Power Transformer Maintenance

Power Transformer Maintenance – Facilities Standards, Instructions, and Techniques

Contents
1. Purpose
2. Introduction to Reclamation Transformers
3. Transformer Cooling Methods
3.1 Dry Type Transformers
3.1.1 Potential Problems and Remedial Actions for Dry Type Transformer Cooling Systems
3.2 Liquid-Immersed Transformers
3.2.1 Liquid-Immersed, Air-Cooled
3.2.2 Liquid-Immersed, Air-Cooled/Forced Liquid-Cooled
3.2.3 Liquid-Immersed, Water-Cooled
3.2.4 Liquid-Immersed, Forced Liquid-Cooled
3.2.5 Potential Problems and Remedial Actions for Liquid Filled Transformer Cooling Systems
3.2.6 Cooling System Inspections
4. Oil-Filled Transformer Inspections
4.1 Oil-Filled Transformers
4.1.1 Transformer Tank
4.1.2 Top Oil Thermometers
4.1.3 Winding Temperature Thermometers
4.1.4 Oil Level Indicators
4.1.5 Pressure Relief Devices
4.1.6 Sudden Pressure Relay
4.1.7 Buchholz Relay
4.1.8 Transformer Bushings: Testing and Maintenance of High-Voltage Bushings
4.2 Oil Preservation Sealing Systems
4.2.1 Sealing Systems Types
4.2.2 Gas Pressure Control Components
4.3 Gaskets
4.4 Transformer Oils
4.4.1 Transformer Oil Functions
4.4.2 Dissolved Gas Analysis
4.4.3 Key Gas Method
4.4.4 Transformer Diagnosis Using Individual and Total Dissolved Key Gas Concentrations
4.4.5 Rogers Ratio Method of DGA
4.5 Moisture Problems
4.5.1 Dissolved Moisture in Transformer Oil
4.5.2 Moisture in Transformer Insulation
4.6 Transformer Oil Tests That Should Be Done Annually With the Dissolved Gas Analysis
4.6.1 Dielectric Strength
4.6.2 Interfacial Tension (IFT)
4.6.3 Acid Number
4.6.4 Test for Oxygen Inhibitor
4.6.5 Power Factor
4.6.6 Furans
4.6.7 Taking Oil Samples for DGA
4.6.8 Silicone Oil-Filled Transformers
4.7 Transformer Testing
4.7.1 Winding Resistances
4.7.2 Core Insulation Resistance and Inadvertent Core Ground Test

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