Transformer Diagnostics Technique
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The document discusses transformer diagnostics, covering failure patterns, classifications of faults by severity, occurrence, and detection, along with Failure Modes and Effects Analysis (FMEA) techniques. It identifies common transformer failures and outlines various definitions of transformer lifetime, including ageing rate, economic, technical, strategic, and equivalent lifetimes. The aim is to improve transformer reliability and reduce failures through systematic analysis and identification of potential issues.
Transformer Diagnostics Technique
- 1. Transformer Diagnostics Technique By Ankit Singh Basera 1
- 2. Transformer Failure Pattern And Failure Analysis 2
- 3. INTRODUCTION • Like all electrical devices faults also happen in the transformers which cause failures. • One failure can cause many problems. 3
- 4. Classification of Fault in Transformer • MIL-STD-1629A standard is used to classify different faults that occurs in transformer. 1) On The Basis Of Severity Of The Fault: Value Description Criteria 1 Category IV (Minor) Primary function can be done but urgent repair needed 2 Category III (Marginal) Reduction in ability to primary function 3 Category II(Critical) Causes a loss of primary function 4 Category I (Catastrophic) Product becomes inappropriate Reference: Severity Classification For Power Transformers 4
- 5. Classification of Fault in Transformer 2) On The Basis Of The Occurrence Of The Fault: Value Description Criteria 1 Level E (Extremely unlikely) Probability of occurrence less than 0.001 2 Level D (Remote) Probability of occurrence more than 0.001and less than 0.01 3 Level C (occasional) Probability of occurrence more than 0.01and less than 0.1 4 Level B (Reasonably Probable) Probability of occurrence more than 0.1and less than 0.2 5 Level A (Frequent) Probability of occurrence more than 0.2 Reference: Occurrence Classification For Power Transformers 5
- 6. Classification of Fault in Transformer 3) On The Basis Of The Detection: Value Description Criteria 1 Level F Good Identification 2 Level E Fair Identification 3 Level D Good detection and rough identification 4 Level C Fair detection 5 Level B Rough detection 6 Level A Complementary test Reference: Detection Classification For Power Transformers 6
- 7. Failure Modes and Effect Analysis (FMEA) • Failure modes means the ways in which something could fail. • Effects analysis refers to studying the consequences of those failures. • The purpose of the FMEA is to take actions to eliminate or reduce failures, starting with the highest-priority ones. 7
- 8. Steps in Failure Modes and Effect Analysis (FMEA) Define the system to be analysed Identify failure modes Identify potential effects of failure modes. rank how serious each effect is determine all the potential root causes identify available detection methods Identify recommended actions for each cause that can reduce the severity of each failure. 8
- 9. FMEA for the Transformer Transformer Winding Tank Bushing Tap Changer Cooling Oil Insulation 9
- 10. Commonly Occurring Failures Of The Transformer 1) Winding Failure a) Dielectric Stress b) Thermal Stress c) Mechanical stress 2) Bushing Failure 3) Tap Changer Failure 4) Tank Failure 5) Cooling System Failure 6) Core Failure 7) Oil Insulation Failure 10
- 11. Different Lifetime Definitions Reference IEC Standards 60076-7. 1) Ageing Rate : 2) Loss of Life: 𝑉𝑛 = 2 𝜃 𝑛−96 8 𝐿 = 𝑡1 𝑡2 𝑉𝑛 𝑑𝑡 11
- 12. Different Lifetime Definitions 3) Economical Life Time: It refers to the time up to the replacement time which gives the optimal profit. 4) Technical Lifetime: The technical lifetime for a component is defined as the time until the component is unable to perform the desired function and it is impossible to repair the component. 5) Strategic Lifetime: When the strategic lifetime of the transformer is at the end, it is replaced because of changes in the power system. 12
- 13. Different Lifetime Definitions 6) Equivalent lifetime: Different transformers are situated on different places in the power system and naturally they are exposed to different stresses. Therefore, in order to compare different transformers with each other it can be useful to define an equivalent lifetime. 𝐿 𝑒 = 𝐴 + 𝐿𝐾 + 𝐿𝑀 Transformer age stresses from lifetime consuming factors stresses from lifetime intensifying factors. 13