Indepth Electrical engineering

  🔧 Transformer Maintenance Values and Limits 1. Oil-Type Transformers A. Oil Testing Parameters Parameter Typical Limit / Value Notes Dielectric Strength ≥ 30 kV (1 mm gap) Below this, oil needs filtration or replacement Moisture Content ≤ 30 ppm (for new/healthy oil) Higher moisture → reduce insulation strength Dissolved Gas Analysis (DGA) Gas ratios per IEC standard (e.g., Rogers ratio, Doernenburg ratio) Used to detect overheating/arcing Acidity (Neutralization Number) ≤ 0.1 mg KOH/g Higher value indicates oil deterioration Interfacial Tension ≥ 40 mN/m Indicates presence of polar contaminants Flash Point ≥ 140°C Safety limit for oil B. Electrical Tests Test Typical Value / Limit...

  Transformer Nameplate Details: A Complete Guide for Engineers The nameplate of a transformer is often referred to as the “identity card” of the equipment. It carries critical information about the transformer’s design, performance, and operational limits. For engineers, operators, and maintenance teams, understanding these details is essential for safe operation, correct installation, and effective troubleshooting. In my 20+ years of working with transformers—ranging from distribution units in urban substations to large power transformers in industrial plants—I’ve seen how misinterpretation of nameplate data can lead to costly errors, system inefficiencies, and even equipment failures. This article provides a detailed explanation of transformer nameplate details , along with their significance. 1. Manufacturer Details Name of Manufacturer : Identifies the maker of the transformer. Crucial for spare parts, warranty, and service support. Serial Number : A uni...

  Differential Protection Relay (87T) – Brief Overview Purpose: Detects internal transformer faults (winding-to-winding, winding-to-earth, turn-to-turn). Provides fast and selective protection , minimizing damage and downtime. Working Principle: Based on Kirchhoff’s Current Law : Sum of currents entering and leaving the transformer winding = 0 under normal conditions. CTs on primary and secondary sides feed the relay. If sum ≠ 0 → Internal fault → Relay trips the breaker. Figure – Working Concept:     HV Side CT ---------\                         \                                   Differential Relay 87T ----> Trip CB  ...