Post on 25-Jan-2021
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Sharon MushabeEskom Holdings SOC Ltd
Paper Number 5.04
Session Number 5
15 November 2017
Shortcomings And Proposed
Improvements To The Current Practice
Used By Eskom Transmission To
Determine Asset Health Index Of
Overhead Transmission Lines
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Content
• Overview of the Asset Profile• Description of the Transmission Line Health Index• Challenges and Shortcomings• Recommendations
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities3
• 358 overhead transmission lines in 10 grids• 85000+ towers• 32 500+ km (route length)• 275 000+ km of conductor (excl. Earthwire and
OPGW)
Transmission Line Asset Profile 1
1 Profile at the end of the 2016/2017 financial year
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities4
Free State has the most
kilometers of Overhead
transmission line to cover
East Grid has the most
number of lines
Transmission Line Asset Profile
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Eskom Transmission Line Teams
• Design Team– Full detail designs for HVAC up to 765 kV and HVDC up to 800
kV
– Team of over 70 engineers, technologists and technicians – Facilities include tower test station and corona cage test – Software: PLSCADD, SolidWorks, FALLS, ATP
• Maintenance Team– Maintenance teams in 10 grids/operating units– Live line teams
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Eskom Maintenance Strategy
• Currently, the strategy is a time based inspection and assessment approach
• Eskom Transmission is moving towards adopting a condition based approach
• The condition based approach includes determining the asset health of the overhead line
• Part of this approach required a health index to be defined
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Transmission Line Health Index (ideal)
• Two asset classes for Overhead Transmission lines are defined,
namely: Steel Structures and
Overhead Conductor systems.
• Failure mode and effects analysis (FMEA) is compiled.
• Condition monitoring task and activity schedule is created
based on results.
• End-of-life criteria are developed for various
components of the asset class.
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Electricity Supply to Africa and Developing Economies: Challenges and Opportunities8
Abbreviated Transmission Line Health Index
The following abbreviated Health Measures were applied
when conducting this survey:
– A line will be rated as a whole and not per individual structure, span etc.
– Overall ratings of components based on visual inspection reports.
– Fibre Optic systems will be excluded from the line ratings.– The age of the line is based on the earliest recorded date on
TxSiS.
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Health Index rating
Health index
Condition Description Requirements
85 - 100Very Good
(A)
Some ageing or minor deterioration of a limited number of components
Normal maintenance
70 - 85Good
(B)Significant deterioration of some components
Normal maintenance
50 - 70Fair
(C)
Widespread significant deterioration or serious deterioration of specific components
Increase diagnostic testing, possible remedial work or replacement needed depending on criticality
30 - 50Poor
(D)Widespread serious deterioration
Start planning process to replace or rebuild considering risk and consequences of failure
0 - 30Very Poor
(E)Extensive serious deterioration
At end-of-life, immediately assess risk; replace or rebuild based on assessment
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Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Transmission Line Health Index
10
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Challenges and Shortcomings
• Type and Frequency of Inspections
• Data Capturing
• Data Storage
• Sampling and Testing
• Resources
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Type and Frequency of Inspections
• Fast aerial inspection at least once year on each line– Purpose to the pick up serious defects that could result in
failure in
• Detailed aerial inspection every four years on each line.– Visual inspection with multi-spectural camera of line
hardware, conductors, spacers, insulators with the use of
helicopter
• Both inspections neglect the foundations as well as sections of tower that are not visible from the air
• Pole top inspection – Similar to detail aerial inspection but with inspectors physically
on the tower
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Data Capturing
• Detailed aerial inspections captures the defects at each tower.– Defects are supported with photos and videos. – No assignment of a condition rating for each component.– No information is given for towers that have no defects. – Reports vary from operator to operator.
• No measurements, tests or samples are performed to determine remaining life of the assets.
• Inspection checksheet or report is ambiguous and leads to various interpretations.
• Operators are not clear on what to look for during a visual inspection nor how to identify all signs of deterioration on
transmission lines.
• Budget constraints limiting number of hours flown by helicopter.
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Data Storage
• Accurate records of as-built infrastructure is needed. • Records of all the major components/assemblies including
material, type, size, manufacturer and installation year must be
stored.
• Data must be updated after each inspection cycle and following changes due to maintenance and construction activities.
• No central storage facility of inspection photos, reports and/or investigations.
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Sampling and Testing
• Samples are required to be taken for various tests. – Conductor and Earthwire samples are required for tensile
tests, tensile ductility tests, wrapping tests, zinc coating
measurements and torsional ductility tests.
– Hardware samples are required for corrosion examinations. – Insulator strings are required for pollution conductivity
testing.
• Some cases network constraints prevent outages for significant periods to allow teams to acquire the samples.
• Some lines more than one conductor sample is required to give a suitable representation of the line.
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Tests or Inspections
• Conductor clearance measurements• Corrosion and wear on tower
members and hardware
• IR and UV scanning • Tower footing resistance
measurements
• Line impedance measurements
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Resources
• Field operators are responsible for collecting the data while analysis of the data is performed by the relevant engineering
department.
• Movement of staff from grid to grid means that local knowledge of lines diminishes as new staff move in and out.
• Testing facilities, labs, equipment and tools are required to run tests on samples.
Advancements in technology
• The maintenance strategy includes the use of multi-spectral cameras and hand-held tough books that are linked to the plant
management system.
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
UAV’s and Line Robots
• The use of unmanned aerial vehicles and line robots for overhead line inspections is still being reviewed.
• Integrating vibration sensors on towers are still being investigated. • These interventions all require trained and skilled personnel to
operate and produce quality reports.
Power Line Robot: Developed by Eskom and UKZN (image from: www.powerlinerobot.com)
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Recommendations
• Detailed and complete asset registry is required – (including manufacturer, material type, installation year, etc)
• Revision of the inspection check sheet such that the data can be captured accurately without ambiguity.
• Review of the frequency of inspections to complete an audit that can be used to compile a complete health index.
• System is under development that allows operators to capture data in the field, integrate seamlessly with the current plant
management systems and be available online for all the relevant
stakeholders.
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Recommendations
• Develop a training program for line audits so that the operators are:
– Fully knowledgeable of the components on the transmission lines
– Can identify defects and accurately comment on the condition of the transmission line
– Equipped and trained to use and interpret the results
Electricity Supply to Africa and Developing Economies: Challenges and Opportunities
Acknowledgements
• Team within the following Eskom departments:– Transmission Grid Supervisors, Operators and
Engineers
– Research, Testing and Development– Line Engineering Services – Asset Investment Planning, and– Asset Management Execution