B. Transformers

1. Properties and Types

Identify properties, types, and applications ^{2, 3, 4}

• Types of transformers
• Transformer Terms and Definitions
• Guide to Delta and Wye Transformer Connections
• Types and Construction of Power and Distribution Transformers
• Transformer Cooling Systems and Methods Explained
• Guide to Transformer Cooling Classes
• Transformer Temperature Ratings
• Guide to Transformer Windings & Coils
• Aluminum vs. copper in distribution transformers
• Guide to transformer harmonics and k-factor
• K-Factor Transformers
• Autotransformers: applications, advantages, & disadvantages
• Guide to Drive Isolation Transformers

Identify properties, types, and applications of auxiliary devices ^{2, 3, 4}

• Types of Bayonet Fuses: Dual Element, Current Sensing, etc...
• Functional Testing for a Sudden Pressure Relay
• Transformer Pressure Relief & Fault Detection Devices
• Transformer Auxiliary Protection Devices
• Transformer Tap Changers: Basic Principles and Testing Explained
• Effect of CT Saturation on Transformer Differential Protection
• Guide to Transformer Electrostatic Shields (E-shields)
• The Benefits of FR3® Fluid in Transformers
• Guide to Kirk Keys Interlocks on Transformers

2. Inspection and Test Procedures

Apply visual and mechanical inspections ^{2, 3, 4}

• NFPA 70 2017: Article 450 Transformers and Transformer Vaults ^2 3 4
• Routine Transformer Maintenance
• Article 450: Transformers and Transformer Vaults
• IEEE C57.12.00 Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers ⁴
• High Resistance Grounding... Is It More Than Just a Big Heater? ³
• 3 Routine Inspections and Checks for Liquid Filled Transformers
• Understanding Transformer Noise
• Transformer Humming Noise Explained

Employ methods and procedures for electrical tests ^{2, 3, 4}

• Guide to transformer testing standards
• NFPA 70B: 11.11 Transformer Tests ^2 3 4
• Transformer Diagnostics Handbook Instructions, Standards, and Techniques ³
• IEEE C57.12.90 Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers ³
• Transformer Diagnostics and Condition Assessment
• Introduction to Transformer Turns Ratio Testing
• Transformer Turns Ratio (TTR) Explained
• Transformer Polarity Test Procedures
• Transformer Winding Resistance Testing Explained
• Shorting transformer windings for PI, why is it done?
• Transformer Testing — Are You Missing the Test Point?
• Application guide for power factor testing of power & distribution transformers
• Power Factor Testing Dry-Type Transformers

3. Interpretation of Test Results

Evaluate results of electrical tests ^{2, 3, 4}

• NETA-ATS 2017: Section 7.2 Transformers ^{2, 3, 4}
• NETA-MTS 2019: Section 7.2 Transformers ^{2, 3, 4}
• Fundamental Understanding of Frequency Response Characteristic
• How Transformer Age
• How Old is Your Transformer?
• A Guide to Transformer Winding Resistance Measurements

Last Update: Jun 03, 2025