165 articles
1. Choosing a transformer
PillarDesign
Power vs Distribution Transformers: What Is the Difference?
SpecifyApplicationsDry-Type vs Oil-Filled Transformers: Which to Choose?
SpecifyApplicationsWhat Is an Autotransformer and How Is It Different?
SpecifyApplicationsWhat Is a Generator Step-Up (GSU) Transformer?
SpecifyApplicationsWhat Is a Traction Transformer?
SpecifyApplicationsWhat Is a Scott Transformer?
SpecifyApplicationsThree-Phase vs Single-Phase Transformers?
SpecifyApplicationsWhat Is a Pad-Mounted Transformer?
SpecifyApplicationsWhat Is a Pole-Mounted Transformer?
SpecifyApplicationsWhat Is a Unit (Station) Transformer?
SpecifyApplicationsHow Do You Choose the Right Transformer Type?
SpecifyApplicationsWhat Are the Transformer Enclosure / Housing Types?
SpecifyApplicationsWhat Are the Common Distribution Voltage Levels?
SpecifyGridWhat Is a Reserve (Spare) Transformer?
BuyApplicationsHow Do You Increase the Capacity of a Transformer?
Refurbish & replace2. Cooling and temperature rise
PillarApplications
ONAN vs ONAF vs OFAF: What Is the Difference?
SpecifyDesignHow Are Transformer Radiators Designed?
SpecifyDesignHow Does the Cooling Class Affect the Transformer Rating?
SpecifyDesignHow Are Transformer Cooling (Radiator) Banks Arranged?
SpecifyApplicationsHow Are Dry-Type Transformers Cooled?
SpecifyComponentsWhat Does a Transformer Oil Pump Do?
SpecifyField ServiceHow Is a Transformer Cooling System Maintained?
Operate & diagnoseTestingWhat Is a Transformer Temperature Rise Test?
Manufacture & FATStandardsWhat Is the Standard Temperature Rise of a Transformer?
SpecifyStandardsHow Does Altitude Affect a Transformer?
Specify3. Losses, impedance and rating
PillarDesign
How Is Transformer Impedance Calculated and Why Does It Matter?
SpecifyDesignWhat Are Transformer No-Load and Load Losses?
SpecifyDesignWhat Are Hysteresis and Eddy Current (Core) Losses?
SpecifyDesignWhat Is Stray (Eddy) Loss in a Transformer?
SpecifyDesignWhat Is Transformer Voltage Regulation?
SpecifyDesignHow Do You Size a Transformer?
SpecifyDesignHow Do You Calculate Transformer Fault Current?
SpecifyDesignWhat Are the Forces on a Transformer During a Short Circuit?
SpecifyTestingWhy Does a Transformer Fail a Short-Circuit Test?
Manufacture & FATDesignWhat Is the K-Factor for a Transformer?
SpecifyStandardsWhat Do kVA and kV Ratings Mean on a Transformer?
SpecifyStandardsWhat Is the Difference Between kVA and kW on a Transformer?
SpecifyStandardsWhat Is on a Transformer Rating Plate?
SpecifyProcurementWhat Is Loss Evaluation / Capitalisation?
BuyStandardsWhat Are the Transformer Efficiency (Eco-design) Requirements?
SpecifyApplicationsHow Does a Transformer Affect Power Quality?
SpecifyApplicationsCan You Overload a Transformer? (Loading Guide)
Operate & diagnose4. Core
PillarDesign
What Is the Difference Between a Core-Type and Shell-Type Transformer?
SpecifyManufacturingWound Core vs Stacked (Laminated) Transformer Core?
Manufacture & FATManufacturingHow Is a Transformer Core Built?
Manufacture & FATManufacturingWhy Is a Transformer Core and Clamping Important?
Manufacture & FATManufacturingWhat Is Core Annealing?
Manufacture & FATDesignWhat Determines a Transformer Noise Level?
Specify5. Windings and conductors
PillarDesign
Concentric vs Disc (Layer) Transformer Windings?
SpecifyManufacturingWhat Is a Continuously Transposed Conductor (CTC)?
Manufacture & FATManufacturingHow Are Transformer Windings Made?
Manufacture & FATManufacturingHow Are Transformer Windings Formed and Shaped?
Manufacture & FATManufacturingWhat Are Winding Oil Ducts and Why Do They Matter?
Manufacture & FATDesignHow Are Transformer Windings Clamped?
SpecifyDesignWhat Are Transformer Leads and How Are They Designed?
SpecifyDesignHow Is a Dry-Type Transformer Designed?
SpecifyManufacturingWhat Is VPI (Vacuum Pressure Impregnation)?
Manufacture & FAT6. Insulation system
PillarInsulation
What Is the Paper-Oil Insulation System?
SpecifyInsulationWhat Is Diamond Dotted Paper (DDP)?
SpecifyInsulationPressboard vs Transformerboard: What Is the Difference?
SpecifyInsulationWhat Are Transformer Insulation Classes (A, E, B, F, H)?
SpecifyInsulationWhat Is Aromatic (Aramid) Paper Insulation?
SpecifyInsulationHow Does Transformer Insulation Age?
Operate & diagnoseInsulationWhat Is the Dielectric Strength of a Transformer?
SpecifyInsulationHow Are Transformer Insulation Barriers Designed?
SpecifyInsulationWhat Are the Grades of Transformer Insulation Paper?
SpecifyInsulationWhat Is Clearance vs Creepage in a Transformer?
SpecifyStandardsWhat Is Creepage Distance and Why Does It Matter?
SpecifyStandardsHow Are Transformer Insulation Materials Selected?
SpecifyComponentsWhat Insulating Liquids Are Used in Transformers?
Specify7. Standards and insulation coordination
PillarStandards
What Is Insulation Coordination?
SpecifyStandardsWhat Is BIL (Basic Insulation Level)?
SpecifyStandardsWhat Is IEC 60076?
SpecifyStandardsIEC vs IEEE Transformer Standards: What Is the Difference?
SpecifyStandardsWhat Tests Does a Transformer Standard Require?
SpecifyDesignWhat Is a Switching (Transient) Overvoltage on a Transformer?
SpecifyDesignWhat Are Transformer Vector Groups (e.g. Dyn11, YNd1)?
Specify8. Factory build and test
PillarManufacturing
How Is a Transformer Manufactured?
Manufacture & FATManufacturingHow Is a Transformer Tanked and Assembled?
Manufacture & FATManufacturingWhat Is Vacuum Drying of a Transformer?
Manufacture & FATTestingType, Routine and Special Tests? What Is the Difference?
Manufacture & FATProcurementWhat Is FAT vs SAT in Transformer Procurement?
BuyTestingWhat Is the Order of Transformer Tests?
Manufacture & FATTestingWhat Is Acceptance Testing of a Transformer?
Manufacture & FATTestingWhat Is a Partial Discharge (PD) Test?
Manufacture & FATTestingWhat Is a Power Factor (tan-delta) Test?
Manufacture & FATTestingWhat Is an Insulation Resistance (IR / Megger) Test?
Manufacture & FATTestingWhat Is a Winding Resistance Test?
Manufacture & FATTestingWhat Is a Transformer Oil Breakdown Voltage (BDV) Test?
Manufacture & FATTestingWhat Is a Frequency Response Analysis (FRA) Test?
Manufacture & FATTestingWhat Is a Zero-Sequence Test?
Manufacture & FATTestingWhat Is a Lightning Impulse Test?
Manufacture & FATTestingWhat Is an Induced Voltage Test (IVT)?
Manufacture & FAT9. Bushings, tap-changers and accessories
PillarComponents
Transformer Bushings: Types and Selection
SpecifyComponentsWhat Is a Dry / SF6 (Gas-Filled) Bushing?
SpecifyFailuresWhy Do Transformer Bushings Fail?
Operate & diagnoseComponentsWhat Is a Buchholz Relay and What Does It Protect?
Operate & diagnoseComponentsWhat Is a Conservator and Dehydrating Breather?
SpecifyComponentsHow Does an On-Load Tap-Changer (OLTC) Work?
Operate & diagnoseComponentsWhat Is the Tap Selector in an OLTC?
SpecifyComponentsWhat Is the OLTC Oil and How Is It Maintained?
Operate & diagnoseField ServiceHow Is an On-Load Tap-Changer (OLTC) Maintained?
Operate & diagnoseFailuresWhat Faults Occur in an On-Load Tap-Changer (OLTC)?
Operate & diagnoseComponentsWhat Is a Transformer Pressure Relief Device (PRD)?
SpecifyComponentsWhat Is a Hermetically Sealed Transformer?
SpecifyComponentsWhat Is a Winding CT (Bushing CT)?
Specify10. Oil and dissolved-gas analysis
PillarDiagnostics
Why Is Hydrogen High in Transformer Oil DGA?
Operate & diagnoseDiagnosticsWhat Transformer Oil Tests Are Performed?
Operate & diagnoseDiagnosticsHow Is a Duval Triangle Used to Diagnose a Transformer?
Operate & diagnoseDiagnosticsHow Are the DGA Gas Ratios Interpreted?
Operate & diagnoseDiagnosticsHow Often Should Transformer Oil (DGA) Be Sampled?
Operate & diagnoseDiagnosticsWhat Is Online DGA Monitoring?
Operate & diagnoseDiagnosticsHow Is Moisture Measured in a Transformer?
Operate & diagnoseDiagnosticsWhat Is Furan Analysis?
Operate & diagnoseDiagnosticsWhat Is the Transformer Oil Acidity (Neutralisation) Test?
Operate & diagnoseDiagnosticsWhat Is Transformer Oil Oxidation and How Is It Controlled?
Operate & diagnoseField ServiceHow Is Transformer Oil Sampled Correctly?
Operate & diagnoseField ServiceHow Is Transformer Oil Filtered and Regenerated?
Refurbish & replaceField ServiceWhat Is Transformer Oil Regeneration?
Refurbish & replaceField ServiceHow Is a Transformer Filled and Degassed?
Install & commissionField ServiceHow Is a Transformer Insulation Dried?
Refurbish & replace11. Reactors and reactive power
PillarGrid
What Is a Shunt Reactor and Why Is It Used?
SpecifyGridWhat Is the Difference Between a Shunt and a Series Reactor?
SpecifyGridWhat Is the Difference Between a Reactor and a Transformer?
SpecifyGridWhat Is a Phase-Shifting Transformer (PST)?
SpecifyGridHow Does a Transformer Help Control Reactive Power?
Specify12. Grid connection and protection
PillarGrid
What Is Involved in Connecting a Transformer to the Grid?
Install & commissionGridHow Is a Transformer Fitted Into a Substation?
Install & commissionGridWhat Is Protection Coordination for a Transformer?
SpecifyGridHow Is a Transformer Neutral Earthed?
SpecifyField ServiceHow Should a Transformer Be Earthed (Grounded)?
Install & commissionGridHow Do You Parallel (Reinforce) Two Transformers?
SpecifyGridWhat Is Transformer Inrush Current?
Operate & diagnoseGridWhat Is Ferroresonance in a Transformer?
Operate & diagnoseDesignHow Are Transformers Designed for Seismic Zones?
Specify13. Failures, life and condition
PillarFailures
What Are the Common Causes of Transformer Failure?
Operate & diagnoseFailuresWhy Do Transformer Windings Fail?
Operate & diagnoseFailuresWhat Causes a Transformer Oil Leak?
Operate & diagnoseFailuresWhat Causes a Transformer Tank to Rupture?
Operate & diagnoseFailuresHow Are Transformers Protected Against Fire?
SpecifyApplicationsWhat Are Transformer Fire Containment Measures?
SpecifyFailuresWhat Determines the Life of a Transformer?
Operate & diagnoseField ServiceHow Is a Transformer Failure Investigated?
Operate & diagnoseProcurementWhat Does a Transformer Failure Cost?
BuyDiagnosticsWhat Is Partial Discharge (PD) in a Transformer?
Operate & diagnoseDiagnosticsWhat Is a Transformer Condition Assessment?
Operate & diagnoseDiagnosticsHow Is Transformer Insulation Monitored?
Operate & diagnoseField ServiceWhat Is a Borescope (Internal) Inspection of a Transformer?
Operate & diagnoseFailuresWhat Causes a Transformer to Overheat?
Operate & diagnoseFailuresWhat Causes Winding Overheating and Hot Spots?
Operate & diagnose14. Buying a transformer
PillarProcurement
How to Buy a Power Transformer: A Checklist
BuyProcurementWhat to Include in a Transformer RFQ / Specification
SpecifyProcurementHow Do You Compare Transformer Quotes?
BuyProcurementWhy Are Transformer Lead Times So Long?
BuyProcurementWhat Does a Transformer Warranty Cover?
BuyProcurementWhat Transformer Spare Parts Should You Hold?
Buy15. Transport, storage and receipt
Field Service
How Should a Transformer Be Transported and Handled?
Transport & receiveProcurementWhat Are the Transport and Access Limits for a Transformer?
Transport & receiveField ServiceHow Do You Inspect a Transformer for Transport Damage?
Transport & receiveField ServiceHow Should a Transformer Be Stored?
Transport & receive16. Installation, commissioning and maintenance
PillarField Service
What Happens During Transformer Commissioning?
Install & commissionProcurementWhat Site Preparation Does a Transformer Need?
Install & commissionField ServiceWhat Is a Transformer Maintenance Checklist?
Operate & diagnoseField ServiceHow Is Transformer Winding Temperature Monitored?
Operate & diagnoseField ServiceHow Is a Transformer Decommissioned?
Refurbish & replaceTechnical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.