Insulator Contamination
and Washing
Presenter: C.K. Ng
Overview
Introduction
• Insulators
• Flashover
Washing
• Lines
• Stations
Contamination
• Sources
• Contamination
Flashover Mitigation
Advancements
Insulators
What is an insulator?
• Mechanical support
• Electrical insulation
What does an insulator do?
• Maintains an air gap
3
Insulation
Mediums
Air
SF6
Oil
XLPE
4
Flashover Mechanisms
Surface contamination
Surrounding air breakdown
Material puncture/failure
Flashover Causes
Lightning impulse
Switching surge
Contaminants & leakage current
Material defects
Icing
5
Sources of Contamination
Roads
Salt
Agricultural
Fertilizers
Marine
Sea salt
Industrial carbon
Soot
Metallic particles, etc.
6
Contamination Flashover
Contamination Buildup
Clean insulator
Contamination deposited
7
Contamination Flashover
Wetting
Cleaning
Blue Path Btw
Metallic parts is
Leakage Distance
Wetting of contamination layer
(fog, dew, humidity, etc.)
Cleaning
(rain)
8
Contamination Flashover
Discharge Activity
Formation of dry bands
Dry band arcing
9
Growth of dry band arcs
Contamination Flashover
Flashover
Flashover
10
Contamination Flashover
Mechanism
1)
2)
3)
4)
Buildup of contaminants
Insulator wetting
Discharge activity
Flashover
11
Dry Band Arcing
12
Flashover
13
Determining Contamination
Severity
Environmental conditions*
ESDD* and NSDD
Leakage current*
Infrared*
Dust deposit gauge
Surface conductance
14
Contamination on Monitoring Stations
ESDD
Infrared
Cardiff TS
Cherrywood TS
Claireville TS
Hurontario SS
Milton SS
Preston TS
Richview TS
Trafalgar TS
Beach TS
Birmingham TS
Gage TS
Kenilworth TS
15
Contamination Mitigation
Methods
Washing
Increase leakage distance
Specialized coatings
Polymer insulators
16
Contamination Mitigation Options
Washing
Remove
contamination
Increase
Leakage
Distance
Specialized
Coatings
Allows for more
contamination
before washing
Improve voltage
distribution (more
uniform)
Improve voltage
distribution (more
uniform)
Reduce dry band
arching
Increased
hydrophobicity
17
Polymer
Insulators
Insulator Washing
Lines
Stations
1000 psi (700 psi min)
Energized
De-energized
Cyclical
Demand (ESDD/IR) & cyclical
Specialized equipment & safety procedures
18
Insulator Washing Restrictions
Actual air
Temperature
(oC)
Wind Speed (km/h)
8
16
24
32
Resultant Apparent Temperature (oC)
0
-2
-8
-11
-14
-5
-7
-14
-18
-21
-10
-12
-20
-25
-28
-15
-18
-26
-32
-35
* washing must not be done below -12oC (shaded area)
19
Insulator Washing Stations
15
High contamination stations
Industrial areas &
major highways
Typical washing stations
20
Insulator Washing Stations
21
Insulator Washing - Lines
658
Circuit structures
Twice per year, yearly or
every two years
Cycle
Industrial areas &
major highways
Typical washing stations
22
500 kV Live Line Washing
“Hydro On e Works Live to
Double Productivity”
“Can adian utilit y uses ae rial
work platform to wash live lin e in sulators in h alf th e
tim e.”
- T&D World Magazine
(25-Nov-2013)
23
Leakage Current Sensors
24
Leakage Current Sensors
Flashovers
25
Questions?
26