Hands On Relay School Transformer Protection Open Lecture Hands On Relay School Transformer Protection Open Lecture Class Outline • Transformer protection overview • Review transformer connections • Discuss challenges and methods of current differential Protection • Discuss other protective elements used in transformer protection Scott Cooper
[email protected] (727)415-5843 Eastern Regional Manager 204 37th Avenue North #281 Manta Test Systems Saint Petersburg, FL 33704 Transformer Protection Overview Transformer Protection Zones Types of Protection Mechanical Protection • Analysis of Accumulated Gases – Looks for arcing by‐products • Sudden Pressure Relays – Orifice allows for normal thermal expansion/contraction. Arcing causing pressure waves in oil or gas space overwhelming the orifice and actuating the relay. • Thermal – Caused by overload, over excitation, harmonics and geo magnetically induced currents • Hot spot temperature • Top Oil • LTC Overheating Types of Protection Relay Protection • Internal Short Circuit – Phase: 87HS, 87T – Ground: 87HS, 87T, 87GD • System Short Circuit Back Up Protection – Phase and Ground Faults • Buses: 50, 50N, 51, 51N, 46 • Lines: 50, 50N, 51, 51N, 46 Types of Protection Relay Protection • Abnormal Operating Conditions – Open Circuits: 46 – Overexcitation: 24 – Undervoltage: 27 – Abnormal Frequency: 81U – Breaker Failure: 50BF, 50BF‐N Phase Differential Overview • What goes into a “unit” comes out of I + I + I = 0 a “unit” 1 2 3 • Kirchoff’s Law: The sum of the I I 1 UNIT 2 currents entering and