shed is
broken
ABB
Composite Insulator Training
Summary
Composite Insulators for HV equipment
Value for the Customer
Explosion proof

Explosion proof
Maximum safety of personnel and equipment
Non-brittle

Non-brittle
Reduced handling damage risk

Excellent insulation
Possible to reduce the creepage distance
with at least one pollution level

Low weight
Easier handling and reduced foundation
loads
Excellent insulation

Maintenance free
Low weight
No cleaning in polluted environments

Outstanding seismic performance
For best safety and reliability
Maintenance free
Seismic performance
Composite Insulator Technology
Design for reliable performance

One piece tailored glass fiber composite tube
Best mechanical performance

High Temperature Vulcanized (HTV) silicone
rubber with high amount of ATH filler
Improved tracking and erosion performance and best
long term performance

Seamless helical extrusion process for a
continuous outer silicone housing
No mold lines where dirt/ salt can accumulate or joints/
weak spots

Optimized shed profiles with large shed tip
radius and high protective creepage distance
Lowest possible leakage currents and electrical field

Experience since 1985 and > 80 000 insulators
installed in all climates
Reliable long term performance
Applying Mature Weather Shed Technology
Type O Plus DryTM
© ABB Group
May 18, 2015 | Slide 80
Applying Mature Weather Shed Technology
Type O Plus DryTM
© ABB Group
May 18, 2015 | Slide 81
Applying Mature Weather Shed Technology
Type O Plus DryTM
 Recent
Cigre paper concludes life of HTV
weather sheds good for life of bushing
(copies available).
 This
field study indicates “in service”
insulators in good condition under various
conditions.
 Holding
up well even in the most severe
environments.
© ABB Group
May 18, 2015 | Slide 82
1100 kV Oil-less wall bushings
600 kV DC Dry bushing.
Applying Mature Weather Shed Technology
Type O Plus DryTM
Injection
molding
Helical
extrusion
High electrical field
Low electrical field
Mold lines
No mold lines
Shed profile ≠ Shed profile
© ABB Group
May 18, 2015 | Slide 85
Short term storage of RIP/RIS bushings

Short term = less than one year

Store indoors in the original packaging materials
•
Store where wildlife cannot
damage silicon sheds (rats,
birds etc.)
Longer term storage of RIP/RIS bushings

RIP condensers contain paper and are
machined to finished shape exposing paper

Store indoors away from direct sunlight

Store with silicon sheds not supporting
weight of bushing

Where wildlife cannot damage silicon
sheds (rats, birds etc.)

Must be stored in moisture tight bag or
metal tank over lower end and protected
from all moisture
Longer term storage of RIP/RIS bushings

RIS condensers contain no paper and are not
machined to finished shape

Store indoors away from direct sunlight

Store with silicon sheds not supporting weight of
bushing

Store where wildlife cannot damage silicon
sheds (rats, birds etc.)

Currently recommending moisture tight bag over
lower end
Permanent storage options
Permanent storage options
Wide range of applications
RIP applicable to bus duct installations
Development testing more intense
PD levels
Essentially none
Thermal testing
Specific to materials
Mechanical testing
To Fracture
CAT scans (void detection)
Dielectric testing
Extensive
Long term withstand
Proof of Altitude
New Routine testing
Type O Plus Dry™
Partial discharge:

Essentially background level of
facility (<5 pc) at 2xLG

Withstand extended (5 min.)
Leak tests:

No oil to leak from bushing

Test must ensure xfmr oil cannot
pass through bushing

Helium testing vac&press
Molded condenser verification:

Glass transition temp

Close SPC and chemical
verification
Dry bushing Overload?

OIP has loss of life as insulation polymer chains
disintegrate, but this is function of time and temperature.

Dry bushings made with polymers, such as epoxy, are
much more sensitive to temperature for short times (like the
gaskets in OIP).

When the epoxy reaches glass transition temperature (Tg),
it begins to quickly turn into something(?) new and
dielectric performance is lost. No oil to fill voids. Damage
is irreversible.
Thermal design of RIP/RIS oil-less bushings
© ABB Group
May 18, 2015 | Slide 96
Glass transition vs thermal rating
Tg?
The
users does
not know the
thermal margin of
each design.
Dry bushing Overload?

Thermal Conclusions.

Plan your overload need when you spec your bushings.

Remember that bushings rating rarely are at ratings of
transformer.

Relatively short excursions may compromise the
reliability of a bushing with no obvious evidence.

Be certain about bus/terminal temperatures &
connections
Field assessment of RIP/RIS oil-less bushings

Power Factor and Capacitance is still your best indicator


Capacitance increase indicates shorted layer

5% increase investigate and trend

10% remove from service
Power Factor increase indicates losses increase in
insulation

Thermal damage

Partial discharge in voids

50% investigate and trend

100% increase remove from service
Field assessment of RIP/RIS oil-less bushings
 Power
Factor and Capacitance is still your
best indicator

Test before installation to match Name Plate

Test after installation to establish baseline

Test at 15 years in service

Test each five years thereafter

Test after long term storage
 Thermal
 Visual
scan annually and after first loading
inspection annually
Field assessment of RIP/RIS oil-less bushings


Monitoring devices are available

Power Factor

Capacitance

Partial Discharge
Lab testing can be performed if suspect:


AC

Withstand at 85% of original withstand with PD

Extended 1.5 X L-G with PD
Impulse

Lightning (1.5 X 50μs)

Switching surge at 85% original levels
Technical limits of Dry
 RIP
lower ends absorb moisture
 Hard
limit for temperature
 Order
to Overload requirements
 Vulnerable
to rough handling
Your ABB Guardian Angel (or Transformer Troll?)
Michelin Man??
© ABB Group
May 18, 2015 | Slide 104