5.04 Shortcomings and proposed improvements to the asset … · 2017. 11. 23. · – Software:...

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


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


Free State has the most

kilometers of Overhead

transmission line to cover

East Grid has the most

number of lines

Transmission Line Asset Profile


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


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


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.

7


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.


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

9


Transmission Line Health Index

10


Challenges and Shortcomings

• Type and Frequency of Inspections

• Data Capturing

• Data Storage

• Sampling and Testing

• Resources


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


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.


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.


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.


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


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.


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)


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.


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


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

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