GUIDELINES AND BEST PRACTICES FOR OPERATION & ΜΑΙΝΤΕΝΑNCE OF DISTRIBUTION TRANSFORMERS

Central Electricity Authority prepared the Guidelines after due consultation with stakeholders.

March 2023

Copyright © Central Electricity Authority

CONTENTS
Introduction ………………………………………………………………………………………………………………… 1
Chapter-1
Transformer Design & Material………………………………………………………………………………….. 6
Core Construction
Losses in Transformers
No-load losses
Load losses
Stray Losses
Windings
Insulation System Characteristics (Cellulose & Oil)
Some important specifications of Distribution Transformer
Chapter-2
Life Expectancy & Failure of DTs (Theoretical V/S Practical Life)…………………………… 16
Failure of Distribution Transformers
Details of Major Reasons for failure of DTs
(a) Operation & maintenance problems
(b) Manufacturing side Defects
(c) Utility Side Defects
Chapter-3
Adoption of Best Practices …………………………………………………………………..28
Standardization of operational practices of utilities
Analysis of cause of failure & maintaining history card for Distribution Transformer
Examination of failed Distribution Transformer
Some General Observations / Case studies on Averting DT failure
Case Studies of Transformer failure with Analysis
Asset management Practices
Chapter-4
Preventive & Predictive Maintenance Schedules for Oil filled/Dry type Distribution
Transformers …………………………………………………………………………………………………………….. 43
Check list for Distribution transformers
1. For oil filled Distribution Transformers
2. For Mobile Trolies
3. Checklist for testing
4. For Dry Type Transformers
5. Maintenance Schedule for DTs of capacity less than 1000 KVA
6. Maintenance Schedule for DTs of Capacity 1000KVA and above
7. Troubleshooting Chart for all Transformers
8. Checklist for maintenance schedule of DTs
9. Causes & Effects
10. Storage and handing of Insulating Oil
Chapter-5
Tests, Recommended Tools and Test Data ……………………………………………………………….. 57
Routine Tests
Special Tests
Type Tests to be conducted on one Unit
Typical Tests carried out before commissioning / energizing of DTs
List of Tools for maintenance & testing equipment
List of Consumables for repairing/Refurbishment Job at site
Guidelines for interpreting the field test data
Site Testing Report
Chapter-6
IT/OT/Al Cloud based asset management tools & applications ……………………….69
Smart Substation
Smart Transformers (VFI)
Smart Meter for Performance Monitoring /Remote monitoring of Distribution Transformers
IT based preventive and predictive maintenance of DTs
Distribution Transformer Monitoring Unit (DTMU)
Use Case- DT Health Monitoring using DIDO of Smart Meters
IOT based solution for Transformer overloading and life extension
Chapter-7
National & International Quality Standards, Energy Standards, Manufacturing
Process Standards, Guidelines & Manuals ………………………………………………………………. 79
Reference: ………………………………………………………………………………………………………………….. 80