MANAGING THE RISKS ON TRANSFORMER ASSETS by ARUN D YARGOLE & TONY McGRAIL DOBLE ENGINEERING COMPANY ayargole@doble.com
What is an Asset? In commercial terms- It is an Entity that gives the owner the revenue through out it s life. In Social terms- It provides the service to the nation. In ISO 55000 terms it is an item, thing or entity which has value, or potential value, to an organization The standard really covers just about anything! It is very important to take care of the Asset/s that help in National growth. And therefore, operating & maintaining such assets becomes very important. 2
Managing Transformer Assets Keeping Assets out of risks Maintain if no Risk Sense Risk if any Plan Risk management Monitor & Avoid failure and retire the asset right before the failure or when the risk is too great Plan optimum deliveries from asset before it retires (Risk analysis) Consider cost consequences on Risks if any (Sudden failure, failure mode, damage to environment, impact on revenue ) Consider cost required to eliminate the Risk Consider cost of unexpected reduction in service life due to forced retirement of an Asset in case of Risk Identifying and ranking the Risks is the important aspect of successful Asset management. 3
Risks [Asset Health Index * Impact Factor ( ) = Risk ( )] Safety- How safe? Mode of failures? Will it damage other apparatus on failure? How safe for personnel working in the field? Is appropriate care taken for safe operation? Availability- What is probability of outage duration in case of trouble? Few hours? One day? More than day? Reliability- How reliable is it? Are frequent outages being taken? Does it suffice load demands? No load & Load losses? Environmental- Upon failure, what are the damages to environment? Financial- There is a cost to every risk mentioned above. What is the cost involved in, Few thousands? millions? Or tens of millions? 4
Risk ratings and ranking for a fleet of transformers It is very much essential to know which are the transformers on high risks and how do they stand in rank. Robust Health Scoring system is required that helps the organization in taking decision. (Called as Asset Health Index) Typical Scoring Systems- A (Good), B (Bad), I (Investigate), (Good), 2, 3, 4, 5 (Bad). User defines high score, say 0 Logarithmic Scoring- 0,, 3, 0, 30, 00 etc. (Doble Way of Scoring) The score should be auditable, justifiable and useful All scores should be calibrated retain common sense of urgency 5
Risk ratings and ranking For Transformer, Asset Health Index (AHI) is a complex number derived from Health score of its individual component health parameters, and their relevance. Transformer main health parameters- Bushings- C & Tan, Partial Discharges, Oil DGA and other analysis Dielectric (Solid + Oil)- C & Tan, Partial Discharges. Insulating material (oil)- Lab analysis, DGA, moisture etc. LTC- Tap position, Oil DGA, Ratio, Excitation current etc. Operation- Voltage and current continuous monitoring Maintenance history, shifting or transport, repair, refurbishment etc. 6
Risk ratings and ranking Apart from main components there is a significant consideration given to operation and maintenance history. Scores are assigned using substantial amount of statistical data on failures and failure analysis of families of transformers. Scores are assigned using rules developed or evolved over a period using these analysis. Scores then are weighed by their relevance to health. One way to balance the scores is- This gives the distinct difference to the scores and help assign AHI. 7
Risk ratings and ranking (Relevance example) 8
Risk ratings and ranking (Example not limiting to the scope showed) R Bushings R R Analysis test results Analysis test 2 results AHI R IM R R Analysis test results Analysis test 2 results R Dielectric R R Analysis test results Analysis test 2 results 9
Risk ratings and ranking (Example not limiting to the scope showed) R = Relevance 0 7 0 0 30 0 AHI 4 0 7 0 0 00 0 0 3 2 0 0 0
Risk ratings and ranking Assigning the correct relevance and score is important. very This is done by experts using sufficient sized Knowledge database, the Failure Mode Effect Analysis (FMEA), Risk priority analysis. This is a comprehensive analysis which is a collective intelligence offered by experienced experts in the fields. It s a significant task in performing cross correlations of big data, historic information and events over large period. Further it needs to be a dynamic assessment as & when fresh data and information becomes available.
Risk ratings and ranking Without a powerful software solution it is not feasible to get the realistic and holistic assessment of assets that would assist maintenance engineer and asset managers to make the optimal decision. Such Software solutions require minimum basic deliverables. 2
Risk ratings and ranking 3
Minimum basic deliverables. User-friendly Graphical User Interface GUI which presents key information clearly 2. Ability to assess complete fleet of the transformers in a single at a glance view 3. Capable to capture and display the detailed historic information with date and time stamp for all available data including monitoring and operational data 4. Capable to capture nameplate details of all individual transformers, for family assessment 5. Capable to capture the financial consequence data. 6. An interface to take in the off-line test data and maintenance implications 4
Minimum basic deliverables 7. An interface to take in directly the On-line continuously monitored parameters such as H2 levels, Moisture levels in oil, bushing Tan and Capacitance, Partial Discharges in Bushings & transformers etc. 8. Multiple expert algorithms and diagnostic tools continuously running to indicate anomalous performance and generate the AHI, Scores of individual health parameters with date and time stamp all should work with whatever data is available not require further data be gathered 9. Page to show the trends of health parameters and the likely consequences of failure. 0. Capability of alert generation as per user settings.. More deliverables are mentioned in the paper. 5
Some typical screens and ease of navigation 6
Some typical screens and ease of navigation 7
Conclusion Holistic Transformer Asset Management cannot be completed without consideration of Risks associated during life time operation of Transformers in the field and Risks ranking. Analysis tools which generate asset health scores must be completely understood in terms of the question which they address the approach used must be justifiable, auditable and useful. Weighted analysis systems may be misleading. 8
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