This document provides an overview of transformer asset management (TAM). It discusses that TAM focuses on reliability, risk management, and optimizing lifecycle costs for power transformers. A key part of TAM is developing a Transformer Asset Management Plan (TAMP) that qualitatively assesses transformer condition, risks of extended use, and an effective inventory strategy. Condition monitoring and testing are important to assess transformer health and aging. Asset management tools help calculate expected lifetime based on loading and usage. Procuring spare transformers requires evaluating repair costs, load demands, and risks to minimize outages and losses.

1. TRANSFORMER ASSET MANAGEMENT
-AN OVERVIEW
Presented By:
S.M.G. MUZAFFAR HUSSAIN
SUBSTATION ENGINEER
Unrestricted

2. CONTENTS
 INTRODUCTION
 TAM
 TAMP
 TRANSFORMER AGING
 TRANSFORMER FAILURES
 CONDITION MONITORING / TESTING
 ASSET MANAGEMENT TOOLS
 FACTORS DECIDING PROCUREMENT OF SPARE
TRANSFORMER
 CONCLUSION
 REFERENCES AND ACKNOWLEDGEMENTS

3. INTRODUCTION
Asset Management is defined as an efficient way of
utilizing and maintaining a group of assets over their
entire life cycle assuring return on investments,
ensuring defined service, reliability and safety as per
standards.
An asset is the one which is,
 used in production and supply of goods and services.
 utilized maximum throughout its life cycle.
 A vital link in the network and has a specified life
period.

4. TRANSFORMER ASSET MANAGEMENT (TAM)
IN ELECTRICAL UTILITIES
A power transformer being a significant asset in the process of energy
transmission, Transformer Asset Management (TAM) becomes really
necessary that focuses on Plant reliability, Managing risks and
Optimizing life cycle costs.
In simple managing transformer assets for value and risk implies
 Balancing investors, customers and interested parties.
 Aiming uninterrupted long term service to customers.
 Cost effective quality energy supply to avoid customer conflict.
 Evaluating massive risk implications i.e. Cost of transformer Vs
Loss of revenue due to its failure at site
 Using management tools to calculate the life of a transformer to
avoid extending its use beyond planned to avoid windfall.
 Managing redundancy usually built in the network.
 Building teams and developing asset management cultures.
 Encouraging both internal and external interested parties to invest.

5. TRANSFORMER ASSET MANAGEMENT PLAN (TAMP)
A Transformer Asset Management Plan (TAMP) is made with the
business objective of providing a comprehensive
a) Qualitative assessment of condition.
i.e. Healthiness of the transformer
b) Risk Exposed to the business or extended usage of
transformers beyond its lifetime. (Power interruption due to
continued usage of defective transformers without
redundancy till the time it fails and not thinking of repair,
refurbishment or replacement).
c) Developing an effective inventory management
strategy to minimize the life cycle costs / Inventory costs.

6. a. QUALITATIVE ASSESSMENT OF CONDITION
Healthiness of the transformers is assessed during the
various stages of its life cycle through electrical
tests , dielectric tests on oil and insulation and
other diagnostics methods.
Preventive maintenance and Quality inspections are
carried out to detect faults and fix it in time to
ensure and acceptable level of transformer
reliability. However the spare parts and cost of
inventory should be mitigated.

7. b. RISK EXPOSED TO THE BUSINESS
A life extension beyond that planned is a significant
windfall for the utility. Any failure by the
transformer has massive risk implications.
Redundancy built in the network results in power
interruptions to customers and loss of revenue
which is many times its cost to the utility.

8. c. DEVELOPING AN EFFECTIVE INVENTORY MANAGEMENT STRATEGY
The components of the Power transformer are classified into
three categories.
i. Most Expensive Items (OLTC, Bushings Arrestors)
ii. Ordinary Items (Insulating Oil)
iii. Cheap Items (Nuts, Bolts and Gaskets)
The most expensive items that need close control and which
in cults usually high inventory cost are usually not kept in
huge numbers as stock due to capital investment
limitations. Hence the number of spare parts is based on
Minimum Safety Stock (MSS) with acceptable stock
availability.
Statistical distribution techniques such as Poisson and Normal
distribution is used to determine the optimum number of
spare parts after analyzing the failure rate on Power
transformer.

9. c. DEVELOPING AN EFFECTIVE INVENTORY MANAGEMENT STRATEGY
(Continued..)
The Ordinary items that need standard care,
the method of Economic Order Quantity
(EOQ) is proposed to minimize inventory cost.
The cheap items that need little care are
managed by KANBAN System.
With this effective inventory management the
electric utilities not only reduce the inventory
costs but also significantly reduce the hidden
capital costs due to power cuts.

10. 4. TRANSFORMER AGING & END OF LIFE
Aging of a transformer refers to the thermal
degradation of the insulation system during its
normal life cycle. End-of-life refers to a point where it
can no longer withstand the stresses coming on to it
during fault conditions.
 The primary aging factors are temperature, time,
over loads and frequent faults.
 The environmental conditions such as corrosive
atmosphere, excessive vibration may affect actual
service life.
 Agents of deterioration like moisture and tracking
accelerates aging.
Degree of Polarization (DP test) on cellulose insulation
material sample taken from the hottest-spot region is
recommended as a supplementary test to determine
its correlation with transformer aging.

11. 5. TRANSFORMER FAILURES
Failure is described as an insulation breakdown and
that a service outage would result if it occurs in the
field.
Main causes of transformer failure:
 Internal insulation breakdown caused by hot spots,
partial discharges and arcing.
 Oil Contamination caused by oil leaks.
 Voltage spikes caused by lightning surges.
 Movement of coils and weakening of cellulose caused
by external short circuits.
 Moisture content
 Internal flash over of tap changer
 External flash over of insulators
 Bursting out of tank due to enormous pressure
created during short circuits and failure of operation
of pressure relief vent.
 Operating an Off load tap changer without de-
energizing the transformer.

12. 6. CONDITION MONITORING/TESTING
Since it is not possible to predict when a final failure
will occur, it is necessary that a number of
parameters such as dielectric strength,
thermal/mechanical strength and electrical strength
are to be monitored to avoid breakdown.
Maintenance Engineers are required to conduct
analysis, tests, and inspections and review previous
data to assess the condition (Healthiness) of the
power transformer.
INSULATION SYSTEM
Dissolved Gas Analysis (DGA)
Acidity
Water Content (ppm test)
Insulation power factor (Tan ∂ test)
Furan Analysis
Degree of Polymerization (DP test)

13. 6. CONDITION MONITORING/TESTING
(Continued..)
ELECTRICAL SYSTEM
Ratio (TTR test)
DC measurement of Winding Resistance
MECHANICAL SYSTEM
Sweep Frequency Response Analysis
Tightness test for Oil leakage
Core to earth resistance
BENCH MARKING
Previous results
Signatures
Bench mark set by Electric utility companies

14. 7. ASSET MANAGEMENT TOOLS
In practice as necessary tools are not available to determine the
end-of-life of a power transformer, the minimum life expectancy
(elapsed time) is calculated.
Minimum life expectancy calculation as per IEEE C57.100.1999

15. 7. ASSET MANAGEMENT TOOLS (Continued..)
The elapsed time in actual for a transformer in service
will be very much greater than the life determined by
the continuous loading. Therefore it is indicative of
the fact that a transformer operated continuously at
rated hottest-spot temperature should give a
satisfactory life expectancy of 180 000 h
approximately 20.5yrs.
If a transformer fails before its life expectancy due to
material defect or poor workmanship the issue has to
be taken up with the manufacturer for immediate
replacement.
If the transformer fails in the end of life tests (series of
high voltage and high current tests), a service outage
occurs in the field and to refurbish with spare
transformer.

16. 8. FACTORS DECIDING PROCUREMENT OF SPARE
TRANSFORMERS
Transformer is a costly equipment and incurs huge
investment and stock build up.
Even though its failure rate is low it plays an important
role in transmission network. Therefore a wise
decision has to be taken on the procurement of spare
transformers considering system reliability and risk
assessment.
Before procuring the spare transformers, the following
has to be evaluated
 Whether the aged transformers can be repaired.
 Value of the spare transformers V/s Repair cost
 Overloading of aged transformers or its Replacement.

17. 8. FACTORS DECIDING PROCUREMENT OF SPARE
TRANSFORMERS (Continued..)
The other factors deciding on the procurement of
spare transformer are
 Total number of transformers available in the system.
 Load demand on the service transformers
 Condition of aged transformers
 Total years in service
 Risk Management Strategy
◦ Shifting aged transformers to under loaded
substations to minimize failures.
◦ Availability of identical spare transformers to
mitigate the risk of transformer failures and outage
at substation.

18. 9. CONCLUSION
Since it is impracticable to determine the
condition of aged power transformers and its
end of life, the following are the conclusions.
◦ The aged transformers are to be identified in the
system to avoid overloading and failures at site
during its revenue earning period.
◦ Spare transformers to be procured as per the
inventory management strategy to prevent outage
and loss of revenue.
◦ Load demand and Load flow study to be done to
operate transformers in parallel.
◦ Mobile transformers identical to the existing ones
have many advantages in shifting and restoration.
◦ Avoid un-served customers and energy loss.
◦ Quality supply as per customer demand to avoid
customer conflict.

19. 9. CONCLUSION (Continued..)
◦ Increasing transformer life through condition
monitoring and Preventive maintenance.
◦ Lessen Maintenance Costs.
◦ Depreciation on the value of the asset to be
calculated every year to decide on replacement.
◦ When the depreciated value of the asset becomes
equal to the maintenance cost it is the right time
for replacement.
◦ The Residual / Fair value of the asset at the end of
its service shall be an appreciable one.
◦ As such in the whole substation the asset value of
transformers are less compared to its cost of
failure. Hence avoid risk implications.
◦ Data Collection is a must for analysis

20. 9. References and Acknowledgements
 Asset Management in Power Transformers by G. Kalinde
 Asset Management Plan of transformer & Factors affecting the decision on
procurement of spare transformer by Nahar S. Al Mutawah and Navin Rego
 Asset Management for Power transformer in High Voltage Substation by Thanapong
Suwanasri, Rattanakorn Phadungthin and Cattareeya Suwanasri

21. END OF PAPER
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