eskom transmission live line maintenance techniques …icolim2014.org/2014/ppt/195.pdf · eskom...
TRANSCRIPT
Eskom Transmission
Live Line Maintenance
Techniques and
Practices
Eric Marshall
Chief Eng Live Work
Eskom Transmission, South Africa
OVERVIEW
• Eskom Transmission Network and environment
• Typical structures
• Maintainability of designs
• Operational facts considered: TOV’s and clearances
• Maintenance requirements
• Live Work Techniques, tools and PPE
• Live Work Risks
• Operational info of Eskom Transmission Live Work Program
• Questions
Eskom EHV Transmission Network
Eskom Transmission Network
28 790 km of OHL
220 kV = 1 217 km
275 kV = 7 476 km
400 kV = 16 913 km
533 kV DC = 1 035 km
765 kV = 1 153 km
and growing….
Consisting of:
• 80 % Glass cap and pin
insulators
• 20 % Composite insulators
• Multi bundle phase conductor
(up to 6)
• Vast family of conventional and
cross rope structures
95 % of preventative and corrective
maintenance conducted live !!
Environment
Birds and associated pollution
Fires
Lightning
“Tuff” in Africa
1010
Typical Eskom Transmission Structures
Typical Eskom Transmission Structures
11
Typical Eskom Transmission Structures
12
Min Cost vs. Reliability vs. Maintainability
13
Maintainability of designs: Structures
1414
Maintainability of designs: Structures
1515
Maintainability of designs: Structures
1616
7.0 m
7/3 m
Nylon Rope
Tfront Test Sequence
149 us Test 1 No Dummy
244 us Test 2 No Dummy
244 us Test 3 Dummy 7/3 m from positive
244 us Test 4 Dummy 7/2 m from positive
244 us Test 5 Dummy 7/3 m from negative
Maintainability of designs: Hardware
1717
Maintainability of designs: Hardware
1818
Maintainability of designs: Hardware design
1919
Maintainability of designs: Adaptors
Operational facts considered: TOV’s and clearances
Controlled and managed by:
• Inhibiting auto re-close device
• No live work under lightning and thunderstorm activity
• Closing resistors used on circuit breakers
• Bypassing series capacitor banks
ToV’s Caused by:
• Switching on the network
• Lightning ….
Safety Clearance distances
ONE DISTANCE – KEEP IT SIMPLE !!
MINIMUM SAFE WORKING DISTANCES (CLEARANCES)
ESKOM STANDARD HIGH VOLTAGE LIVE WORKING (TST 41-91, REV2)
Nominal Circuit
voltage (kV)
Phase to earth (mm) Phase to phase (mm)
AC 220 1700 2800
275 2000 3400
400 2800 4800
765 5500 9700
DC 533 4250 -
Maintenance requirements
“Constrained Transmission network” – minimal outages available
As a result 95 % plus of routine maintenance is conducted
alive using various live work techniques
Activities includes mainly:
Insulator replacements
Spacer and damper replacements
Conductor repairs
Tools and equipment
In accordance with international
standards
• Conductive clothing IEC 60895
• Insulated foam filled tubes IEC 60855
• Insulated aerial platforms ASTM A92.2
and South African Occupational Health
and Safety Act
Tools and equipment
Live Work Techniques: Eskom Tx (220-765 kV)
Generally….
Combination of Stick and Bare hand techniques
utilising the following means:
• Stick or “distance” method
• Conventional climbing and rigging ladders
• Insulated aerial platform
• Rope Hoisting method
• Helicopter based Aerial under slung & skid
Conventional – Stick V suspension assembly 400kV
2727
Conventional – Stick I suspension assembly 275 kV
2828
Conventional Bare hand I string
Conventional Bare hand I string
Conventional Bare hand I string
Conventional – Bare hand Strain assembly 220 kV
3232
Conventional – Bare hand Strain assembly 220 kV
3333
Insulated Aerial platform Bare Hand 765 kV – Ins. change out
3434
Insulated Aerial platform Bare hand765 kV – Ins. change out
3535
3636
Insulated Aerial platform Bare hand 765 kV - Spacer replacement
Rope Hoisting method Bare hand 400 kV – Ins change out
Rope Hoisting method Bare hand 400 kV – Ins change out
Aerial under slung 400 kV Insulator change out
3939
4040
Aerial under slung 400 kV Insulator change out
4141
Aerial under slung 400 kV Insulator change out
4242
Aerial under slung 400 kV Insulator change out
4343
Aerial under conductor work 765 kV
Aerial “Rack” or Skid work on earth cond.
Aerial Live Spray Washing
4545
Live Work Risks
4646
Mechanical...• Failure of line hardware and insulators
• Failure of mechanical/hydraulic tensioning equipment
Electrical...
• Insulating tool failure and flashover
• Bridging of the air gap resulting in flashover
• Insulator flashover/failure
Other...
• Falling from heights
• Aviation related
• Driving to and from work site
Operational info Eskom Transmission L/L
4747
Resources
• 97 authorised live work staff - stick, bare hand and aerial techniques
• 5 In-house single engine helicopters and 10 Pilots
• 6 Insulated aerial platforms up to 765 kV
• Centrally managed and dispatched
• 7 geographically de concentrated operational units ( 7-15 man strong)
• In house training and assessments.
Governance and control
• Live Work Technology centrally managed and controlled
• 8 Live Work Standards and 21 Live Work Procedures
• Governed by Tx LWSC and Eskom LW CG
• Aviation regulated by Civil Aviation Authority
Questions
Thank you